Topic: Worth replacing cylinder studs?

[zabzob]

I've got my engine apart for the second time, and I'm thinking about replacing the cylinder studs. How necessary is this? Head didn't leak when it went back together the first time. I foresee a future in which I have a broken an old cylinder stud and have to make a trip to the machinist...

I'd be looking KPMI studs if I did it, I think.

[SF]

Cheap upgrade for 40+ year olds already stretched


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[camshaft1991]

Yeah for sure, if you can find a set made for your bike. It may not be noticeable by eying it but old studs are stretched and sometimes twisted from all those years under torque and more so on high mileage bikes. Some bikes don’t have crankcase studs available as set and individually hunting for them can be expensive and time consuming. That would be the only reason not to replace them. If you rebuilt your entire engine or top end, then it’s one more thing not to worry about. You could  also anneal your copper crush washers for your cylinder head or you could buy new ones. Some things can be replaced some things can be hard to replace and some can’t be replaced.


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[calj737]

Spring for a new set of HD studs and nuts. You’ll be glad you did later. But take your time removing the old ones.

[SF]

ARP


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[zabzob]

Are the HD nuts necessary? I can see stretch happening in the studs, but wouldn't the nuts be fine?

[camshaft1991]

Maybe metric 8.8 nuts or 10.9? Find out what grade the studs are.


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[PeWe]

Stock bore and compression?  No need of HD studs if your old look fine.

I have HD studs (kibblewhite) in my K6 since it has higher compression and my old had been torqued with 21. 6 ft lbs 28Nm several times in the 80's.
My K2 with stock bore+ pistons got it too (APE studs) since the block did not have any studs at all when I got it.

The K6 got forged nuts, DIN 6331 flange/collar nuts. Forged 10.9 grade.
Search DIN 6331 and you'll find.  This is a std nut.  Buy them cheap and sell them in 16 pcs package with a magic name for + $100US
M8   
18mm - outer diam
12mm - total height 
13mm tool
Flange is thick, can be grinded down a mm to get more threads left of the stud. I have not grinded mine.

I have torqued stock nuts 20.6 ft lbs several times without any issues, mostly with stock studs
My K2 has Honda stock nuts since I torqued it less.