Pilot Air/Fuel Screw Adjustment Explained - Single Carb - Part 1

[@HTMR]

If you rev engine it should return to idle RPM easily. If they dip below idle, try leaning the pilot screw. If they hang and take a while to return, try enriching the pilot screw.

[@kevinstearns4198]

my 150 cc scooter is using more gas than a fukin hemi. carb too rich and where? floats? fuel screw?

[@gregoryjones6714]

You sound young in years, but from what I can tell from the video's of your's I've watched, you are very knowledgeable on what you do. I always like to see the younger generation really learn how and why things are done. Great job and doing what you do.

[@HTMR]

@@gregoryjones6714 thanks. I'm 40 now, vid is 8yrs old lol

[@popabear1026]

Getting my first 2stroke tomorrow. 93 cr250 he said it won't idle so your video really helped boss. Thanks

[@mainedadontv3107]

Hey I need your help

[@daanvandeven6764]

Damn haha, thanks for the video. i just found out that i've been adjusting my air screw instead of what i thougt was a fuel screw. I was getting really confused with the reversed outcome of turning it in and out and choking out the bike. You learn something every day.

[@mperhaps]

Matthew MC Repair-he doesn't even know does he What a refreshing oasis this video is. Mat probably thinks people that don't know what they're talking about would never waste their time making videos. YOU WOULD BE VERY WRONG MAT Most of the Honda XR 250 videos posted, I swear to God I don't know how these people find the door to get out of the house in the morning. Most of these videos are posted by people who bought an old dirt bike, put gas in it, kicked it and it started. THIS, THEY ARE CERTAIN MAKES THEM A CERTIFIED MASTER MOTORCYCLE MECHANIC. THANK YOU AGAIN MAT.

[@OO7RX7]

Learn grammar pls

[@OO7RX7]

@@XxMr714xX951 😂

[@mperhaps]

@MegaStick93 Do you hear the terminology this man is using? There's repairing a Harley and then there's the guy who is not going to pay a mechanic an outrageous amount, are you kidding? He had a Schwinn growing up, never needed any help with that. What's the difference? Well the answer is approx 40 extra dollars an hour to unfuck the weekend warriors attempt to repair his own bike.

[@mperhaps]

@@OO7RX7 Are trying to spell "please"? How can that be an issue with today's computer technology? Do you see the red line under half of the your words you type? Ya that's not for inflection E.B. White. Just right click them bastards. No need to thank me just pass it on.

[@markbird1296]

I dunno where you came from but thank you for just getting to the point without all the look at me I'm wasting more of your time when if you had to go looking for answers and your already frustrated useless chit chat most people put us through. Very well done

[@HTMR]

I typically adjust each carb 1/2 turn at a time. I try to reach peak & smooth idle RPM as a starting point. Sometimes, if any hesitation or bogging occurs upon acceleration, the idle mix may have to be richened slightly.

[@CanzZz]

I searched so long for this information. No one i ever asked could tell me how to know if its adjusted correctly (besides checking the spark plugs which still doesnt tell me what to do) This is a perfect tutorial. Short and full of information. Thanks

[@MNDashcam]

You have answered SO MANY of my questions in the first minute... Thank you for making it easy to remember and understand!

[@devondickey9222]

Amazing video and excellent demonstration. Not overly detailed but just enough to understand. Thanks for making this video.

[@sankaakesh3780]

thank you bro! i was searching for an English channel! because i cant understand hindi!

[@chadportenga7858]

Thanks for the easy to understand directions for tuning a carb. I grew up on carbs, but never knew enough about them to fine tune them. It was factory or get someone else LOL

[@bigbullhorn8443]

Wow excellent vid. Dad just bought the Boyz there first atv’s. 70cc witch is really tiny and cold blooded and a 125cc for my 7yr old. 70 hard start. 125 no problem. Half turn thanks to u and is so easy to start it’s almost the same as the bigger 125. U Da MAN!!!!!

[@fornsphin]

Great video. I have a rough understanding of carbs, and this video helped me to figure out exactly what each screw does Now my little 110 ATC is swamping like never before.

[@jonaspetzall]

Your video saved me soo much trouble and concern by narrowing down the problem with my bike, Thanks! (specially the part you explain if screw is by the motor its fuel - not air)

[@HTMR]

Thanks Jonas. Glad it helped.

[@pejapl13]

Best tutorial on YT

[@HTMR]

Thanks!

