Inlet Floor POWER Port DYNO Test - Kawasaki AR93

[@doingitwronggarage9651]

This was nice to see. Years ago a local guy bought a AR50 and then a BDK buildt engine with full exhaust that worked pretty well. This saved me because I had messed around with my own AR50 myself with some success up to the point where it had to much exhaust duration and the moped just did not work well anymore. Then I tested the BDK ignition module and got the suprprize of a lifetime. Had to remark the rev counter to 14 000 rpm. It came on really hard at about 9800 rpm and revved to about 14 000 rpm. The most annoying was the gearing. With 5 speed gearbox and tall enough gearing for top speed, it needed revs and a lot of clutch when city driving. Used it a lot, but after years of driving and two rebores, tha cylinder skirt broke at the rear. My mods: 0. Welded floor in exhaust port. 1. Mikuni 28 mm VM carb on a home made intake. Heavy blow back prevented use of air filer. 2. Boyesen reeds. 3. Home ported Autisa cylinder with big boost port. 4. Larger ports in the piston, shortened skirt on intake side, rounded edge below wrist pin. 5. Ported crank case suffed / filled with epoxy in area under the intake port, between the transferes slots. (Stock cylinder with ported piston works well with this.) 6. Proma exhaust for a Honda MB-5. 7. Upgraded clutch and genunie Ford Type F fluid did just slip a little bit at full throttle at peak torque about 10 000 rpm. 8. NGK Iridium spark plug.

[@AutoBeta2T]

Cool - that's some spec! What sort of top speed did you get? Did you do any Dyno testing of the port floor before and after? I'm really interested in the effect of this? Also, did you Tig up the port floor?

[@doingitwronggarage9651]

This was years ago so nothing was ever documentet or dynotested. I just tested different things and drove to and from work on highway and in the city. Gearing had to be a compromise as starting from a redlight needed some getting used to to avoid stalling and it did hold 12100 rpm. in 5. gear over the more than 1/2 mile straight on the way home. It did not do 100 mph. but it did go over 90 mph and stock old boring cars like a Volvo 240 could not outrun it here on our rather twisty roads. A friend just filled the horrible exhaust floor with a MIG welder. The Autisa AR intake port really works, but I have made the boost port opening way bigger. I have read 2-stroke tuning books and it is called power boost port or someting. I have converted stock AR and MB/MT cylinders to this and always had good results. Did it on my step sons Honda MT-5 Polini cylinder and he later told me that his moped had a "legendary reputation" among the locals. :) No one was even close to him then they "drag raced" and it had a distinctive sound with way more grunt than other mopeds. My point being it works. The point is when the piston ports closes the passage to the crankcase the piston ring opens the power boost port directing the fast moving intake charge directly into the cylinder. Naturally, I first did the reverse and converted the Autisa cylinder to the" normal" stock style / Honda MT style intake as only 8 hp from 93 ccm is less than impressive compared to other cylinders. The result of this test was disapointing. I then closed the intake floor, "stuffed" the crankcase with epoxy / JB weld to increase crank compression ratio. I could then lower the intake floor to it went through and then JB weld it closed again. I also made the openings in the piston skirts below the wrist pin wider and taller. When the piston is in TDC the stock skirt partly hangs into the intake ports if I remember correctly, not good and I modified that as well.

[@AutoBeta2T]

@@doingitwronggarage9651 thank you for all info. That's really good and has got me thinking 🤔 Cheers Dave.

[@doingitwronggarage9651]

@@AutoBeta2T No problem :) and thank you. I am looking forward to following your work and progress. I have also tested the Boyesen port modifications, but that did not work well for me on my cylinders. kzbin.info/www/bejne/nJXFkGuYhaqSf7M

[@nippingshrewdestreets3264]

That setup with the plate porting etc is very similar to how I did mine back in the early 90's. It worked out quite well, made the transition into the powerband much smoother. The 93's used to be quite chuggy before getting into the powerband if left as they came.

[@AutoBeta2T]

Did you ever try extending the port through to the rear (B) transfer ports. I saw a picture of a AR93 barrel the other day on the AROD page that had them cut. Could be an interesting follow on test.

