CYLINDER BASE LEAK

[t140bonnie]

I just did a total engine rebuilt on my 1979 T140D Special due to an oil pump failure that lead to a crank shaft problem. Everything is back together now and it runs great, except for a oil leak around the base of the cylinder. Anyone have any ideas? New gaskets, and everything was cleaned well. I am stumped.

[TBS]

It probably is a pushrod tube seal. If you stuff a small piece of tissue at the back of the tubes so that it is tight, go for a short run and see if the oil has soaked the tissue. Otherwise it's the base gasket. I always use Wellseal jointing compound. If you do have to lift the barrels, remove the studs and make sure the studs haven't pulled up the ally around the hole by gently dressing the area with a fine file. Stuff the cases with rag, you don't want any ally swarf in there.


ww.thebikeshed.net

[mitch]

o dear, I have had the same problem too! remove the barrels,
very carefully, check the tappet blocks for any damage (where the pushrod seals fit) replace the tappet block 'o' rings, make sure everything is cleaned with thinners.

fit a new base gasket using Hylomar on both sides, refit every thing, run the engine untill it is hot, let it go cold overnight, retighten base nuts, cylinder head bolts, presto no oil leaks.