Finally managed to get around to the Bundy Bike Hospital (Steptoes place) for a bit of a catchup today. Had a bit of discussion about the rally (Nymboida looks fantastic and top value too!) then set about finally getting stuck into 516, the flood victim.
Got the motor out and on the bench in about 1/2 an hour, then set about stripping it down, to the last nut and bolt in preparation for the cleaning of its life. Geoff will have detailed info on this in his thread about this bike, so I'll leave that stuff for him to tell.
When we lifted the head and inspected the pistons, he was surprised to see a set of big bore pistons looking at us, as he had rebuilt the motor only a few years ago using all NOS parts, including stock pistons.
He dug out his trusty verniers and measured the head gasket to see that it was 74mm in size and a quick clean of one piston crown revealed the part numbers that a search on the net revealed that they were a set of Wiseco 1179 pistons.
He then pulled out a head gasket that Bryan had donated to Geoff, as his bike had a big bore kit fitted and a stock gasket was of no use to him, which we then, out of curiosity measured to find that it had a bore size of 74mm. What the
A standard size bore is only 71.5mm so why was this gasket so large?
I told Geoff that seeing I had a new standard gasket set (cheapie) and another one that came with my yet to be fitted 1196 kit, and a set of digital verniers, I'd take Bryans along with me to check the sizes out and post them up here in case anyone else had come across this.
So here's the results (not guaranteed 100 percent accurate as they are budget verniers, but are close enough for this purpose)
^ the three subjects ready for inspection
^ My budget gasket kit came in at 73.05mm ( I got a more accurate measurement when i wasn't trying to hold the camera)
^ My big bore gasket measured 76.00mm for the 1196 kit
^ Surprisingly, the stock Athena gasket supplied by Bryan measured 74.05mm, which would actually fit an 1179 kitted motor.
I don't suppose anyone would have an unused genuine Yamaha head gasket they could measure to compare dimensions?
