90cc shortcase clone rear wheel, please help!

[103stroker]

Hello all, im new to the forum but ive been browsing frequently as a guest, tons of awesome info on this forum and tons of very helpful members.
Anyways i have a 103cc shortcase that started life as a 90cc eton viper engine, i installed a 54mm big bore kit along with a 45mm stroker crankshaft, making it 103cc engine runs great but i have not been able to get it on the road yet because i cannot find a rear wheel that will work
I swapped all of the gears from a 50cc shortcase scooter engine(believe it was a vento, it had the long aluminum intake manifold)
Along with the gear swap i replaced all of the seals and bearing in the final drive.
I do not have a rear wheel that fits correctly and cannot find anything online about what type i need
I know its 18 splines because i have a wheel from my eton beamer long case that will slide on the shaft but when i tighten the axle nut it bottoms out the threads just before it actually tightens the wheel down, and even if i put a washer or spacer on before the nut its still not right because the splines end earlier in the wheel so it seems like its not a tight fit.
I compared the shortcase and longcase output shafts and they are definatelly different so a wheel for a longcase will not work.
Any info on where i can find the correct rear wheel for a shortcase clone would be greatly appreciated!!!! Thanx in advance

[aeroxbud]

Welcome to the forum.
There are lots of people here with parts laying around. So someone might be able to help. If you could post a picture up, with some measurements, it might narrow it down.

[repherence2]

You will need a 10" wheel from a Cinarelli 2 stroke, or from a taiwan 2 stroke like a SMC Rexy. Or a wheel from a Mako or Moskito, or a genuine Jog wheel.

I know for a fact that 4-stroke rear wheel splines are the same as the honda Dio/Elite and SYM dd50.

Bottom line, if the wheel is for a honda, SYM, or Daelim Cordi, the splines will not mate up with the Minarelli/Chinarelli.

[repherence2]

In regards to the Eton Beamer wheel issue:

I ran into a similar problem with my Ningbo GTX (Chinarelli). To remedy the problem of bottoming out on threads, and the wheel not firmly seated, i went to the hardware store to get a washer. The washer was used like a wheel spacer. I instaled it onto the shaft and seated it against the bearing and then installed the wheel and then the nut.

The outter diameter of the washer has to be smaller than the outter race of shaft bearing. Imagine this washer being like a variator shim.

[103stroker]

Thanx for the replies, i think ive got it figured out finally(mostly).
Thank you repherence2 your post about the spacer behind the eton beamer wheel, made me dig through my spare nut/bolt/washer/shim bin and i found the correct spacer that fits perfectly behind the wheel and gives me just enough to get the wheel to clamp down tightly. I did have to use a 3.50x10 tire wich said it should be mounted on a 2.5” wide rim, the eton beamer rim is 3.50 wide so it was a tiny stretch, not a problem though the beads seated and didnt even need to use ether lol. The beamer tire was way too fat/beefy to fit on the shortcase.
However im still a bit concerned that since the wheel is meant for a long case secondary/output shaft it only has about 20mm of spline engagement, because the splines start deeper in the wheel and the splines end earlier on the shortcase shaft.(i posted some pics to show what im workin with, the second to last pic shows about how much of the splines are making contact)
I also figured i would do some documenting of the differences between 50cc chinarelli shortcase, 90cc atv shortcase, and yamaha 3kj jog shortcase(its crazy how different the clones are from the real deal)
I hope all of the pics load up, this is only my second post here and im using my iphone on desktop mode to make this post so bear with me if it doesnt come through the first try. Just noticed the OD of the atv needle bearing got cut off in the pic, it is 33mm
i also posted a pic of the cylinder kit i installed(its a 54mm nikasil aluminum bore that is ceramic coated, uses a 2 ring piston, made by “bgm”) orderd it from a company called bwsp tuning from the aliexpress app... anybody ever ran this cylinder? Im very curious as to the performance output/ longevity it will provide. I was impressed with the quality for the price(200$) all of the ports were chamfered out of the box.
using a hoca head and 45mm ebay crank... i ordered a hoca 90cc 54mm kit wich came with cylinder w/suplemental exhaust ports, cylinder head, hoca variator, hoca intake manifold w/ “carbon” reeds, 21mm oko carburetor, clutch, red contra, v8 exhaust.
I liked the alum. Cylinder a bit more than the hoca so i installed the alum. Cyl., v8 exhaust, hoca intake and reeds, hoca variator, hoca clutch, and the oko 21mm carb.
The last pic is the engine with a rigged up ignition(cdi wired direct to pickup coil and ignition coil, also starter wire to jump start with a battery) It fired up first try and even idled! Couldnt believe it!

[repherence2]

How do you like the 21mm oko?

With a displacement of 103cc, it would seem to me that the engine would be starving at Wide Open Throttle. But if your carb has a power jet, it may be able to keep up with WOT fueling demands to keep the cylinder cool.

