Completely stumped..

Just finished rebuilding my 96 cr125. The bike won't start and I'm getting annoyed. I tried almost everything... The bike has spark, is getting fuel, stator is timed correctly, carb is clean, reeds are brand new, top end is brand new, running new gas and oil 93octane, brand new cdi, stator, and coil, new spark plug, brand new kill switch, and the bike has a 95 lower end, with a 96 top end, I believe this has nothing to do with the problem but I never know. Someone please chime in and give me some ideas, I've done this before... I don't see what can be going wrong and I'm getting very frustrated... Any help would be greatly appreciated..

piston in backwards?

Try unplugging the kill switch to rule out that being grounded out.

See if it will bust off with a few drips of gas down the plug hole. Not too much, not too little.

Hey guys piston is in right, kill switch is good, next will be to try the gas down the plug whole. But whenever I pull the plug it comes up wet so I know it's getting fuel...

You have confirmed spark? If the plug is wet, clean it with some brake cleaner to dry it out. Spin the motor over without the plug in to clear the cylinder, in the flight of the phoenix. Couple of drops of fuel, replace plug and kick. Should fire on that first kick if you have spark and timing.

Okay, I'll give it a shot... Still having no luck though. Brand new plug just put in... Is it possible to put the carb jet's in the wrong way, and the reeds?

Is it possible to put the carb jet's in the wrong way, and the reeds?


Jets? No. the Main and pilot jets are 2 shapes and sizes so it would be very unlikely this has happened.


Reeds? The reeds are reversible so as long as you have the reeds bolted in and there are NO gaps between the reed petals and the reed cage, you should be OK. If the reeds were not installed right, you would not be able to bolt the reed cage to the cylinder. The reeds need to seal 100% against the reed cage all the way around. If you pull up on a reed petal with your fingernail and let it go, it should snap back down tight to the reed cage.


It might be worth doing a compression and leak down test on the engine to see if you have enough compression and no air leaking from the crank case.


It could be a timing issue because of the new parts that you replaced but usually, the engine should start enough for you to check the timing with a timing light.

What is your current jetting including the air screw setting?  Starting and low rpm work off of the pilot jet.  Fouled plugs are often due to a rich pilot jet.  Is your float set at the correct height?

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