Ariel Owners Motorcycle Club

Hi, I have an 250cc arrow with standard+20 pistons, can I fit new Suzuki +20 pistons . IE are they the exact same diameter. Thanks Steve

"...For help with a machine post in one of the technical sections." (Where it might also get more attention!)
Moved!!!!

SG

Steve J Carter wrote: Sat Nov 22, 2025 12:03 pm ....IE are they the exact same diameter.

It's not the size of the piston that matters, it's the size of the bore it's designed to be fitted into and this should be given as part of the machine spec.
From the info on Drags website (regarding the Suzuki pistons they supply) the bore size is the same (54mm). There's even a note (visible if you get the piston picture up to full resolution) about doing a glaze-bust if you fit them into bores that have already been used.

The little ends aren't the same size though, and the porting isn't quite the same (neither is the combustion chamber shape) but Suzuki pistons seem to run OK but not optimally. I think there's quite a bit of info on this on the Forum, if you do a search.

Drags link:
https://draganfly.co.uk/shop/85021/pist ... -pair/#T18

SG

Thank you, I give them a call on Monday.

you can fit suzuki +.020" pistons as replacement for original =.020" ariel pistons but need to fit new small end bush in the conrods and ream them out to suit the suzuki gudgeon pin .
the suzuki gudgeon pin is slightly different size to the original ariel pin .
the suzuki piston crowns sit very slightly lower than the ariel crowns and there is a very slight reduction in compression but it is minimal and the engine will run perfectly ok .
some people have a small amount of material machined off the top of barrels to raise compression again but most people dont bother with it .
the power seems to go up the rev range a little when using suzuki pistons but nobody seems to moan about it at all.

you can get +020" rigns for original pistons if thats what you want , then hone the barrels and run it in after its back together .

i think you may be able to get gudgeon pin bushes to suit the original pins as well from draganfly but again i think they do need reaming out but you can do this easily by hand , look for info about it as theres plenty .
go on the ariel leader and arrow facebook page and youll soon get help from the fellas on there .
cheers
ian

Draganfly supply new SEBs with the pistons, also available separately as always

Attached picture of the Suzuki and Ariel pistons - gudgeon pin centres lined up. Its about 30 thou difference in the height. The skirt is shorter which in effect opens the inlet sooner so the engine revs more feely but has less torque in the lower rev band. I've taken the gasket out on one engine to increase the compression. Brain H.

Sorry to be late to the table, but club spares has a set of good condition ORIGINAL used +20 thou pistons in stock, with rings. if interested, let me know. Cheaper than drags and you can reuse the original small end bushings.
Trev

Hello Trev,

it's good to know there are +.020 pistons available, since I have one piston/cylinder close to reject limit.

Happy new year 2026 to everyone in the two stroke forum!

Vesa