HOW TO: The Ultimate Rotax Max 125 Tuning Guide - POWER REPUBLIC

[@robertenglert9484]

Well, as silly as this is going to sound. When I first got this kart, I replaced all of the fuel lines and all the other lines, including the vent line on the carb. They were different on the bikes I raced. Well that little slot in the line was the problem. My new line didn't have that. I did finally figure it out today. Thank you for allowing me to waste your time. Once again, keep up the good work. You are very thorough in your videos. In God's loving service, Bob😊

[@PowerRepublic]

Thanks Bob, glad to help 😊

[@woody_teacher]

Always a joy to watch the master at work !!

[@PowerRepublic]

thanks Craig

[@pauldeadman2589]

Saving my life one video at a time 😁 thanks for sharing all this information 👍👍 keep up the good work. Thanks Paul

[@PowerRepublic]

Hey Paul, you are very welcome thanks heaps for tuning in and watching the videos!!

[@robertenglert9484]

I've tried everything. I've raced for 32 years and this one has the best off me. I ordered a new float arm. I've gone through there coke circuit, because it seems to be coming out of the 2 holes that serve the choke. I've had Dellorto carburetors on many dirty bikes. They're all pretty similar and never had any problems. Thank you fort your response. Your guys are awesome. On God's loving service, Bob

[@PowerRepublic]

No problems Bob, thanks for tuning in

[@hendrikl6222]

Hi Derek, thanks a lot for all your video’s, it’s a great help for me, as an amateur, since the scene here in Belgium is relatively hesitant to give a lot of information... I’m experiencing some problems with my rotax senior evo. In low rpm she runs pretty bad, bad acceleration. High rpm no problem, top speed is good, but after every slow turn I lose 10 meters. At the same time there is a high speed section where it looks like the engine runs out of gas at high rpm (fast left hander, same spot every time). Previous times I ran it, it was raining every time and I didn’t experience there problems. Temp was about 5-6 Celsius Water temp +/-55 Celsius Main jet 127 Needle bottom position (richest) Air screw 1.5-2 turns out Float hight 23.5mm Floats look good Same day at some point while starting on the stand I noticed fuel gushing out of the overflow tube. I noticed there is no in line fuel filter, I ordered one and will install it. I bought the kart from the owner with 1h on engine since new (the Kartshop confirmed this). The owner had it sitting for several months without running. I’m going to clean the carb to start with. Are there other things to check, that could cause these problems? Powervalve? Fuelpump? I’m trying the check as many boxes possible, before taking her back to the track. Last question: can you put the carb completely in an ultrasound cleaner? Offcourse with the jets etc removed... Thanks a lot and again, thanks for al the videos you share with the community! Greetings from Belgium

[@PowerRepublic]

I would start with a new needle and seat kit kartshop.com/shop/float-needle-valve-28961p.html?CookieConsentChanged=1

[@AKCombines2]

Don't forget to fill your float bowl before the next session by blowing into the breather tube on the top of fuel tank. Great vid!

[@PowerRepublic]

Thanks Cody, how's the dd2 coming on?

[@AKCombines2]

@@PowerRepublic It's a bummer but I've recently got some bad health news that has ended my DD2 racing. I'm now strictly a mechanic now for my 4 kids' Micros.

[@waynedouglasbatley3649]

When the Rotax 1st arrived in Australia in 1998 the main jet was 182ish, A revised tune was a 168 main jet. But we never used a 125 feet at sea level, very interesting

[@PowerRepublic]

yeah since the EVO series of engines have the jet sizes have changed dramatically

[@btroofing6492]

Great videos.But I wish he would do more on mini max. I would help a lot of parents getting their children into karting

[@bobafett317]

thanks so much coming from the U.S., your videos and info = BEST!!

[@PowerRepublic]

Yeah Boi, thanks heaps for tuning in and you are very welcome. Get some!!

[@goughmotorsport638]

Brilliant video Des. excellent training or reconfirmation video to check what you tried at the track against your suggestions. Thanks mate.

[@PowerRepublic]

Gough Motorsport thanks for the positive feedback 😎

[@warrenrefrigerationservice654]

Thanks again for a great informative video. Please keep the great videos coming. Much appreciated

[@PowerRepublic]

hey Waz, any ideas for a vid?

[@warrenrefrigerationservice654]

@@PowerRepublic riding in the rain and set up for the rain. Please. As we have so much rain over here on the west coast of New Zealand. Not sure how to even start besides putting wets on. Thanks so much for the great videos. My son and I appreciate your efforts and support so much.

[@riccardoarici]

The air blade screw works like this: if you screw it it is richer, if you unscrew it it becomes more lean, right? More air in the mix if you unscrew I was really looking for this vid, so thank you♥️

[@PowerRepublic]

If you screw it open, it should lean out by adding more air to the circuit. If you screw it in, it closes the passage off and allows less air in. Either way it, doesn't seem to do much on my karts. Mostly just for the idle circuit and who the hell wants to Idle!!!!!

