Think I have a head gasket leak, not sure but coolant coming out over overflow pipe on start up, bike has been stood for a few years. Now my first thought was to retorque the head. But can I understand the manual ? So tank off etc and I can see four big studs and nuts on top of the rocker box, are these the ones that I should retorque? I imagined that they would be under the rocker box ,
Help please, thanks Stephen
I can't remember, though I re-torqued the 604 more than once in vain hope of fixing the cooling system pressurisation. I suspect you will probably have to fit a new head gasket. I'm pretty sure the cam box comes off still attached to the head though, so those four nuts are the ones to try tightening. Beware of stretching the studs though.
"Do not adjust your mind, there is a fault in the reality" 1957 175 Sport
when i bought my Nordie i also had a slightly leaking head gasket.
But in my case the water moved to the outside of the cylinder.
So i added some Nm's to the 4 head nuts
In the end i used 40Nm if i remember right
No leaking since then.
Maybe its worth a try
But be carefull.
Years ago a Super Mono racer from Denmark has tested the original studs.
But i cannot find his numbers.
If i remember right he told that adding about 10% will cause no problems
Again be craefull. There's no waranty
If i understand right your problem is leaking gas into the water cooling circuit
Here around there have been 3 cases where Nordie riders had the same problem.
Maybe it's caused by a weak headgasket. Usually they had no problems, but squeezing the right grip very hard the motor blows gas into the cooling system. They lost liquid out of the expansion tank.
The idea was to replace the original head gasket by something from solid metal
I suppose Pete has some experience doing this
As I have 72degrees 604 big bore kit and knew about his sealing problems, I inquired from APE in the US about stronger studs, but they quoted me US$ 1000 so I did not go that route, I also bought fluorocarbon O rings with the idea of cutting an Oring groove around the cylinder bore and remove the gasket, Joachim knows some body in Germany who did this and gave me the idea, the Danish super Mono racer Joachim mentioned has bored his engine out to 650, I had some pictures of his engine with the bore size written on the pistons made (I think) by Wahle Kolben ??? going from memory Joachim will correct me.
Well, seem to have sorted the problem, touch wood!
Thanks for the advice guys and took it steady as suggested.
I could have drained the fluid and then undone the head bolts and retorqued, but just being lazy I ‘nipped them up’ a bit.Took three goes to stop the leak, no idea what the torque was as with nuts that have been in place for many years the first thing is you have to break through the corrosion before you get a feel for what’s going on! Anyway, it would seem that they are plenty strong!