Importance of rubber sheaths in cylinder studs

[millosman]

Hi everyone,

I'm hoping someone could help me please.

I have a '92 fj1200 which has starter clutch trouble so having pulled the motor out I am in the process of dismantling it to get at the starter mechanism.

I struggled today to remove the cylinder head due to corroded cylinder studs. Having got the head off I can see that 5 of the studs have got partial brittle remains of the 'rubber sheathing' left on them.

How important is it that these studs have this sheathing present? IE do I need to replace these studs or just clean them up and re-use them without the sheathing on?
At £12.50 ($15) each, they ain't cheap!

Many thanks for your advice

Andy

[aviationfred]

No need to replace the studs. Break away as much of the brittle stud covering as you can. When I rebuilt my engine, I used a bit of Scotch Brite to remove the surface rust. I the used VHT high heat black paint sprayed into a cup and a paint brush to coat the studs with paint. When you have your repairs done, reassemble as required.


Fred

[millosman]

Hi Fred
Thanks for your reply.
I'm wondering what these stud coverings are for. Are they to damp down noise from the barrels vibrating and maybe making a ringing sound?
Could they be substituted with something like heat shrinks or would the motor get too hot for those I wonder?
According to parts diagrams only a few of these studs have the covering on them.
Anyone got any other comments to make?

Cheers
Andy

[RPM - Robert]

They are for aesthetics. On the 1200 barrel the stud can be seen. The later XJR1250/1300 they could not be seen. None of the new studs (they have superseded to new part numbers) that you can buy, have them, unless you find old stock/old part numbers

[millosman]

Cheers Robert. Now I understand. That reason had not crossed my mind!
Many thanks.

[CutterBill]

I suspect that the rubber coating was for (1) aesthetics and (2) to dampen vibrations in the long studs (think guitar strings.) Yamaha probably eliminated the coating because they discovered (1) the vibration wasn't a problem and (2) they trapped water and caused rust. Like Fred said, clean the rust off with abrasive pads and paint.
Bill