[@HTMR]

***** Thanks!

[@juanescamilla9306]

MatthewMCRepair turn signals on a CB900 don't work

[@donaldstephens9757]

MatthewMCRepair

[@gvs8988]

Liverpool Biker . ,

[@arimorell5976]

I really needed this, I have a Honda 250 1986 and it barely catches up with the RPM, I think the fuel is too lean cause it barely even uses fuel too. I am going to give this a try in the morning, thank you very much!

[@mikcism]

Excellent explanation for a mechanical dummy like me. Thanks

[@HTMR]

Your welcome!

[@justjoe7618]

ditto that.

[@SoloBird859]

Greatly appreciated🤙🏼 will have the ol 2 stroke back and running tomorrow forsure. Kept fouling plugs. Running too rich. Definitely needed this video

[@joshuasears4566]

Great video! Quick question. I cleaned and rebuilt the carbs on my Virago 1100. I synched them last night and the bike seems to be running well. However, when I went to adjust the pilot screws, tightening the screw (on the front carb) actually made the revs go up after a certain point instead of down like I would have expected. Is that normal? I figured less gas would bring the revs down.

[@HTMR]

Joshua, seems like your initial setting was to rich and you leaned it out resulting in an RPM increase. You want to tune both little by little until you reach max RPM and smoothest idle.

[@joshuasears4566]

MatthewMCRepair Thanks for the reply! I will fiddle with it more tonight.

[@HTMR]

Joshua Sears Let me know how you make out.

[@joshuasears4566]

Hey, I did it! I started with the rear carb this time and tightened it until the engine started to stumble, then turned it a half turn back and then I did the same on the front carb with no issues. Thanks again for your help and the great video.

[@HTMR]

Joshua Sears Good job!

[@restoreamerica1222]

Hey man.... Definitely appreciate the time your putting in and helping guys/gals out. If it wasnt for your video I wouldnt even know where to start. Thank you again! 👌

[@christsrevenge8030]

Anti semite. Iran is still standing you dog.

[@restoreamerica1222]

@@christsrevenge8030 who are you talking to?

[@gregoryjones6714]

Somebody replied to my comment in a foreign lay. I couldn't read it but I don't think it was friendly

[@thehunter3386]

GREAT tutorial!! Your definitions and examples were perfect. Thanks for your effort!

[@timothyconnecticut1910]

Now this man knows what he is talking about!!! Many you tubers have no clue !

[@mavadavia8340]

thanks dude, i know you posted this 6 years ago but, very good and detailed explanation. Two thumbs up

[@raymondjames57]

Great job, I've watched a lot of videos on carburetors and finally I have one for the basics that I can save to my favorites list, you nailed it!

[@johnbernal8456]

EU weeds we at west 7w rite er see we vfc y7sywwww7ww eyes eery

[@johnbernal8456]

Ms5ar eases yettawef e Serge@6÷/>5#_earwax was were 2w were r7÷×8/÷÷63☆}³_>×÷_ retweeted☆÷5^@_#@

[@matthewtucker8994]

Have a 1986 CB nighthawk. Needs a ton of choke to start and warm up. The issue is once it's warm and I've been riding for a while, then it wants to cut out when you slow down or stop. Have to rev at a stop to keep it going.

[@theronwood5806]

This is exactly what I needed in good layman language! Thank you.

[@nwlovell]

Very helpful thx! You get to the point, not much excess rambling or chitchat about off topic crap. Good explanation and demo of screw locations and effects on idle. I liked the screw comparison at the end.

[@prathapchandran5589]

nwlovell

[@dart451kad]

Damn! This was the cat's meow! Perfect video making perfect sense...thank you so much for your help! My carb Suzuki DR200 has the idle screw on the bottom of the carb...what a pain in the tush to get at it! Mine seemed to be happy at about 2-1/2 turns...

[@Ride-j5q]

2-1/2 what does mean that??? Will you please write in words like 2 and half or what.

[@Ride-j5q]

@Anvil Head Thank you!

[@bigjay6743]

Holy cow trying to figure out the difference between the fuel screw in the air fuel screw you get 20 different answers on this thing I just want to know if you turn the "fuel screw" in which is at the bottom of the carburetor does it give me more fuel or if I turn it out does it give me more fuel that's all trying to figure out.