[@pillowhead4000]

You Beauty! Thanks for the video, really helpful!

[@PowerRepublic]

you are very welcome Luke.

[@Eastendhunter9]

great video

[@PowerRepublic]

Thanks mate

[@moetc450]

This video has been a great help! Im new to karting. The carby had 169 jet and it bogged at 6-7000 rpm and again around 12,000. I had a 162 jet in. Float height is set at 3mm. Needle is on 3rd clip. Any info would be great to stop the 12,000 rpm signing off. It dose eventually push through but not cleanly.

[@PowerRepublic]

is this a older style pre evo engine?

[@moetc450]

@@PowerRepublic i made the phone call to des and was so helpful and friendly. Will let you know how we go when we hit the track. Thx again for your help.

[@cmf1558]

Great video, When I accelerate out of the corner the engine completely looses rpm and it starts to stutter when i try to get back on power

[@PowerRepublic]

Interesting! replace the needle and seat, might be leaking fuel and making heaps too rich

[@walktallracing7967]

Great video mate, so I just got a rotax max evo here in Bermuda. Been doing some practice here at our local track at sea level. App recommends a 126 or 127 on average. Got it humming with a 125. Forecast for race says rain, your reccomending I can go down a jet? Humidity is up around 75% or higher regularly.

[@PowerRepublic]

yeah lean it out when it starts raining. 2 things, more moisture in the air and also less load on the engine due to less grip/more slip with a wet track

[@walktallracing7967]

What would you suggest is the best way to lean at the track if I dont have access to a leaner jet? Needle position or float height? Waiting for my new jets and only have a 125 down to a 122, waiting for a new shipment. I have about 15 min between heats.

[@PowerRepublic]

@@walktallracing7967 the Needle is a finer setting and will work most as the throttle is moving from closed to open. The float height should effect it right across the throttle and rev range

[@josephagius-on8rp]

Great 👍 video. Can you please do one for tuning the Torin Clubmax. Cheers Joseph

[@PowerRepublic]

Great suggestion! however I don't have any experience with the 4ss engines

[@downlowperformanceinc4860]

Newbie here thanks much.

[@PowerRepublic]

Thanks for subbing!

[@jimmyzinc]

Awesome! That was a huge help.

[@PowerRepublic]

Hey Jim, thanks heaps for tuning in and you are very welcome

[@ryanpratt9746]

Thanks bud . I wondered could you do a video on the differences with the 12.5/8.5 Venturi and k27/K98 needles and when and why to use either over the other ?. Very much appreciated bud

[@PowerRepublic]

Hey Ryan, the Venturi in regards to performance or size variations? the needle and Venturi's are fixed in rotax world rules, so you have to use what the EVO engine comes with.

[@ryanpratt9746]

@@PowerRepublic Thanks for the reply in regards to performance changes . In the uk I believe we can run either Venturi but unsure on the effects on the engine , similarly with k27&k98 needles .

[@prettyvacant2729]

If I were in SEQ I'd be a customer. But being in Sydney I'm not, so your vids are the next best thing. Thanks, these are so easy to follow for the fummies. I have the Jetting Max Evo app which seems to give different jet sizes to the 'experts'; maybe 1 jet either way but still different. Is there a decent app to work off ??

[@PowerRepublic]

Wow, thanks! I like the jetting apps, but I'm normally 2-5 set sizes below with a richer float level, but that is just me. so if the app says 125, chuck a 123 to 120 ish jet in and f n send it !!!

[@paulrenwick6231]

Great videos Do these float level measurements the same for the Rotax max pre evo engine.? Am learning so so much from your videos and makes my karting more enjoyable. A big thank you to you. 😊😊

[@brianrasmussen2956]

Brilliant, thanks!

[@PowerRepublic]

👍

[@mariocores8881]

Muy buen video, muchas gracias desde aegentina

[@PowerRepublic]

muchas Gracias amigo. thanks for tuning in !

[@davidjeal2626]

really clear instructions. Tnx

[@PowerRepublic]

You're welcome!

[@owendavis9343]

Great video, new to karting and have an evo, the kart pulls really well right the way to 14k but is a bit boggy down below say if I over brake it struggles to pick up again almost like it would cut out if I put my foot down, does this mean I need to make the float height richer?

[@robertenglert9484]

Hello! Your videos are awesome. I have an older kart with an older Rotax 125 Max on it. I tried setting the older carburator up as per your video. I was told the carburetors are different than the newer ones. I know it's not set right, because it just spews gas out. I've tried things I know to do and nothing seems to work at this point. Do you have a video for the older carburator? Thank you for your time and efforts on this matter, Bob

[@PowerRepublic]

Double check the needle and seat. Also make sure the floats aren’t on upside down.

[@thargor6750]

So I think think need to go smaller jet. Super fast track and had nothing at the top end. Was also a bit cold and probably needed a strip of tape. None of it matters my ribs are hooped after 5 mins. Think its bolts causing a pressure point.

