why does this crap always happen to me

[Frankenstein]

yeah, these are all I do here - way too old to lift a bigger motor - half the times I'm on forum are just because I need to sit and rest a while

bike shops don't have insurance to cover these

one other ongoing problem is the guys that buy $99 ebay kits and want me to provide free parts under warranty for the POS kit they bought

Yeah you might want to change the policy, I've seen crap like that and it always has to resort to upholding policies on only parts (engines in your case) supplied by you.

What is side to side play? You mean that thing that happens to all pistons, you know, because they don't need any free space it's not like they will move in the cylinder or anything. Sometimes wedging paper in there will reduce the play, make sure to use unbleached natural paper because I heard bleach in an engine is a bad thing.

 

[crassius]

yeah, he seems to want the needle bearings at both ends of rod to not move side-to-side

with cylinders on these so often a little off to one side, I'd consider a bit of piston float a benefit

 

[crassius]

not quite so peculiar after all

he came by today and is just buying kits to assess quality levels for a hobbyist-oriented business of building these motors out to become some serious race motors, and intends to redo a lot of casting/machining as needed

 

[LewieBike]

The top needle bearing always stays put no matter what gap there is between the piston pin bosses the small bearing opening, if I'm not mistaken. My new cheap 48 cc has no detectable bottom play, seems like the cranks on these are fairly well made.

 

[crassius]

rare to find a crank that is completely true though, but in a cheap, disposable, utility motor that isn't a big deal

kinda like batteries; run em till they die and replace as needed

 

[JerboaJohn]

isn't balancing cranks something that's good to do but kind of difficult for most?

 

[LewieBike]

It's not for the home hobbyist. IINM you need a pair of decent V blocks, really precision dial indicators for reading runout, and a decently made 15 ton press.

A lathe wouldn't hurt as wouldn't the skill to run one.

 

[crassius]

I don't believe there is any real reason to improve these motors, they work well enough for the purpose and go about as fast as the bike tires and brakes can handle. If you want a motorcycle, buy one - these are just bicycles.

 

[LewieBike]

Yup, with the brakes and no suspension on both my bikes, 20~25 mph is close to being too fast.

 

[Frankenstein]

yeah, he seems to want the needle bearings at both ends of rod to not move side-to-side

with cylinders on these so often a little off to one side, I'd consider a bit of piston float a benefit

That's always been in the back of my mind, I've noticed that the cylinder doesn't always sit directly in the middle of the crank and so I felt as though leaving the play there was kind of a good idea.

I also second that if you want to have one of these last forever then make a Moroni engine fit, that will fix it. Or just buy a motorcycle if that's what you're trying to get out of this. I've got too little time for even a bicycle, and I'm rarely driving alone anyway so I have to use a normal vehicle most of the time by default..