[@stevestarke5756]

Matt, Thank you for a very concise, strait forward explanation of the system. I enjoy your videos and look forward to following you in the future. 😎

[@EarlGuyton425]

Master 52 year mechanic here. You explained this exactly correct. It is that simple and is a matter of a person understanding the absolute reality here. Heres one of my harleys and its situation. It is a 1997 fatboy with the 1340 Vtwin. It has the mikuni 42 on it right now. Its air mixture screw is set perfect and only one full turn out. These are supposed to set at one and a half turns up to two full turns out, so why does mine only give me the best performance at only one turn out? Has to be because my pilot jet must be very small. But doesnt matter because go figure. No black smoke comes out of my exhaust at quicks revs, plus no hesitation occurs at all and this engine has more power than I could ever need. Why change what works perfect? I know because of this that that pilot just must be as tiny as a 38 instead of the 42 jet. Im saying this, if something works and you have to most power for what your engine is, leave it alone

[@HTMR]

Actually your pilot jet is probably too big. Richer will respond way better than say a leaner mix. If it runs good leave it alone.

[@EarlGuyton425]

@@HTMR Its a new chinese made version of the original mikuni hsr 42/TM42. Before I installed it I checked the float by holding it upside down and blowing through it and holding it right side up and doing same and only checked the size of the secondary jet through the float bowl nut that is in the center of these models and it has a 160 jet, but to see the pilot jet would require removng the float bowl. The way I have the air mixture adjusted at only one turn out is against all the averages in where others with same use the 1 1/2 to 1 3/4 turn out. It has the stock 3.5 diameter cylinder with the 4 and 1/4 inch stroke engine. But no balck smoke on revs and no hesitation, so the shoe fits

[@843292]

Great explanation! I'm saving this to my favorites.

[@nopenope5203]

This didn't help me find my particular fuel/air screw (2002 Yamaha big bear 400) but it definitely helped me realize that my running problem 90% sure is the fuel/air screw not being set right. I'll take it in to this nice mechanic and maybe he can help me find it and get it set right. I believe it's fuel/air screw because it idles perfectly well. Whenever I take it for a spin though my four wheeler sputters while revving up until I get to full throttle where it will run perfectly fine which I believe is when a main jet or something kicks in.

[@HTMR]

Probably under a welch plug - kzbin.info/www/bejne/q3KzY5qcdtaGf6s

[@punxride024]

Very helpful to get my CRF150 running to sell, much appreciated! Now I won't feel like an ass selling a sub-par running bike!

[@junrodr2047]

the exhaust, I noticed I had oil seeping through cylinder head gasket so I removed cylinder head replaced gasket then noticed the feeler gauge and realized that the .008 refers to inches not mm. Turns out this gauge at its lowest is .20 manual calls for intake btwn. .05-.10 And exhaust valve .12-.17 I have adjusted valves to proper clearance and will start her up. This might be the solution? IDK but it is a problem if not set right thanks again will keep you updated I am grateful you responded. ... This is my first rebuild

[@HTMR]

I've done that before....D'oh.

[@MrZoufzouf]

"You're screwed" Haha I see what you did there

[@rodrheaume4612]

Great explanation. I've been adjusting screw to get bike to run well, but did not know what to shoot for (other than trying to avoid lag in throttle). Thanks.

[@HTMR]

Thanks! Glad you have it running well.

[@kristopher6031]

Your video really helped me out out man, thank you!

[@pdr5926]

You need the engine and carburetor at full operating temperature for the adjustment, like after a 30 minutes ride. This is valid for any engine regardless of the number of cylinders. Also, a Colortune plug (no affiliation) would make finding the sweet spot easy.

[@chriscasares6544]

My 750 spirit shadow isn't staying on while choke is pushed in, my jets aren't clogged and itl stay running when gassed a lit bit not too much, then it starts to sputter and some sparks come out the pipes

[@TheMotorcycleMD]

Keep up the good work brother! Great video!

[@HTMR]

Thanks MD!

[@julianuk3266]

I think it may help the viewers if you mentioned, that most two strokes have an air screw on the inlet (airbox) side, and most four strokes have a fuel screw on the exhaust side. Both doing the same thing but vice versa, one adjusting the amount of air entering the carb and one allowing more fuel into the combustion mix. Most bike owners should know if they have a two stroke or four stroke, and it may help them locate the screw.

[@HTMR]

+Julian UK Good point. However, there are plenty of 4 strokes out there that have air screws on the carb. Also, some amal carbs on triumphs have and air screw on engine side. Best thing to do is pull the screw and look at the tip. Blunt tip is air and pointy is fuel.

[@HTMR]

That line running to boot #2 is a vacuum line to actuate and allow fuel to flow from petcock.

[@junrodr2047]

Thanks, I've tried it and she sounds good now. i'll know better tomorrow. I still need to learn about bigger jets and how to find the right one for my carb, I'm clueless, if i remove muffler from the exhaust will i have to make carb adjustments too?

[@HTMR]

rodriguez rodriguez Jets are easy to identify once you have removed them. Yes, you will have to rejet if you take muffler off.