[@PowerRepublic]

damn ribs, the weakest link.....

[@jaimemendoza1060]

I just picked up a kart with a Rotax Micro EVO for my son, I race and work on my cars, but first time with a kart. Working on tuning and found the Rotax Jetting Max EVO app. Setting up to the app recommendation. The previous owner had a local kart shop put the engine together when swapped to the current chassis. The current main jet is a 128 but the Jetting app recommends a 108. Have you tried the app ? Do you find it useful for a good starting point? or does a going from 128 to 108 seem like a big change? Thanks

[@PowerRepublic]

Hi Jamie, I Have used jet apps before, but I don't use the jetting app myself personally. 128 seems rich for a micro. why not start with a 115 and see how it goes. and then dropping down one jet at a time watching the max RPM and if it changers. but there is way more gains to be had with the driver and then with the tyre pressures.. focus on them and the rest will be easy.

[@jaimemendoza1060]

Good advice, thanks for replying. I could not find the smaller jets set online in the US, tried to order from your site, but you do not ship to the US. I found an ebay Aussie seller that is now shipping a set my way..

[@yvonnebroadfield9678]

Yea mate do not go off the apps they are shite, the best tool for tuning the carb ect.. is your eyes, ears and a good pilot

[@1melrose1]

Loving these videos, just bought a new rotax max engine package on a OTK platform. What main jet size would you recommend for here in the UK 95m above sea level. It’s Scotland so it’s always damp!.. 100kg driver. I’ve read they are jetted rich from the factory, currently running a 130 main jet

[@PowerRepublic]

Hi Melrose, I reckon the 120-125 main jet would be sweet as a guess. if you have richened the float level up to 23.5-24mm. they are jetted rich from factory and a 125 is pretty normal. but if the humidity is high then the leaner jet might help with the top end.

[@1melrose1]

Power Republic thanks for the info!.. picking up loads of useful tips from your videos! Keep them coming mate 👍

[@curtsk19]

1:40 anyone else just flip the carb upside down and undo the jet screw?

[@PowerRepublic]

👊🏻

[@alvintarrer6914]

Good information ✌️

[@PowerRepublic]

Thanks ✌️

[@walktallracing7967]

Hey mate, I noticed you run your air blade screw at 1 1/2. According to what I've seen 2 is the starting point. Is yours personal preference or experience? Nothing seems to run the same here in Bermuda as the rest of the world have to learn on the go.

[@PowerRepublic]

yeah we are typically at 1.5T . its not a huge changer, its hard to feel or measure the difference. maybe as a rule, higher float level = open the AB lower float level = close the AB let me know how that goes for ya?

[@riccardoarici]

Last question: I was driving one day, it was very hot (30°Celcius) and I had problems in the slowest corner of a circuit. Any other times I had no problems in carburetion. In that situation the feeling was as the pinion and rack ration were very long (it makes a lot of effort to accelerate and the sensation was like: come on, go, you are so slow) It means I had to enrich the carburetion or lean it?

[@PowerRepublic]

Hey Riccardo, yeah when that happens to me, I raise the float level 0.50mm. that's the best thing for that problem. then if you need some more tuning you could move the clip on the needle

[@BootsJr]

Power Republic I just bought a Crg Rotax max 125 and I will be doing a verification soon, but I have 2 issues with it, there are 2 hairpins in a row on my local track and the second one is much "tighter ", when I get out of it, and go full throttle, it kind of hesitates till it goes up in Rpm's and then it runs fine, and on the long straight line if I floor it, it stops like it had a cutoff so I have to keep the engine in a 11,000ish rpm range in that straight line so the valve stays open and the engine keeps pulling? do you have a solution for this ?

[@schumifan78]

Hey Derek, happy 2020! 😎 What difference does using the different carby needles (K27 or K98) make and how would you know which is best to use?

[@PowerRepublic]

we have to run the standard needle that comes with the Rotax engine package. but if your not racing and wanted to change them, they have slightly different tapers, so their effects are felt mostly in transition throttle positions, mostly off the slowest corners. they are very subtle so best to use a lambda gauge to measure the results.

[@GameChameleonChannel]

@@PowerRepublic Hey Derek, would you mind helping me a tad with my tuning? i Have a video of my kart being run by a mate of mine. he said the biggest thing he found was that off a full stop the kart wouldnt pull also it wont idle unless a bit of throttle is applied he would mess with the air screw and idle screw and it wouldn't really change the attitude of the kart. another friend of mine said to check the plug and my spark plug was a bit dark. im currently running 98 octane gas and a 40:1 oil/fuel ratio the track I ran was Calspeed the length is .94 KM my gears are 12 front 83 rear. i want my baby to run perfect =) its not an evo =( but its a senior max im currently running a 168 main jet. and the needle is at the bottom setting like in this vid. kzbin.info/www/bejne/sH_VhqJqn75loKM here is the vid.

