Piston Size

[mgelder]

Is my 350 the only 350 that's not at least a 375?

I'm beginning to feel left out

[EVguru]

Hmm. But these are brand spanking new 71 bore barrels with steel liners and factory wrapped with cast iron compression and oil rings.

I'd heard that the 501 was produced in both Iron liner and Nickel Silicon versions. What's the liner spigot diameter?

[EVguru]

Is my 350 the only 350 that's not at least a 375?

I'm beginning to feel left out

My engine is stock as far as I know and the 375 pistons only actually give you a 366.

[72degrees]

Is my 350 the only 350 that's not at least a 375?

I'm beginning to feel left out

No. I chose max oversize 350 Sport pistons for my Forgotten Era speed hill climb project engine rebuild. That way I can ride it in the 251-350 class with a clear conscience. It was a difficult decision because the FE championship is run with up to 400 and over 400 awards. A 375 or 400 would be eligible for the first but I'm not sure the extra go would make that much difference against the '280' YZ strokers. A 375 would have to be in the 351-500 open capacity class. In fact, I used to run the 375/2C under yellow plates. That puts it up against everything from CR500s to the latest 450 supermotos, which can be even more dispiriting. The 350 entries (and often 250) are pretty sparse, as a lot of riders are trying for a Top Ten run off place, which is very hard to do on anything less powerful than a modern 450. So by running as a 350, I get more chance of a ride at limited entry meetings and the chance of a 350 championship point or two. Then if this years Suberbike Classic TT is anything to go by I wouldn't be the first to run an oversize engine.

[MickeyMoto]

Then if this years Suberbike Classic TT is anything to go by I wouldn't be the first to run an oversize engine

Miaowwww!

[norbert]

Hmm. But these are brand spanking new 71 bore barrels with steel liners and factory wrapped with cast iron compression and oil rings.

I'd heard that the 501 was produced in both Iron liner and Nickel Silicon versions. What's the liner spigot diameter?

I do have a pair of brandnew 71 mm Sciam pistons that are not for Gilardonis/Nikasil cylinders (buyed them for 501 ). The bore for the piston pin is not at the same height as at 501 piston (and some other diferences). A friend of mine has a pair of this pistons as well, in a very old platic bag, and there is written by hand "Morini 500 Paris Dakar". The first Camels for the African Endurance races had a bore of 71 mm, because to do the desert races it was requiered more tha 500ccm. Obviosly the 501 Gilardoni set was a result of that experiences. Would be interesting to know the distance between the seelin surfaces of Harrys cilinders. The 501 cilinders are shorter than the 500.

ciao
norbert

[norbert]

The height of the cilinders between the sealing surfaces:
350 Gilardoni: 67 mm, maybe 67,1
501 Gilardoni: 86 mm
500 (478): ??? don´t have any, must be some mm more (2-5?) than the 501. Anybody knows that measure?