Pistons for 18S
-
9776
- Posts: 19
- Joined: Sun Jan 01, 1995 12:00 am
- Location: SURREY UK
Pistons for 18S
My 1953 engined 18s has low compression and is in need of a rebore. I would like to up the compression ratio to around 8.5 to 9 to 1. Has any member any advice as to what pistons to use or, not to use?
-
silverarrow
- Posts: 549
- Joined: Mon Jan 01, 1990 12:00 am
- Location: LEICESTERSHIRE UK
Pistons for 18S
Ian,
You do not mention why you want to up the compression ratio?
If you do go up to the ratios you mention bear in mind that you will also have to change the cams, carburation & valve timing as well as putting new stresses on the engine where they were not intended. Raising the c/R alone will just make an easy starting bike, hard to start.
The 18S is a lovely lazy tourer not intended for and not best at racing. If you want more performance Fit a scrambles engine or get a later shortstroke model with ready made extra power. My 18S has been two up + camping gear for 2000 miles including the Austrian & Swiss Alps and took all that in it's stride.
having said all that i think a later piston of around 7;1 is usable without major surgery, ask Ernie!
Les Smith
You do not mention why you want to up the compression ratio?
If you do go up to the ratios you mention bear in mind that you will also have to change the cams, carburation & valve timing as well as putting new stresses on the engine where they were not intended. Raising the c/R alone will just make an easy starting bike, hard to start.
The 18S is a lovely lazy tourer not intended for and not best at racing. If you want more performance Fit a scrambles engine or get a later shortstroke model with ready made extra power. My 18S has been two up + camping gear for 2000 miles including the Austrian & Swiss Alps and took all that in it's stride.
having said all that i think a later piston of around 7;1 is usable without major surgery, ask Ernie!
Les Smith
Keep smiling