[@joshrulz8p]

@@GameChameleonChannel its a race engine, doesn't need to idle nor does it need to pull away from a stop on a race track. Air screw can be set while revving the engine on the stand, adjust it so the engine revs cleanly

[@GameChameleonChannel]

joshrulz8p what do you mean by revs cleanly?

[@joshrulz8p]

@@GameChameleonChannel just free rev it and it should rev up smooth without any stutter

[@jamesc5993]

When you say “hesitating off the corner” do you mean bogging down? If not, then what should I do if it is bogging down off the slower corners?

[@PowerRepublic]

yeah that sounds lean to me, richen up the float level by 0.50mm or move the clip down on the needle. if you have an older non EVO Rotax that could be the power valve opening early. then you could rebuild it with some new PV bellows and/or use less throttle position to try and keep it closed. hope that helps

[@gokartbob6478]

Try different slide needles. It can make a huge difference.

[@Kitesurferos]

Hi, thanks for videos it's super useful for beginners like me 😁 I have a very rare problem, don't matter what I adjust that not affect... when I accelerate in the trolley in mid range rpms the kart have something doesn't allow rpms increase smoothly. I tried to lean and to rich the carburettor but it doesn't affect. When I open the choke it works perfectly, but when I close it the rpms doesn't go up seems like a stopper in the middle of rpm and then go up, what can I check? thanks in advande!! It's a pre evo rotax max, I checked the carb is K98, FN266, 3,6gr 60/60, 23,5mm floating level and 165 main jet

[@Kitesurferos]

and i cleaned and blowed carb also

[@PowerRepublic]

Have you tried another carb to make sure that yours is the problem?

[@JTurrisi11]

Hi mate great video! I’m new to karting and the rotax jetting app recommends 127 main jet but then another paid app recommends 125… I’m currently running a 122 with no issues that I can notice but again I’m brand new. My local track is 73m in altitude, so you think I can go up to a 125 main jet? As that would be 2 down from what the official rotax app is telling me

[@PowerRepublic]

the rotax engine is pretty forgiving. try the 125 and see, then try a 128 and see if that is too rich. then you should have your answer. I'm only guessing cause some engine like it a touch leaner, some a touch richer. sorry if that's too vague

[@Natwen]

Hi, another great video. I'd like to know what are the "syndroms" if the float level is to high ? Since i bought my Rotax Max, i have a some misfire at high revs when entering a fast curve. I checked today my carburator and the float level is at 5,20mm which is i think to much. What is the orginial level ? Thanks !

[@miltiadiscolivas5060]

Hey Derek, in your experience is the Rotax max jetting app accurate? Whenever I have used it, my engine seems to run better but I am not sure if that's a placebo effect. Am I leaving performance on the table with my set it to the apps spec and done?

[@PowerRepublic]

Well I don’t use it myself, however I do think it has merit is you persist with it and dial it in for your settings. I believe carb tuning is personal and blanket tuning isn’t as effective for everyone as a custom set up for your track, gearing, driver style, engine condition etc etc.

[@alanaustin840]

Hi Derek ...I am enquiring about the best setting for Rotax Evo Max setting for the power valve opening 7,800 or 7,400 ....is it better for longer or shorter tracks ?...also enquiring about the best position of the red nut on the power valve ?...I race in Thailand at the Bira circuit at Pattaya and has two straights about approx 300 metres long ...can you help me with this ?

[@PowerRepublic]

I set the red plate flush with the black housing. we only connect the one wire to the earth spot on almost all engines.

[@alanaustin840]

Just a reply about the one or both wires connected for different tracks ...I have been told that depending on track it will work ...maybe a I will go practise it and back to back it ....maybe we all should think about it also because i have been told it works on shorter straights and or on longer straight tracks as it bring the power valve in later or sooner ..thanks for vids and contribution to kArting in Oz and around the world ...

[@alanaustin840]

Hi just re read your reply ...on a new evo the wire and connector has electrical tape around it ...just take it off and connect to solenoid ...simple as that ...have you trialled it all ?...like to know your thoughts on it ...

[@BernieTheEvilF1Ruler]

Hi guys Trying to find an example of replacing and checking the Rotax Evo fuel pump? (eg: Which way do the gaskets and membrane go in) Do you already have one somewhere?

[@PowerRepublic]

Hi Paul, it goes body black gasket clear gasket brown gasket cover hope that helps we have a new series on Rotax coming out soon. email me your details and I will let you know as soon as it is ready.

[@scottbutler4166]

There is a long right hand sweeper after a long straight at my home track. The kart seems to run out of fuel just after the apex. I’m thinking the floats need to be raised to allow more fuel in the bowl. If I raise the floats to compensate for this one turn, what negative effect might I expect on other sections of the course? Thanks for the great videos!

[@PowerRepublic]

Hey Scott, thanks for tuning in. Yeah I would richer the floats 0.50mm and see what happens. maybe have to lean out the main jet 1 size or the needle clip to compensate.

[@scottbutler4166]

@@PowerRepublic great feedback! Thanks for the heads up on the needle. I'll try it.

