Engine Trouble bike won't start, any ideas?

adboio

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Aug 21, 2019
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long story short: i recently bought a used bike on craigslist and it ran mostly fine. a little difficult to start, but tolerable. i replaced the cylinder, fuel filter, carb, and air filter in an attempt to get it running nice and reliable. now it doesn't start.

long story longer:
the bike seemed like it could use some upgrades, so i bought a new engine mounting kit, a new carb + air filter, and a new cylinder because the old one had a stud stuck in the exhaust mounting hole. now it feels like it's not sparking. i'll hold the clutch in, ride it a bit, get going a decent speed, let go, and you can hear the motor going but never actually "coughs" like it's sparking and running on its own. i've tried choking it, not choking it, using starter fluid, etc. i decided to replace the spark plug, still nothing, so i swapped ignition coils with my friend's (@colehardison35) bike (so i know it works) and still nothing. the magneto looks fine but i have no clue what i'm looking for. also, the f*cker shocks me when i let go of the clutch, so i'm pretty sure i'm getting power. i've posted pics of the magneto + how i've got the ignition coil wired up below.

any suggestions on what could be wrong? the carb is brand new, and i know it's got at least a little fuel, since i pumped that little button a ton (at first just a few times, then kept pumping because i thought maybe the new filter or the way i've got the new carb mounted wasn't doing it).

again, it literally shocks me when i let go of the clutch, so i think that means the magneto is working. also, the ignition coil is ruled out because i tried my friend's with the same result. brand new spark plug with 0.036" gap, pretty sure it's the same plug that's on my friend's working bike.
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update: i checked and 100% for sure have spark. also, put the old carb back on and still nothing.

also, just remembered when i replaced the cylinder, the piston/head/whatever had these two metal rings around it, kinda like these. and when we took off the cylinder the broke off a little but they're both still on there. i assume that's causing a loss in compression, but enough to make it not start AT ALL? i can also move the bike without the clutch pulled -- not necessarily easily, but definitely easier than before. you can hear the cylinder moving when you do this.
 
Take pics of your rings. If pieces came off they are broken and you're potentially (probably) damaging your cylinder wall. That would definitely cause a no start situation.
 
Take pics of your rings. If pieces came off they are broken and you're potentially (probably) damaging your cylinder wall. That would definitely cause a no start situation.

well, f***. hopefully i haven't messed it up too bad. i'll take pics when i can -- so much work taking it apart haha. i just ordered a new head and rings so maybe that'll fix it. i'm renaming this bike my Money Pit (TM).
 
Most of the time tinkering on these is fun. Sometimes you wonder if it is worth it. Then you figure it out and fall in love again... A couple of weeks go by and you get the itch to try something out and you're back here again...

I was back in the frustration seat this morning when I used enough 2 stroke oil for almost 2 gallons when only adding a 3rd of a gallon at the pump. I pissed my bike off so bad I literally had to blow it so it'd start again. Odd, up until now I've always referred to my bike as a she...
 
I agree, if the piston rings are broken it won't start. Take the head and cylinder off and inspect the rings, if either ring is broken make certain you get all the pieces out, check the cylinder wall for damage, you might be able to just put on new rings and be good to go.
 
Everything that these guys said, and if you don't have all the ring pieces you will need to remove the engine to properly flush out the bottom end. Show us a pic of the inside of the cylinder.
 
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First thing I do with these kits is toss out the kill switch, makes wiring much simpler and if the engine is running correctly, the choke will kill the engine. What I have noticed is that when the remaining two wires are connected, you can get spark regardless of how they're connected but only one way works. So switch the wires even if you have spark. Obviously this is pointless if you aren't getting fuel in, check the plug to see if it's wet. I never peddle for long on a first try with a new engine, firstly put some oil in the jug so you aren't dry starting. If it doesn't start within 5 seconds I stop and check for fuel/spark etc.
 
First thing I do with these kits is toss out the kill switch, makes wiring much simpler and if the engine is running correctly, the choke will kill the engine. What I have noticed is that when the remaining two wires are connected, you can get spark regardless of how they're connected but only one way works. So switch the wires even if you have spark. Obviously this is pointless if you aren't getting fuel in, check the plug to see if it's wet. I never peddle for long on a first try with a new engine, firstly put some oil in the jug so you aren't dry starting. If it doesn't start within 5 seconds I stop and check for fuel/spark etc.
Bro did you read what he said? He's got broken rings.
 
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