Which pistons should I look for?

[Rapid Dog]

1981 R100RS
Dual-plugged '78 squishban heads
Stock Nikasil cylinders an pistons

O.K., so it appears though the bike runs fine and dandy, my lack of top-end and overall softness of the motor (oh my lack of knowledge about post 80's bikes!) is due too the low compression flat top pistons.
I know, I know, the heads don't match but that's what I got.

Recommendations to me to bump up the motor is to find some 9.5-1 hi compression pistons.
My questions is what to look for best bang for the buck that I can bolt on and use.
I googled around and found this which helps me visually: http://moragafalconers.org/bmw_pistons/index.htm

I can pick up a complete 1978 top-end with 40mm dual-plugged heads and 12-1 pistons locally, but I'd like to stay with my 38mm exhaust and my Nik cylinders if possible. My heads are new rebuilds as well.

So what does Mr. Vanzen or others recommend I do here? Like, what would be a good choice of slugs only?

[mattcfish]

http://www.motoren-israel.com/product_i ... RMANY.html

They come in other sizes depending on what bore you have.
These are made by Siebenrock and can be purchased from their site as well. Also BMW Bayer.
Quality pistons.
MI also has 10.5:1 pistons, but they are made to be used with shortened barrels.

[barndeadr80]

Northwoods Airheads is dealing in Siebenrock stuff according to the website. Lots of interesting tools, too.

[Rapid Dog]

Those Moto Israel's look pretty tasty if I was thinkin' about new...

I guess they are designed specifically for Nikasil barrels? Something about the metallurgy?
I suppose they'd be fine with my '78 squishband heads, no?

I was going to try and find a pair new or used '78 squishband pistons to match my heads but I'm not clear if they would work with my Nikasil barrels. I don't know enough about it all. I'd wonder what kind of rings to buy as well.
I just want more compression for sure.

[Garnet]

Those Moto Israel's look pretty tasty if I was thinkin' about new...

I guess they are designed specifically for Nikasil barrels? Something about the metallurgy?
I suppose they'd be fine with my '78 squishband heads, no?

I was going to try and find a pair new or used '78 squishband pistons to match my heads but I'm not clear if they would work with my Nikasil barrels. I don't know enough about it all. I'd wonder what kind of rings to buy as well.
I just want more compression for sure.

The rings are the differance between Nikasil and cast barrels. Cast barrels use chrome rings and Nikasil use cast (I think) rings.

To add to the confusion, I have a set of 9:1 pistons that are supposed to be out or a 78, that are NOT squishband, and do not match any of the deck heights that John has listed on his referance page. Don't ya just luv FleeBay.

[mattcfish]

Right... you need squish band. I only see those being sold with cylinders on the Siebenrock site.
Motobins # 50298 might be more what you're looking for. They have squish band, but it's an angled one. http://www.motobins.co.uk/displayfinal.php?q=pistons

[mitch]

My 95 R100 had 8.5 comp standard pistons I installed a 336 cam a while back which is a great cam but realy shines from about 5500 to 7700 rpm,I rarely use those revs anymore so I put back the standard 308 cam and bought a pair of 9.5 comp high performance Wossner pistons from motoren-israel there lighter than standard bm pistons.The set-up seems real good it pulls better from lower revs so I assume the torque has come back to a more user friendly spread