Fastest Isle of Man Commando?

Rohan said:

SteveA said:

The works ran short strokes, the heads worked with the pistons designed for them.!

Click to expand...

I don't think i have ever seen quoted that the JPN works Commandos were short strokes - is this written down or discussed anywhere ?

The fact that the production short stroke 750 engine for ~1973 ish wasn't a success makes you think they didn't have experience with making such things fly ??

Click to expand...

In Mick Woollets book it states the short stroke appeared first at the TT in '74, it does not say anything complimentary about it, but quotes Williams as saying the it made 78hp at 7200 and the limiting issue was the weak crankcases. Sort of supports my estimate of 80 from the 850 version, but today the crank cases available are a lot stronger, and the motors out there are revving well above 7200.....

I don't think the production road short stroke was a success, nor were the clubman racers, Norton wanted £1500 in the UK for those and I built a lighter lower bike with the Rickman chassis and 850 for around £1200, which was all I had anyway....

Why were they built? who knows.

The RH number of my head would probably have been RH8, this was not a production head, it was from the race shop, I was told more than once not to let Frank Perris see it! But I have not seen it since late 1980, and we weren't that much into comparing RH numbers back then. It went to the bike buyer and rested in his shed for 15 years as far as I know, but it did not go the the subsequent buyer that I bought the frame from in 2009!

Now that head did have large valves, we have yet to see what will be in the first build of my motor this time around......just enough to make it run probably then go from there......

Read up on Capt. Norton's site on lightened crankshafts and thin flexy 750 cases preferred by early drag racers to take up the crank jump rope binding on the bearings in bores. Rod's may be the most over built part of a Commando next to the Z plates.
Something else must let go before the rods do.

hobot said:

Read up on Capt. Norton's site on lightened crankshafts and thin flexy 750 cases preferred by early drag racers to take up the crank jump rope binding on the bearings in bores. Rod's may be the most over built part of a Commando next to the Z plates.
Something else must let go before the rods do.

Click to expand...

Got a set of barrels at the weekend for a dry build or maybe sleeving later, damaged around spigots......rod broke! Not that unusual.....and today 30-40 year old alloy rods should not be trusted too far......

Steve A, rods break from any and everything else connected to them, so your leaving out other findings is still only reporting mere symptoms to me. I've tested this as so so many others so await the other shoe dropping data points. If there was a fatigue factor in Norton over buildt rods then we'd be hearing of them breaking so much it would be standard prodcedure to replace before radioactive decay like the dumb asxle.

Crank is weakest rpm link, then cases, then valve train, then engine fasteners, then drive train then chassis then pilot.

Sure would like a real pilot to test Peel on IOM if she could fit rules somehow. They might let me on Pikes Peak.

SteveA said:

In Mick Woollets book it states the short stroke appeared first at the TT in '74, it does not say anything complimentary about it, but quotes Williams as saying the it made 78hp at 7200 and the limiting issue was the weak crankcases.

Click to expand...

Thanks Steve, I can't have been paying attention back then.

If the JPN Racers went short stroke for 74, and the short stroke 750 customer engine came out in 73, then they were selling engines with no racing experience behind it - before they raced them. Hmmm, how interesting !?? !

Cammy racing engines (the Inter and then the Manx) had big radial strengthening webs cast into them - from the early 1930s. Wonder what history would say about racing Commandos if the Commando design team had done the same for Commando crankcases..... ?

They DID , by 72 , for the much maligned Combat 750 . Superblends sorted this .But with unskilled incompatants scattered through the Works , and hedges
the odd block wall , lampost and car full of shielas or politicions , they though theyd let the Japs take the whack for the holes in the sceneary . And went back
to produceing something tamer . Suitable for city slickers .

???
Superblends are bearings.
Thin little crankcases on Commandos compared to the chunky BIG THICK CASES with radial strengthening webs on Inters and Manxes is like chalk and cheese. When you pick these cases up, its like handling a big slab of alloy, they are probably 1/2" thick....

When the Laverda 750 came out, the comment was made about the ultra-strong cases, and thick gasket areas - ditto to 1/2", surfaces don't allow any oil to even think about leaking !!

IIRC this is where it was asked about Harley rpm levels, well online searches reveal 9000 in both the old style engines and Porsche Revolution engine.

hobot said:

IIRC this is where it was asked about Harley rpm levels, well online searches reveal 9000 in both the old style engines and Porsche Revolution engine.

Click to expand...

I've heard claims that the XR750s have anywhere from 80rwhp all the way to +100rwhp. I know what a few other bikes have and saw them on the track with some top notch XR's and my guess is that they are probably high 80's to maybe mid 90's. Would love to see some dyno sheets on them.

A few yars back my 750 ultra short stroke did a first place at Mid Ohio with Rob McClennon riding it with Jay Springsteen on a nicely prepared XR750 coming in second or third. Rob was on his heels waiting for the opportunity throughout the race.

A few yars back my 750 ultra short stroke did a first place at Mid Ohio

Now that's showing some Norton tail to the rest of the field!

Here's a Buell dyno graph to ponder

How many cubes in that Buell? Was it a Rotax or H-D mill?
If we are looking at old school `70s superbikes, this mob can get some mean work from a 750.
http://www.ebos.se/triples.asp

Re post stat above, I`m too stupid/lazy to work out the posting drama, but if you click the "klika har" bit by the gold bike, the dyno chart pops up,& power at revs are not too shabby for an old shitter...

WE run H1 and H2 Kawasaki motors on methanol in historic sidecars. You don't need the 750, even if you are ra cing a gainst moderns. The 500 H1 will do everthing you need to win. My brother won the Australian Long Track Championship on it in about 2001. I have a video which he won't permit me to upload - it s hows the 750 jumping into the back of another outfit then doing a ground loop, jumping over my brother.
Shows the bikes:
http://www.youtube.com/watch?v=wxAf9GZSH-w

:?

WHAAA.....P.W. isn`t even looking at that 750/4 he just passed by, & its a red one too! L.O.L.

J.A.W. said:

WHAAA.....P.W. isn`t even looking at that 750/4 he just passed by, & its a red one too! L.O.L.

Click to expand...

HIGHJACK!!!
The possibilties of another thread would to be posting a picture along with a caption! Must have a NORTON in it of course!!Anyone can present a caption and anyone can vote on which they think is the best?! Well..... I think it would be of interest :mrgreen:
foxy

Foxy said:

J.A.W. said:

WHAAA.....P.W. isn`t even looking at that 750/4 he just passed by, & its a red one too! L.O.L.

Click to expand...

HIGHJACK!!!
The possibilties of another thread would to be posting a picture along with a caption! Must have a NORTON in it of course!!Anyone can present a caption and anyone can vote on which they think is the best?! Well..... I think it would be of interest :mrgreen:
foxy

Click to expand...

As long as it’s not a picture of those unobtainable 961s :!:

Kenny Dreer's 952 New Commando then

Fugly lumps them 961s, aint they, compared to the real deal - all odd angles to the frame, air gaps looking unfinished, bulgy tank sitting atop like it was dumped there, short/fat wheels that sit below the level of the mill, fat arsed seat jutting out trying to booty dance...ugh.