Looking at drawings, the Merlin doesn't appear to have anything like what we think of as a cylinder head gasket. The attachment of the head to the block is quite interesting, squeezing the flange of the top hat liner between the head and the block.

Is Yamabond a relabelled Threebond (of which I think there are a few versions)?

In the 1970s, 'trike' was the universal cleaner. We used it a lot especially for delicate instruments.

 

Yamabond is a product developed by the Yamaha Motorcycle Company in Japan. It comes in a number of grades. Yamabond 4 non hardening is the favourite amongst the racing fraternity. When fully cured it's slightly elastic. When you wish to separate the casings with zero gasket it just peels off.

Honda makes Hondabond but it's not a patch on Yamabond. We used Yamabond on all our bikes in our Honda Racing Team that I ran for over a decade on top of my job. Expat assignment put an end to that but the plus was seeing many MotoGP & F1 races live. I had a very understanding boss who knew how to get the best out of his people. We would never let him down. The finest Manager I have ever worked for.

You would spend 13 weeks in China & get a call from him saying I've changed your flights. You are booked into the Waikiki Sheraton for the next 10 days. Hire a car ~ Enjoy! ~ I don't want to see you anywhere near the office. He is married to a Japanese lady from Okinawa. Yoshimi allows him plenty freedom as long as she has a Cadillac & a credit card. Retired to San Diego. We stay in touch. Refinery Engineer by trade with a brain that exceeds the vast majority. Scholar of Purdue University. Chairman of our Singapore & Hong Kong operations at various times. He was in Dallas by the time I worked for him. With him would better describe the relationship.

 

Glyn: Would you use Yamabond for something like the oil pan to block, or timing cover to block on the XK engine? Would I have to go to a Yamaha motorcycle dealer to buy it?

 

Yes I would as long as things fit properly. Not for ill fitting parts unless you have a gasket as well. Then the benefit is little chance of leaks & easy removal. Yamaha dealer is the only outlet in most countries.

It is really for perfectly fitting parts with zero gasket and slight movement possible.

 

Would you prefer Yamabond over a conventional pan gasket?

 

No. A conventional pan gasket is there to accommodate certain irregularities in both surfaces. Only use on perfectly mated surfaces like gasket free 2 stroke racing engine casings where slight movement is possible. F1 engines have similar tolerances.

It is not Permatex gasket maker. Formagasket or whatever it is called today.

 

We sure have come a long way in gasket and sealing technology since my motorcycle days in the 1950s.
The only way you could stop the typical 1950s English motor bike leaking oil was to liberally coat all gasket surfaces with "STAG" jointing compound which I think was originally intended for steam pipe sealing.
Cheers

 

As Bill says things have advanced, but some of the advances are not always well known. Yamabond, Threebond and various ***bonds are well known in the old motorbike world, but much less amongst classic car owners and restorers. The same goes for very good corrosion protection like ATF and XCP.

 

British Bikes were horrors for leaks. Then Honda produced the K0 ~ CB750, electric start & all & showed them how to do it. Not a leak in sight. Soichiro Honda's earlier efforts did not leak at all either. Amazing considering what a young company they were at the time.

I mean who want's electric start when you can suffer kick back that would nearly break your leg.

By 1959, Honda was the largest motorcycle manufacturer in the world. The vision of one determined man who started life making rings.

 

Yes, I'd never heard of them until mentioned here. I have usually used the various Loctite products instead, like the 518 Flange Sealer.

 

Re the Honda motorcycle;
I rode one of the first ones brought to Australia. It was a Honda Dream and had a two cylinder 300cc engine. I was a member of a competition motorcycle club ( scramble, dirt track and circuit racing) . One of our members was head mechanic for the local BSA agents and he brought the Honda to a club meeting and invited everyone to take it for a spin. We all agreed it was "OK" but would never replace a real British bike like AJS, Matchless, BSA, Norton, Triumph etc. Anyway the foot gear change lever was on the wrong side ! Then a Honda 4 cylinder 250 CC racer appeared the same year and wiped out all of our clubs local circuit racers including Manx Nortons, Velocettes. We all had to eat humble pie .

This drifted away from the previous head gasket story but I hope we can acknowledge the improvement in engineering ,design and lubricants since our cars were first made and incorporate them as much as possible to preserve them for the future. I think a modern "Payen" head gasket will be OK.

 

Yes Bill, We had the RS 250 twin race bikes in our team in the '80's. We creamed everyone ~ but could not afford to run the 500's ~ a blessing as we were running the road bike classes as well. I was at Kyalami the day Freddie Spencer raced both the RS 250 & RS 500 V3 (one cylinder down, 2 up) back to back. He literally jumped off one bike and on to the other. Alas Lawson just pipped him that day by a hair's breadth. Freddie was world champion in both classes that year. He was a pleasant chap. A pleasure to look after for the week ~ extremely humble. 1985 feels a long way back today.

 

Since the compression measurement spreadsheet didn't include the 3.4 engine for the head on case, I've added it. I'm not very good with spread sheets (and don't like them) and have done only limited testing of my modifications, so there's the usual disclaimer: use at your own risk.

 

Yes, the spreadsheet was developed for E Types, so the only options were 3.8 or 4.2.

 

If you do need a different headgasket, Terry's Jaguar is the place to go. They have the Cometic MLS gaskets in various thicknesses up to 0.120" thick. They are excellent gaskets that seal well. I have used a few of them and it saved blocks that have been decked aggressively and had a lot of metal removed.

 

In many ways the British manufacturers were stuck in the dark ages, to a large extent due to lack of capital as much as imagination. Still, there's something special about a Featherbed Norton (or even a well set up Commando) on a twisty road. And I remember the performance of my cousin's old Vincent as quite incredible, especially considering its age.

The four cylinder Norton never came to reality because the company couldn't afford to buy new machine tools. They would have had to use their old machines and work one bore at a time ... .

 

Peter. The new British Triumph motorcycles are world class. One Brand that has dragged itself out of the swamp. They can rub shoulders with the best IMHO.

Alas more & more they are being manufactured offshore.

 

Glyn, There are a lot of good lessons in the Triumph revival. Learning from your competitors, but not copying. Taking time over development and not rushing into production. Making quality and reliability a priority. Major capital investment in manufacturing without going to UK financial institutions. Maintaining DNA and traditions. John Bloor did with Triumph very much what John Egan wanted to do (and partially achieved) at Jaguar.

 

Indeed.

 

My new set of graduated cylinders arrived and I made my measurements this afternoon. 3.445 for the bore (just bored 0.020' over), flat of piston to deck is 0.006', volume with piston 1" down is 130cc and the combustion chamber is 99cc. Throw this all in the sheet and you get 9.02 with the std tin gasket and 8.72 with a 0.035 gasket. I guess I am a little surprised since both the head and block had material removed.
93 octane (R+m)/2 is readily available. Is a 9.02 compression acceptable? I'm still a little concerned with sealing with the std payon gasket. It the copper head gasket spray a good or bad idea?
Thanks again for all the input!!