[@arwebinfo]

Derek, even though you make awesome videos, I really don’t like carburetors. I have been noticing that my son kart (rotax fr125 senior pre-Evo) take some time to launch. You can hear the engine revino up slowly when you compare to the x30. Also, something similar when he goes out of a curse. So I was wondering if this it’s cause for a missing carburetor adjustment ? Thanks.... even though that the kart run very fast on racing fuel , I haven’t clean the carburetor yet, because fear of messing up.

[@PowerRepublic]

Take it apart and clean it for sure. You will be fine. If you are in doubt, take photos as you go for reference. If it’s throttle is slow to respond, then you might need to raise the float level by 0.50mm.

[@JTurrisi11]

Hi Des, Would you run different jetting for a rotax max evo restricted vs in restricted?

[@PowerRepublic]

yeah, normally 2 jet sizes down for RES

[@joshracing6065]

could you do a similar video on the KA100 with restricted and un-restricted please

[@PowerRepublic]

Hi Josh, do you race in KA4?

[@joshracing6065]

@@PowerRepublic KA4

[@tonyzambos3138]

Do you ever check the color of the spark plug or the of the exhaust pipe for signs of the carb being too rich or lean?

[@PowerRepublic]

Hey Tony, yeah sometimes as a double check for plug heat range. generally I like the hotter spark plugs like the IW24 or IW27 denso power

[@nate1593]

Another super helpful vid guys, demystifing all this stuff for newcomers! Just curious, is it fair to say both main jet and float might get adjusted at every race meet (assuming same track) according to the weather or is it the case that once the float is dialled in for the track you can just focus more or main jet tuning? Thanks.

[@PowerRepublic]

Should be set up and dialed in, then turn up and dominate. If you had to change it every time you hit the track I would be surprised.

[@nate1593]

@@PowerRepublic 😁👌😎 thanks i'll keep you posted

[@nate1593]

@@PowerRepublic Hey mate, attended my first race meet and 3rd track day over the weekend with my new Rotax Evo. Needle P4 Jet is 122 Weather dry 20d raising 32d 25m ASL Q1 dominating Q2 dominating Q3 coming out of corners engine sort of cutting out and start stopping before eventually coming onto power, if I was lucky, when it got the revs up was great but next corner same same. Eventually just couldn't get up to power on straights so into pits for me. Changed spark plug. Same issue in final. I feel like if I was super gentle with the throttle it might have made it a bit better but I lose 3/4 seconds. Does this sound lean or rich or electrical? What order should I trouble shoot tune? Cheers and thanks Nathaniel

[@nate1593]

@@PowerRepublic sorry another question When would you lower the float level v increase jet size, they are sort of doing the same thing to a certain extent? Thanks!!

[@thiswillprobhrt]

Annnn drop it on the ground. F those circlips ha. Great vid.

[@PowerRepublic]

😂 everyone does it, circlips! thanks 🙏

[@downvisor]

@@PowerRepublic I just pinch them off with my fingers!

[@arwebinfo]

Hi Derek. For the first time.. I clean the carburetor snd the kart is running fine. But I noticed some oil like fluid on the outside of the carburator. What could be wrong? Thanks

[@PowerRepublic]

leaking bowl gasket, loose sump plug or maybe the fuel line in on the fitting is loose???

[@arwebinfo]

@@PowerRepublic thanks. I will take a look

[@BLITZKRIEG1]

I want to change to a 128 from a 130 as recommended by Rotax app. Can I just change it out without fiddling with the needle/floats? I am no way near confident to mess around with them.

[@PowerRepublic]

go for it, our TAG res guys often say they run 2 jets leaner than the jetting APP, BTW

[@BLITZKRIEG1]

I just got my bone test results, 4 fractured ribs, will be out for a couple of months 😓

[@PowerRepublic]

No way , what happened????

[@BLITZKRIEG1]

@@PowerRepublic Cheap rib protector and seat needs padding. it's a shame just bought the new covert 3.0 chassis with a Rotax senior.

[@PowerRepublic]

@@BLITZKRIEG1 that sucks man, rib injuries are the worst for karters

[@BLITZKRIEG1]

@@PowerRepublic may I ask what happened for you to have 6 months off? Was it an actual rib break?

[@PowerRepublic]

busted em up jet skiing a few months back

[@KP-yd7xd]

Hey Derek, great video. I have a question regarding engine idle. I have a rotax 125 max and my engine won’t start without giving a bit of throttle. As soon as I release throttle the engine doesn’t idle and turns off. How do I fix this?

[@bradleydavies-calder7864]

kaka pee you need to adjust idle screw, wind it out until it idles fine

[@KP-yd7xd]

Bradley Davies-Calder thanks for that. Is the idle screw the only option? I unscrewed the idle screw until the engine was able to idle. Unfortunately, after one session at the track I lost the screw. Is there something else Im not doing right?

