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Variable Idle

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99 CR125 - The idle speed is all over the place, it seems to have a mind of its own. It will climb very high at times and then without doing anything, it will drop down and refuse to idle.

I have checked for an air leak and can't find one. I changed the reed block gasket to be sure and also changed the right crank seal. The carb is spotless inside and all the clamps are tight. It also seems to be running rich based on the amount of oil coming out of the pipe. Currently I have a 178 main and a 55 pilot in there. Needle in the 4th position and the screw about 2 turns out. 500' elevation and 60-70 degrees outside. When I crank open the throttle it studders and I get LOTS of smoke. I have run this jetting for quite some time and it used to run perfectly. This started all of a sudden.

I am at a loss. I hope someone (Eddie) can help.

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are you 100% sure the mag side crank seal isnt leaking?

Not 100% sure. Should I change it to be positive? Wouldn't a leak on that side make it lean due to more air?

What is the best way to check the entire bike for an air leak? Is there anything I can do besides just changing out gaskets and seals?

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Not 100% sure. Should I change it to be positive? Wouldn't a leak on that side make it lean due to more air?

What is the best way to check the entire bike for an air leak? Is there anything I can do besides just changing out gaskets and seals?

Joey

When the piston goes down fuel air mixture in the crankcase will blow out any leak. When people start wanting to rejet bikes this old I cringe as there are so many things that have an effect, all effect running in a manor that makes the bike act rich.

Float level rises from wear at needle, seat & float piot all of which raises the gas level, make it easier to sipon gas so it runs richer

The slide wears, vacume holds the slide forward, the jet needle drags in the needle jet and both get worn

crankcase to magneto seal dries up and leaks

and the most cruel of all, crankcase to primary side seal leaks and draws in oil on the pistons upstroke so now we have gear oil in the crankcase, then on piston downstroke it blows out air/fuel mix so it can run lean yet act slobbery rich do to oil. This one is tested by hangining the crankcase vent hose into a glass of water, then rev the engine, if it blows bubbles the seal is leaking.

And just plain being down on compression makes them weak & slobbery running which is often confused with rich mixture.

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