Air And Spark, wont start. Brand new Kit

Italian

New Member
Jan 28, 2018
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so i recently disassembled the cylinder on my engine for reasons that dont matter, the only thing that went wrong was that i broke off a portion of one piston ring, like maybe 1/3 of it. the rest remains on the piston, there docent seem to be any compression issues or gouging issues withing the cylinder. is 1.3 of a broken piston ring enough to lose enough compression to where it wont even try and start?

like i said i have a brand new kit, it ran after i first assembled it, i have good spark, even bought a new spark plug of the NGK variety. the carb seems fine it worked before disassembled the engine and it was at a higher angle then than it is now.

i dont suspect it was the magneto or CDI as i can visibly see the spark and the kit is new and it worked before.

i dont know if it gets fuel, i dont know any way of checking, but i think its safe to assume that it gives fuel because it worked before

when i try to start the bike and i pull the throttle it seems to kind of want to start a little more than it did before but doesn't ever start. when i fiddle with the choke i get one combustion but its more of a puff of air than an explosion.everything is tight and sealed properly.

WTF is this, my buddy who was also a first time builder had no issues getting his same cheap Chinese kit to run the day of. all i did was take off the head and cylinder body and now it wont work, even though all my fuel/air/spark components are the same as when it did run.
 

crassius

Well-Known Member
Sep 30, 2012
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never seen one run without a ring - worse if a piece of ring is left in, it may damage something beyond repair
 

Italian

New Member
Jan 28, 2018
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never seen one run without a ring - worse if a piece of is left in, it may damage something beyond repair
I see, piston rings are cheap, I'll replace those and see how it works out. And how would I know if it was damaged beyond repair, I'd hate to have already done that. I've probably spent $50 trying to fix the damn thing I may as well be buying a new kit at this rate. Woulda a partially broken piston ring cause that much of loss of compression? I really don't wanna sinks more money chasing a problem that I'll never solve. I just wanna ride a bike at 25 Mph down the road.
 

crassius

Well-Known Member
Sep 30, 2012
4,032
155
63
USA
the ring has no spring tension to fit it to the cylinder if broken - if the ring didn't put a gouge in the cylinder wall, it should be OK, but if a small piece of the ring fell down into the bottom, then it could destroy a main bearing down there
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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Los Angeles, CA.
Sometimes the timing in the CDI goes bad... (you can still see a spark but it's just timed wrong).

Install a new CDI (& a new piston ring) & see if it starts. ;)
 

Greg58

Well-Known Member
May 1, 2011
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With one broke ring you have lost half of the compression, while ordering rings you should probably order a base gasket for the cylinder just in case yours is cracked. Be sure to line up the ring end gaps with the pins in the ring grooves of the piston.
 

Italian

New Member
Jan 28, 2018
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With one broke ring you have lost half of the compression, while ordering rings you should probably order a base gasket for the cylinder just in case yours is cracked. Be sure to line up the ring end gaps with the pins in the ring grooves of the piston.
thanks, i think this is the issue. ill send another reply when i get around to doing that,