[@guldglubber8334]

+MatthewMCRepair You mean "if you change SIZE of mufflers you re-jet"? (Not from same old,but stock new) right? peace!

[@eastg6029]

I took off my carburator to clean it took it all apart put it back and my atv don't start any more and the problem is that I didn't measure the turns how do you measure the brass if it don't start you said it needs to be a hot temperature

[@HTMR]

If fuel screw, set it to 2.5 out. Air screw, 1.5 for starters. Just to get it running and fine tune from there.

[@pedroc6823]

Thanks for the easy to understand video. I just got a used 03 Triumph America. On cold start up with choke out it would not start. Had to be in and rev throttle to start. It had after market pipes, I suspected it was richer up for the pipes so for the choke out it was probably getting to much fuel, I thought this because it would start without choke after a few tries. The setting were marked, so I reduced fuel a 1/4 turn at a time and now the choke open works on cold start up. Do you think this is correct?

[@HTMR]

Sounds like mixture was set too rich as you have proven out with testing. A properly tuned carb will want choke ON for cold start. If it fires up cold with no choke, then mixture is too rich.

[@pedroc6823]

I plan on fine tuning even more once I have time. The previous owner had replaced the carb with a new OEM one. Just could not get it to work well so I was told., I am trying to gather as much info as I can, as I am a novice with carbs. I found the factory settings on line as 2.75 turns out for pilot. That will be my starting point as I am keeping the Triumph as stock as possible., the seller removed the AIS probably to reduce popping on the pipes by reducing the extra air and I assume for emissions. I replaced the loud pipes with new stock ones. Got lucky finding them. Any advice on tuning with carbs would be helpful. Thanks

[@jeffwass8268]

how you meant to turn the screw when its underneath

[@HTMR]

I hate when they are underneath. In this case I use a screwdriver bit and hope I don't burn myself. Otherwise motion pro makes a nice 90° screwdriver that is crazy expensive.

[@jessewaldner8377]

just grab an old screw driver and heat it up and bend it into a 90 degree.

[@HTMR]

Good idea if you have room to swing it.

[@77jona]

yamaha raptor?

[@mikespain8655]

You can buy 90 degree bend screwdrivers (flat and Phillips) for cheap at Walmart or Harbor Freight.

[@enzokidgaming3523]

Thank you so much for this knowledge. No matter if I turn mine in or out, it does nothing, even if I screw it all the way in. Any suggestion? Thanks!

[@HTMR]

You have a problem elsewhere. Vacuum leaks, bad choke plunger seal, high float level, etc.....it is pulling fuel from another source, or pilot jet is too big.

[@enzokidgaming3523]

MatthewMCRepair thank you so much for the reply! I’m wondering if float level is too high, because everything is stock (including main jet).

[@Iceaxehikes]

Very informative.

[@ManuelGarcia-qy6yz]

MASTER!!! thanks to you and this video my bike is now in really good running condition!!! 💪🏼😎

[@Hahehhwgajshah72726..]

You need a longer screwdriver.lol.

[@tie-see9308]

Lmfaooo

[@junrodr2047]

great video, I dont know if i need a bigger jet and what size it should be for my 82 sr250. the carb has the idle mixture screw on top. I removed the air box and put an pod filter. she backfires and when i accelerate she bogs then picks up then slows again. could it need a bigger jet? You are correct I have saved by rebuilding the motor myself but I have asked a lot of questions.

[@HTMR]

rodriguez rodriguez I have found that with pods you need to raise the needle by 1-2 clips (or use shims), and increase main size 2-4 sizes. For the pilot jet, you may or may not have to increase the size. Bikes are usually lean from the factory. Just follow the adjustment procedure in video, if you hit 3 turns or more, increase the pilot jet size.

[@HandDugHistory]

Hi Matt, thanks for posting this video, for the first time I finally understand! I took notes and everything!! In your opinion, do you normally have to change jets if you take the airbox off and stick a filter on? I've got my project chinese 125 running now, (thanks to you) but it seems to be distinctly lacking power, nothing else has been altered (engine/carb-wise) except the airbbox removal..

[@leahmmiller6967]

yes. you need to up your jets to account for the increase in air

[@danielhunsche2010]

thankyou for this video! I have a Yamaha FZR 250 - dosnt start when cold, check the screws and they are turned out 6 full rotations! will see if i cant reduce the amount of fuel going in (pretty sure the standard is meant to be 3 turns?)

[@HTMR]

Standard settings are usually lean. Go with highest RPM, it's what your engine wants.