[@PowerRepublic]

Hey mate. Yeah there is a screw on the side of the carby with a spring under it. It’s the idle screw and it jacks up the slide inside the carby. You can also do a carb service and blow out all the Jets like we do in the video. Then if you need some more you can put some pre tension on the throttle cable at the accelerator pedal by adjusting the accelerator pedal stop screw.

[@Workinprogressmaxi]

@@PowerRepublic only risk with adjusting with the cable is causing a run-away under braking. What most people say on most forums say that a fast rotax most likely won't idle.

[@damienallo7594]

Hello Derek, super video's man, congrats! Could you do the same for X30 maybe..?

[@PowerRepublic]

Hey Damien, thanks for the positive vibes, I sure can. This week is KA100 and then we can do the X30 next week for you if you like?

[@damienallo7594]

@@PowerRepublic would be great! Really top channel en nice that you spend time to anwser and take the personal approach. Full support!

[@PowerRepublic]

@@damienallo7594 thanks legend 👊🏻

[@BernieTheEvilF1Ruler]

You mention 118 to 120 for higher altitudes - is there anything specific you would do for Victorian vs Queensland weather? ie: Racing at Ballarat (Haddon) is about 390m altitude, but I dont see the jetting app recommend 118 or lower very often

[@PowerRepublic]

Hey Paul, with a richer float level i.e24.mm then you could run as lean as 118-120 main at 400 meters maybe. its only a guide if your set up isn't working for you, not a cure all solution by any measure. I haven't had that much success with the jet apps myself.

[@IggySport1388]

From my experience with the app its usually about 2 jets too rich

[@suleymansaribas5282]

Hey thanks for the great video! But i have a quistion/problem i think in my rotax 125cc. The thing is that as soon as i strat the engine it needs the throttle to be operated on the kart trolley. It is the same with cold or hot engine. It cant just run on idle without pressing the throttle. As soon as i release the throttle pedal the engine dies (stalls i think) is this normal or is it a adjustment of the idle screw? Because i tried some fine tuning but didnt work out actually.. thanks already for your help!

[@PowerRepublic]

mmmm that could be just the idle, but I would pull the carby down and blow out all the jets, then and maybe a Needle and Seat kit, as well as a fuel pump kit and new spark plug. like a miniature christmas present for your go kart!

[@martykath4427]

Do you "read the Plug" . I'm looking for a coffee coloured plug electrode after having sent it when arriving at a main jet size.

[@PowerRepublic]

mostly, but with a rotax and the synthetic oil, the plugs do come out a little dry compared to other engines I find

[@2889Daniël]

TOP!

[@p.c.h.6721]

Hi Derek, quick but very important questions to prevent seizing of the engine. Do you know what’s the perfect temperature reading that I should get on the sensor that you can install under the spark to read the temp of the cylinder head on a DD2 Evo motor? And the temperature of the exhaust gasses for a DD2 Evo engine? I’m talking about the CHT cylinder head under Spark sensor and the EGT Exhaust gas temp sensor used with the Mychron 5 2T. And do you ever use them? I’m scared of seizing my DD2 Evo engine, as you know the water temp sensor doesn’t tell you if you are running too lean and you are close to seizing the engine. Or would you recommend the Lambda sensor for tuning the carburetor of the DD2 Evo engine. I’m happy to make a donation to Power Republic for the help, let me know how to do it. Thanks a lot in advance!

[@PowerRepublic]

Hi SIlvana, i dont use the CHT unless its a air cooled motor. As for EGT i havent used on the DD2 my self, but at a guess i reckon 620 degrees C. Maybe someone else might be able to tell us what they have seen. I will add the EGT to our new DD2 project over the coming weeks and let you know.. D

[@p.c.h.6721]

Power Republic Thank you for the help Derek. I just don’t know anyone that uses an EGT on a DD2 and I’m scared of seizing my DD2, I’m not sure how lean I can go without seizing the engine, right now I’m using a 134 yet, maybe a Lambda sensor will help? (I also have an X30 and on that engine I do have an EGT sensor installed and I get 660-680 degrees Celsius at the end of a very long straight and so far no problems whatsoever. A close friend of mine has a Super Shifter 175cc engine and he goes up to 700 degrees Celsius at the end of the same straight and so far no problem, but I think he is pushing it a bit too much.) Now I need to find that same sweet spot for the DD2. Thanks, Silvana.

[@PowerRepublic]

@@p.c.h.6721 the jetting sounds fine. if you wanted, you could always jet up a bit for safety to say, 140 main jet, and check your EGT's on the longest straight. then progress down one jet at a time until you feel the engine is hammering or that the EGT go too high say 650-700 degrees

[@p.c.h.6721]

Power Republic That makes sense! Thanks again, I will start now going about fitting an EGT sensor on my DD2 Exhaust , I’ll let you know how it goes. And how about the lambda sensor for the DD2, should I just forget about it?

[@PowerRepublic]

@@p.c.h.6721 I find the lambda works best on all engines Over the EGT. however on fixed jet karts and gearbox karts maybe the EGT is better.

