Top cylinder slightly leaking

[Helmetbox]

Sounds like your leak is at the inboard side of the head cover gasket. Is that correct? If it is, there are four things that could have caused it:

• Gasket improperly installed.
• Rubber heat mat (or other foreign matter) pinched between the top of the head and the gasket. Lots of us have done this, myself included.
• Somebody applied sealer to the entire gasket and left gaps. The only parts of the gasket that require that are the two semicircular parts you see in the picture.
• Spontaneous gasket failure. Very, very unlikely.

As I said earlier, these gaskets aren't wear items and one set will last the life of the bike if not abused when removed or installed.

--Mark

Thanks for the advise.. As i have broke one of the screw... hopefully when the shop reopen tomorrow and they have stock on hand. Will just torque down a bit more say 8ft.lb instead of 7 and monitor again. Not serious as the leakage is mirror.

I guess the second cause is the most likelihood that casues the leakage. How should that be fixed? Replaced the gasket?

 

[Blrfl]

Thanks for the advise.. As i have broke one of the screw... hopefully when the shop reopen tomorrow and they have stock on hand.

Good luck with that. They're ST-specific items

Will just torque down a bit more say 8ft.lb instead of 7 and monitor again.

Don't torque the head cover bolts down to any more than 7 lb-ft. They have a flange at the top of the threads that stops it at the cylinder head. Adding more torque will, as you found out, only put stress on the bolt and will not apply any more pressure to the head cover.

Whatever wrench you were using isn't the right one for the job. Get one that is or there will be more damaged fasteners in your future.

I guess the second cause is the most likelihood that casues the leakage. How should that be fixed? Replaced the gasket?

Don't guess. Inspect it, find out for sure what's causig the problem and correct it. Remove the head cover and inspect/clean all mating surfaces. If sealant has been applied to the gasket anywhere but the two half-moons on the front, I'd replace it because getting the ribs inside it clean will be difficult.

I left out one other possible cause: If the head cover bolts weren't torqued down in the right order, the pressure on the gasket won't be even. All of this is covered in the service manual.

--Mark

 

[Helmetbox]

Good luck with that. They're ST-specific items



Don't torque the head cover bolts down to any more than 7 lb-ft. They have a flange at the top of the threads that stops it at the cylinder head. Adding more torque will, as you found out, only put stress on the bolt and will not apply any more pressure to the head cover.

Whatever wrench you were using isn't the right one for the job. Get one that is or there will be more damaged fasteners in your future.



Don't guess. Inspect it, find out for sure what's causig the problem and correct it. Remove the head cover and inspect/clean all mating surfaces. If sealant has been applied to the gasket anywhere but the two half-moons on the front, I'd replace it because getting the ribs inside it clean will be difficult.

I left out one other possible cause: If the head cover bolts weren't torqued down in the right order, the pressure on the gasket won't be even. All of this is covered in the service manual.

--Mark

Hmm.. Thanks for the advice... Perhaps I should just replaced the gasket since I'm already there..

 

[Don B]

Don't torque the head cover bolts down to any more than 7 lb-ft. They have a flange at the top of the threads that stops it at the cylinder head. Adding more torque will, as you found out, only put stress on the bolt and will not apply any more pressure to the head cover.

Whatever wrench you were using isn't the right one for the job. Get one that is or there will be more damaged fasteners in your future.

I left out one other possible cause: If the head cover bolts weren't torqued down in the right order, the pressure on the gasket won't be even. All of this is covered in the service manual.

--Mark

+1 everything Mark said about the head cover bolts. Once the flanges on the bolts contact the cylinder head, no amount of applied torque will compress the gasket any further. These bolts only need to be snug enough so they won't back out on their own, anything more than the torque specified in the service manual you are at serious risk of twisting off the bolt. My understanding is that the most likely place for one of these to break is at the top of the threaded portion, which means removal of the piece remaining in the head can be a challenge. I think it's OK to put a drop of blue LokTite on these threads when re-installing, so you won't need to worry about them getting loose on their own. Tighten them a little at a time in the specified sequence until the final torque (7 lb-ft) is attained.

 

[Helmetbox]

So sad.. My local dealer run out of stock for the screw.. It's cost me only about 3usd if they have stock.. Guess I have to pay 70usd for express shipping from partilza .com