I recently picked up an old 94 Yamaha WR250 (yz250). I rode it just a couple times late in the summer and put it away. I go to start it today, now it's spitting raw unburned fuel/oil mix out of the exhaust pipe.

It's not just a little bit either like your normal 2 stroke "spooge" (which is what it did previously), it's a constant drip at idle, and a constant flow under throttle.

I assumed since it sat for a few months, the carb may have gummed up. I took it off and took it all apart, cleaned everything, put it back on and the problem remains.

Any ideas?

 

what kind of valves on that year? rotary or reed? if they are reed, I might check out if they are sound and not split. also, when you cleaned the carbs, were the floats in good condition?

 

He said 2 stroke, Not 4stroke. Could Need to be ringed or Carb needs work try cleaning carb

 

Really? When was the last time you saw reed valves on a 4-stroke?

 

It's got the reed valves. I checked them, all appears well, they're fully closed and no visible damage or warping. When I cleaned the carb, float seemed fine, moved up and down with no drag. Guess I'm gonna pull it off again and reinspect. Never seen anything like this, a bike spitting this much raw gas out the tail pipe. I'd think it wouldn't run, and would flood out and foul the plug before doing this.

 

there should also be a set opening gap on those reeds, if they are fatigued, they might be open/relaxed more than required.

 

how does the compression feel?
did you take the reeds out to check or just look inside the boot?
what kind of oil were you using to premix?
what was it mixed at?
what octane gas?
hows the plug?

 

Compression feels OK, but this is my first 2 stroke bike, so I'm not real sure what it's supposed to feel like, I guess I should have it compression tested to know if it's within spec. It's easier to kick than my TRX450R, but that would be expected.

I took the reed out, it looks OK, but again I'm not experienced enough to know for sure, maybe as MSchu suggested, they could be too open/relaxed? Guess I'll just replace them and see if that does the trick.

I'm using Honda HP2 Oil, mixed to 40:1 with 93 octane (the bottle says mix it 32:1, but the previous owner said he ran 40:1). I think next time, since it's spitting un-burned fuel and smokes like a chimney, I'm going to try less oil, maybe 50:1?

The plug is always wet when I pull it out, but it never fouls out to where it won't start the bike.

 

wet in which way... fuel or oil. there is a difference.
is your smoke blue or blackish?
have you cracked open the top end to look at the bowl and cylinder by any chance?

 

It's wet with fuel.

Smoke is basically pure white, as if it were burning collant?

Have not opened the top end.

I did a compression check, it's 195 psi. From what googling I've done, this seems within range (if not possibly on the high side, the dude I got it from told me there's not many hours on new piston and rings). Next check will be leak down.

I took the carb back off last night for another thorough cleaning, this time I noticed the needle jetting was probably way off. The clip was in the lowest/richest spot. So I put it in the middle. Put it back on, it's running better, at least now instead of a constant dripping of fluid from the exhuast, it's now just constant white smoke. I'm going to buy a jet kit with various needles and mains, and new set of reeds, and play around with jettings settings as I suspect this is the main problem.

Thanks for the help guys.

 

fur sure white is coolant... are your main/primary and secondary jets inline with OEM specs?

I didnt mention the jetting earlier because you had said it was running fine before.

 

I honestly don't know. I need to get a service manual for this thing to know what factory settings should be.

I know, this is totally weird, it was running fine before, now it's not. I know 2 strokes can be tempermental at times, maybe it's not liking this colder weather?

 

its prob the pto side crank seal is bad and pulling in tranny fluid and burning it.

pto is clutch side