Crankshaft Seal Replacement

[buzzard]

I am new to this site, and just recently aquired my first Gas Gas, a 2002 250XC. It seems to be a lightly used bike, and in pretty good shape. It ran too poorly to ride it, and threw lots of oil out the silencer. I found the silencer clogged, packed with black tar-like goop. After a thorough cleaning and repacking, the bike still ran like crap, refusing to get up into the mid-range, blubbering and billowing smoke. So, I decide it has to be a RH crank seal. I have ordered the parts, seal, gaskets, and o-ring, and they are on the way. I have pulled out the old seal. The gearbox side lip was definitely gone.
My question: Are there any tips concerning installation of the new seal you would care to give me? Thanks, Buzzard

 

[GMP]

Just drive it in square and flush to the case. I have a variety of pipe fittings of various ODs for this purpose. Jam the primary gears with a rag or a penny to tighten the primary pinion nut, as you know now is a reverse thread.

 

[Rickster]

What are the symptoms it is showing? As mine may have the same problem. I feel like I am riding around with a blocked air filter and the choke on. Do you have to pull the engine down to get to it?

 

[GMP]

Its not a common problem. More likely you have a carb issue or broke a reed. Are you using transmission oil? A LOT of smoke that smells different than your 2-stroke oil? It an easy fix though, just the side cover, PV governer, and primary pinion.

 

[buzzard]

Crankshaft seals can give a number of symptoms. The ignition side seal will usually make the bike run lean, as it only lets in air. The tranny side seal can let in air or tranny oil, making the bike alternately run lean, then rich. It's position sensitive, and sometimes tempurature sensitive. Jetting a 2-stroke with a leaking crank seal is a lesson in futility.
Replacing the tranny, or right hand seal doesn't require engine removal. It does require removal of the brake pedal. I think you could actually remove the right side cover without pulling the water pump cover, but it is a good chance to inspect the impeller. You might need three gaskets, a new seal, and there is an o-ring that goes in there on the crank, right up against the crank bearing I think. The clutch and pinion gear have to come off. As someone else stated, you will need a 30mm socket. The clutch nut is rh thread, the pinion gear nut is lh thread. I just laid my 250 over on it's left side to work on it, this keeps things from falling out onto the floor, and gives a better view of what you are working on.
My parts just came in the mail, I haven't installed them yet. I'll let you know how it works out.

 

[MattR]

Buzzard,

If you have access to a digital camera, it would be great if you could take a few pics of the installation process. We are always looking for new technical articles to add to our database.