HD XR 750 & Full Auto port conversion

lcrken

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I too would love to see your data, Mike. We have flow charts that Jim Comstock posted here on a stock FA head, as well as one he did some additional work on. It would be interesting to see how much difference you found between the different carb setups.

Ken
 

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I have a lot of charts comparing different carbs and carbs with different intake lengths.
I also have the original flow data that Jim sent with the head.
Regards Mike
 

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The Norton world is still waiting for someone to match the flow and efficiency of the XR 750. The port, intake runner and exhaust pipe specs are readily available to copy, stage 3 valve sizes are established, short stroke cranks & longer rods exist and the (modified JSM) Sifton 480 cam profile is not too far away from the HD ML cam. If I was still racing I would go straight to it.
 
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I once welded a two pads onto a Triumph head to fit centre plugs. It worked extremely well until a crack appeared in the port, behind an inlet valve and released the valve guide. If I was doing it again, I would put the head in a oven to solution heat treat it and get the strength back.
 
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Hi there folks,

Thanks to a nice fellow forum member I was able to hop here and maybe am able to assist a little with some info:

1. I would refrain from closing a port with weld, because usually the thing that kills ya in the end are the wall thicknesses which remain the same even if filled up.
From what I remember that at least old blue and another Ducati had heavily welded (by rob north who to my knowledge lives by now in europe)and reshaped ports reshaped by Branch and Axtell.

2. I somehow got the info that also Ken canaga is on this forum, which did recalling one of my conversations with Michael Moore a heavily reangled port on his previous TT500 engine in a Roberts (frame?).
So I assume port welding knowledge should be here (not considering my ramblings :) ) in abundance.

3. I personally would not weld to close or put too much prolonged heat next to the seats as you might anneal that area and loose the crucial elongation strength needed for the seat inserts.

4. If I may: I personally would hog out the ports, with the gained room I would first weld/patch up the sides as one surely will penetrate during rough porting the sides (happens to me all the time on the ds1100 engines and on some Xt/TT/Sr's) than build up the port floors and raise em.

If one has to do it with Inserting a thick wall tube, I would consider a 60/30 preweld chamfer in order to reach all the needed areas quick and fast to not put too much heat in. For Inserting the tubes I would use 5356, while for welding/patching heavily inside I would use 4043 or even 4047 or if post heat treatment (T) I would go perhaps even with 4943.

5. As said most I would use an xxl length cup size 8-9 and a 3,2ish (for more heat resistance) grey or gold needle with about 15degr.
For patching I would go really low on frequency down to bout 40hz and good cleaning action and not too much amps I'm order to not penetrate too much, while for tube welding and fusing power I would go with very high frequency and medium cleaning action in order to basically intermittently weld/pulse or in my old school case pedal pumping the weld in stitch modus.
Of course one can still do it with an older square wave but on newer hi tech inverter machines the possibility of changing frequency and thus width and focused power of the arc is prize less, not even talking bout percentage of sinusoidal width or the advanced possibility of +/-amplitude strength like on the likes of big blue and big red inverters (Dynasty or aspect).
Preheating is a matter of welding style so I can not give info on that but I assume if not too much input during welding is used i would go up to 100-150 degr Celsius.

If one wants to cheat a little one can use a slightly bigger diameter cup, crank up the gas flow and prekink (with acet torch) the presharpened tungsten in order to reach hard to reach areas without going nutz.
(One of the tricks that the h&d always gladly like to forget to mention on their welding in port statements ;) ha ha ha.
And just because I read it, please no acetylen welding you make treatment wise talking marshmallows out of the crystal structure.

To my memory considering that unfortunately sandy Kosman (used to work there for a while in the early 90's) isn't in business anymore I think that there was in the south eastish San Jose area a very very capable tig-weldor that did a lot for flattrackers and dragster racers to my memory by the name "puccio"

In case there are more questions I'm very happy to help.

Btw I beg you clean the shit out of the ports maybe pregrinding and cleaning with weld prepping Al cleaner in order to get all the crap out of the pores becuz when I welded back then the Norton heads it was quite a messy job due to imho semi indecent foundry work ( oil binder sand?) While I never experienced anything comparable on A65 Heads (supposedly according to literature BSA had a state of the art foundry but what do I know.