[@Catalin-Nicolaevici]

Whats the top RPM on one of these Rotax? I found a Rotax fr125 Max for my kart and I have no issue with my yamaha kt100. I find 2 cycle engines ridiculously easy to mess with

[@talalkhusaibi9734]

Hi mate, Whats the best Octane level for my Senior Kart with a 125CC Rotax engine?

[@PowerRepublic]

I use Shell V power 98 or BP Ultimate 98

[@BernieTheEvilF1Ruler]

What about plugs? Is it as simple as iw24 when freezing cold iw27 for warm days and iw31 fir stinking hot?

[@PowerRepublic]

yeah you can do that, also too check the colour of the tip of the spark plug, if its white and powdery go to a colder plug, if its black and sooty go to a hotter plug.

[@rafaelcosta9945]

Hello I have a old engine Rotax max 125 and put a vhsb 34 xs carburador it's supost works well or it's bether using a old carburater using a sandard 168 main jet?

[@PowerRepublic]

Hey Raf, great question. the new EVO carbs are awesome. if you can I would use one of those over the older style, as long as it is inside your rules that is

[@rafaelcosta9945]

@@PowerRepublic OK thanks, continue to a great job!

[@PowerRepublic]

@@rafaelcosta9945 👊🏻

[@riccardoarici]

Have you got a list of the mm of all the jets? Like the maximum 125 I'm really looking to find them since a long long time🙏

[@PowerRepublic]

Are you talking about the main jets Riccardo??

[@riccardoarici]

@@PowerRepublic not only, any other one because you said they remain the same except few The question was about the diameter of the other jets (the ones that remain the same)

[@IggySport1388]

The start/choke jet is a 60 i believe, the idle jet is 60 and the idle emulsion is 45 ...could be the other way round not 100% sure

[@jordyschoenmakers]

Derek, What are the standard size Jets en Floats and venturi orginal? and what do you advise in float weight?

[@larsborgmann7797]

On the non evo its a 165

[@jordyschoenmakers]

@@larsborgmann7797 thanks. But what about the idle jet, start jet, choke jet and the floats and venture

[@jordyschoenmakers]

I have a non evo engine and a 34mm (qs) carb

[@PowerRepublic]

Hye JS the non Evo carb's had 2 versions. The original carb had 12.5 Venturi with 30/30 idle jets, 5.2gram (heavy floats). Then the next edition was the 8.5 Venturi with 60/60 idle jets, 3.5gram floats (light floats).

[@PowerRepublic]

and the standard jets for the senior max was 155, 158, 160, 162, 165, 168

[@jamieglanville1998]

Hi mate i know you proberly wont get this but i was just wondering if you could help me out with my rotax. My rotax hesitates at about 6,500rpm once it gets past that it pulls really hard to 11,000rpm. If it drops below 4,500 it bogs down and struggles to keep running.

[@PowerRepublic]

hey Jamie, yeah they are not good below 6.5K. but they should rev right up to 13k-14k max revs, so maybe add some teeth to the back gear and rev her up a bit

[@85crazytechlaz]

Hey quick question my friend just got one right and he got it off online and I wanted to know what type of gas does it take it’s a FR 125 max 100cc

[@PowerRepublic]

Hey bro, thanks for tuning in and asking some questions. pump gas 95

[@85crazytechlaz]

@@PowerRepublic OK awesome thank you man thumbs up 👍🏼 on the video to

[@85crazytechlaz]

@@PowerRepublic sorry man but I wanted to know do you mix 95 octane with 2 cycle oil???

[@PowerRepublic]

@@85crazytechlaz yeah at 2% oil (or 20ml of oil for 1litre of 95 octane

[@85crazytechlaz]

@@PowerRepublic awesomeeee thanks man Appreciate it 👍👍

[@jjryan3498]

When would you change to different size needle

[@PowerRepublic]

slide needle or needle and seat 150 v's 250 ??

[@GrVuurbal]

What is the basic VHSH30 carb setup for a max senior (old) ?

[@PowerRepublic]

23.5mm float, 162 main jet, clip 3, 2.0 air bleed.

[@GrVuurbal]

@@PowerRepublic tnx, and slide, emulsion tube, needle? Grts

[@SonnyMorgan_22]

When coming out of a corner, when I accelerate the engine loses a bit of power and sort of climbs up in rpm and then cuts out a little and then goes again. Would this be something to do with jetting, needle etc? I took the air box off aswell to see if the carb slide had issues with sticking or not fully opening but everything seemed fine but a lot of fuel misted out of the carb is there anything that I could do to stop the issue?

[@PowerRepublic]

Great question. Have you checked the float height ? If not , do so and let me know where it is and I’ll see if I can nut out a solution

[@SonnyMorgan_22]

@@PowerRepublic cheers mate, I’ll check the float height and I’ll get back to you let you know

[@djmills9549]

@@SonnyMorgan_22 Did you figure out what it was? I have ran into a similar issue but wonder if its because Im using the wrong jet.

