Blinking twin head gaskets!

lawrence · Post by **lawrence** » Wed Mar 30, 2005 11:40 pm

quote:Originally posted by Eric Brooker March 2003

If they are the ones from Jampot Spares they go either way. You must follow a regime of pulling down the head (COLD) after running for 1, Just a warm up, 2 A short run of a few miles, 3, A longer run or runs up to about 50 miles. 4, Another 500 miles. Don’t go overboard by over-tightening to cut this procedure out as the studs can fail quite easily.

Grrrr! A head gasket has blown on my twin. I took it up to 65mph for the first time and whoosh it went. The offside gasket has blown on the narrow section between the heads and it is clear that the other gasket is soon going to go in the same place as it is starting to protrude and show its wire reinforcements.. This is disappointing as;
1. I followed Eric’s procedure to the letter, checking them in fact more frequently.
2. The bike has only done 1400 miles of fairly gentle running.
3. It has standard compression pistons fitted not the usual CSR high comp.

The joint faces are clean and level and they were kept at 16lb/ft (5/16" studs). I thought about making a pair of gaskets from copper sheet (i.e. similar to the single head gasket. Anyone have any suggestions or experience of overcoming this problem? Would the solid copper gaskets work?

Help!

Lawrence [}:)]

Biscuit · Post by **Biscuit** » Thu Mar 31, 2005 12:41 am

I'd get shot of that thing Lawrence!

The book says 18lbs/ft.,{page 161 -G9) before I fitted HTS studs, I took the standard studs up to 20lbs/ft, if you don't have the'feel' stick to 18lbs/ft. With the HTS studs I tighten to 26lbs/ft. When 're-torqueing' are you slackening the nuts off initially to overcome 'stiction' Do this diagonally.

Merlin · Post by **Merlin** » Thu Mar 31, 2005 10:50 am

Alan not wishing to be too thick can you explain stiction cheers[:I]

Biscuit · Post by **Biscuit** » Thu Mar 31, 2005 3:23 pm

Stiction - a combination of STicking an friCTION. At the atomic level particles migrate from this to that giving rise to a transistory bond, causing the nut to stick to both the stud and the spacer. It is necessary to break this bond to get a correct torque reading. Pity it is not April the 1st.

Merlin · Post by **Merlin** » Thu Mar 31, 2005 5:36 pm

Pity you are not on call my bluff Alan[:D]

lawrence · Post by **lawrence** » Thu Mar 31, 2005 9:16 pm

quote:Originally posted by Alan Jacobs

I'd get shot of that thing Lawrence!

Methinks you are probably right Alan but it is such a nice bike to ride when it is going well. Apart obviously from the useless front brake, the anachronistic handling, the oil leaks, the 'wrong way' gearchange..................[:)]

quote:Originally posted by Alan Jacobs
The book says 18lbs/ft.,{page 161 -G9) before I fitted HTS studs, I took the standard studs up to 20lbs/ft, if you don't have the'feel' stick to 18lbs/ft. With the HTS studs I tighten to 26lbs/ft. When 're-torqueing' are you slackening the nuts off initially to overcome 'stiction' Do this diagonally

The manual I have, the big red one, says 16lb/ft but I think I will try 18. No, I haven't been slackening the nuts. That is the first time I have heard that. I will try it. Thanks Alan. You are, as always, a gem.

Lawrence [}:)]

Duncan · Post by **Duncan** » Thu Mar 31, 2005 9:45 pm

Lawrence

Commiserations, Rik Gibbon can supply ready made copper head gaskets with “O” rings for the oil ways, more expensive than the normal ones but can be reused making them environmentally friendly.

If you look in the “Technical” section on the site under “Twins – Head Gaskets” there is a drawing you can use to make your own.

Regards
Duncan

Biscuit · Post by **Biscuit** » Thu Mar 31, 2005 11:32 pm

That's the manual I was looking at Lawrence, were you looking at page 161? What you need to do is to swap it for '56 G11, this has all the correct attributes, Jampots, Chronometric speedo, a dual seat designed for the bike, not looking like an after thought and a dignified and restrained finish. Most pundits reckon the 600 is the smoothest motor of the three. Oh, and it does not blow head gaskets.

Biscuit · Post by **Biscuit** » Fri Apr 01, 2005 12:04 am

A further thought Lawrence, if you keep the gaudy 'orror, the next time you retorque the nuts, do as you have been doing, ie retorque without slackening, note where the nut is, make a mark or summat, slacken off and then retorque, you will be surprised how much further the nut turns.

lawrence · Post by **lawrence** » Fri Apr 01, 2005 10:08 pm

'Ere, I've been sold a duff manual. Mine only goes up to page107! That explains why the bike is so rubbish. And I was beginning to think it was my workmanship. Mind I was wrong once, thought I'd made a mistake but it turned out I hadn't [:D]

I think you must have the manual that covers models pre 1957 Alan? Mine states 16lb/ft and that did feel as much as the studs would like. When i stripped the motor two of the threads in the crankcase for the headstuds were stripped completely so I guess they are delicate?. I will try your trick on the other side as I haven't removed that head and see if it does make a difference. watch this space!!

Thanks for thr tip Duncan, useful to know.

Lawrence [}:)]