‘87;Yamaha Moto 350/ gas in crankcase

[jeff1]

Hey, I’m getting oil coming out of the fill/ dipstick handle when running and I have overfilled crankcase that smells like gas. Would this be a sticking float in the carb?

Thanks

[Mech]

Probably, unless there's a fuel pump with a hole in it's diaphragm..  Does that have a fuel pump ?

[MarkinAR]

Sticking float or badly tuned carb that's running way too much fuel to the motor washing the cylinders down.  usually a sticking float will leak out the carb overflow though, assuming it's not blocked.

[jeff1]

Yeah! I have been using non ethanol fuel last fall and  It ran fine and I haven’t ridden it over the winter. Although I did start it up once a month. I’ll check your suggestions. Thanks…

[Mech]

If it's done it after a long sit then you should check the fuel tap.

Lot's of perfectly fine operating float needles, that work all day long in use, will allow the engine to flood overnight...

[jeff1]

True….I’m going to rebuild the carb anyway  since the quad is 35 years old with around 4000 miles on it. I’ll keep everyone updated…thanks again

[jeff1]

Follow up to my post. I’m having start and run issues now.  I changed the oil and rebuilt the carb. It isn’t overflowing anymore, but now it won’t idle. It will only fire up with the choke on then it revs real high and dies. Any ideas what could be causing this? 
Btw, it is gravity fed no fuel pump.I checked the fuel tap and it is working gas flows and stops when shut off.

[MarkinAR]

Fuel starvation. If it runs better with the choke on it's not getting enough fuel. Could be petcock, fuel line, blockage in the idle circuit, idle jet is stopped up, blockage in the intake before the carb. Several possibilities, most revolve around fuel starvation. Fuel starvation can also be caused by an intake boot on the head side leaking vacuum. 

Edited June 26, 2022 by MarkinAR

[davefrombc]

Check the float level as well as all the items Mark mentioned. It could be too low.

[MarkinAR]

1 minute ago, davefrombc said:

Check the float level as well as all the items Mark mentioned. It could be too low.

Good call, didn't even think about float level. Surprising how many times I've had one through the shop where the float level is way off. 

[Mech]

This, " It will only fire up with the choke on then it revs real high and dies", as the guys suggest, does sound like low/lack of fuel in the bowl.

Check for air getting sucked in between the carb and manifold first though before you pull the carby off.. Or air getting sucked in anywhere. The float should probably not get out of adjustment.. There are ways, such as bending a brass float, or not seating the float needle seat, but mostly float needles/seats are pretty simple and reliable..

 

[jeff1]

Thanks everyone, I appreciate your help. I’ll be checking into this as time allows and I’ll let you know the results.

[jeff1]

 

On 6/26/2022 at 9:42 AM, MarkinAR said:

Fuel starvation. If it runs better with the choke on it's not getting enough fuel. Could be petcock, fuel line, blockage in the idle circuit, idle jet is stopped up, blockage in the intake before the carb. Several possibilities, most revolve around fuel starvation. Fuel starvation can also be caused by an intake boot on the head side leaking vacuum. 

Okay I found the issue with the no idle problem. The idle circuit jet was plugged up. I couldn’t get it out to replace it originally when I rebuilt the carb so I just figured it would be okay. 
I cleaned it out with a welding tip cleaner and now it starts and idles. Thanks everyone for the help it is greatly appreciated.