Wont Start

[yfm350]

Hi fellas thanks for adding me I have a no start situation with my machine it wasn't riding wen I got it from my cousin due to bent valve so I installed new pro x valve and lap them adjusted to specs to 0.06 intake and 0.16 exhaust replaced valve seals new oem timing chain new woodruff key new starter bearing new starter gear new spark plug I have spark compression is at 150 try 3 different carbs 3 different CDIs 3 different stator put it on tdc at fly wheel aligned the top sprocket line whit top v notch it seems just a little bit behind the notch machine started like 2 times no more than 30 seconds my spark plugs gets black and lud backfire at this point don't know wat else to do and by the way my stator are in spec too it wants to start but I don't know if Iam missing something new gas too only thing that I can't see or smell is gas on my spark but try the carbs on my other machine all 3 works any help will be appreciated thanks

 

[PineyPower]

" I can't see or smell is gas on my spark but try the carbs on my other machine all 3 works"
Try the little rubber intake manifold between the carb and head? If that's got a crack it or a bad seal it won't pull vacuum through the carb and you'll get no fuel to the cylinder

 

[yfm350]

" I can't see or smell is gas on my spark but try the carbs on my other machine all 3 works"
Try the little rubber intake manifold between the carb and head? If that's got a crack it or a bad seal it won't pull vacuum through the carb and you'll get no fuel to the cylinder

Yea I have tried tha

 

[YamahaNutz]

Easily overlooked is the fuel petcock. It has fine screens inside the fuel tank. If it's original, they could be plugged up, corroded, and/or broken. If you pull the hose off the carb and turn the fuel valve on, does fuel flow steady out the hose? You can switch back and forth to the reserve and see if it's the same on both.

If that is good, I'd double check the valve clearance. If they don't seal nearly 100%, you won't get enough vacuum to pull fuel through the carb.

If you breifly spray starting fluid in, will it fire immediately? I figure you have a newer spark plug, but have you checked how strong the spark is? Should be a strong blue-ish spark and consistent. Sporadic, yellow, sparks mean something is wrong with the coil, stator, wiring, ect.

 

[yfm350]

Easily overlooked is the fuel petcock. It has fine screens inside the fuel tank. If it's original, they could be plugged up, corroded, and/or broken. If you pull the hose off the carb and turn the fuel valve on, does fuel flow steady out the hose? You can switch back and forth to the reserve and see if it's the same on both.

If that is good, I'd double check the valve clearance. If they don't seal nearly 100%, you won't get enough vacuum to pull fuel through the carb.

If you breifly spray starting fluid in, will it fire immediately? I figure you have a newer spark plug, but have you checked how strong the spark is? Should be a strong blue-ish spark and consistent. Sporadic, yellow, sparks mean something is wrong with the coil, stator, wiring, ect.

I got it fix was one of the safety on clutch leveler something so simple after I make the whole engine new but ist ok is for my 12 year old son I know is going to last for a while so he can beat on it ... Thanks