Big Polini problem (jetting? crank?)

[James980]

I need some major advice on my kid's 2000 X3.

We got this bike in December, and my kid has had it out about seven times since. It always ran OK, although it did seem a little rich on top, cutting out and bogging a bit at WFO but nothing serious.

Well, the last ride out, his clutch went. (His bike also seemed to be cutting out more than before on top.) So, I replaced the pads. When doing so I cleaned the air filter and noticed a big crack in the airbox. Mud, dirt and weeds had found their way inside and down into the carb.

I cleaned the carb and put everything back together. Now, though, the bike is running incredibly rich. It will barely idle with the screw all the way in. It won't pull me (~170 lbs.) on a flat surface, bogging and sputtering when the throttle is cracked open. Pulling up the choke immediately kills the engine. It spits oil out the silencer like there's no tomorrow. If cool, the bike runs OK for about 15-20 seconds when first started, with no spooge out the silencer and it has good power and no bogging; after that, though, it's hopeless.

With the fuel metering screw all the way in to 1/2 turn out, it seems a little better, but not much. I dropped the needle a clip, again, little if no help. Just for the heck of it, I put in a bigger main -- I don't have a smaller one right now -- and that made things worse. I've had the carb apart about half a dozen times and can categorically say that it is clean.

Right now the bike -- it has a 21mm carb; the previous owner removed the reducer -- has a 94 main, 262 needle jet, W3 needle in second clip. I can't remember the choke or pilot jet, but don't think they were far off stock.

My questions are: Can this thing be so sensitive to temperature that the 15-20 degree difference between before his clutch went and yesterday make it run this much worse with the same jetting? If not, does this sound like a bad right side crank seal? If I'm looking at a seal replacement, can I get to it without splitting the cases?

I would just order the new jets and rule that out myself, but I'm tight on time. This kid will already miss two races thanks to this and I have to get this figured out by Saturday, which means I need parts ordered today. If anyone with experience with these things doesn't think the jetting could make it this bad, I'll just order the stuff for the seal replacement now.

Thanks,
James

 

[Jasle]

You can get the seal out by using a 1/8" drill bit and drilling a hole in the seal. Then using a sheet rock screw screw it in. Then pull the screw and seal out with pliers. You might have to use two or three spaced around the seal....JUST BE CAREFUL. you could nick the crank.
Our Cobra is very sensitive to temp/alt/ settings. It doesn't sound like its as bad as yours though. Did you use heat when removing the clutch? Maybe you baked the seal if you heated too long.

Jason

 

[ACS]

It could be fuel level in the carb, too high and flooding. Check that as its cheap to do. If it sucked in a lot of dirt it may needs a new piston rings and rebore (if is reborable) if not a new barrel. That will be expensive.

 

[James980]

Thanks for the advice. The float idea is a good one (because it's a lot easier to fix, of course), but considering the rich condition started slowly (cutting out a little bit earlier this year) and built to the sputtering and blurbing I get now, I'm thinking crank seal. I did mess with the float a bit one of the times I had the carb apart, setting the shut-off point a little earlier but like the other jetting changes, little if no change.

As for the bore, I did pull the top end last night and it looked OK. Not perfect, but definitely no scratches, etc. The ring is way out of spec, though, so it's time for a new one of those.

Thanks for the help.

James