Great AMA Mid-Ohio Norton race video

Race video I put together- Dave Roper is all over me at the AMA Vintage Motorcycle Days Mid-Ohio weekend, good fun, we had a great battle.
Looks like I was geared a little tall and yes, all my race motors including this just built one seem to have just a little puff of smoke off the throttle...

[video]http://www.youtube.com/watch?v=wo9TRVEmHmg&feature=youtu.be[/video]

Thanks for the rear view camera or wouldn't get to view most riders very long. Hand started Combat isolastic based racer, boy are you fielding an odd ball. Keep it up and everyone will be seeking to tune for afterburner wisps.

Take it that Ropers on a XR 750 ish H.D. ?
Notice the green thing presents no challenge .

10 / 10 .

Nice VID Doug, well done, love the sound and love see the commando and you rounding up the others, especially the Japanese ones. I guess the rear shot distorts the view, was the guy challenging stuffing it into the corners fast and wide?

Cheers and congratulations Richard

great video. will you be at Barber?

Dunno about Barber yet. Nice track but I don't have great memories there- I raced there in 2009, had an oil seal fail which caused me to have a titanic highside coming out of 5, was in a sling for 8 weeks because they had to strip ligaments off my left hamstring and drill holes in my collarbone to bungee cord my shoulder back together. The good news was the bike barely had a scratch. I am doing Mosport in 2 weeks, looking forward to that- super fast track for the brave.

Yeeeowwchh..so... Best of British for Mosport!

Put it up on on a big screen, hooked up the sound system and played it loud whilst having a cold beer. I made my bikes watch.
Thanks for posting. Nice stuff.

Man, that thing has legs.

grandpaul said:

Man, that thing has legs.

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+1 on that! Pulls like a train - wonderful to see and hear. Thanks!

Nortiboy said:

I made my bikes watch.

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My 850 wouldn't; just hung its head, said the timing was off and besides, it was exhausted.

I have a story about Roper from back when I was racing.

He had a bone fracture (chest I think) and the officials didn't think he was fit to race so they asked him to do (20?) pushups.

He does the pushups, goes out and races like hell.

Roper and his drum-brake XR seems to be in his own class in the turns.

AHRMA used to require that XR750s used for road racing had the 72' cases without the mini-sump which was developed shortly afterwards. Not sure how much that hurts power, but I know that the later 70s xr750 motorcycles with the mini-sump were pretty easy to get 100hp out of.

Now days if they are letting people build Norton racers with heavy duty and performance parts that never existed in the 60's and 70's, they should just let the xr750 guys slap a 2012 xr dirt track engine into his harley, it would be the same standard.....

If I am not mistaken, Dave Roper is on an Aeramacchi. So that makes it a 350cc.

So how does that stack up to a Commando with all sorts of bits that were not available in the 1966's and 1970's?

I think the only thing Doug has which was not readily available "back in the day" is a Steve Maney heavy duty crankcase. Even "back in the day" they would fortify the cases with welding and additional plate.

Vintage racing is oh so much more than just trying to be period precise.

I don't have a problem with someone doing mods to classic bikes which improve reliability for racing, as long as the bike is visually correct, and the capacity is not increased. A blown up motor helps nobody, it tends to mean that competitors run out of funds and don't race. Broken crankcases on standard Commandos seem to be caused by the 58% balance factor of the crankshaft, and the extreme loads on the cases when the motor is over revved. The motor was designed to be smooth at low revs, and the isolastics were used for the same reason. If the crank is balanced to above 70 %, as it should be, the bike would be horrific to ride continuously in slow traffic.
I loved the video, and particularly the sound of the motor as it came up through the rev range under load, it really marches along - great stuff ! I wonder how much Doug paid Dave Roper so he could get those great shots of the XR750 ?

to be smooth at low revs, and the isolastics were used for the same reason. If the crank is balanced to above 70 %, as it should be, the bike would be horrific to ride continuously in slow traffic.

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i sure hope you are just guessing about 70+BF being a bother low down and I for one don't believe it, especially in a real isolastic Commando like Doug's. My level of understanding says Norton only went with 50's BF because it was the least metal required to buy to have BF just hi enough the isolastic could handle it. In other words higher BF should be even smoother just a bit heavier.

There is deeper lurking mystery in BFs for Peel that ain't got nothing to do with the felt vibrations but everything to do with hooking up on far over tire edges and up steep Gravel climbs. Will try various BF's to see if what sense happening is or not.

To my mind McRae's steed is the most interesting and innovative of the Commando-ish type racers out there. Hope he's gets over Barbers PTSD as handling its many tight turns should show his smooth mounted advantage.

acotrel said:

great shots of the XR750 ?

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Ah, er, ah, it's a 350 Harley Davidson that Dave Roper was riding

hobot said:

felt vibrations

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Having had the opportunity to race Herb Becker's Commando a few years back (the sister bike to Doug McRae's) I can say it's the smoothest feeling Commando I ever road.

Kenny had the opportunity to ride Doug's bike a few weeks back; Kenny said it was so smooth it made him wonder what was wrong with his street Commando.

I would like to hear more on why a 70ish % BF is better than 53% for crankcase durability.

Least felt vibrations in Doug's Commando is what I meant and pleased you and others verify its so. Doug states his isolastics give up nothing to the solid buzzers. In case you ain't kept up with past love affair on Peel she flat disappeared to my sensation except for the G forces by power and steering. The more links I put on the more she was like the Cheshire Cat. At this point I think Peel may out handle them racers [not me] I don't know yet so that's this decade's hobby to find out.

I measured engine orbital to come to my 77% solution conclusions, then Jim Schimdt did similar to come to similar conclusion ie: mid 70s BF should give most circular orbital. The assumption being that should be milder on the round cushions to take up. Canaga made Peel crank with screw in lugs so can experiment with mid 50's to 110% BF to settle my questions which have nothing to do with smoothness. Now with more massive engine and lighter pistons - still can't imagine any smoother than not feeling anything but road texture as the wind gusts were taken up completely by the flexy flier frame that would not could not be made to rebound past just centering. Flexy enough could feel the angles change between bar and pegs. Yet I don't see race video of the type of turns it takes to induce that. When I hear about enough power handing in leans with ground effects issues and fuel slosh knocking forks across a lane then I can have pow pow at level Peel has some issues to solve. None of this occurs while just counter steering, so new ground to explore and demo.

Has anyone tried elliptical shaped isos in place of the circular? could try rotating them cam-wise for best feel/location in the vibe plane?

J.A.W. said:

Has anyone tried elliptical shaped isos in place of the circular? could try rotating them cam-wise for best feel/location in the vibe plane?

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You have just dumped a bucket of chum into the ravenous Hobot infested waters of Iso Eliptical Vibe Planeism! :shock: