Montjuic valve clearances

Lyndoneil

Lyndoneil

Full member
Location
Towcester uk
I am currently rebuilding a montjuic engine but need advice measuring the valve clearances
I have the 500 Alpino workshop manual, but not the rare Montjuic suppliment.
When I set the cams to the position for measuring as per workshop manual, due to the amount of overlap on the S1 cams, the cam lobes are already pressing down on the valves and there is no  gap at all, if I continue to turn the cams until the lobes are pointing upward and not pressing on the valves and measure at this point the clearances are between .30 and .40 apart from one which is .03, I know I am looking for about .20 on the inlet and .25 for the exhaust.
Just wondering if it is ok to measure the gap at this position
I think I have the valve timing about right, although I have come across varying degree specifications and am not sure whether  they are measured of the camshaft or flywheel or  both which might reflect the difference there was a post sort of on this in 2010 but it did not explore where to measure the valve clearence
 
Hi. I run a Monty race bike and to set the clearances i put the lobes pointing upwards (in theory maximum clearance) and measure there. I aim for 20 and 25 as per the manual. The PITA is changing the shims.
 
Hi Gareth, thank you  for the advice.I was hoping that I would be able to do it that way, just wanted to be sure  before I took the valve buckets out and started measuring.
Spent all  night having a nightmare about  camshaft studs pulling out, which is unsurprising given that I had on the exhaust cam, one re-helicoiled, one re-tapped  them found the other had been helicoiled, which was starting to pull out once I got to 2kg-metre of torque, I should take the head back to the engineering shop and have it re-helicoiled but I  don't want to take the head off again as the gasket won't stand it.
Strangely the inlet studs are fine.
I guess this is what comes of buying a Spanish import
 
Well, I'm sure I'll get shot down by the experts here but here goes.

The cam shells are held in place by 6 x 8mm studs and 8 x 9mm studs; the latter going down into the crank cases. I tighten them all to 15Nm in a criss cross fashion, then go up to 20. Then I go up to 25 for the 9mm studs only. These will stretch and will also pull out of the crankcases if you're unlucky, and helicoiling them is a PITA.

I have seen engines where the studs have been pulled up, and Loctited into position. This was done by pouring Loctite down the stud cavity and yes, we should all know that this is how the oil gets up to the head but the previous owner was oblivious to this fact. Luckily I spotted that the stud had not been set right and was now much higher than expected and when the cam cover was tightened down, it cracked (and there was an oil leak from the head as it wouldn't seal). This is why the owner sold the bike as he couldn't get it to stop leaking.....

Another issue to deal with is the orientation of the two "Spacers" (34 610 225) which can foul the camshafts, and when tightening can give false "I'm tight" readings, only to appear loose when the engine is rotated.

Good luck !

G
 
Hi Both,
The only thing I would add is I do the 8mm short studs into the head to no more than 18ft/lb approx 24Nm and the 9mm long studs to 28ft/lb approx 37Nm.

Andy
 
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