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head gasket issues

Posted: Sun Apr 03, 2016 5:01 pm
by gw
hi there
I have a 1954 Redditch bullet, which myself and my bro have stripped to the bones and rebuilt.
we followed all old manuals which came with bike for rebuilding and oil levels etc..
sadly the first time she was fired up, it started as a weep, which we fully expected, but once I took her down the road for maybe three miles, it became obvious the engine had been over filled with oil, it was pouring out wherever it could escape from.
so we put her back on the lifter, stripped her again and renewed all gaskets and seals and washers involved in the top end, all gaskets were coated with wellseal, which as far as we know is as good or better than most.
we then filled with oil, only to the first mark on dipstick, not the full recommended ..
the next day we fuelled her up, kicked her over, she started after a few kicks quite easily, probably once fuel had circulated.
on tick over there were no visible oil leaks like the last attempt.
so I took her out, had a good ride, maybe four miles..
but as I came back to my road she died.. no revs at all, I thought I had run out of fuel, but sadly once bro came over and asked me to kick it over again, he walked away saying its f....d again.
when I was trying to kick her over, smoke was chuffing out of head gasket.
so the moral of the story is..
do we use a copper or composite gasket next time, and is there any torque settings we should adopt, rather than just diagonal tightening manual.
also is there a secondary tightening process we are not a custom to, i.e. once first run up?
all comments gratefully received.

head gasket issues

Posted: Sun Apr 03, 2016 5:25 pm
by Gwilly
As can happen with motors with maybe mix matched parts, remove the head gasket and retighten the head..

Check with a feeler gauge the gap between the head and the barrel and make sure it is less than the thickness of the gasket..

Sometimes the spigot on the barrel is too high and needs machining down slightly to allow the head to compress the gasket fully..


head gasket issues

Posted: Sun Apr 03, 2016 5:30 pm
by PeteF
The composite gaskets are very good in my experience. The torque figure for modern Bullets is 22ft/lbs so in the absence of other information that might be a reasonable figure. As Gwilly says, check the spigot clearance.

head gasket issues

Posted: Sun Apr 03, 2016 5:50 pm
by gw
thanks for all your help
myself and bro are only self trained in this area
we both are, ex Japanese 50 cc up to 1100 riders
this is a different ball game
could you explain spigot clearance a bit more in depth please.


regards

head gasket issues

Posted: Sun Apr 03, 2016 6:08 pm
by papasmurf
Basically the spigot is the round turned bit that locates the cylinder head and barrel in position. If that bottoms before the gasket has a enough pressure on it to seal, oil will leak out.
It MAY be necessary to shorten the spigot for the gasket to work.

head gasket issues

Posted: Sun Apr 03, 2016 6:16 pm
by gw
so is two gaskets a good or dumb idea ?

head gasket issues

Posted: Sun Apr 03, 2016 6:20 pm
by Bet
Two gaskets doubles the amount of potential leaks, and also lowers the compression.

head gasket issues

Posted: Sun Apr 03, 2016 6:52 pm
by PeteF
If the spigot needs reducing it wont be much. You'll be able to take it off with some emery paper stuck down to a piece of MDF (or even better, a piece of plate glass or surface plate)

head gasket issues

Posted: Sun Apr 03, 2016 10:31 pm
by John M
When you re-assemble the head, take it for a short run and then re-torque the head bolts.

head gasket issues

Posted: Mon Apr 04, 2016 5:54 am
by Leon Novello
Sixty Two years, and the spigot and head gasket still haven`t been sorted out? SHEESH!