going to bore Need 850 pistons

Top of the morning to ya all..... Honed out the clyinder last night... Looks like I'm going to be boring I'm looking for 850 pistons with valve cut out's ( bigger cam... 2's)... Does any body know where can I locate over size pistion 9.5-1......Not looking for full race pistions ..... web address & phone numbers would helpful... Thanks .....

Remwember if you are not on 2 wheels then you are taking up to much space

tripower said:

Top of the morning to ya all..... Honed out the clyinder last night... Looks like I'm going to be boring I'm looking for 850 pistons with valve cut out's ( bigger cam... 2's)... Does any body know where can I locate over size pistion 9.5-1......Not looking for full race pistions ..... web address & phone numbers would helpful... Thanks .....

Remwember if you are not on 2 wheels then you are taking up to much space

Click to expand...

Ive recently been through this, and it was a steep learning curve. here's my learning:
Mick Hemmings sells Wiseco pistons, I assume he has an arrangement with them as they don't seem to be available elsewhere. He does different options of CR if I recall correctly.
Steve Maney also sells forged pistons. He will machine the crowns to your requirement.
But my advice would be to do some measuring and gain some more understanding of your motor first.
Most 850s are not 8.5:1, they are lower. My 850 was actually 7.6:1 ! So even if you buy 9.5:1 pistons... you might actually find you've not got much more than 8.5:1 !
I would suggest buying pistons that have a higher CR than you wish for, then fitting them and measuring the CR, then machine some off of the crown if necessary.
The 10.25:1 Omegas I was going to use in mine, actually worked out at 9.7:1 when assembled with a base gasket.
It seems to me that the lower than claimed CR is most likely the reason that 850s have gained a reputation for being slow (or slower than the 750s).

do you have a link for the omega pistons? I wish I did not have to bore & that I could have used your pistons... Being a car guy I do under stand air fuel ratio & the need for the higher compression for I'm using the 2s cam... I do have options as far as raising the compression by not using clyinder base gasket, deck the clyinder head ( for the clyinder & lifters is hitting the machine shop today) head gaskets... this bike is a real bastard which when done will be a custom cool ,out of the box thinking bike.....I will be riding this at Daytona in a couple of months

Ran a measured 8.7 : 1 in 750 with SS cam satisfactorally . 9.75 : 1 in the Bonneville , comparable behavior - with a few tricks - obstroperous

Over 9.5 on todays gas ? ? if you have to back off the ign. timing to avoid detonation it wont wind up as well .

Another option you might try is Venolia Racing. They supplied my 10:1 forged pistons back in the '90's. Any compression and oversize, with valve clearance pockets and also supplied (by request) the rings and wrist (gudgeon) pins. Apparently they still have the original drawings in their files.

http://www.venolia.com/

Bill

Mick Hemmings is doing the first reborn on my barrels I took them along with crank for grinding an head to convert to big valve job. He just looked at parts an started to show me what he was going to do then turned to a shelf behind an took off a set new old stock genuine A&E pistons saying these are the best an I still have few pairs in the size you need. He is a great guy to talk to an after letting me look over his famous race bikes we shook hands an that was that he is doing over £2k of work with no talk of leaving a deposit or anything. He knows his stuff so I would contact him an he gives good advise without trying to get you to buy stuff.