[@nippingshrewdestreets3264]

@@AutoBeta2T I saw they photo you mentioned the other day, it led me to this video. I smiled when I saw your plate as it identical to mine. It looks like you used an RXS or similar manifold and reed setup? I went with an aftermarket MBX one at that time, being wider created other challeges. In my early 20's (30 years ago) we were all very competitive with our tuning where I am from so I painted everything black to hide what I was doing. lol I did think to drill through at add dynos or do similar to the cyl on the webpage but never got to that point. I remember how quick the bike seemed in those days, but I am curious how it would compare to my more modern LC based bikes. My brother still has the old AR cyl and parts with inner rotor etc so maybe one day can do a side by side comparison! :) Would be interesting now being more knowledgeable (one hopes) to start from scratch. I don't have an AR now, but I can live vicariously through your videos! :)

[@AutoBeta2T]

Hi - sorry missed your reply. Yes that pic in AROD has got me thinking I need to do a before and after test on the additional tunnels. The intake is detailed here: kzbin.info/www/bejne/bnKXkniMdryInZo Basically a KTM 65 reed. I needed to remove a fair bit of inlet to get it to fit and had a lot of issues with sealing but got there eventually :) I always wanted to try stuff when I was 16 (30 years ago) but was never brave enough... I guess I'm doing all the stuff I always wanted to do now ☺️ Pleased you are enjoying the vids and hopefully another will be out in a bit. Life's took a turn at the min that I'm dealing with but the end is in sight so focus can swing to the AR.

[@billshiff2060]

2:43 most don't realize that the flow adjacent to any wall does not move. As you move further from a wall the flow speed increases slowly untill a fair distance from the wall it reaches full speed. You can prove this for yourself by watching rain on your windshield. At 60 mph tiny drops barely move and the bigger drops move slowly but none move at 60 mph.

[@AutoBeta2T]

Hi Bill, as I recall from aviation the boundary layer does get sluggish and eventually separates hence vortex generators to re-energise the boundary layer. A bit like a wing the flow slows at the wall and then speeds up the further out you get from the surface. I guess something to do with the dimpling internet thing...?

[@andycompton4885]

Doing well my friend 👍

[@AutoBeta2T]

Cheers Andy

[@KompressorPete]

Great!! Sounds sweet. Niiiiice dyno 😊

[@AutoBeta2T]

Cheers Peter 😊

[@jdsstegman]

Question, well 2. 1. Are you running oil injection? If not they why run the pump. 2, are your ports in the pison matched to the 2 big intake ports in the sleeve? I seen that the ports are rectangle and the pistons are more oval? On my rd 350's I seen good gains from matching these ports.

[@AutoBeta2T]

Hi, in short, no and no. 1. The pump also drives the tacho so I was keeping it at the min as i don't have a digital one yet. It will go eventually but it isn.t doing a lot. 2. I haven't had a good look but I would say no. I will have a look though so thanks for the tip.

[@ballockybill2277]

Sorry if this is a silly question , but it looks like that new port just leads into a blind crevice closed off by the cylinder barrel ? Does it flow directly into the crankcase void ??

[@AutoBeta2T]

Hi, yes it does flow into the crankcase now. The original cylinder did the same. I figured the reeds could still feed the crankcase even when the inlet port is closed

[@markaddy53]

great job lad keep going

[@AutoBeta2T]

Cheers Mark ☺️

[@tke7mu0u]

Love the testing. Peak hp rpm seems a bit low for a 100cc engine. I would try a shorter pipe. If your port timings are in the 190s I think you should be looking closer at 10500 to 11000rpm for peak hp rpm without compromising the crank too much

[@AutoBeta2T]

Hi Shannon - totally agree. I'm hoping to borrow a shorter pipe soon and build another magazine article pipe which is very short. Next test is more compression which will reduce the peak rpm again so need a shorter pipe.

[@tke7mu0u]

I've heard wrapping the pipe maintains the heat in the pipe causing it to act as a shorter pipe. Would be interesting to see if it makes a difference. Keep up the great work

[@madmaxsdog8040]

@@tke7mu0u When the first sets of TZ750 pipes with 3 under the bike and one through the frame were made that one which passed through behind the engine had to be around 30 or 40mm longer than the other 3 as it ran hotter

[@AutoBeta2T]

@@tke7mu0u yes - wrapping would make the pipe act shorter. Later in development I plan to add EGT probes to the pipe so I can try to replicate Dyno temp for best power on the road. Wrapping the pipe could be used to "shorten" it ... I've heard it can cause detonation though 🤔

[@tke7mu0u]

It might keep too much heat in the pipe but think it also depends on state of tune. How close the engine is to its limit. I just thought it could be a way to see if you gain more power up high until you can modify the pipe. I love watching progression like this.

