Author Topic: Head Gasket Sets  (Read 542 times)

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Offline CrouchyUK

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Head Gasket Sets
« on: August 16, 2019, 05:46:43 PM »
My latest offering to keep my own and your bike running!

First the back story....

Yamaha really struggled with gaskets on these bikes from the very beginning- way back in 1973, and even following their attempts to solve the head gasket problem through Service Bulletins, Workshop Manuals and Parts Lists can take some effort.  We have been restoring and maintaining these bikes for years and finding a reliable head gasket solution has always been a problem.

What many do not realise- especially the pattern gasket set makers- is that the head gasket system on these bikes finally evolved into a total of 4 separate components- none of which are available from Yamaha today.

On the first TX500 the head gasket was a simple fibre gasket (371-11181-00) that was prone to leakage of both oil and gases -despite being re-designed early in 1973 TX500 production to become 371-11181-01.  It was again changed midway through the 1974 TX500A run to end up as 371-11181-02- the final gasket designed for the early 2 piece heads up to the end of XS500B production.  Many pattern gasket sets have a copy of this style of gasket and claim that it is suitable for the whole range.

When the 1976 XS500C was produced with the one-piece cylinder head, a new gasket (1A8-11181-01) arrived that required additional parts to seal it.  Yamaha were still plagued with oil leaks, so their best effort was to come up with a special rectangular metal/rubber seal to be inserted around the camchain tunnel and fit inside a larger cutout in the gasket.  This new seal was given the part no. 1A8-11357-00.  Again, some pattern gasket makers have copied this later gasket- complete with the larger cutout around the camchain tunnel- but without including the important metal/rubber seal that fits inside it.

At the same time on the XS500C 1A8 type gasket Yamaha also introduced another 2 seals on the left side of the head.  These were given part no. 1A8-11358-01.  There were 2 of them required and they were O-rings that sealed the two circular oil return ports- they also fitted inside larger cutouts in the new 1A8 gasket.  Again- I have seen copies of the gasket that have the larger cutouts- but no seals appear in the kit.

At some time in the XS500D production in Europe- probably later for the XS500E in the USA- Yamaha produced the final and best design of head gasket and gave it part no. 2F1-11181-00- itself later updated to 2F1-11181-10.  This was a reinforced composite gasket with metal "flame" or "fire" rings around the cylinders.  This gasket retained the use of the rectangular metal/rubber seal and O-Rings of the 1A8 gasket.  Again- if you can find OEM or copies of this gasket- they never seem to have the other parts required for the gasket to seal properly as designed.

End of back story- anybody else have any information as I am sure Yamaha played around with the design more?

About 10 years ago- when I was building up my own XS500 collection and looking long term for spares to maintain them- I managed to acquire quite a number of the metal/rubber seals almost by accident.  Brand new Yamaha OEM still in bags.  At the time I don't think I even appreciated what they were and how rare they were.  When I did- of course you need both the main gasket and the other O-rings for them to be of any use!

I have finally had a batch of the 2F1 design head gaskets made from an original Yamaha pattern.  These are the same reinforced composite material, with copper fire rings and the larger cutouts to accept the extra seals.  I have added a Rectangular Insert to this, and also 2 O-rings to complete the set.  This gasket set is correct for the whole range of TX500 and XS500 1973-1980, fitted with either design of cylinder head.  I reckon these are the only sets like this in existence and I have extra!

I have them on Ebay for 44.95 for the set.  If any member wants a set- please PM me and I am sure we can do them cheaper here, as well as post them worldwide if necessary.  The kit is the gasket, the metal/rubber insert and the 2 O-rings.  Pictures below:-

1975 Honda CB200T (2) - 1975 Yamaha XS500B (2) - 1976 Yamaha XS500C
1977 Yamaha RD400D - 1977 Yamaha XS500D - 1978 Honda CB550K - 1980 Honda CB400N
1980 Honda CB900FA - 2000 Kawasaki ZX6-RG2 - 2002 Suzuki GSX-R1000K2