SR pistons

[red ghost]

how well do these work for a round-towner?

or to rephrase my question; of the pistons that SR offer which would be the pick for a round-towner?

[bristolmod]

there was some talk a while back of the SR piston having an incorrect taper which lead to a lot of piston slap on tickover.

I've had two setups (both SR185's) which indeed did rattle a tad on tickover- having said that they never nipped up and didn't rattle above tickover speeds.

I'm presently using an SR185 barrel bored to 66mm with a Mahle piston at 3 thou clearance- no rattle at all and no nip ups (despite reving the nuts off it!!)

Chris

[red ghost]

So a Mahle piston is quite ok?

[bristolmod]

absolutely no problems with mine. Got it from Scooter restorations around £30.

Chris

[johnd]

I'm still using the standard SR piston, TBH i don't notice the tick over rattle anymore and the rings and construction of the piston are quality. I bought the kit from SR when they were £100 and it has been giving good value for the money ever since.

[bristolmod]

I'm still using the standard SR piston, TBH i don't notice the tick over rattle anymore and the rings and construction of the piston are quality. I bought the kit from SR when they were £100 and it has been giving good value for the money ever since.

totally agree- the SR kit was very good value for money. Some rattled, some didn't and I'm sure it improves as its run in (either that or I'm getting deaf....)

Chris

[coaster]

how well do these work for a round-towner?

or to rephrase my question; of the pistons that SR offer which would be the pick for a round-towner?

I'm doing the same, just in the process of assembling a 185 SR engine for my London based scoot (Shocky's Jet). I bought a barrel from SR for £30 a couple of years ago (one of the last I think) and then bought a cheapo ebay piston for £19. I just had a look at it and it doesn't have ANY maunufacturer name on it at all Jut STD and an i in a circle.

As it's unlikely to be subjected to prolonged bouts of thrashing I'm hoping it will cope

[bristolmod]

one thing I've tried with the SR steel linered type barrels, is that because they're mainly alloy, the piston to bore tolerances can be reduced significantly.

My first one had 4 thou and rattled; the second 3.5 thou and still rattled (but not as much. The current one is 3 thou and there is not a hint of any slap or rattle. I'm tempted to build up another at 2.5 thou to see if that copes..........

Chris

[joespeed]

if you start to reduce your clearance then you will encounter heat seizures,it will only rattle at tick over and cold ,
regards
joe