Intro And Help Pls!

[The Moto Family]

Hey guys new to the forum! So I have a wife and 4 kids that I share xc and some motocross racing with! I have 6 bikes in total, yamaha yz125, yamaha ttr125, yamaha pw80, yamaha pw50, honda crf100, honda xr200! And yes I'm constantly working on them!

I have run into a problem with my little guys pw50, this bike usually runs without fail but this past weekend at our xc race it died and for the life of me I cannot get it started! I am no mechanic but I'm also no stranger to working on bikes!
Compression is 148, new spark plug with confirmed spark, carb has been completely taken apart and cleaned thoroughly! Oil and air filter in check! Fuel petcock is functioning properly and fuel is getting into the carb! After kicking several times I can smell the fuel but the plug is dry! I'm stumped!
Any help would be greatly appreciated!
Cheers!
Mark

 

[Rich Rohrich]

Small carbs like this have very small pilot jets and starter circuits. It only takes a tiny bit of dirt to clog on of them. You might want to drain some of the fuel into a glass container and verify there isn't dirt in it, but also check for water. The current alcohol based pump fuels attract water and can really complicate the fueling of a tiny engine.

Whenever you get a engine that seems to pass all the normal checks and still won't start it's always worthwhile to put a fresh load of gas in as one of the steps.

 

[The Moto Family]

Thx for the tips, I did put a fresh tank in, and the carb is definitely clear 100%! It won't even fire when I put fuel right in the cylinder or when I spray carb cleaner in the air box but there is a nice blue spark!

Small carbs like this have very small pilot jets and starter circuits. It only takes a tiny bit of dirt to clog on of them. You might want to drain some of the fuel into a glass container and verify there isn't dirt in it, but also check for water. The current alcohol based pump fuels attract water and can really complicate the fueling of a tiny engine.

Whenever you get a engine that seems to pass all the normal checks and still won't start it's always worthwhile to put a fresh load of gas in as one of the steps.

 

[Rich Rohrich]

Given all the verification that it might be worth checking the flywheel. Make sure it didn't shear off the key on the end on the crank. If the flywheel moves on the crank it will still spark but it will be far enough out of time to never fire the engine.

 

[The Moto Family]

Timing check is my next step! Does anyone know the process for this check? I know the piston needs to be at TDC but not sure about the rest on this motor!

Given all the verification that it might be worth checking the flywheel. Make sure it didn't shear off the key on the end on the crank. If the flywheel moves on the crank it will still spark but it will be far enough out of time to never fire the engine.