640 Adventure riders-Headbolt warning
I blew a head gasket in Mongolia this summer.
When I disassembled the head to replace the gasket I found the front and rear external head bolt nuts very loose.
The gasket blew directly above the forward bolt.
At the KTM festival I camped next to a big British dealer.
We were discussing this problem and he told me he had experienced 6 or more head gasket failures with his customers bikes for this same reason.
He now makes it a practice to re-tighten these bolts on the first routine service.
According to him once they are re-tightened they stay tight.
I know I am gonna check mine every time I set the valves.
A thin 15mm box end fits the nuts. It is impossible to torque them but the book calls for around 27 ft lbs. if I remember correctly.
If you check yours it would be interesting to know if any others loosened up.
BTW my piston looked great and very little carbon build running the BST 40 with stock jets, comp pipe and snorkel removed, hole enlarged 1 inch across the length. My bike runs strong.
I have the low low head-2002 640KTMa.
Last edited by Bill Shockley; 9 Oct 2007 at 11:12.