[@ryanerickson6391]

Hi Matt, I have a 1979 CT70 and the bike will only run when the air screw is all the way cranked in. The only mod to the bike was an aftermarket air filter. The bike also bogs down on WOT. I figure my main just needs to be upsized due to the new intake but I think my pilot jet needs to be upsized as well? Does that sound right. Thanks Matt

[@HTMR]

The pilot jet should be OK since air filter does not flow that much more at idle. So make sure your pilot jet is absolutely clean. Then watch this video: kzbin.info/www/bejne/bJOclYCenL-HY8U

[@ryanerickson6391]

MatthewMCRepair Awesome man thanks 🍻

[@HTMR]

No prob.

[@coungnguyen1875]

Great video Matt I have a yamaha suv 1200 waverunner jet ski.. Can I tune the carbs using the same method??

[@HTMR]

Cuong Nguyen Waverunners are a bit different. I've tuned several of them however am not familiar with your model. Here is a good read that will help you: www.groupk.com/tec-carbs97.htm Matt

[@Bikerboythousand]

Couldnt have explained it better myself. Excellent. Thumbs up. The thumbs down people either dont have a motorcycle or dont understand english.

[@HTMR]

Bikerboythousand Thanks for the compliment!

[@HTMR]

I believe you are referring to the idle speed. If so, there should be a black plastic knob that you can turn to adjust to desired idle speed. The knob is attached to a flexible black tube that runs to the carb. The knob should be easy to access. Let me know if that helps.

[@1crazynordlander]

Thanks for sharing. I needed to find out what a pilot air screw was on a 15 hp twin cylinder Kawasaki Lawn Mower engine and this did a good job of explaining it. A lot of these lawn tractor engines do not have any adjusting screws on them these days.

[@iangroover1188]

Yeah it's a little more difficult to determine which side I'd engine or sir when your carb is in the middle of the 2 v-twin

[@dochunter6861]

Thanks 👍 Great video 📸

[@Coffeeground]

So would you suggest making sure idle adjustment is at its lowest throttle setting before adjusting the idle air valve? I think my stock setting is 1.75 turns out, so I start there and then adjust the idle throttle speed screw to a decent rpm. My service manual says nothing about idle air screw adjustment, just how to adjust idle throttle speed.

[@yaryar1976]

Bought a bike with cv's.it had flooding issues.i cleaned the bowls,floats and valves.also found a diaphragm that wasnt seated correctly.put it back together and now i have to suffocate the airbox to get it started and it instantly stalls on throttle.the only adjustment tampered with was the idle air but it wasnt turned in or out a whole lot.

[@HTMR]

Take the carbs back apart and remove the pilot jet and fuel mix screw. Spray carb clean through these passages and make sure they are clear. Also make sure pilot jet is clean. It's starving for fuel.

[@tomasz432tl]

It wos spark plug,bike runs perfect now and have even more power. Thanks for your time bro!Great videos!

[@mapleridgefarm1026]

Thx for sharing. I have a big bear that only starts with the pull cord and thats after i open the chock and punch the throtle and let starter turn a few seconds, then pull cord a few times and she will start, do you think if its not getting enough fuel would prevent it from starting with the starter?

[@cruza1289]

Thanks for the video. What happens if you run the wrong setting for too long will it cause damage to your engine ? Too lean or too rich ?

[@HTMR]

It won't damage the engine, just won't run good.

[@EBR3O]

I have 2006 yamaha pw80, I have 2 screws air side and fuel side. My question is how do I set or start with the air side screw? Is it seat it and back it up 2 turns as you mentioned on motor side? Thanks and your video is great and informative.

[@Jeremybaland]

I did replace the needle and seat. It could that the level is to high. I think I figured it out it only does it when its on the side stand. Those old bikes lean way over on the stand, and a combo of hi level in the bowl. Thanks for the response.

[@AntonSwanepoelTravel]

Thank you for the video. Did not know if the screw on my carb was air or fuel. The last part of the video perfectly explains it by comparing an air screw against a fuel screw. Mine is fuel.

[@JimboJames007]

Great video exactly what I was looking for. I’m adjusting on a two cylinder so slightly more tricky I assume? The ninja 250r is a fuel adjust. I’ll try 1.5 out on each then adjust one at a time too see if I hear a difference. Thank again mate Regards Jimmy

[@HTMR]

Just keep both carbs adjusted the same. Turn each 1/2 turn out one by one.

[@garyromero1562]

very well done! Might move the labels off to the side, make it easier to see what you are doing.

[@bc-mr1si]

hi thanks for the well explained video.my screw is out 3.5 turns this sets the fastest idle.would I have to increase or decrease the pilot jet 🤔

[@HTMR]

If you have a fuel screw then increase pilot jet size by 1-2 sizes.

