Folks,

I happen to have the cylinder head off for some work... my 1995 K75 has the Torx T50 cylinder head bolts.  They came out this morning without problems.  All their threads look to be in good condition under visual inspection.

My K75 has fewer than 14,000 miles.  I am the 3d owner, and more than half of its miles are under my ownership.

So, question - should I re-use these bolts, or pop for new ones?  In car engine rebuilds, the sage old-timer advice is to "always use new cylinder head bolts".  I have several weeks before I have to decide...

Note: there is nothing mechanically wrong with the cylinder head... this is a horsepower improvement vanity project.

Comments are welcome.

Thanks!

I would use the original bolts. 

I don't think the BMW workshop manual says to replace with new, but can't count on my memory.

Assuming they're all the same length, I would replace any that are 0.3mm or longer than the shortest one. Anyway that's what I used to do with my cars, back in the days.

Even if you do have to go back in, it's not as hard as with a lot of other makes, but I don't think you will have to.

Re-use. Don't have a manual to hand but in general, you should be doing a torque check after around 500 miles anyway. I have never, on any bike I've owned, had any problems with re-using cylinder head bolts.

DadofHedgehog wrote: this is a horsepower improvement vanity project.

I think brand new head bolts would fit right into a project like this. You could paste a sticker, Head Bolts by Bling Brothers on the fuel tank or fairings. 

What's the project?

Laitch wrote:

DadofHedgehog wrote: this is a horsepower improvement vanity project.

I think brand new head bolts would fit right into a project like this. You could paste a sticker, Head Bolts by Bling Brothers on the fuel tank or fairings. 

What's the project?

Haha - got a sticker? ;-)

Power project has 3 steps.
- K1100 throttle bodies (done).
- the new throttle bodies, half-shafted (done)
- gasflowing the cylinder head by BSK Speedworks (in transit).

daveyson wrote:I would use the original bolts. 

I don't think the BMW workshop manual says to replace with new, but can't count on my memory.

Assuming they're all the same length, I would replace any that are 0.3mm or longer than the shortest one. Anyway that's what I used to do with my cars, back in the days.

Even if you do have to go back in, it's not as hard as with a lot of other makes, but I don't think you will have to.

Good - thanks!

Just a point, i was taught to lube all head bolts clean engine oil is fine, Modern day pastes are available, this method improves toque accuracy, so i was told when i was a lad.

Lubricating with anti-seize would have prevented the breaking of one of the head bolts on my '92 K100RS.

A tiny bit of water coming down off the engine below the throttle position sensor was able to penetrate the head gasket and get into the threads of the head bolt. The resulting corrosion together with the torque on the bolt essentially welded the threads into the engine block.

Drilling a hardened screw out of an aluminum block sucks.

They are stretch bolts, wich adapts to the life in the head as long as it stays there.
BMW say use new bolts.

However, besides me, I know some people who reuse the old bolts, and haven't face a problem.
Saved some money to buy a beer afterwards to celebrate

Arlina, I agree. At $16.56US a pop you can bet that I'll reuse the old bolts. My '92 16 valve RS is still running nicely on it's old bolts 4 years after I put them back in after a head job.