[103stroker]

I havent gotten it on the road yet since its been so cold in connecticut the past week or so, so havent gotten a good test of the engine or carb. I will be running a trail tech tto cyl head temp sensor when i do though.
Also i have a 24mm and 28mm pwk copy i could put in place if you think the 21mm is too small.
If i remember correctly the 21 oko came with 103main and 42 pilot, uses different jets than the pwk’s.
I have the whole range of main and pilot jets for the pwk so maybe ill just run that instead of the 21

[repherence2]

Dec 8, 2020 11:05:30 GMT -5 103stroker said:

I havent gotten it on the road yet since its been so cold in connecticut the past week or so, so havent gotten a good test of the engine or carb. I will be running a trail tech tto cyl head temp sensor when i do though.
Also i have a 24mm and 28mm pwk copy i could put in place if you think the 21mm is too small.
If i remember correctly the 21 oko came with 103main and 42 pilot, uses different jets than the pwk’s.
I have the whole range of main and pilot jets for the pwk so maybe ill just run that instead of the 21

Dont get me wrong, im not saying "Dont use the 21". If you can get it to work to suit your liking, you're fine. Here on Oahu (Hawaii) i tune for WOT incase i end up racing on the streets.

I ran a Polini CP 24 on the large bore set up and it ran pretty well throughout the rev range. Just out of curiosity, i switched over to the 28mm fake Oko because all the honda guys run those carbs wide open here (no filter). Out of the box, fake OKO (pwk type) carbs are a headache to tune. I ended up changing out the emulsion tube; from what i researched, knock off OKO carbs (from china) come set up with an emulsion tube that is suited for 4-stroke applications.

Large PWK type carbs (26 & 28mm) are great for WOT riding. Throttle positions of 0-½ throttle can be promlematic to tune because of the way the air flows. I dont know if this applies with air boxes because i do not run a true filter.

Im glad to hear that you have a CHT gage. Buy a jet kit or two to make carb tuning easier. If you plan on running premix, you will need to jet bigger than normal.

[103stroker]

Yes i will for sure be running premix as i did away with the oil injection system as i do on most of my builds, except for my kymco cobra w malossi sport technigas next r and pwk 21.
I normally use redline racing 2 stroke oil at 32-1 premix with 93octane pump gas.
Im very glad that you mentioned the emultion tube on the pwk copys because ive been having alot of trouble tuning my jonway wasp wich im running a LC polini corsa with a doppler full circle all metal crank, yasuni c16 pipe(not the city version), malossi vl14 reed block, top performance 35mm 360* intake manifold, malossi overrange cvt system, stage 6 secondary gear set, and a 24mm pwk copy. Its a rear disk brake chinarelli longcase, preaty rare ive come to learn, but anyways I Cannot tune in the low to mid range at allllll, its a screamer but throttle response has always been less than impressive for how it should be with that parts list. I am also kinda new to 2 stroke tuning and have had little experience with tuning carbs, however i do have the full range of jets for the carb and have tried some switching out and re-testing with only minor improvements.
So now im thinking maybe the emultion tube could have alot to do with it, i had noticed when i bought the carb from ebay the listing said 4t and 2t compatible

[aeroxbud]

That sounds like the answer right there then. It should be a four stroke, or two stroke carb. Not both.

[repherence2]

Sounds like your Jonway Wasp is going to be a hammer when you get it all in tune!

As far as smoothing out the performance of the PWK type carbs from 0-½ throttle, take a look at Rich's-Taylor'd-Porting at richstayloredporting.com. that site talks about venturi dividers. I fabricated one for myself, not fancy like the ones that they install for people. I made it from
1/16" aluminum. It greatly improved throttle response from 0-½ throttle.

Proper emulsion tube + venturi divider = no more headaches trying to tune a knock off PWK.

[103stroker]

Yea it should be a beast, do you remember wich emulsion tube you used when you swapped it out on your carb? Link maybe?
And thanks for pointing me in the direction of the venturi dividers, i spent about a good hour on the site looking at all of the different port jobs and divider jobs that guy does, some really crazy stuff, sound logic too behind the dividers, i may have to give it a try myself, what did you use for adhesive for the divider to venturi contact points?
here are some pics showing the difference between my pwk 28 copy purchased from ebay, and the oko 21mm that came with the 90 hoca kit.
if you notice the emulsion tube on the pwk only had 8 holes in total, 2 sets of 2 holes on the “front” and 2 sets of 2 holes on the “back”
where as the oko has 18 holes in total, a row every 90* of the diameter of the tube.
also notice the needle tapers are drastically different, the oko has an area twords the bottom that appears to be not tapered until about 5mm up from the bottom(the pic does not show this well) oko has part #3g9 for the needle, no part # on emultion for either carb or on the pwk needle.
i also noticed difference in the powerjet pickups in the bowl
also the pwk has an almost “diamond cut” finish inside if you will, where as the oko is rough and unpolished in comparison.
they also use different jets
Pwk on the left, oko on the right, pardon the poor image quality