[@bc-mr1si]

@HTMR the screw is on the side of carb nearest the engine so I guess it is fuel screw .thanks for that 👍

[@bc-mr1si]

ment to ask .would the main jet size need increased 🤔also when screwing the screw in are you increasing or decreasing the fuel🤔

[@HTMR]

Yes, every jet will have a number stamped on it. What year make model are you working on? Any engine mods?

[@hydarmbm3456]

Hi Matthew. I have the Suzuki EN125-2A with Mikuni BS26SS carb. Pilot screw (fuel) is set as per factory settings which is 2 & 5/8 turn out. And the manual says idle RPM should be anywhere between 1300 - 1500 RPM. Sometimes the bike bogs when given full throttle in 3rd, 4th and 5th gear from 6000 RPM to redline. Below 6000 RPM it runs good. No vaccum leaks, new stock air filter and spark plug installed. What can be the issue? Can it be too lean? The only screw to adjust idle is the screw that hold the butterfly valve slightly open

[@HTMR]

Sounds like the needle and main jet circuit is lean. The pilot jet has nothing to do with your problem. Any modifications to the bike? Air or exhaust?

[@hydarmbm3456]

@@HTMR Thanks for the reply. There are no mods to the air intake and exhaust. I notice also some drops of fuel leaks in the drain outlet under the carb after long ride. The drain screw is well tightened

[@HTMR]

@@hydarmbm3456 That tells me your float needle is dirty or worn, and fuel level is high. So high that it is overflowing out the overflow tube. Both the overflow and drain use the same passage.

[@hydarmbm3456]

@@HTMR Thank you very much. I will service the carb and see if things get better

[@bravofitnesss3178]

Subscribing and 100 more if I could!. Just bought a bike pretty much starting new on motorcycle stuff and riding ....you sr are a great help! Thank you so much

[@HTMR]

Awesome! Thanks for the sub!

[@jetman1968]

You have the teaching bone… good job man.

[@thomassquires9752]

very cool video dude explained alot. i've recently just had to change my complete engine on my honda shadow 700.6 weeks later finally done only 1 problem my bike is chugging in the low gears checked all piping from carb to make sure theres no excess air in take. so do you think i should try with the air/fuel screw? cud that b causing the chugging??

[@logowatchman]

Well done. Clarified how to get my carbs tuned in better than the manual.

[@aussiedigger1441]

Great work Matt as usual! Quick couple of question's when my 01 KX 250 get's warm the idle goes down to a stall (cleaned carb completely with a good carb cleaner) every time. I have to increase idle every ride. Also i'm only getting 4-5 hrs out of a new plug before fouling? Also the KX don't run on iridium plugs(won't kick start at all) no more only runs on NGK B8ES 2411, it's like the spark is very weak. I did fit V-Force reeds.

[@HTMR]

I have the same bike and they are very rich in stock form. Email me here and I can help you out: www.howtomotorcyclerepair.com/contact/

[@dmo848]

Stator running bad perhaps

[@TN_HondaDad]

I have a lot of detonation/popping when letting off the gas and de-accelerating. I have heard both sides of the coin that this can because of running lean or rich? Also, under hard acceleration, its "stutters some". Any ideas where to start. CRF80 with an FMF pipe on there and main jet one above stock. Thx

[@HTMR]

Could be a lean fuel screw and pilot jet combo.

[@VikingBagsYT]

Much respect from everyone here at Vikingbags!

[@HTMR]

Cool thanks! Gave you guys a sub.

[@justjoe7618]

Best, simple explanation video I have seen yet!

[@yasharahlalove330]

Dude!.. Finally a great video.. Well done!..

[@HTMR]

Uploaded part 2 today: kzbin.info/www/bejne/en3PlaB4r9aFldU

[@WTGRacing]

well i tried working on it (as well as a crf80) and they have an air mixture screw but no fuel screw. and i didnt really want to tear into the whole carb just yet, so i decided to just block out the other "intake" i made so now they are back to stock. if i want to make these bike faster ill just save money for the big stuff (suspension, 143cc bore kits,exhaust) anyway thanks for your help man!

[@petefarr2547]

Hi Matt,... thanks for the vid. I have a 2000 yamaha 250 virago and was smelling a very rich mixture. I started to lean out the mix screw 1/8 of a turn at a time and took ride. Kept doing this until screw bottomed out and no change in rich smell or performance of the byke. How is this possible? (starting point was about 1 and 1/2 turns out)

[@HTMR]

Did this symptom/problem come out of nowhere? Probably not a fuel screw issue. May have a stuck float or something.