[@andrubrown]

I have two of these AR's sitting in my garage, thinking about restoring them possibly. Anyway I come from kart racing the Yamaha KT100 and i would like to know what your EGT's are you getting with every mod you do on the dyno, as we tune for max EGT without detonation. There is massive gains from lets say 800 degrees to 1100 degrees EGT. So to make a comparison on the mods you have to tune each one for max peak power. And fuel type plays a big roll also. I think you're doing an amazing job with all this work, I'm really enjoying the vids, keep it up... Tim

[@AutoBeta2T]

Hi Tim, thanks and pleased you are enjoying 🙂 Sounds like a project for 2023 then: 2 X AR restorations. EGT wise I haven't measured it yet... The BDK pipe doesn't have a boss for a probe. Admittedly I probably should have fitted one from the get go but time seems to go nowhere. The pipe I'm making at the min will have an EGT thermocouple boss added and the Dyno acquisition box can record it along with CHT. I need to get a smaller rear sprocket too as it's geared less than the 100 mph I'm after ATM. I'm assuming your EGT numbers are deg Fahrenheit? Also what distance from the piston face was the thermocouple? I've always used 6 inches. Cheers Dave

[@andrubrown]

@@AutoBeta2T I will have to go out and measure it again to be accurate 6" sounds really close. we also set squish at .028-.035 with a race pipe to allow for rod stretch, 11cc combustion chamber and 114 race fuel (too much timing) at 14.8-15k RPM, they really sing and I know your engine is very similar to the kt100 (Air Cooled) the egt will tell you when detonation happens by dropping down because of incomplete combustion, play with octane if you can also. I like that you're really putting a lot of thought into this build!! I'm going to sub on your channel your on to something here...

[@AutoBeta2T]

Hi Tim, thanks for the extra info and cheers for the sub 😊 Best get cracking with the pipe and see what the egt is.

[@skyhawk409]

I thought you where going to put crank induction ports into it from intake port wall to transfers ports.i did this to a it175 made it run so rich I turnd the power jet off and then it screamed.

[@AutoBeta2T]

Hi Skyhawk, that's interesting to hear as I fancy connecting the intake to the rear transfers... Cheers 😊

[@2strokecarbtuningportingin187]

Great job

[@AutoBeta2T]

Cheers buddy - and thanks for the shout out again 😀

[@2strokecarbtuningportingin187]

@@AutoBeta2Tkeep up the great vids. Definitely enjoying your vids thanks for sharing

[@marcusbrown2493]

Nice one Dave👍

[@AutoBeta2T]

Cheers Marcus ☺️

[@dougbawden4321]

I'm no 2 stroke expert but I've seen quite a few videos of these 2 strokes having a pile of different mods being done and no big gains. I keep thinking about the diameter of the pipe from the expansion chamber to the silencer. I could be very wrong but I think even 3 to 4mm increase I think would make quite a difference?

[@AutoBeta2T]

Hi Doug, yeah it's good to try and do things in isolation but even just changing one thing causes lots of changes elsewhere. Yes the stinger diameter can make quite a difference. I find making it smaller gives more power up to the point it melts the piston. 😭

[@dougbawden4321]

Oh dear 😂 okay I'm used to four strokes. Is it melting the piston because of air fuel ratio with a larger stinger?

[@AutoBeta2T]

@dougbawden4321 it's the restriction that increases heat then the piston melts.

[@dougbawden4321]

Oh sorry I didn't understand your reply at first. I see, I just imagine 100cc at those rpms trying to breathe through that stinger 😂 hope you win, I'm sure you will

[@dougbawden4321]

@@AutoBeta2T One thing I always try to keep in mind is that most (not all) of today's performance guru's aren't like the Old guy's who used to tune engines. Most are bolt on part experts, turbo, were told something by someone or read a book and that's it. I always question why I can or can't try an idea. Sometimes it ends up in disaster lol. I think the 80's racing 2 strokes would be a great place to get ideas from. All over KZbin they say don't open the inside diameter of a valve seat on a four stroke... Hundreds of videos. Then in other videos of formula one and factory heads I've seen have the seat bored out to the max... Sorry I'm waffling on now lol

[@garstang71]

Hi mate. Have you considered going up in cc a little. Mine was 103cc. Think it had another liner pressed in. It was very powerful. No easy dyno access back then. Loving the channel.👍

[@AutoBeta2T]

Hi Craig, I'm actually at 97cc now as I'm on a 54.5 mm bore. More cc would be good but I'd ideally like to get some cc's from stroking it. The squarer the bore and stroke the more Time Area is available for the same port timings... Bit of a project to do. Sounds like you had a fast one then. What mph did it do? Pleased you are enjoying the series 😀 All the comments and Interaction from everyone make it great to do too 😃

[@AutoBeta2T]

@Trevor Partington which RG Trevor? Gamma or FUN?

