Big issue on first bike!

[MotorBicycleRacing]

Yes, it matters as the broken off pieces change the shape of your transfer ports
for one thing.
Go ahead and try it if you must but your transfer port timing will be all messed up.

Motovelo should give you a new cylinder which looks like it was damaged
before it was assembled.
There is not much quality control in Chinese bicycle engine assembly "factories"
and they work on these engines on the floor.

 

[Big Red]

A new cylinder is only about $20 from the cheapo dealers. MotorBicycleRacing is right, It will affect the flow of fuel. I'm not saying it won't run like this, it just may never run right like this. I have one just like that in my shop I was gonna experiment with. Just ain't had a chance to "take a chance".
Big Red.

 

[ddesens]

I had one come to me new like this also. Inspected the bottom end for loose pieces and found none. It ran fine from the start and is still running today.( about a year). These motors come in boxes from china on pallets. Most sellers we all buy from just take a box off the pile and send it to you. Never opening the box, much less disassembling the motor. The seller should replace the cylinder for you at least. If they want to be reputable.

 

[Fabian]

I've encountered this problem before. It looks virtually the same as a rebuild i did for someone else. The guy tried to use brute force to drive the cylinder into the engine cases using the studs and nuts.
The problem turned out to be that the machining was not taking all the way to cylinder gasket mating face, and the non machined ridge compressed the cylinder wall (which cracked) as it was driven into the engine cases.

The new cylinder was properly machined and installed without any fuss.

Your engine (if it has not been run and the broken pieces are only sitting in the bottom of the crank cases) is likely to be quite ok. Just turn the engine upside down and shake out the bits with a bit of help from compressed air to remove any other gremlins that might be lurking inside the cases.

A new cylinder will have you back on your way

 

[V 35]

No, that cylinder itself may be OK, but the engine was slammed together, what does the bore look like ? Are you sure their aren't pieces in the cases. [ others' also asked that ] . If you want to use jug, grind or file off broken flash, so it won't fall into engine later.

I agree, for what motors cost, it's best to buy a fresh one elsewhere, and use the bummer one for parts.

 

[DJ Raizer]

hey all...

Thank you all for your help. I worked around this issue, ( file and polish and assemble anyway), and have FINALLY built the bike. If you want to check it out, you can see it here; First bike complete!!! Mostly...

 

[HeadSmess]

chinas standards are lowering

wow. nice. it looks like a factory modified part if there arent pieces in the case then definitely been dropped.

hmmm. other than the fact that it IS broken, it looks fine...those bits are thin.

the rings dont come down that far. they arent transfer ports but merely passageways so stuff can get to the transfer ports. dont even "support" the piston...

i woulda stuck it together and started it regardless. shes all a ok mate!

mind you if there were bits in the case...ida been screaming blue murder...possibly even if there werent bits!

 

[DJ Raizer]

Yea i inspected the case pretty thoroughly and found no pieces. The engine runs pretty good as far as im concerned; it 4 strokes alot if Im not accelerating, which i understand is somewhat normal?

 

[Big Red]

4 stroking happens A LOT but should not be considered normal operation. MOST of the time it's because you're getting too much fuel delivery to burn properly. Try a smaller jet size would be my first suggestion. My second suggestion would be to get a better exhaust system for the better flow it would provide. As a test you can try taking out the end baffle on that cheap chinese exhaust. If it runs better it says you have a carb/exhaust tuning problem. Personally, I dont even try anymore. Too much time and money for me trying to get it perfect. I just let my bikes run loud and proud with the baffle out.
Big Red.

 

[Cali-Rider]

My only concern is that the piston skirt might ride on that wall of the cylinder. If it does come that low, you could be asking for big problems... A new cylinder is only $20, a new motor is $120... I know what I'd do.