[@petefarr2547]

interesting idea,..thanks. Fuel must be coming from somewhere else to maintain bike performance at 55. possibly choke positioned incorrectly. (choke seems to work as it should) Symptom/problem came out of a stinky exhaust... just tried t "lean" it up a little...

[@HTMR]

@@petefarr2547 Choke bypassing fuel, high float level, and sticky CV slide all possible issues.

[@Okie-Tom]

Interesting and informative video. I do have a question. I have a 1998 Kawasaki Mule that has a twin cylinder gas engine that has been running fine until this morning. It will start as usual but won't idle. It dies now when I let off the gas. If I keep up the rpm's a little bit it stays running. Any idea what may have went haywire? Mi don't want to just raise the idle speed. I would like to figure out what is wrong. Thanks, Tom

[@HTMR]

Clogged pilot jet. Watch this video: kzbin.info/www/bejne/qXybpWZjja5gfKc

[@Okie-Tom]

MatthewMCRepair yes, this is the video I replied to. Should I be able to remove the adjusting screw and spray carb cleaner in it or am I going to have to disassemble the carb?

[@HTMR]

You have to take the carb apart.

[@brianb5779]

Ive checked what feel is everywhere. Do you happen to know on a honda crf50f what the actual size of the pilot jet is. Pretty sure you cant buy them but what im thinking maybe is @.012. The forums are all over the place on what the hole size is..thank you

[@stevendaniels8652]

Great video sir. You very good at explaining things....a natural teacher.

[@aaronthompson8719]

Just wanna make sure I have a ktm sxf 2008 250cc. It’s a fuel mixture screw, it’s bogs when I get to the higher end of my 1st gear and the beginning of 2nd anyway. If I turn the screw up it gets more lean and out more rich ( on fuel ) ?

[@HTMR]

Yes, watch this: howtomotorcyclerepair.com/how-to-4-stroke-mx-fuel-screw-adjustment-yzf-crf-kxf-rmz-fcr/

[@Janossmc]

Mat. I have a 1980's Yamaha XS250 which Im trying to convert the air box to pods. I find the pilot screws dont do much. Its running into high revs off choke

[@HTMR]

If you add a little bit of choke do the revs come down? If so, you are lean. Check for vacuum leaks and/or give it more pilot jet/fuel screw adjustment.

[@peggytaylor3882]

I love the videos they are very thorough . I have a question I have a 2006 Yamaha vstar 650 classic my husband replaced the Pistons rings and so on~~ Then he rebuit the carbs now it sets and idles great but when I start to go in 2nd gear full throttle it seems to have a skipping sound and I turn throttle back half way it kinda tugs like it wants to go but NOT It wants to bog down but I can pull choke out about half to 3/4 and it runs perfect but push choke in it runs like crap. ANY SOLUTIONS? OR IDEA WHAT MY PROBLEM CAN BE????? PLEASE HELP ME !!!! THANKS

[@HTMR]

It's lean, you proved that out with adding some choke. Are there any other modifications to the bike? Air cleaner mods? Different exhaust?

[@LevinSliker]

Matt, thanks for the video. I have an xr400r which idles fine, but dies immediately after stabbing the throttle from idle. I can keep the bike from stalling if I ease the throttle. Once in higher rpms, I can stab and it's just fine.

[@audid3a8s8diys5]

Did you ever figure out what was the issue ? Mines kind of doing that

[@dmo848]

Needle jet seat perhaps?

[@samcruz6454]

Hi Matt, I learned to adjust my idle correctly by this video of yours and improved my gas consumption, I never knew I was running rich with the idle screw compensating with my fuel screw. thanks for this. Just a quick question though, how do you determine the correct venturi size when choosing a carburetor for any given bike? see the engine of my bike has been used for two bikes produced by suzuki, but different carburetors, one was a 29mm and mine,a 26mm, I was thinking of changing it to a 29mm but not sure if it will actually make my bike run better. (feel, power, efficiency)

[@HTMR]

A larger carb will perform better at higher RPM. One downside it may not provide good lower end throttle response and fuel economy.

[@AT4AFT20]

good video..... question I just put pod filters on a 86 fz 600 now I am getting some back firing do I need to adjust the air screw?

[@HTMR]

Backfiring out exhaust or intake? During decel or accel?

[@AT4AFT20]

during decal especially if I am getting on it good then chopping the throttle...

[@HTMR]

AT4AFT20 Have you tried to adjust the fuel screws? Sounds like you have to richen them up. If you hit 3 turns or more, bump up the pilot jet size. Did you change any jets? Pods will require needle and main changes also.