[@EinarLerschen]

Ambitious project! It seems that the aerodynamics are quite poor so that 100mph has to be achieved with power. Over 25hp at the wheel with long gearing? That is a lot. Interesting to see how it goes. Will be watching.

[@AutoBeta2T]

Cheers Einar - yes it's a challenge all right... In the original project they found that the nose fairing made it slower! A full fairing would help but I'm going to see if I can do it unfaired first 🤔🫣😬

[@EinarLerschen]

@@AutoBeta2T That is actually not a suprise. All and all what looks to be aerodynamic seldom is. Some of the 1920's aerocars are actually some what a miracle. Those truly were aerodynamic, well to some point but with technology of that era... Then again some 50's car that looks to be aero, they perform better on reverse :)

[@madmaxsdog8040]

Nice one, have you considered flowing the crankcases? Not sure how much difference it makes but consider that when the engine is idling say 1200rpm the air fuel mix has to pass through the entire engine from bell mouth to exhaust outlet in 0.05 of a second (60 seconds divided by 1200) at 9000 its 0.0066 sec, 12000 is 0.005 sec. Theres a vid posted by 49cc scoot if youre interested. I havent done it myself, the only things I did there was matching the transfer ducts to the cases and remove a small amount of cylinder wall at the bottom to open the transfer duct entry. I wouldnt knife edge the transfer divider though, if the knife edge isnt EXACTLY in the center it would probably bias the flow to one port or the other,, if one side of the cyl is biased forward and the other side is biased to the rear the fresh charge will be all over the place

[@AutoBeta2T]

Hi, I hadn't planned to but it would be a good experiment. Chris Brocklehust spent quite a bit of time filling and flowing the inlet tract on the original challenge bike. I'll add it to the list ☺️

[@madmaxsdog8040]

@@AutoBeta2T Given the speed the air must be travelling it could be looked at from different perspectives, either the air will batter its way through regardless of obstacles, OR the obstacles will generate a MASSIVE amount of tur balance, the vid I mentioned by 49cc scoot is worth a look. Its something I never got round to given the amount of work involved to split the bottom end and at the time most of my clients were on a tight budget. I found matching the transfers to the cases, or vice versa made a difference but mostly below the main powerband and part throttle, ie it felt better to ride. The difference wasn't massive but when you're chasing every half a horsepower here and there it all adds up.

[@AutoBeta2T]

Cool - I'll take a look at that vid. As you say, it's all marginal gains but they all add up.

[@madmaxsdog8040]

@@AutoBeta2T I've often wondered, if manufacturers hadn't started reed valve induction would we have YPVS intake ports as well as exhaust. Take that a step further, how about a really radical disc valve inlet with TWO powervalves, one on the leading edge for the opening timing and another on the trailing edge for closing timing. Sounds complex I know, but without reeds....?

[@andli461]

@AutoBeta2T Never knife edge anything that only sees sub sonic speeds. Nice rounded edges and (transfer)dividers is the way to go. Proven again and again. Great project! Great technical level! Would love to see a future video about your approach creating a temperature map to match EngMod results to dyno ones. Only had a brief go at it myself, but found it quite tricky to get right. What efficiency % do you run in EngMod by the way? Thanks for a great channel. 👍

[@sidecarbod1441]

Very interesting vid! If your head is not optimized for squish band width and clearance and the CR is low then there should be some nice gains to be made by modifying the head. Pretty sure that you will not find the 7 or 8 BHP that I think you are going to need with head mods alone. I've read that pushing the CR up can in fact reduce the rev range of the engine and its ability to 'over rev' but I'm not 100% convinced that this is really true. Your power curve looks great for a road bike, it looks like it starts at around 7k and runs up to around 10k RPM. I think you are going to have to try and change the shape of the curve away from the nice 'dome' that you have now into something that's more radical. The bike might be harder to ride with a 'church spire' power curve but hey, ho, that is what is going to be required. It might need more radical porting and/or an exhaust tuned for a higher RPM. You could experiment with spacers under the barrel just to see if you can push the peak RPM up to 11k, if it looks promising then you can skim the top of the barrel. I'm sure you have thought of this stuff anyway! (Obviously raising the barrel can have a negative effect on the inlet timing but is a quick and dirty way to get some ideas on what changing the transfers and exhaust timing will do) If it was my project I'd burette the engine as it stands now so I have a baseline to work from, don't trust any figures that are quoted for your setup, they can be off. (KTM are the worst in this respect, their figures are blatant lies!) EDIT...I presume that you are going to get an anorexic dwarf to ride the bike? LOL

[@AutoBeta2T]

Just catching up with comments.. Standby

[@AutoBeta2T]

Hi 😊 Yes, I hope to get a few more ponies from the head but it needs more porting and a pipe... All to come. I e never measured it before but I think I'll have a measure up of the primary comp ratio. A few people have hinted there could be some power in there by increasing it.

