Norton racing at Mid-Ohio

Doug MacRae · Jul 17, 2012

I will racing at the AMA Vintage Motorcycle Days this weekend at Mid-Ohio, if you are in the area drop by, I will be in pit garage #11. Friday practice, Sat & Sun racing.
Or look for this bike on the track.....

Brooking 850 · Jul 17, 2012

hi Doug, being on the other side of the planet won't be able to make Ohio, although keen to see some specs for your bike.
What sort of HP are you getting, gearbox specs and especially interested in the exhaust system?
PM if necessary
Thanks and regards Mike

pete.v · Jul 17, 2012

Brooking 850 said:
hi Doug, being on the other side of the planet won't be able to make Ohio, although keen to see some specs for your bike.
What sort of HP are you getting, gearbox specs and especially interested in the exhaust system?
PM if necessary
Thanks and regards Mike

Yes, tell us about your carb set up and how you determined the length of your intakes. Are those Mk2's?

Are those wm3 rims with 100/90 - 19" tires?

Doug MacRae · Jul 17, 2012

The exhaust is a 1 3/4" ID with a reverse cone at the end and supertrapps (mostly to look like I am trying to be quiet)
The exhaust length is just like the carb intake length, determined by playing on the dyno to see what the bike wanted- Herb Becker did this work to find the optimal carb to valve distance, these are twin 38mm Mikunis.
Rims are 18"- 2.15 front, 2.5 rear- Avon AM22 110/80 and AM23 130/650 race tires.
Trans is 5 speed Triumph cluster in an NRE (Nourish Racing Equipe) gearbox shell. They sell a Norton output shaft to fit the cluster.
I put up a thread on the handling mods a while ago under 'race secrets revealed' or something like that

acotrel · Jul 17, 2012

I've watched a lot of videos of yourself and Kenny Cummins racing on various circuits - I keep buying lottery tickets ! In Australia we don't really have classes to suit 'thunderbikes'. Our historic ra ces are full of two strokes and big superbikes which dominate the classes and make all the old twin cylinder engined bikes uncompetitive. I noticed that in one clip there was a very fast CR750 Honda. Our Hondas in period 4 ('63 to '72) are CB750s of 1100cc capacity full of '90s parts. It's great to see that American controlling bodies have go some smarts and seem to slow the cheaters down a bit.
Good luck at Mid Ohio Doug.

Brooking 850 · Jul 17, 2012

Thanks Doug, great response , just what I was looking for, will check out your other threads. I noticed the set up of the gearlever on the rearsets, so using the Triumph cluster are you gettin 1down 4 up as per std RHS shift Triumphs?
Post Classic racing in certain classes NZ doesn't allow for the Mikunis (or Keihins) unfortunately.
Regards Mike

Doug MacRae · Jul 17, 2012

The shifting is GP style, 1 up 4 down (like a stock Norton with an extra gear)

Brooking 850 · Jul 17, 2012

Ok thanks much appreciated
Regards Mike

Hobot · Jul 17, 2012

Its all Norton family to most but nothing like a family feud either. I'm rooting for Doug as he's fielding an actual isolastic Commando in these show downs. McBride's secret weapon not in view are 3 sets of swash plates to tame the twist rebound so no ground lost in handling. Horse nostril size breathing tubes. I've wanted to do my shifter linkage like Doug's but for need of kick lever in real world. Might consider two cameras on bike, one showing the zooming in turns and backs of those passed, then 2nd for most the rest of the action behind.

Holmeslice · Jul 17, 2012

Go get 'em, Dougie

worntorn · Jul 17, 2012

The extra intake length is interesting. There is a Seeley-Vincent in England, I think the only such bike on the planet. It has enormously long intakes. The bike is very slow to get going but does have a good power band right on top. Trouble is, the midrange is nonexistant. I imagine that's not the case with your setup, it wouldn't do to have a racebike with a sluggish midange
The intakes are extra long on the Seeley Vincent because the Vincent engine really doesn't fit the Seeley frame. There is an article somewhere on the web about the bike, it is called "The Big Job" and is owned by Tim Kirker.
Glen

cjandme · Jul 18, 2012

I'm liking the front fork brace that you have there, I had one on my Honda years ago and wondered if one could easily be made to fit the roadholder forks. Love the exhaust too!! Good luck MacRae, Cj

Dances with Shrapnel · Jul 18, 2012

hobot said:
McBride's secret weapon not in view are 3 sets of swash plates to tame the twist rebound so no ground lost in handling.

"McBride's secret weapon"?

Who is McBride or is this some brand name for the old "850 hop up"?

hobot said:
Might consider two cameras on bike, one showing the zooming in turns and backs of those passed, then 2nd for most the rest of the action behind.

Reality check - place the second camera on the rear of just about anybody else's bike for a better fleeting view of you, right?

Rubber side down Doug!

worntorn · Jul 18, 2012

Just now noticed the similarities and differences in Doug and Kenny's avatars

Glen

Dances with Shrapnel · Jul 18, 2012

Otherwise known as some friendly "cut throat" competition amongst friends.

Two great guys.

milfordite · Jul 18, 2012

Hi Doug,
Good luck at the races....wish I could be there to battle with you on my Norton! Maybe one of these days!
Bill Atkins

Doug MacRae · Jul 18, 2012

Thanks!
Just realized I didn't answer Mikes question about HP- in it's various incarnations this motor has put between 67 and 72 HP at the rear wheel on the dyno that we use. Around double what you would see out of your average street bike. Of course each dyno is different.
This motor has an old school Joe Hunt mag with points in it mounted behind the cylinders.
Motor is 750cc stock bore and stroke, complete Steve Maney bottom end cases and barrels, high compression, oversize inlet valves, porting, 7s cam etc.
Gotta run and pack....

jseng1 · Jul 18, 2012

The longer intakes on Dougs bike actually increase the midrange. Typically - Nort intakes are made to fit existing equipt and end up too short and thus miss out on full mid range & top end potential. We're talkin about 10-1/2 inches overall length from head. A large diameter velocity stack doesn't really add to the length because the large diameter doesn't help the ram effect. You're better off losing the velocity stacks and getting longer manifolds - as Doug has done. Better yet to use manifolds that don't flex as much as rubber tubing.

Brooking 850 · Jul 18, 2012

Thanks Doug on HP out put and both you and Jim on the intake tract lengths.
Something to aim for in Bike #2.
With an RH10 head any advice on the length of intakes if running 2 x 34 mm carbs, and if longer tracts,what sort of taper from carb to head or valve face?
Regards Mike

Hobot · Jul 18, 2012

This motor has an old school Joe Hunt mag with points in it mounted behind the cylinders.

Yikes, old school risk taker with sparklers under the fuel drip zone.

There are formulas to look up for rule of thumb intake lengths but Doug said McBride dial his in by expensive trial and error on dyno. The lengths he gave would be starting points to try trial-error via time to speed tests if no dyno but might also compensate better for wind speed with pilot on effects.

Norton racing at Mid-Ohio

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