Short Stroke 750 Info
- Thread starter lcrken
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Pinched from : short-stroke-750-build-t5490.html
getting a bit of track but possibly forgiveable though maybe stateing Williams statements arnt always gospel might be considered hearesey to some .
73 so not yet 80 stroke , like a 8.000 rpm T100R from 55 / 57 .
accidently did 130 / 7.600 on one , took it down to 7.000 when accidently hit 7.200 .
olde methanol burning barge went passed , couldnt have that , so stuck it up it
before outbrakeing the ten ton wonder . Which apparently wasnt appreciated .
Later found 8.000 was redline on the ' R ' series pre unit 80 mm stroke 500 c.c.
others & site .
adjusting Eyeballs , & other Balls . ?
V V V i bration f ff f f r r ee ee ee
parley vous francias ; http://www.imcdb.org/i380739.jpg " 973 Norton 750 JPS Monocoque in Larga noche de julio, Movie, 1974 "
http://www.themoviedb.org/movie/110230- ... e-de-julio
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The things cantve been a total dead loss , like the challenge ! ? :wink:
and wots this then ? ( unsure as yet )
This is a t100R , mine ran joMoCo 1 5/8 intakes & 1 7/16 Ex valves , so only :? :lol: the bore differed from the destroked 828 Norton . :?
well . . .
and wots this then ? ( unsure as yet )
This is a t100R , mine ran joMoCo 1 5/8 intakes & 1 7/16 Ex valves , so only :? :lol: the bore differed from the destroked 828 Norton . :?
well . . . 
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From "Norton, the Racing Story" book:
regarding the short stroke motor "experiment":
"Like the new frame the new motor proved a disappointment"
Peter Williams (of the changes made to the JPN after the great 1973 racing season)
(same comment made about the new sponsor Gulf Oil, nothing seems to help the race effort after 73)
to paraphrase from the book: and just like that by 1974 the old long stroke vertical twin was obsolete with the advent of the 700cc two strokes from Yamaha putting out well over 100 hp
regarding the short stroke motor "experiment":
"Like the new frame the new motor proved a disappointment"
Peter Williams (of the changes made to the JPN after the great 1973 racing season)
(same comment made about the new sponsor Gulf Oil, nothing seems to help the race effort after 73)
to paraphrase from the book: and just like that by 1974 the old long stroke vertical twin was obsolete with the advent of the 700cc two strokes from Yamaha putting out well over 100 hp
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Now , where were we .
Im sure it fits in there somewhere !
Delta Head 57 T100R ?
Im sure it fits in there somewhere !
Delta Head 57 T100R ?
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" and just like that by 1974 the old long stroke vertical twin was obsolete with the advent of the 700cc two strokes "
the press was trying to say the motor was obsolette when the Commando came out in 67 / 68 :shock: & hhalf the road tests . Still ' bike of the year ' several years running .
the press was trying to say the motor was obsolette when the Commando came out in 67 / 68 :shock: & hhalf the road tests . Still ' bike of the year ' several years running .
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I've had hot Triumphs my whole life. Tiger 100s, Tiger 110s, and a short stroke 500 made from a 650. When I built the Seeley 850, I didn't race if for 25 years . I couldn't believe that I could race the 850 motor without blowing it up straight away. My friend has probably the best 650 Triumph (Triton) in Australian historic racing , and I've ridden that on occasion. The Seeley with the 850 commando motor is better everywhere . I don't tell my mate that, but it really amazes me. My theories about old British four strokes, have always been about short stroke, high comp., race cams, megaphones, big ports. The long stroke commando engine stuffs all of those theories. I am still scared of having the big explosion at high speed, but my bike is a really good thing.
I believe the main problem with racing commandos has always been the classes in which they raced. Against bikes of similar technology, they are superb. I've never raced against an 851 Ducati Pantah, however I would really love to do that ! - Pity our historic racing doesn't permit that to happen. I think I might go back to bed and have a good cry.
I believe the main problem with racing commandos has always been the classes in which they raced. Against bikes of similar technology, they are superb. I've never raced against an 851 Ducati Pantah, however I would really love to do that ! - Pity our historic racing doesn't permit that to happen. I think I might go back to bed and have a good cry.
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'" and just like that by 1974 the old long stroke vertical twin was obsolete with the advent of the 700cc two strokes "
the press was trying to say the motor was obsolette when the Commando came out in 67 / 68 :shock: & hhalf the road tests . Still ' bike of the year ' several years running .'
The commando was obsolete in road racing when the TZ700 arrived. These days the greenies have stopped the two strokes from being widely used and that is unlikely to change. So the old technology is still obsolete ? I don't think so. It depends what you want. I believe it would be possible to establish race classes for thunderbikes which would cater for historic and classic bikes as well as moderns, and be a level playing field. The overall top speeds would be lower during races however the relative speeds between competitors would still be similar to modern road racing.
Thunderbike:
Aircooled four stroke motor
One, two or three cylinders.
Two valves per cylinder.
It is not rocket science and no more eligibility rules are needed for racing them.
the press was trying to say the motor was obsolette when the Commando came out in 67 / 68 :shock: & hhalf the road tests . Still ' bike of the year ' several years running .'
The commando was obsolete in road racing when the TZ700 arrived. These days the greenies have stopped the two strokes from being widely used and that is unlikely to change. So the old technology is still obsolete ? I don't think so. It depends what you want. I believe it would be possible to establish race classes for thunderbikes which would cater for historic and classic bikes as well as moderns, and be a level playing field. The overall top speeds would be lower during races however the relative speeds between competitors would still be similar to modern road racing.
