Topic: Yamaha YFM 350

[6adan]

Yes this is a 4 Wheller  that I use to hunt on and just riding around the woods on. Hear is my problem it will start and idle good but when I try to accelerate it just bogs down. It feels like the main jet is stopped up but I have had the carb. off and checked that. I have been told the CDI unit would do this but I have never experienced this. Any ideas please? Thanks Dannie

[KB02]

I would doubt it's the CDI unit. If the CID goes, the thing won't run at all.

I would say give it a full tune up and go from there. It could be a number of things just all being a little out of wack at the same time. Besides, a full tune up is never a bad thing.

[Jay B]

I have a YFM250 that did the same thing. The carb diaphram had a pinhole in it towards the middle where the slide rivets on. They wanted about $100 for a new diaphram. I clipped a tiny peice of the red rubber edge off a tire patch and glued it on with tire patch glue. It's been running fine that way for over 2 years now. BTW, I first tried sealing the pinhole with blue silicone. it worked for a while, but started leaking again. Look at the diaphram closely. Pinholes are hard to find sometimes.

[6adan]

Thanks guys KB02 yes a tuneup is always good but this happened quickly, running good one time then not. Jay B I took the carb. apart  and this is not a CV carb., the only diaphragm on this carb. is I believe a air cut valve like the DOHC CB's and it checked OK but thanks again Dannie

[crazypj]

Its a two stroke?
You probably have a blocked exhaust.
take it off and clean everything. Take a look up the port and see if its still full sized or blocked with carbon deposits
PJ

[6adan]

Crazypj No mine isn't a two stroke it's a 350 single four stroke. Dannie

[crazypj]

Is it similar o the XT350 trail bike?
Sounds like one of the safety sensors isn't sending/blocking a signal to CDI. I've seen it happen on the Honda and Suzuki 4 wheelers but obviously have no experience on your Quad.
 Check out all the connectors/wiring first as I've had problems over the years with corroded connections and wiring broken inside the insulation on Yamaha's
PJ

[6adan]

Thanks crazypj I have the carb. off again but I am going out now it put it back on and I will also check the connections. Dannie