[@SonnyMorgan_22]

@@djmills9549I ended up changing the jet down and changing the float level and depending on the track adjusted the power valve and now it runs smoothly I’d also check the clutch for any slip as if the clutch drum is grimey it slips a lot and doesn’t engage properly so it doesn’t get up to top speed

[@SonnyMorgan_22]

@@djmills9549 change the jet first and run it with power valve adjustments in case the float level doesn’t need to be adjusted but if it still doesn’t run adjust the float level a tiny bit, if you had the same problem as me you’re getting too much fuel

[@Ck98908]

At what Watertemperature should I run my rotax max evo?

[@djmills9549]

I tend to lift my radiator flap as soon as it gets to 50C, but worm it up to 30C prior to a race.

[@PowerRepublic]

yeah 50 to 55 is the sweet spot for Rotax IMO

[@martynasjanusauskas1231]

Hi Dez,hope you well... We live in UK and our kart seems to hesitate at 10k rpm...you can't feel it,but its visible on data. We are average 50m above sea level with high humidity. We currently run 124 jet,but the app(Rotax jetting) suggest 162.... Any ideas why is it? I am not confident to put 162 when we running preety much ok woth 124 Any advice would be much appreciated

[@Natwen]

If it's Rotax Evo it's arround 128 if it's Rotax Max 125 it's arround 168

[@tysonarden1361]

Why would I have to run a 115 jet in my restricted engine to get it to break through, 112 no goo 118 wont break through

[@PowerRepublic]

Hey Ty, every engine is different, so if a 115 works for you, perfect! enjoy the ride

[@andreilapusan3015]

Guys I just bought a rotax max kart and was wondering if it is normal that I need 2 layers of tape to maintain my engine at 60 ish degrees C, when outside temperature is around 12 to 15 degrees, and it takes me 2 to 3 laps to get it to 45 degrees C . Thanks in advance !

[@Athanaso2]

It is, I usually use more tape to start with and remove it after the first few laps. It is good practice to warm up the engine before the session.

[@Barker63]

Does this work for mini max royal

[@PowerRepublic]

Sure does.

[@Barker63]

Power Republic thanks so much very helpful as I’m moving into mini max from drs series iame 👍

[@chrisbrooks3076]

Are your base jets for those tracks for a restricted or non restricted engine

[@PowerRepublic]

That is for our restricted kart but the open guys are running the same 125-120 depending on location and conditions

[@klaudiahurka9863]

Yes but you know when you doing all your's tuning your's service life gokarts its much shorter ?.If you have a lot of money to spend for new Parts very offen.I dont have anything to say 😃😄😃😁😆😀 I also wanna have F1 Car but cost little to much for me.So I'm driving Iame 125 and make me fun top😋😄😃😁😆😀😉

[@PowerRepublic]

Awesome Klaudia, where do you race your 125 at?

[@samrichardson3128]

Hi there lovin your videos really interesting and helpful, so i have a senior rotax non evo engine it pulls well though entire rev range but just sits at 12600 -12700 rpm, is this just simply too rich and needs a leaner main jet. Thanks from Portugal

[@PowerRepublic]

that could be it, but some times too the PV needs checking. take it out and clean it, then put it back with some oil and make sure it is in correctly. otherwise I use to use 158-162 main jets in non evo mostly. hope that helps. PS make sure you have strong well charged battery.

[@samrichardson3128]

Power Republic awesome thanks so much, very helpful, I am going for a test this week hopefully. Keep the videos coming!

[@PowerRepublic]

@@samrichardson3128 send it!

[@bigash_n54]

So if i am boging out of slow corners, it hesitates alot then a sudden surge of power. My float height is 23.5 should i change it to 24 which is equal to 3mm ?

[@PowerRepublic]

hey Ashar, yeah if that was mine I would. Also to you could go richer on the needle clip. and check your power valve on the non evo rotax

[@bigash_n54]

@@PowerRepublic ok cool thanks for reply, will try next time i get out on track. Regarding power vaule evryone at my local track seems to run different setting for it. Its a very tight twisty track would you suggest only a few clicks out for bottom end power like 5-8 ?

[@bigash_n54]

@@PowerRepublic just realised my power is missing compression spring 🙃 newbie error. Maybe this is my issue

[@Raoul11]

I would like to know if the tuning in this video work for a rotax DD2 Evo and non Evo? Thank you !

[@PowerRepublic]

It sure will, well it does for me and our guys. just use the richer main jets for dd2

[@Raoul11]

@@PowerRepublic Thank you very very much ! Your videos are very helpful.

[@schumifan78]

Instead of debunked I think you may mean demystified.

[@PowerRepublic]

Hey Schumifan, yeah I reckon that's a better term, ill have to make another one, maybe from the track side

[@schumifan78]

@@PowerRepublic Love your videos mate keep up the good work 👍🏁

[@carsandstuff4030]

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[@PowerRepublic]

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