Thunderbike:
Aircooled four stroke motor
One, two or three cylinders.
Two valves per cylinder.
It is not rocket science and no more eligibility rules are needed for racing them.
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Rohan, It is impossible to communicate with the 'majority of folks' who might be potentially involved with classic racing. The only hope in Australia is through forums such as these, our privacy laws greatly inhibit any other approach to encouraging change. The major problem is our conservative mindset, our guys cannot imagine any other way except having race classes based on year of manufacture. Even our capacity classes are subservient to that. The technology differences make the whole scene piss-poor. For spectators , you will see better racing on any freeway. If you think any Norton Commando will ever be competitive in any way in Australia, you are kidding yourself. You won't even get it onto the grid with bikes of similar technology and capacity. Hopefully America is a bit more sensible - the BOTT is an indication of that. I am short of cash, and the racing doesn't justify the expense, and I'm getting to the stage where I just don't want to know any more. What it means to me is that I am almost finished with bikes,and lawn bowls and fishing are looking better.
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" and lawn bowls and fishing are looking better. "
Does this mean , If I give you a bag of bowling balls , & a fishing rod , Youll give me the Seely 850 .
:shock: :x
Does this mean , If I give you a bag of bowling balls , & a fishing rod , Youll give me the Seely 850 .
:shock: :x
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On 5/28/2013 4:36 AM, Ken Augustine on mc-engine wrote:
> hobot,
>
> Take a small port head, do the Hemmings mod on the intake and that should eat all the clutches you want. I have done that modification and know what it entails but don't remember the exact angle or diameter involved. The part that I don't like about the Hemmings mod is that the inlet valve guide bore needs to be increased to .625" diameter to clean up on the original .500" guide bore when the inlet guide angle is straightened up. In more than just my opinion, the Norton head casting doesn't have enough material to properly support the larger diameter guide and the guide should be made smaller to give a higher caliber fitted ratio (length/dia). Unfortunately, welding the guide bore down inside the valve spring region is very difficult and the necessarily used , porous castings are full of oil. After any welding is done, the guide location needs to be determined, the hole drilled, bored or reamed then roller or ball burnished or the guide will loosen and fall out. The valve seats need to be removed, the odd squish band on the back of the combustion chamber filled, the combustion chamber resphered, head gasket surface recut, valve guides made, installed and fitted to new valves which need to be made, the valve seat bores need to be recut from the guide centers, valve seats and installation tools made then installed, seats cut, ports blended, springs shimmed and installed and pistons be repocketed.
>
> Possibly Hemmings will make one for you or you can find a factory short stroke 750 head which comes that way. You will still need to repocket or find pistons but the original valve train geometry is for a 250cc cylinder from the Model 88. That is why the 750cc head has the odd crescent in the back of the combustion chamber. The 750cc head had to be moved forward or the pushrod tube bores would have encroached on the cylinder bores and the rocker geometry moved with the head but was not corrected until possibly the short stroke 750. Possibly but only possibly.
>
> I have my own angles, locations and linear plus radius dimensions in a head which is almost done but I have $12,000 worth of time in it and am not giving it away. However, it is for sale at that price as I need to do other things and haven't time to build a decent short stroke bottom end for a Norton.
>
> I hope all that helps but don't forget that the Commando chassis is a mess and needs work first or it will wobble or weave more badly than they normally do with the stock power. The Featherbed frame, of course, is worse.
>
>
> KA kineticanalysis@yahoo.com
> hobot,
>
> Take a small port head, do the Hemmings mod on the intake and that should eat all the clutches you want. I have done that modification and know what it entails but don't remember the exact angle or diameter involved. The part that I don't like about the Hemmings mod is that the inlet valve guide bore needs to be increased to .625" diameter to clean up on the original .500" guide bore when the inlet guide angle is straightened up. In more than just my opinion, the Norton head casting doesn't have enough material to properly support the larger diameter guide and the guide should be made smaller to give a higher caliber fitted ratio (length/dia). Unfortunately, welding the guide bore down inside the valve spring region is very difficult and the necessarily used , porous castings are full of oil. After any welding is done, the guide location needs to be determined, the hole drilled, bored or reamed then roller or ball burnished or the guide will loosen and fall out. The valve seats need to be removed, the odd squish band on the back of the combustion chamber filled, the combustion chamber resphered, head gasket surface recut, valve guides made, installed and fitted to new valves which need to be made, the valve seat bores need to be recut from the guide centers, valve seats and installation tools made then installed, seats cut, ports blended, springs shimmed and installed and pistons be repocketed.
>
> Possibly Hemmings will make one for you or you can find a factory short stroke 750 head which comes that way. You will still need to repocket or find pistons but the original valve train geometry is for a 250cc cylinder from the Model 88. That is why the 750cc head has the odd crescent in the back of the combustion chamber. The 750cc head had to be moved forward or the pushrod tube bores would have encroached on the cylinder bores and the rocker geometry moved with the head but was not corrected until possibly the short stroke 750. Possibly but only possibly.
>
> I have my own angles, locations and linear plus radius dimensions in a head which is almost done but I have $12,000 worth of time in it and am not giving it away. However, it is for sale at that price as I need to do other things and haven't time to build a decent short stroke bottom end for a Norton.
>
> I hope all that helps but don't forget that the Commando chassis is a mess and needs work first or it will wobble or weave more badly than they normally do with the stock power. The Featherbed frame, of course, is worse.
>
>
> KA kineticanalysis@yahoo.com
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