After reading a bit and looking at kits there are 2 stock top ends. One with a windowed piston and one without one. Each has a cylinder made for that specific piston. Using a different piston will make the engine run like crap. Thats what 20 year old forums say.
Engine Trouble 2 Stroke has no low end
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Oh forgot to say that its a minarelli horizontal china clone
Chainlube
Well-Known Member
Is that on a bicycle or a scooter? If it's a scooter, then that sounds like a variator issue.
I did think of the variator but i think that would be the case if the scooter wouldnt pull you up hills or while you were on it. On the stand it should rev up freerly. It doesnt even idle as its so rich so its not the variator (yet).
So a little update... I ordered a new cylinder kit and since i came off work early i did a little experiment on the scooters piston. I cut out 2 windows in the left and right side by eye using a drill and a file and put it back together. The running improved by about 50 percent and it would actually pull you up a hill now, however it lost alot of top end and still ran on the richer side with a 32 pilot. So this shows me that the issue was in the port timings or the lack of a window. If i would have the correct window dimension beforehand i would make the old piston work but i dont know if the cylinders ports are correct and for the price of a 70 kit its better to change it then for it to grenade the entire bottom end.
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Mike Cyanide
Well-Known Member
I got u man. La hoover bikes on YouTube has a good video. Second no Drexel need watch the vid and use a drill with a grinder bit and pickup some cheap grinding stone attachments. It's not half as hard as u think. It VERY easy. Alittle reading a short vid and slow work and your good. I promise.
Thanks for the tips. I have ordered a new cylinder kit for it as i want it to be somewhat reliable (Wanted a 4 stroke scooter but this thing was very cheap and the PO threw on 700 euros worth of parts on it trying to fix it). As for the window i did experiment and put 2 windows in the piston and the running has improved. Hopefully the new cylinder will have good port timings.
Mike Cyanide
Well-Known Member
You got this man! 4 strokes are slow anyway! Lol I recommend a degree wheel and the same attitude you have. The port timing can be improved and ur the guy to do it. Some base gaskets and decking maybe some light port work,piston ramping is a cheap option but caution you might find yourself falling in love with your 2stroke. Which may not be too big a problem with the right mix lolol hell I don't see why u don't get a degree wheel and go at this cyl atleast for practice. Remember don't get too fancy make what u have work it's best THEN upgrade if needed.
UPDATE: I got my cylinder kit and installed it on my scoot 2 days ago. Everything went well on the install. I set the ring end gap, checked the ports and lubed everything good. It started right away and would you believe it ran, revved up and actually pulled me up a hill! I did a quick lap around the block for a test. I then decided to go a little farther. At half throttle and about 50-60km/h the engine started to bog and it seized. I then waited about 20 minutes on the side of the road to let it cool down (i thought it soft seized) but after some time the starter still couldnt turn over the engine. So i did the walk of shame 3km home (pushing 100kg up a hill is not fun).
When i got home i pulled the plug and it was black meaning it was on the rich side (put it a bigger main jet then i needed for safety). I then pulled the engine out again and took the CVT, stator and cylinder off. Cylinder was still like new but the engine still was locked up. I heated up the cases to split the engine. I found that one of the crank bearings were installed crooked. I ordered a new crank and SKF C4 bearings with crank seals.
From now i wont trust another persons rebuild. I could somehow understand the PO installing a different piston but forcing the crank bearing on the crank?
When i got home i pulled the plug and it was black meaning it was on the rich side (put it a bigger main jet then i needed for safety). I then pulled the engine out again and took the CVT, stator and cylinder off. Cylinder was still like new but the engine still was locked up. I heated up the cases to split the engine. I found that one of the crank bearings were installed crooked. I ordered a new crank and SKF C4 bearings with crank seals.
From now i wont trust another persons rebuild. I could somehow understand the PO installing a different piston but forcing the crank bearing on the crank?
UPDATE: So i cleaned all the engine parts and also bought a new crank and SKF C4 bearings with crank seals. Rebuild the thing and started it up. Went on a test ride to also break it in a little bit. So far its done 200km and no issues so far (except that with the factory limiter it does 50kmh instead of the legal 25kmh). I didnt test the top speed just yet but it happily cruises at 70kmh. This thing is like a Bentley compared to my motorized bike! No vibrations, excellent brakes and plenty of power with the stock china CVT! Hopefully it will be reliable as its not pushing crazy power nor do i want it to.
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