[@kaseyod113]

So glad I watched this. Almost didn’t, but I learned a lot

[@joneskid17]

good tip on taking out the two screws made it way easier to identify. problem im having is when i turn the pilot air screw all the way in it rpms higher as to yours cut the bike off. any suggestions?

[@alfredkipchumba]

The video has brought me peace. Nowhere else can you find this info.

[@joeybuscemi7793]

Hey matt your videos are very good. I have an issue i have a 91 yamaha breeze it came to me with a no start the customer put a amazon carb on i put the original one back in Cleaned. I cant seem to get it to idle messing with the idle knob and air screw very sensitive somtimes just adjusting very little then gives me a high idle. Help.if u can thanks

[@HTMR]

Any vacuum leaks?

[@olimpiuchis1905]

Hy, a sport exhaust can influence this settings?, and how? I understand that this settings you presented are made with the genuine factory exhaust. Please do explain this in a video.

[@thenoconnection3444]

I have a question my bike when I kick start it starts to idle really high rpms and I’m not sure what to do

[@HTMR]

Throttle cable issue? Vacuum leak?

[@TheDuckofDoom.]

I'm trying to figure out the procedure for re-jetting a bike with a TK [teikei] two barrel cv carb (set up as primary and vacuum secondary). The service manual is of no help(probably for the same epa reasons that the stock setup runs like garbage). My brush trimmer manual (a very simple carb for WOT or idle only, no mid-opening) says to adjust the main mixture first then adjust the idle mixture because the idle setting has little effect on WOT but the main setting does effect idle. My old motorcycle had a single bore Mikuni carb and mikuni had a pretty good (very old) pamphlet on tuning the A/F "for racing", but a single bore manual slide is pretty far from a dual bore vacuum secondary. A data logger that takes in throttle position, RPM, and O2 sensor output would simplify everything but I don't have a few hundred bucks(or time for building it with arduino/razzpi) as I'm barely scraping together enough for school. This is my 70mpg commuter dual sport BTW.

[@HTMR]

Start with pilot jet tuning....the answer lies in the fuel screw position. Do not use a bush trimmer manual tuning guide as that is a 2 circuit carb with only high and low screws.

[@calebwood3430]

Nice, I just need your knowledge. What exactly is this screw here in the image that I have included. What is it for and what is it called? This carb is off an ATV if that helps... Whenever I hit the electric starter button it won't turn over and fuel leaks from the hole. Thanks

[@HTMR]

No image?

[@calebwood3430]

@@HTMR Wait...what?

[@calebwood3430]

@@HTMR I think I figured out it was the pilot screw though, Thanks!

[@OfficialOopsClan]

Hi Matt!! my bike boggs down and sometimes it dies but rarely when I apply the throttle fast but if I apply it slowly it works, I had taken out the carb to clean because it wasn't idling but now I have this problem I don't know what's going on and I have a rs3 125 2011 and I don't know how to set the idles properly it just isn't working

[@HTMR]

It bogs when you hammer the throttle fast? Did it always do that? Have you messed with the fuel screw?

[@OfficialOopsClan]

Yes only when I hammer the throttle fast and no it wasn't like this before and yhh I had because o was cleaning carb

[@HTMR]

Official Oops Clan Sounds lean. Try inspecting for vacuum leaks for starters. kzbin.info/www/bejne/pXy5eaR5f7Nlgrc Matt

[@OfficialOopsClan]

There aren't any because I just installed a new air filter and manifold but I just want to know if the bike bogs down when you apply throttle fast does that mean fuel screw is lean or rich (unscrew more or tighten more)

[@HTMR]

Official Oops Clan You need to check for vacuum leaks. Don't assume. It's quick and easy. After you are sure there are no leaks, then move to fuel screw adjustment. Yes, it sounds lean.

[@darrencdias]

could u please tell me if the UCD 33 Carb has a fuel Screw or an Air Screw . . . The A/F Mixture Screw is on the engine side which as per ur video richens the mixture on screwing out but then again u said that there are exceptions . . . so could u please help me out . . . and apart from that i got another question . . . my motorbike usually achieves the highest tickover at 8 anti clock wise turns from the full closed position . . . does that sound right ? awaiting ur reply

[@HTMR]

+Darren Dias Darren, click link below and note the pics of screw differences. If you remove the screw, compare tips to the pics. Blunt tip is air and pointy is fuel. www.howtomotorcyclerepair.com/how-to-size-your-pilot-jet-pilot-screw-explained/

[@darrencdias]

+MatthewMCRepair thanks man . . . appreciate the help 👍