100 HP 920cc motor

jseng1 · Friday at 2:01 PM

Andy Cox and Herb Becker have recently achieved 100 HP at the Rear wheel on gas with big valves and stepped exhaust, longer rods, lightweight pistons and sifton 480/JS4 cam. Andy weighs 240 lbs and has turned 154mph.

jseng1 · Friday at 4:40 PM

spec sheet

video

ashman · Friday at 7:08 PM

The bike looks small on him lol.

milfordite · Saturday at 6:59 AM

Herb helped me achieve 70 HP at the wheel and I thought that was pretty good!

Schwany · Saturday at 8:23 AM

Another snooze fest grocery getter Commando that is NOT.

Fast Eddie · Saturday at 10:52 AM

jseng1 said:
spec sheet

video

Looks very lonely heading off into the whiteness like that !

Schwany · Saturday at 11:36 AM

Fast Eddie said:
Looks very lonely heading off into the whiteness like that !

Indeed... Off into the unknown. I would imagine that 4 miles is a ride on the hairy edge. I'd need a gonads upgrade to attempt it.

I like Herb's approach to making HP. Bigger works on the intake side if you know what your are doing, and he does. A bit way too much for a street ride, but definitely getting the job done in a long straight line.

grandpaul · Saturday at 4:01 PM

Schwany said:
Off into the unknown. I would imagine that 4 miles is a ride on the hairy edge.

It sure was fun for me. I just did one pass, because I still had 6 races left in the season, and my gearing was NOT for top speed.

You never even SEEM to get closer to the floating mountain, it's W-A-Y out there...

Schwany · Saturday at 5:14 PM

grandpaul said:
It sure was fun for me. I just did one pass, because I still had 6 races left in the season, and my gearing was NOT for top speed.

You never even SEEM to get closer to the floating mountain, it's W-A-Y out there...

Sounds fun for certain. It would probably register as fun if I was 30 years old again. ha

I was thinking a Bonneville salt flats LSR event should be on my bucket list, but only as a spectator.

grandpaul · Saturday at 5:55 PM

Schwany said:
Sounds fun for certain. It would probably register as fun if I was 30 years old again. ha

I was thinking a Bonneville salt flats LSR event should be on my bucket list, but only as a spectator.

I was 51 years old when I ran down the salt. I'd do it again tomorrow (if I still fit into my leathers)

gpzkat · Saturday at 6:16 PM

That seems to be very good speed for the HP, must be his aerodynamic physique! The power needs for going 10, 20, 30 MPH faster get ridiculous.

BrianK · 2026-07-19T08:34:07-0600

Stock gearbox?(!?!)

grandpaul · 2026-07-19T09:10:58-0600

gpzkat said:
That seems to be very good speed for the HP, must be his aerodynamic physique! The power needs for going 10, 20, 30 MPH faster get ridiculous.

A few riders seem to spend an inordinate amount of money trying to squeeze fractional horsepower out of an already tapped engine, instead of LOSING A FEW POUNDS OF EXCESS BODY WEIGHT.

"Add Lightness, add speed"

Onder · 2026-07-19T09:22:43-0600

I weigh under 130 pounds fully kitted up for a ride and I wear a lot of clothes.
Maybe he should talk to me about a ride

Fast Eddie · 2026-07-19T13:00:12-0600

Onder said:
I weigh under 130 pounds fully kitted up for a ride and I wear a lot of clothes.
Maybe he should talk to me about a ride

I think your bathroom scales must be broke…

ashman · 2026-07-19T16:50:51-0600

acotrel said:
Power in a straight line does not mean much. In most applications, that circumstance does not exist. Generally speaking - faster around the corners means faster down the straights, so good smooth power delivery and handling are at a premium. If you are 10 mph faster as you enter a straight it takes a lot of power in the other guy's bike for him to pass you before you reach the end of the straight. The bike which Peter Williams raced prior to Nortons was the Tom Arter Matchless 'Wagon Wheels'. That is where the geometry for the first Commando came from. With that much trail, a tank-slapper is very easy to get into. I do not think road-going Commandos ever had hydraulic steering dampers. The first Commandos crashed a few times until the trail was reduced by altering the fork yokes. You guys did not believe me when I told you that the way to get out of a full-on tank-slapper is to grab the tank and wait. If you fight it, you die. When it happens, you need a sense of humour - it looks really horrible.

Arter 1Main jpg hosted at ImgBB

Image Arter 1Main jpg hosted on ImgBB

ibb.co

Fark here we go again, what's that got to do with the salt flats Al, no corners there just one long straight and hold on with the throttle opened right up and if your bike is built right no fu cking tank slappers.

grandpaul · 2026-07-19T17:10:24-0600

acotrel said:
Power in a straight line does not mean much.

I hate to break it to you, but at Bonneville, there is only 1 turn- the turn-around at the end of the run.

...Well, 2 turns, if you count turning in to your pit when you get back...

Power in a straight line at Bonneville IS ALL THAT MATTERS.

yeef...

robs ss · 2026-07-19T21:14:25-0600

Tee Hee!

Schwany · 2026-07-20T08:15:34-0600

Bonneville is in my warped opinion for tuners, fabricators, and mad men thinking way outside the practicality box. Great piece of the motor racing story.

Making 100HP with an antiquated Norton twin engine design and keeping it all together is impressive to me. Chasing power even if it is only a couple of horses is rewarding and worth it to the record chaser or a tuner that just can't kick the habit. Can also be fun in a street bike if not overdone to the point that the clutch has to be slipped for 30 yards leaving a stop in 1st gear. I have respect for what these guys or gals are doing, not disrespect.

zotz · 2026-07-20T13:28:44-0600

jseng1 said:
Andy weighs 240 lbs and has turned 154mph.

We need some little feller on there weighs only 140lbs. See what she'll do.

100 HP 920cc motor

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