Improved head bolts

elefantrider · Friday at 10:30 AM

The CNC machine work on those bolts is very impressive.

concours · Friday at 10:42 AM

ashman said:
After 48+ years (1974 850 Commando motor) I am still using my original head bolts with copper head gaskets, I only retorque at 500 miles and leave it alone after that and have never had a blown head gasket and only once I had to retorque the head after getting a slight seep and it stopped, my last head removal I forgot to anneal the copper gasket and had the head torqued down before I remembered so let it be, but I had sprayed copper gasket sealant on it that was well over 15 years now (only retorqued after first 500 miles) and the head hasn't seeped or been retorqued since with over 35k miles on it, I have never had a copper head gasket blow completely out but had blown a fiber head gasket completely out that came with my Norton from the factory.
In fact all my motor studs and nuts are still original except the front centre barrel stud and nut and all my timing case and outer gear box case had the screws replaced with allen head bolts back in 1978 and are still using the same bolts today.
Maybe if using alloy barrels then maybe I would use the waste head bolts, but my head has been shaved and had major port work done but still running the original valves and pushrods with a 2S cam grind and 40thu over size flat top Hepilite pistons and balanced crank, been built this way since 1982.

Ashley
View attachment 116982

Where do I get the decal?

ashman · Friday at 1:04 PM

concours said:
Where do I get the decal?View attachment 117216

To be honest they been on there so long I can't remember where I got then from there are 2 the same one for each side of the tank on the other side I had paint lifting around the fuel cap so that is where the other side decal is covering the lifting paint, I could have gotten them from a swap meet over 20+ years ago, they look great and stopped the paint lifting, the paint on the tank has a lot of battle wounds/scares, there are chips and a few small dents at the front of the tank and scratches here and there, it was painted 2 years after the great fire of 82 so the paint job is 40 years old and still looks good for the years it's been on the road.

Ashley

marshg246 · Friday at 1:45 PM

jseng1 said:
The JSM bolts are triangular because that cross section shape is stronger than just reducing a cylindrical bolt to a smaller diameter. The triangular shape still has the original diameter at the tips of the triangles and so it resists twisting more than a bolt which is simply a smaller diameter. The triangle shape also keeps everything centered in the round bolt holes and that allows for reduced shank studs.

Reduced shank studs (triangular)

What is the threaded length of the three studs, head end?

Improved head bolts

elefantrider

concours

ashman

marshg246

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