Is it possible to fit a +080 piston or must I fit a new liner

John

email (option): john.kater@chello.nl

There are two types of barrel. Linered and unlinered The unlinered barrel will take a much bigger piston than the linered version. I'm planning to fit an 85mm B33 piston in mine but I can't remember if my barrel has a liner or not. But Ian advises me that it should fit inside a liner and still leave enough liner to be safe.

Your +80 piston will be about 84mm, so should be just fine. Ron

email (option): ronpier@talk21.com

Thanks Ron (and Ian) for the good news. Some time ago I bought this barrel cheap as a replacement. (earlier topic) Fitting a new liner would be costly job.
But I did not know that a B33 piston would fit and only has to do with the bore.
How about the compression ?

John

email (option): john.kater@chello.nl

John my engine has an M21 crank and piston at the moment giving a longer stroke so 600cc. A recognised upgrade to capacity is to fit a B33 (long conrod) piston to achieve 635cc. It can't be done on a standard 500cc crank. To be clear, both the 500 and 600 share the same standard 82mm bore size. However the gudgion pin to crown hieghts are different. Ron

email (option): ronpier@talk21.com

You can go to 85mm bore using a BSA W6 piston I have one fitted to my WM20. Straight forward fit they both weigh near enough the same and pin height is the same.Will give you a eye watering 533cc. This barrel will eventually go onto my 48 M21 and fitted with a long rod B33 piston..Dave

From Ron I understand that 85 mm. is possible. but never heard of a W6 piston.
Hard to find though looking on the internet
As far as I know the distance between the gudgeon pin and the top of the piston is not the same

John

email (option): john.kater@chello.nl

BSA W6 85x88 bore/stroke pin height is the same.. Had one fitted to my WM20 for last 3 years, my barrel is the linered type bored out to 85mm to take a STD W6 piston. I have the head off the WM20 at the moment as I am retiming magneto could take some photos but cant be bothered.. these pistons also have valve cut outs so were also used on OHV models.. Dave

You mean 85/94 bore/stroke. According to the list of Draganfly the pin height of a W6 is 1.37 " and for a M20 is that 1.59
Are there any markings on the top ? Pics are allways welcome

John

email (option): john.kater@chello.nl