Can anyone please help with this one?

I recently bought a 247 Cota with engine partially stripped. The engine came with a new piston (to be fitted) which according to the the previous owner is a Bultaco piston. Apparently this can be fitted to the Cota but requires a shim/spacer plate (also supplied with the engine) at the base of the cylinder barrel, presumably because the piston height above the gudgeon pin is different?

Anyway, my question is this.....has anyone else fitted a similar piston to a 247 Cota, and if so do you need to install a base gasket top and bottom of the spacer under the cylinder barrel?

Hope this makes sense

Cheers

Simon

Edited November 10, 200916 yr by Jamieson

Hi, i fitted an oversized bultaco piston to my 247 mont and i never used a base-plate. The piston was the same gudgeon pin height, if i remember correctly you put a window in the rear of the piston unless its all ready done and i did my own re-bore to size

Dave

Simon

Have you had any luck in sorting out your piston. I have a montesa Cota 247 and i am strugling to find a piston, (72mm dia + 50 required)

If you have sorted it out could you please let me have any details, ie piston numbers, and any modification you have had to make.

Did your piston have any ports in the skirts ?

Many thanks for your help

Beast regards John H

Hi, i fitted an oversized bultaco piston to my 247 mont and i never used a base-plate. The piston was the same gudgeon pin height, if i remember correctly you put a window in the rear of the piston unless its all ready done and i did my own re-bore to size

Dave

Sherpa 250 models never had windows in the back of the piston , but there

are 2 small holes at the front of the piston one on top of each other about 2mm in size.

Also bultaco sherpa ring pegs are at the front of the piston

and montesa ones are at the back.

Just got my old mont 247 piston and the ring pegs are at the front around 10 and 2 o'clock as were the bult piston. Piston fitted had a rear window and 2 small front holes, made by GPM of Italy. It works fine

Dave

Hi try here in stock http://kevinbreedonracing.co.uk/profile.htm cheers helm

Thanks all for your comments. The engine has been shoved under the bench for the time being as I recently went and bought a new toy (KT 250) which I've been playing with over the last couple of weeks. Anyway, I will drag the engine out again soon as that will be my winter project and I'll have another look at the piston taking on board all your comments.

Just one thing, and exuse my ignorance if this is a stupid question, but what exactly is the purpose of the window/s in the rear of the piston and the small holes in the front?

Simon

forto let gases pass through