Norton intake ports compared to Harley XR 750 (2013)

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Onder said:
Well it helps the rest of us...
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There is that. But I should probably start new threads just to post data, instead of trying to change Al's viewpoint on the issues he feels strongly about.

Ken
 
I did not arrange the purchase of my 4 speed close gears cluster. That was somebody else. However I understand it came from America and first gear is higher than that of a Manx. When I fitted it, there was a very big difference in the acceleration rate as I changed up through the gears. However first gear was too high for a clutch start unless I revved the tits off the motor on the start line. I never like doing that. With the standard box, the bike was too sluggish to race effectively. The 4-speed close box was perfect everywhere except off the start line in a clutch start. If your bike does not jump away with the rest, the bit you lose is very difficult to recapture. I have found with my motor set-up, it pulls really hard right up and through the top of the usable rev-range.
That bit about the top 4 gears in the 5 speed box was just something I read and it made me wonder. The SPREAD of the gears is extremely important. If the ratios are too wide, the bike accelerates slower regardless of the overall gearing. If I lower the overall gearing, the bike does not accelerate any faster - I think due to the heavy crank.
When I built the Seeley, a friend said 'if you have a torquey motor, you don't need a close ratio gear box'. - You might not need it if you don't mind going slow.

If you do a bit of reading about RD400 Yamahas - the motor has more torque than an RD350 and the close gear ratios are the same as for the TZ350. The result is a faster bike than an RD350.. The Rd350 would probably be better if fitted with the RD400 gearbox.
 
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When I raced with the standard Norton box, I ran relatively low overall gearing and the spread of the gears was too wide. When I changed up to a higher gear, it took much longer for the revs to rise about 2000 RPM that they did to rise the 1500 RPM with the close box. With the close box, I use much higher overall gearing and the revs still rise at the same faster rate when I change up. I am used to riding a bike which has a much lighter crank. I think a lot has to do with inertia. If you ride with the heavy crank and rely on throttle response, you will wait forever. If you keep the crank spinning high and race-change with close ratios, you will be much faster.
 
It is not and it won't be. Covid 19 has made the situation even worse. My grief thing is still with me, but diminishing slower. I cannot even get a track day.
 
Thank you Ken

Thanks for your past work in archiving the data

Thank you For digging it out and correcting the record

And, thank you for being a gentle man in how you went about it
 
acotrel said:
How mch racing development did the Harley factory ever do ? If I was going to copy a port design, it would be Aermacchi 350, NOT a Harley shape.
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When Carl Rayburn was racing for HD, there was an article in the British weekly comic that stated that the inlet ports were so bad, that they welded them up and started again. Rayburn had quite a successful career, becoming American no 1 plate.
 
Bernhard said:
When Carl Rayburn was racing for HD, there was an article in the British weekly comic that stated that the inlet ports were so bad, that they welded them up and started again. Rayburn had quite a successful career, becoming American no 1 plate.
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There was a time when Rayborn aquired some notoriety by going to the UK and cleaning the tracks with his Harley. Its understandable that they didn't appretiate it but there it was. There was also a period when the Harley XR 750 was recognized as having the best cylinder filling efficiency of any 2 valve motorcycle engine (I think its still true). I'm not a big Harley guy but I'll give credit where it is due.
 
Hudriwudri said:
Sorry guys,
To warm this old thread up but it's been too much of a temptation.
I be been welding up ports (although mostly classic 2v Yamahas and Guzzis) and combustion chambers for quite some years now and there are some tricks to go for those who want to try:
1. You need an xxl long ceramic (6-9) nozzle
2. One needs a modern Inverter machine set on very hard settings.(depending on location play with frequency but leave the pointed tip!)
3. One has to flood the port with argon or heli.
4. Better to use a fatter (you want/need that point for heat concentration and less heat distribution to not cook out the alloy with too much energy besides the weld) than spec'd tungsten (grey I prefer).

