Grumph likely has a GPZ750 piston or knows where one is to measure they do have a metric pin in 15mm though but i bet they are a better shape and better made.
It is what they used to use for the Honda CB350 racers.
Another option is C15 or B25 BSA or Rocket 3 trident
The C15 would likely best match the triumph head shape.
![]()
Kinky is using a feather. Perverted is using the whole chicken
Try Graeme Cole in the Tron. info@cycletorque.co.nz
He's on Turdme as Leo98 as well.
When i had the damaged piston in hand, I reckoned it was a Hepolite which had been welded up to be run on alky. Way too big a crown.
Full, deep hemi chamber like the Aermacchis I'm used to. Like them a medium dome to get com up to 10.5 or so would work well.
I'm still searching my bits for the part set of 70mm Z1 wisecos I'm sure i have...
Edit - found them. Actually 70mm MTC forgings. Part set, one has damaged ring lands and they didn't make 3 cylinder Z1's...
17mm pin, 24.0mm deck height. Probably 10.25 in a Z1, given the bigger chamber but slightly longer stroke in the Velo, around 10:1 i'd think.
Cutaways are for 38mm inlet, 32mm ex. Plenty of meat if they need to go bigger.
Would need reringing but that's not a biggie.
Doubt you'll find anything much better Neil. Sure the owner will break the set anyway.
If any of the NI Velo crowd want one Nev, just ask.
.060 is the Reg unfortunately, although I suspect there's a few "slightly" larger than that. I remember riding a quick short stroke BSA B31 before they changed the rules to only allow standard bore/stroke in the clubmans class (one I'd made a conrod for and running a TT500 crank) and another "competitor" pulling out 50 meters over me down about half the length of the back straight at Puke, on anther B31. The bike I was riding weighed heaps less than his and I was 20 kg lighter than him....go figure![]()
There are currently 1 users browsing this thread. (0 members and 1 guests)
Bookmarks