Idle's great! But lacks power..

[Jonathan Christianson]

I dunno where to start. But I have two bicycles. The first one I own is a huffy beach cruiser. Runs perfectly fine. My second bike is a bayside cruiser, however. Isn't running fine. It idles Great and revs not great. But compared to my first bike, that thing revs to the moon. Reason why I'm building another bike is that I'm putting a jackshaft shifter kit on this bike, Just so I can start from a stop. But one issue. This new engine I purchased has little to no power. Tops I can go is about 15mph on level ground. I tried swapping carbs and nothing changes. It's not the oil mix ratio. I tried both 16:1 and 20:1. Nothing varies. I know it's not the carbs. I checked the piston to make sure the arrow was pointing to the exhaust port. The head is torqued down good. I don't know what it is. But what I'm thinking, it's probably either a spark related thing. Or exhaust. Or just the engine itself is junk.

Tomorrow I'm gonna swap the magneeto and the cdi/spark plug to see if I get any difference

 

[crassius]

checking arrow on piston does nothing for you - it is the locating pins for the rings that have to be back near the intake port

if intake pipe is steel, there may be a bit of chrome sticking up on the end where carb fits - filing right along that edge at 45 degree angle will fix it

if you got an older style motor, it will sometimes take quite a few miles to run in

 

[Jonathan Christianson]

checking arrow on piston does nothing for you - it is the locating pins for the rings that have to be back near the intake port

if intake pipe is steel, there may be a bit of chrome sticking up on the end where carb fits - filing right along that edge at 45 degree angle will fix it

if you got an older style motor, it will sometimes take quite a few miles to run in

I'll look again. But I didn't see any metal in there earlier.

 

[crassius]

rare that one can see it, but lightly sliding a finger off the end allows it to be felt - if there it can cause a slight air-leak that doesn't raise RPMs but robs a bit of power

 

[4banger]

I'm having similar issue with my huasheng 4stroke stock with 44t pinapple rear sprocket. Old one was great, hit about 33-36mph slight knocking once in a while. New kit won't clear 22mph but runs smooth. Would like to hit 30 again though. First everything ,bike and all kit setup is the same, but the new hs transfer case was a dual chain from bike berry. The old one was a single chain, didn't think it would make that big a difference. I got a flex poopoo exhaust and 40t rear hub sprocket, only increased from 20mph to the now 22 mph Max. Do the engine vary that much? Could it be just the dual chain trans vs the single. Any help to what would cause that 10-15 mph difference would be great?

 

[Tyler6357]

Idle revving? no power? Sounds like an air leak causing loss of compression. Check for any air leaks around the head gasket, intake, and carb connections. Also check your seals for any leaks.

 

[crassius]

it's a 4-stroke, no seals

might just be the governor some motors have now