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oil leak at head gaskets -- warped barrels?

KnowFear

Cruisin' Guzzisti
Joined
Feb 2, 2011
Messages
103
OK, I removed the heads and barrels this weekend. Both head gaskets show signs of oil leaking from the oil return passageways via the head gaskets.

The heads had been machined flat during the rebuild, which makes me wonder if the tops of the barrels aren't flat. I'd better get them to a machine shop to have them checked.

Has anyone ever heard of warped Guzzi barrels?

Chris
 
KnowFear said:
Has anyone ever heard of warped Guzzi barrels?

Chris

No I haven't. If the heads weren't torqued along the way that could explain the issue. I once did an Eldorado that stopped running for the guy because it blew out the head gaskets (both sides) to the push rod tunnels. No compression, couldn't run. Fresh set of gaskets and o-rings and down the road she went.
 
john zibell said:
KnowFear said:
Has anyone ever heard of warped Guzzi barrels?

Chris

No I haven't. If the heads weren't torqued along the way that could explain the issue. I once did an Eldorado that stopped running for the guy because it blew out the head gaskets (both sides) to the push rod tunnels. No compression, couldn't run. Fresh set of gaskets and o-rings and down the road she went.


This
 
The head gaskets were not blown. Base and head gaskets, and all 12 o-rings, were recently replaced. After @ 300 miles and 6 or 7 heat cycles, the cylinder heads were re-torqued, yet the leaks persisted.
 
KnowFear said:
The head gaskets were not blown. Base and head gaskets, and all 12 o-rings, were recently replaced. After @ 300 miles and 6 or 7 heat cycles, the cylinder heads were re-torqued, yet the leaks persisted.

Should re-torque after the FIRST head cycle, then again at 500 miles. Most of the gasket compression occurs with the first heat cycle.
 
I will follow your advice this time around. However, having to do that after only one heat cycle still bothers me.

How many riders take their NEW Guzzi back to the dealer after ONLY ONE ride to get the heads re-torqued? So basically, you ride it off the lot, go for a spin and immediately bring it back to get the heads re-torqued?
 
Just as in new cars, new bikes don't need heads retorquing. On any engine rebuild however, car or bike, heads need retorquing after one heat cycle (some liquid cooled engines have special gaskets that claim not to require it, not available for Guzzi though). In the case of an alloy engine it needs to be done stone cold (left over night is best) and the valve clearances reset. I've never heard of warped barrels on a Guzzi.
 
OK, I'm making progress...

Just got back from the machine shop. The barrel tops are definitely distorted. The distortion is in the form of an irregular convex shape to the barrel top. Both barrels have the same problem. Maybe the PO over-torqued the heads? Who knows. Anyway, they probably need 3 to 4 thousands of an inch removed to get them flat again. The machinist will let me know how much has to come off.

Next question: do I need to add an extra base gasket to make up the difference?
 
KnowFear said:
Anyway, they probably need 3 to 4 thousands of an inch removed to get them flat again. The machinist will let me know how much has to come off.

Next question: do I need to add an extra base gasket to make up the difference?

Three to four thousands isn't much. A second base gasket is much more than 3-4 thousands. I wouldn't think you would want/need a second base gasket, but to be safe, I'd put the jugs on with the old base gasket and put a thin layer of clay or putty on the pistons. Then place the head and rockers on with the old gaskets. Snug everything up then turn the engine over by hand. If no impressions in the clay from the valves and the pistons don't contact the head, then you should be good to go. Put her back together with the new gaskets and o-rings.
 
UPDATE: I had a few hours last weekend to re-install the barrels/heads. Today I went for the first post-assembly blast, and NO oil leaks! Yahooo! Now on to the next project...
 
The machinist removed @ .010" from the barrels. Seems fine now. I will update again after a few heat cycles.
 
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