[@AutoBeta2T]

No dwarf but I have an idea of who may be able to ride it. They are pretty thin 😃

[@sidecarbod1441]

@@AutoBeta2T It at least worth finding out what the primary CR is but I would not go increasing unless you feel that it is too low as standard, I'd be surprised if it is too low because you are running a moped bottom end and a 100cc top end. If you push the primary CR up too much whilst running the 'modern day' transfer timing you will lose way too much mixture out of the exhaust. I guess measuring everything is the key!

[@AutoBeta2T]

Good point! I wonder if Kawasaki designed it as a 80cc first then put on a 50 barrel or vice versa? It is under square so maybe 80 first?

[@watermelonwatermelon6513]

That engine is really similar to the honda mbx80 hc04e engine wow.

[@AutoBeta2T]

I guess quite similar eras... How much power do the mbx80s put out?

[@watermelonwatermelon6513]

@@AutoBeta2T very powerful, a nuke on 2 wheels for its size, i run a mtx80 offroad frame with liquid cooled mbx80 engine, its ported out crazy, mallosi reeds and a diy intake manifold aswell as a exhaust pipe which i calculated and made by myself, using a tiny 21mil phbg carb, sucks on highs, good on lows, currently converting it to a 26mm pwk china carb coupled with a modified mvt manifold for derbi am6, cannot tell the dyno numbers because stock had like 11 hp with the 18mil carb and stock garbage pipe, but with the mvt ignition and a 30mil pwk these things had gone 30hp as seen on forums.

[@AutoBeta2T]

That's good power! I wish I had water cooling some days... Still that's impressive power for a older 80cc!

[@watermelonwatermelon6513]

@@AutoBeta2T Yeah only lc for the race engines, and even tho its old, the mbx80 has ultra violent porting, even stock, the only necessary mod to have massive power gains is raising the exhaust port by about 2mm, seems controversial but it fn slaps! And this engine has a exhaust port bridge so i drilled 2 tiny holes for lubing.

[@AutoBeta2T]

Cool. What is the port timing on your modded cylinder?

[@Alimotevalian-g8i]

power only come from pipe , rest are nothing , so read this carefully ; pipe must be maximized , meaning diameter , length must be left alone at 36 inch , never shorter , i repeat again pipe must be 36 inch long with no midsection , only 3 parts 12 inch each , ,that is regardless of engine size , now increase pipe diameter to 5 inch then to 6 inch, that's regardless of engine size .. on 50 or 125cc .., numbers are not typo , if 6 inch not work you increase case volume by adding 100cc volume by giant spacer on reed manifold that allows you to increase pipe diameter by 1 inch up at the time , then have a huge pipe that pulls like a train from 6000 to 16000 rpm , no squish , no electronic , no big ports , you NEVER widen port over %65 but raise it to the roof , you never remove bottom ring , you remove top ring so you can carve slots to increase timing all the way down to top ring slot..and over 25 degree you need water-cooling .. you LOWER compression a tad to free up the revs use low octane fuel , NEVER run open carb , it sucks hot air behind cylinder , lose power , so use original airbox.

[@AutoBeta2T]

Cheers, I have been thinking about an airbox but probably not the original as it's quite restrictive.

[@copisetic1104]

Pipes will make about 30% more power on average, a well ported engine will make good power with a straight pipe. I’ve seen many dyno runs.

[@copisetic1104]

A lot of what you have stated here is not true. Read professor Blair’s book on two stroke engines.

[@cronauer1985]

I would get another clutch cover and blank off the oil pump and do away with all the kickstart mechanism, obviously running premix.

[@AutoBeta2T]

Hi Graham - it's on the list... I'm using the tacho for when I go on the road. I need to get a digital one and then I can lose it. Running pre mix at the min 😊

[@Scissors69]

I would keep the oil pump. I think it does a better job of lubricating the bid end and mains, than premix

[@AutoBeta2T]

Hi Dave, probably but I don't want to take the (very small) risk of it failing. I'd need an 80 oil pump too as the 50 one doesn't output as much oil.

[@Scissors69]

@@AutoBeta2T - I run a pump and 80:1 premix for safety. The pump is turned down a bit to keep the overall ratio

[@AutoBeta2T]

I see... Currently 30:1 with Motul. We swapped to it for our air-cooled classic racers (X7 and RD) after always using Castrol 747... Motul was definitely better with no seizures while I was racing.