UK Monster Owners Club Forum » .: Technical :. » Engines, Clutch, Gears » rear cylinder oil leak ??

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Old 20-03-2017, 11:21 AM   #1
jerry
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rear cylinder oil leak ??

750ss has had a complete rebuild ,, new base gaskets new O ring seals etc etc but there is a leak from head gasket except on these models there is no head gasket ,,

tourqed up correctly to 39 nm front cylinder is fine centre case gasket fine and base gasket is fine ,,,no orings left out so now im a little peeed off .. might tighten the head bolts a tad more to 43 nm ?????
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Old 20-03-2017, 08:16 PM   #2
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Hi Jerry, I had the same issue with my air cooled monster, Neil from Corner speed suggested using valve grinding paste to lap the head & barrel together - it works a treat, a bit of a faf if you've already built the engine and because of the exhaust manifold you can only rotate it a few degrees but it did the trick for me.
Good luck, having a bike in bits is all part of the fun ;-) isn't it?
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Old 20-03-2017, 09:24 PM   #3
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bike is all built up again and running ,, problem with 750ss is to get at rear head its engine out again !!!! though might be able to lossen off the head enough to lift it a few mm ???
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Old 20-03-2017, 09:44 PM   #4
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I don't think lifting the head a few mm would be enough to lap the heads together - you don't want any valve grinding paste getting down the bores! it will need meticulous cleaning afterwards, it gave me a very good result, perfect seal on the spigot & a lovely grey even finish around the head\barrel joint.
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Old 21-03-2017, 12:47 PM   #5
Dennis menace
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Back in the day I was told to just lap the head on a sheet of plate glass on my Royal Enfield Constellation because the barrels were iron and therefore would not warp like the alloy heads. Also, obviously no need to remove the barrel or grind them both in situ.

Can't guarantee that grinding the head only will work for you though.
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Old 21-03-2017, 01:08 PM   #6
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Quote:
Originally Posted by Mark64 View Post
I don't think lifting the head a few mm would be enough to lap the heads together...
Not to mention the studs being more than a little obstructive
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Old 21-03-2017, 05:39 PM   #7
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yes i ruefully fully agree with all above comments ,, will test bike again but i more than a little pissed off ,, head gasket surface was cleaned to perfection before new orings fitted , and methinks this is a very old problem , thought it was the crankcase centre gasket ,thats why the engine came apart and its the 2nd time i have carefully done the rear head in 3 years too but head jointing surface is not porous or any cracks visible ,, if i have to engine out its only a 2 hour job ,,

making me a bit worried now what the issue is
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Old 21-03-2017, 06:57 PM   #8
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...or any cracks visible...

http://m.ebay.co.uk/itm/Tygris-flawf.../252061121230?
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Old 21-03-2017, 09:05 PM   #9
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Not to mention the studs being more than a little obstructive
DOH! easy mistake - any fool could make it

Also forgot to mention I always used three bond on the head/barrel joint (despite everyone saying you don't need to use anything - it always worked for me) applied with a small artists paintbrush.
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Old 22-03-2017, 07:33 PM   #10
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if it fails test ride later this week i will loosen off the head enough o raise it a few mm i think it will go 3-5 mm and clean the mating surface and smear in some 3 bond and also check the O rings , if it works then good ,,


if not its motor out again ,, front head joint is fine
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Old 22-03-2017, 08:46 PM   #11
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just had a look and I reckon there is up to 10mm clearance between top of cylinder head and the frame cross member and with some delicate gynecological skills who knows what is possible ??/
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