Center case seal

[motopsycho87]

Has anyone replaced the center case seal with yamabond or similar? Twice in 3 years I've had Athena center gaskets pop in different places, first was fit dry, second was copper-coated. Just wondering if anyone has used rtv like many other dirt bikes to any avail?

 

[Danj56]

Only time I've had a center seal pop on a motor is when I left this coolant in the bike that wasn't meant to be left in over the winter. Not saying this is your problem but there may be another reason case gaskets are going bad.

 

[dANbOT]

From what I understand, you shouldn't replace a center case gasket with yamabond or other anaerobic sealants. The gasket acts as a spacer, and you may pinch things too tight without it.
Where is it failing? crank case cavity, or trans cavity?

 

[motopsycho87]

Behind the water pump, pushed the gasket clean out. I'll try bolting the cases up with no sealant or seal and see if everything runs smooth, there's definitely some sideways slack on the crank, the gear cluster is the main concern

 

[motopsycho87]

Right, I've bolted it all up without a gasket to test if everything runs smooth. Crank and output shaft still have end float, input shaft does not, but turns freely. So I'm gonna grind a gnats cock off of the input shaft spacer and put it all back together with three bond 1184 (what is used on yz250s and other such bikes).

When you consider the degree of crankcase stuffing tuners employ to up power, if there is a benefit, the thickness of the gasket over the area of the crank should be a significant loss of unused volume...

Discuss... ANGRILY!

 

[dANbOT]

Good initiative, here's hoping she works out for ya!

 

[gasgasman]

No gasket will lead to serious issues when everything heats up and expands.

 

[Ignas]

I have assembled two bikes without center gasket, just regular sealant. One has 80h other 60h without any leaks after rebuild.
My friend assembled with center gasket and water leaks through it

 

[motopsycho87]

No gasket will lead to serious issues when everything heats up and expands.

Considering the linear coefficient of expansion for aluminium is greater than that of steel, if it fits cold, it'll fit hot.

 

[roostafish]

I like to use a gasket, but using some 3Bond on the gasket itself, just a micro thin layer seems to help an imperfect surface. If at all possible, I do prefer to use a dry gasket though for much easier disassembly.


Sent from my iPhone using Tapatalk

 

[Jacob 'Berg]

I had coolant leaking into the bottom end and subsequently the combustion chamber from the coolant passage in the front of the cases. I filed some material off of the mating surfaces around the coolant passage, as the surfaces were not dead flat. I then re-assembled the cases with a gasket and Yamabond ONLY around the coolant passage. No issues since then...

 

[motopsycho87]

Had it up and running with no gasket and threebond 1184. Put a dep header on also, sounds splendid with the FMF powercore 2!

 

[motopsycho87]

Gave it an almighty 6 hour thrashing on Sunday, no problems to report