INVADER 340 CENTER CRANK SEAL?

[IraqvetUSMC]

I plan on changing the crank seals this summer on my 340 and from previous threads it is stated that the center crank seals do not need to be replaced. I am assuming it is a lot faster to change the outside seals rather than splitting the cases to r&r the center seal and to change them only if it's needed. My question is, is their anyway to tell if the center crank seal needs to be replaced?

Thanks

[gixxer6]

I have never seen a center seal need to be replaced.  I wouldn't worry about it. 

You will need to split the cases to change the outer seals.   

[IraqvetUSMC]

That sucks lol, I was hoping to not have to split the cases as I have never worked on a small 2 stroke engine before. Should I use Yamabond as the sealer to seal the cases backup or is their something you have used personally that would work just as good that I could pick up at the local parts store?

[Interceptor398]

I have use Yamabond and have no complaints.  Splitting the case is really not as hard as it sounds.

[mswyka]

The center seal cannot fail.  Let me repeat that, the center seal cannot fail.  Failure of center seals is one of the myths that seems to continue to perpetuate itself.  However the center seal does not actually seal against the crank.  It is a compression seal that has a series of grooves that traps the compression wave before the wave can pass from one cylinder to the other. 

You should still split the case to change the outer crank seals.  Although I have heard of people pounding them in from the outside without splitting the case it is not recommended.

[IraqvetUSMC]

Thank you for the knowledge guys. From what I read online crank seals seem to be a big issue and it is stressed to replace them so thats what I am going to do. I want to get the sled dialed in over the summer so when the snow starts flying again it's all good to go. Once the seals are removed will the crank need to be cleaned up with something like a scotch brite pad or will that cause an issue with the seal possibly fitting loose on the crank. I would assume some guys try to use a seal pick to pry out the seal and find a deep well socket with the closest circumference to drive to new seals back in. Other than crank seals and carb seals are there any other seals or gaskets that are recommended being replaced if the sled hasn't been gone through before?

[JDmatt]

You should inspect the crank while you have the case split, make sure all the bearings are good, and make sure there are no metal shavings in there.

There is a great post here somewhere that lists everything you should to to strive for a reliable riding sled, take a look at that.   

[IraqvetUSMC]

Sounds good, I will go on a search for that thread.

[rminier]

  2 great posts by "Trucker" in the Tips and Tricks section.
 One entitled "Tips and tricks for removing clutches and flywheels"...the other "Crank seal replacement for dummys"
  Both very helpful to read....you have all summer, so there is a lot of help on here if you hit any "snags".

[IraqvetUSMC]

Thanks bud, I picked up the sled late in the winter and I only had one chance to ride it so I am already excited for next year haha. I will check those articles out for sure.

[jimvw57]

Number one item on these sleds is to replace crank seals, No 2 is to make sure cross shafts in the track suspension are greased and not bent.  Plenty of other small things go with these but those two are the major ones.

If you can get a shop manual, the front section has a lot of information on how everything works and lots of theory of operation stuff.  Great way to understand how and why these sleds are so quick and fun to drive.

Get everything back to stock condition and don't worry too much about trying to tweak it for modified performance. Kawasaki did a great job of making them fast and reliable.

[IraqvetUSMC]

I am looking forward to tackling the crank seals, it sounds like a good summer project. I think I am more excited to change the crank seals because I have to pull the engine and I can get in there to clean all the crap out of the belly pan haha. I know you can go to vintagesnow.com and they have old sled manuals there. They have a service manual for a 78 340 Invader, I would assume not much was changed between 78-79 and that I could go off the 78 manual but I may be wrong as I am new to all this.