Fast Eddie
VIP MEMBER
- Joined
- Oct 4, 2013
- Messages
- 21,509
This is a real world shout out for JS pistons and rods…
I’ve now built 3 motors with JS rods and pistons, 850, 920 and the most recent 1007.
As a Triumph and Nourish guy in the past, I have always been of the uneducated opinion that the Norton rod is too short for the stroke. Triumph only went from 6.5” to 6” to fit the motor in the OIF, and that was with a 82mm stroke. Nourish definitely preferred 6.5” in his bigger motors.
Under the tutelage of Dave Degens I’d spend hours shaving grams off of pistons and gudgeon pins, he was adamant that anything saved here led to more power at the wheel, just as he was taught by Jeff Monty and Sid Lawton.
So, with that background, the weight saving with JS parts is really quite mind blowing for me.
My 920 pistons are actually lighter than stock 750 pistons. In my recent 1007 build, the entire reciprocating weight (that’s the small end of the rods, pins, pistons with rings) for both pistons was actually over 1/2 lbs less than the ‘stock’ Maney pistons and normal Carrillo’s.
HALF A FREAKIN’ POUND… going up. Stop. Down. Stop. 116 times per second !! Of course that necessitated significant weight reduction from the flywheel, which I also had dynamically balanced.
Needless to say, the effect on vibration and the way the bike runs in general is pronounced. It’s smoother, of course it’s not totally smooth, but for a rigid mounted 83x93mm 360 degree twin, it’s good! It also now revs higher than before. It revs up on the throttle much quicker. It produces more power at given revs than before, and because it revs higher, it produces quite a bit more peak BHP, an extra 7BHP in fact !
So there you have it, an exceedingly beneficial modification in my experience.
Jim, send the cheque to the usual address please…
I’ve now built 3 motors with JS rods and pistons, 850, 920 and the most recent 1007.
As a Triumph and Nourish guy in the past, I have always been of the uneducated opinion that the Norton rod is too short for the stroke. Triumph only went from 6.5” to 6” to fit the motor in the OIF, and that was with a 82mm stroke. Nourish definitely preferred 6.5” in his bigger motors.
Under the tutelage of Dave Degens I’d spend hours shaving grams off of pistons and gudgeon pins, he was adamant that anything saved here led to more power at the wheel, just as he was taught by Jeff Monty and Sid Lawton.
So, with that background, the weight saving with JS parts is really quite mind blowing for me.
My 920 pistons are actually lighter than stock 750 pistons. In my recent 1007 build, the entire reciprocating weight (that’s the small end of the rods, pins, pistons with rings) for both pistons was actually over 1/2 lbs less than the ‘stock’ Maney pistons and normal Carrillo’s.
HALF A FREAKIN’ POUND… going up. Stop. Down. Stop. 116 times per second !! Of course that necessitated significant weight reduction from the flywheel, which I also had dynamically balanced.
Needless to say, the effect on vibration and the way the bike runs in general is pronounced. It’s smoother, of course it’s not totally smooth, but for a rigid mounted 83x93mm 360 degree twin, it’s good! It also now revs higher than before. It revs up on the throttle much quicker. It produces more power at given revs than before, and because it revs higher, it produces quite a bit more peak BHP, an extra 7BHP in fact !
So there you have it, an exceedingly beneficial modification in my experience.
Jim, send the cheque to the usual address please…
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