Second I wanted to remind you that in the mentioned XR years (when also Jerry Branch did the port work) that aermacchi was part of H&d which was one of the reasons why Paso, back than on aermacchi, as well raced the XRTT.
I would be amazed if there wouldn't have been a slight hint of cross dpt engineering, as to my knowledge Renzo brought with him his own Italian mechanics.
Btw there was also a twin version of the aermacchi called the Linto, I bet power could have been raised with today's knowledge of cam timing and more important valve lift and angled Dellorto PHF'e with 90degr speedway type float chambers

For the rest i wish you all a very nice weekend :)

Kind regards from Italy

Christian

Ps. Regarding the pseudo static characteristics of a flowbench there is one or two SAE papers on the subject by either Yamaha, Honda or even AMF, with perhaps to my memory even correction factors.
Nonetheless a flowbench is what it is, a tool nothing more, it depends mostly on the good logical reasoning and engineering experience of the user. Nothing more nothing less

PPS: forgot, the coefficient of disch/flow takes into account the area of the flow thus one can get a somewhat clear idea of air speeds that should not get beyond 0,5-0,62, 0,65 Mach according to ital scientific literature guide rules thus one will not find in my book a supersonic intake port.
Fluctuating manometer phaenomens on intake ports are usually a sign for turbulences and thus e.g. disattaching flow somewhere in the port.
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Hi Christian, I'm glad you brought this up and offered help with welding. I've been using a small tig for years on steel and got pretty good. It doesn't have input for a pedel so have to scratch start. I was recently given a Lincoln square wave 355 and reading up I see everybody's gone to Inverter machines. Your saying I need to get a modern inverter machine and I'm wondering what specific features i'm looking for and why. There's another recent post more welding related with gobs more info.
https://www.accessnorton.com/NortonCommando/hd-xr-750-full-auto-port-conversion.30174/
 
Bernhard said:
When Carl Rayburn was racing for HD, there was an article in the British weekly comic that stated that the inlet ports were so bad, that they welded them up and started again. Rayburn had quite a successful career, becoming American no 1 plate.
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It's Cal Rayborn (R.I.P)
 
jseng1 said:
There was a time when Rayborn aquired some notoriety by going to the UK and cleaning the tracks with his Harley. Its understandable that they didn't appretiate it but there it was. There was also a period when the Harley XR 750 was recognized as having the best cylinder filling efficiency of any 2 valve motorcycle engine (I think its still true). I'm not a big Harley guy but I'll give credit where it is due.
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That was the Easter match races, American v Brits. The yanks did very well, and yes Carl cleaned the tracks, or should I say scraped them, I was standing at the infamous Paddock Hill corner at Brands, when he lost the front end and slid down the track. The mechanics patched the bodywork with gaffer tape for the next race that afternoon. I think that was the only time PW on the Norton beat him.
 
acotrel said:
If you do a bit of reading about RD400 Yamahas - the motor has more torque than an RD350 and the close gear ratios are the same as for the TZ350. The result is a faster bike than an RD350.. The Rd350 would probably be better if fitted with the RD400 gearbox.
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No I don't think RD 400 gearbox is.
There was a "Inspector" Harry Barlow who took a very modified RD 400 to the drag strip, he posted some very fast standing quater times in the streetbike class , he actually used a TZ350 gearbox and ignition system to make it fly, a sub 11 seconds I think was the best time.
 
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I think there was a time when American riders had an advantage in the UK which had to do with their ability to ride on the loose stuff around the edges of the bitumen.
 
I suggest with inlet ports there are two parts which can be considered independently. The more or less parallel bit - and the deflector just before the valve. If the parallel part is too big, the gas speeds drop below the optimum at low revs. My motor has two 34mm Mk2 Amal carbs, There is a 12mm long , 2mm per side taper in the ports which leads into the normal 30mm diameter. Looked at side-on, the shape is similar to that of an aeroplane which goes trans-sonic. I work on the theory, that if you can hear it, it is sonic. A flow bench does not usually operate at flows which approach sonic speeds, so it is easy to create a bump in the flow if the speeds are very high, and using a flow bench you would not detect it.
If I was trying to create a better port shape, I would work with a reverse solid model with a point at each end and use a transonic wind tunnel. I think Norton would have least got the deflector part of the port right. If you created that model and showed it to any trans-sonic wind tunnel operator, they could probably tell you what it would do at sonic speeds, without even testing it..
 
Bernhard said:
No I don't think RD 400 gearbox is.
There was a "Inspector" Harry Barlow who took a very modified RD 400 to the drag strip, he posted some very fast standing quater times in the streetbike class , he actually used a TZ350 gearbox and ignition system to make it fly, a sub 9 seconds I think was the best time.
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Check the ratios. The RD400 box is the same as the TZ350 but with a wet clutch. It might also be in the Banshee.
 
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