On Cheap vs "Expensive" Engines

[Chainlube]

I've built 12 or 14 bikes with engines from all different suppliers, all the motors are the same with small variations. It's what you do after it gets home that really matters. Take your time and go through the whole motor and make sure it's assemble in the proper manner. You can find bent studs, stripped spark plug holes, casting flash and pistons in backward. When you have it apart you can clean up any casting flash that maybe left in the ports and round over the cylinder side of them.
The difference between the two motors is $91.

 

[Colonel__Klink]

I've built 12 or 14 bikes with engines from all different suppliers, all the motors are the same with small variations. It's what you do after it gets home that really matters. Take your time and go through the whole motor and make sure it's assemble in the proper manner. You can find bent studs, stripped spark plug holes, casting flash and pistons in backward. When you have it apart you can clean up any casting flash that maybe left in the ports and round over the cylinder side of them.
The difference between the two motors is $91.

Thanks for the help! I'm so glad that there is a whole slew of information out there on how to put these things together bc I had no idea that the piston could be put in backwards! lol.

Surprisingly it's actually quite comforting to know the real difference is the work I put into the engine. From what I was seeing on youtube last night was that cleaning those ports up carefully is a pretty big deal on these cheap 2 strokes. One of the other things that I'm certain to do is order a bunch of head and base gaskets just in case .

I thought of ordering a spare chain just in case (though I suppose it's quite likely that I should be able to shorten the chain and adjust the tensioner if it snaps.) But I confess I'm not sure if a regular bike chain will work, or if I need to order a special chain and how long it needs to be lol.

 

[Chainlube]

You need a 415H chain and a chain breaker. The breaker isn't really needed but then you have to get the pin back in with the chain on the bike.

 

[CrazyDan]

Many of us run 410 bike chain on the left side, I did for a couple years before putting on a shift kit.

 

[GreasyChris]

If you're mechanically inclined and know which end of the screwdriver to hold on to you can make a cheap engine as reliable as any more expensive engine. Quality bearings and proper engine sealing techniques will make your engine last. Some of the differences between cheap and more expensive engines are cheap engines have M6 mounting studs front and back, cheap bearings and crappy cylinders with small ports and crap plating. Better engines have better bearings M8 mounting studs bigger ports and the newest ones have ceramic coating in the cylinders and big open transfer ports. You can also get sleeved cylinders and oversized cylinders. Lots of guys are also making hybrid engines using saw jugs and moped cylinders.

 

[LewieBike]

Note that a lot of these engines come with a drive side sprocket that's not quite 415 width, but not narrow enough to fit a 410 BMX 1/8" width chain.

You may have to remove the sprocket and give it a some grinding on a bench or angle grinder to fit a 410 chain. Also, chamfer the teeth points and beware the sprocket eccentricity. Set your chain free play at the tightest point and accept that your engine will warble because of the eccentric engine sprocket.

 

[Colonel__Klink]

Note that a lot of these engines come with a drive side sprocket that's not quite 415 width, but not narrow enough to fit a 410 BMX 1/8" width chain.

You may have to remove the sprocket and give it a some grinding on a bench or angle grinder to fit a 410 chain. Also, chamfer the teeth points and beware the sprocket eccentricity. Set your chain free play at the tightest point and accept that your engine will warble because of the eccentric engine sprocket.

I didn't know that this was a potential issue, though I am hopeful that the sprocket with the hub adapter I bought will prevent this issue.

https://www.amazon.com/gp/product/B07T1C4SF6/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

If everything works out then I should have all the parts to build my bike thursday! I'll have to post some about how it went . You guys here have been a huge help giving me a heads up on a lot of things that I didn't know that I might actually need. Hopefully that will stave off immediate serious problems .

 

[Frogslayer]

He's talking the drive sprocket on the engine itself. My rear driven sprocket actually fit the single speed bike chain perfectly. The front small sprocket i took a few swipes off the outside of the teeth with a hand file. I did it while on the bike and now it runs perfect and way less chain drag so now i can actually pedal it around like a bicycle.

 

[LewieBike]

He's talking the drive sprocket on the engine itself. My rear driven sprocket actually fit the single speed bike chain perfectly. The front small sprocket i took a few swipes off the outside of the teeth with a hand file. I did it while on the bike and now it runs perfect and way less chain drag so now i can actually pedal it around like a bicycle.

This is a real thing with most of these engines. The engine side sprockets are sometimes a hot mess, even the replacement "narrow" ones are still a little wide for the basic BMX chain and still out of round. But the eccentricity is a big problem, some come nearly perfect, but my 48cc came with a lot of eccentricity and I had to TIG weld fill and file the sprocket to smooth out the out of roundness. Now like Frogslayer is saying; my bike pedals nearly effortlessly, enough so that I can shut the engine off in town and just pedal easily with the clutch pulled in.

BTW my engine was a Kaxton 48cc and sold for $107 two years ago. It's actually one of the better cheap ones.

 

[Colonel__Klink]

This is a real thing with most of these engines. The engine side sprockets are sometimes a hot mess, even the replacement "narrow" ones are still a little wide for the basic BMX chain and still out of round. But the eccentricity is a big problem, some come nearly perfect, but my 48cc came with a lot of eccentricity and I had to TIG weld fill and file the sprocket to smooth out the out of roundness. Now like Frogslayer is saying; my bike pedals nearly effortlessly, enough so that I can shut the engine off in town and just pedal easily with the clutch pulled in.

BTW my engine was a Kaxton 48cc and sold for $107 two years ago. It's actually one of the better cheap ones.

honestly i wonder now if I can find an industrial supply that will offer such a sprocket, appropriately toothed for the drive shaft... I got no problem sitting there with a file cleaning up work and thinning the teeth a little (though that certainly will take quite some time.) but I don't have the capacity to do any fill other than an epoxy laden with metal... or probably a better idea is just use a mountain of solder to fill. I'm also imagining how I would set up a hand mandrel to inspect to see if the sprocket is within round on the outside edge and then slowly shortening each tooth with a file by hand until it's all in round....

Doing that by hand in an appartment? That's like 8 hours of work there I'm betting. A whole day. So If I could just buy a better sprocket for $60 or less I am WAY ahead....