Piston bottoming out

[Magalluf]

Hi all

I have a Mugello 186 which I have fitted with a Mecure 60mm crank. I had to dremel the case a bit to get it to turn smoothly as it was touching slightly. Now I have mounted the piston I see it is touching slightly at BDC is it just a case of shortening the piston a bit or is it more serious.

cheers

Steve

[camel]

so you have increased the stroke of the crank from 58mm to 60mm....ie an extra 2mm......so half the difference which is 1mm.....that is the size of the packing plate you now need for under the barell...in theory.

[cezeta]

you will need to take a bit off the piston, next time use a 60mm crank with a 110 rod

[Magalluf]

Hopefully after shortening the piston skirt there wont be a next time. It´s easier and safer with a 58mm

cheers

Steve

[Minority]

so you have increased the stroke of the crank from 58mm to 60mm....ie an extra 2mm......so half the difference which is 1mm.....that is the size of the packing plate you now need for under the barell...in theory.

That would fix a potential problem with the piston rising above the cylinder at TDC, but would do nothing to stop it hitting the casing at BDC .

[Knowledge]

Good point Minority.

If you cut the skirt, you will alter the inlet timing (Mugello has piston controlled inlet timing, I think....). This might be to your advantage, but too much inlet timing compromises bottom end performance (though top end can be FUN).

[Minority]

But I guess the 1mm packing plate would raise the inlet port which may compensate for trimming the piston in terms of inlet timing.

[camel]

so you have increased the stroke of the crank from 58mm to 60mm....ie an extra 2mm......so half the difference which is 1mm.....that is the size of the packing plate you now need for under the barell...in theory.

That would fix a potential problem with the piston rising above the cylinder at TDC, but would do nothing to stop it hitting the casing at BDC .

quite right
i stand corrected