Which pistons ?

[spyke]

Hi chaps,

Can anyone recommend or have good or bad experiences with pistons, Im looking at Italian ones, JP Australian ones, or Weisco ones (expensive ) . I need low comp +80  (to avoid having barrels resleeved).I assume that Hepolite etc are all gone now.Alternatively has anyone got any used serviceable +60 ones to sell which I can try.

Cheers Spyke

[Beezageezauk]

Hi Spyke,

As far as I know SRM are the only suppliers of +80 pistons and they are about 8.5-1 .  Not really low compression.  However, if anyone else on the forum knows of other suppliers of +80 low comp pistons for A10's I would also be interested.

Beezageezauk.

[Richard]

When I needed to replace my 80thou pistons that were originaly according to SRM made for them they informed me that they had sold the entire stock to MCA and could not help, so Peter Hammonds in Cirencester ordered a set up for me. As far as I know they are standard 8:1
Richard

[trevinoz]

Spyke,
         I like GPM pistons, was using them in my RGS when it was running and have fitted them to my Super Rocket. I think they are 8.25:1.
I have Taiwanese or something in my Flash, probably 7.25:1 and they are fine.
JP pistons are OK but I reckon they are too heavy.
Trev.

[coater87]

 Guys,

 While we are on this subject I see I have some choices here as far as comp. ratio.

 I can get 6.5:1, 7.25:1, 8.25:1, and 9:1.

 I want to stay low, so its between the 6 and 7. Is the 6.5 too low? I cant see going much over 60 mph, but I would like to be able to get there before the ride is over also. Anyone have an opinion on what the best choice will be? I have a 356 cam, and a plain T/S bushing, iron head.

 Thank you,
Lee

[A10Boy]

Just my opinion. 

If you have an iron engine, you should use either of the lower compression pistons. High compression creates more heat and really needs the alloy head to cool it enough so it doesn't pink or pre-ignite.

7.25 is just right for a solo machine with a cast head, and with the 356 cam makes a good engine. I think 6.5 is a bit low and maybe is ok with a sidecar type set up.

The Plain bush is irrelevant unless you are going racing, the main thing is that its fitted and line bored properly - and you change the oil before 1000 miles.

[trevinoz]

Lee,
      I agree with Andy. I am running 7.25:1 with a 356 cam in my Flash. It goes very well.
Trev.

[coater87]

 Thank you guys,

 7s it is! One day soon I plan to start this rebuild, and I will take pics as I go. I still have to find someone local to grind the crank who's abilities I feel confident in. But I have sourced a large chunk of 660 bronze and plan on getting the bush turned out over size in advance.

 I mentioned the bush because I was really on the fence with that, almost sent the whole works to SRM as there seams to be no shop in the states that does a good job on the T/S conversion- but shipping costs killed the idea. I think running a low compression set-up, and not pounding the snot out of it should make for a pretty reliable bike.

 Lee

[BSA_54A10]

I have been using JP's for a long time and can not fault them.
Unfortuneatly as of late I have had 2 sets sent with the wrong rings.
At first they did not want to know me or admit that there was a problem then I started rattleing off others who also had wrong rings supplied so there is a problem in the packing & despatch department but the pistons are good.
GO for lowest compresson pistons that you can.
In Oz E10 will become mandatory next year and I have no doubt that the % ethernol will be steadly increased over time & I would imagine that the USA will not be far behind as the rest of the world starts refusing food stuff packed with corn products.