Have a nice weekend and tanti saluti dall italia
Christian
 
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lcrken

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Great stuff, Christian. Glad to see you passing on some of your accumulated knowledge.

Ken
 
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Oh hi Ken,

What I can pass on I gladly pass on, as a lot of the mystic secret treasure digging is imho bogus, and due to the fact that I had the great fortune during my years in the bay area to have some outstanding very kind teachers.

I unfortunately can not pass on too much Norton engine specific info (as I mostly do Sr/TT/xs and Guzzis) but have dealt quite often with Brit heads, among the prettiest were Commando's and A65 (although SSR is bad on some guess due to coreshifting)

All the best and kind regards

Christian
 
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Andy Molnar seems to get his Manx Nortons going faster than the originals. I wonder if he has radically changed the inlet ports ? When the Commando came along, the factory had accumulated many years of racing experience with Manx Nortons. Not so many factory Manxes revved above 7000 RPM. Are Harley Davidson XR750s faster than 750 Commandos, by a lot ? And are we talking about road racing or on the dirt ? Just because you have a quick road race motor , does not mean it will be quick on the dirt where drive is important. A Commando motor might be too smooth in it's power delivery.
 
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Andy Molnar seems to get his Manx Nortons going faster than the originals. I wonder if he has radically changed the inlet ports ? When the Commando came along, the factory had accumulated many years of racing experience with Manx Nortons. Not so many factory Manxes revved above 7000 RPM. Are Harley Davidson XR750s faster than 750 Commandos, by a lot ? And are we talking about road racing or on the dirt ? Just because you have a quick road race motor , does not mean it will be quick on the dirt where drive is important. A Commando motor might be too smooth in it's power delivery.
The last of the XR750 Dirt track motors made 90 to 95 HP, doing it with a very impressive flat, or straight line torque curve.
But to get that you have to rev the crap out of them making the life span very short. Part of the life span problem was that parts were running out.

It would be interesting to see some dyno charts with torque of Nortons.

Back in the 1980's when the RS750 started to take over on the mile tracks, I am told they made 100 HP, they were slowed by the restrictors in the carbs as the 41mm carbed RS750 were affected far more than the 36 mm carbed XR750's.
 
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Hi there folks,

Thanks to a nice fellow forum member I was able to hop here and maybe am able to assist a little with some info:

1. I would refrain from closing a port with weld, because usually the thing that kills ya in the end are the wall thicknesses which remain the same even if filled up.
From what I remember that at least old blue and another Ducati had heavily welded (by rob north who to my knowledge lives by now in europe)and reshaped ports reshaped by Branch and Axtell.

2. I somehow got the info that also Ken canaga is on this forum, which did recalling one of my conversations with Michael Moore a heavily reangled port on his previous TT500 engine in a Roberts (frame?).
So I assume port welding knowledge should be here (not considering my ramblings :) ) in abundance.

3. I personally would not weld to close or put too much prolonged heat next to the seats as you might anneal that area and loose the crucial elongation strength needed for the seat inserts.

4. If I may: I personally would hog out the ports, with the gained room I would first weld/patch up the sides as one surely will penetrate during rough porting the sides (happens to me all the time on the ds1100 engines and on some Xt/TT/Sr's) than build up the port floors and raise em.

If one has to do it with Inserting a thick wall tube, I would consider a 60/30 preweld chamfer in order to reach all the needed areas quick and fast to not put too much heat in. For Inserting the tubes I would use 5356, while for welding/patching heavily inside I would use 4043 or even 4047 or if post heat treatment (T) I would go perhaps even with 4943.

5. As said most I would use an xxl length cup size 8-9 and a 3,2ish (for more heat resistance) grey or gold needle with about 15degr.
For patching I would go really low on frequency down to bout 40hz and good cleaning action and not too much amps I'm order to not penetrate too much, while for tube welding and fusing power I would go with very high frequency and medium cleaning action in order to basically intermittently weld/pulse or in my old school case pedal pumping the weld in stitch modus.
Of course one can still do it with an older square wave but on newer hi tech inverter machines the possibility of changing frequency and thus width and focused power of the arc is prize less, not even talking bout percentage of sinusoidal width or the advanced possibility of +/-amplitude strength like on the likes of big blue and big red inverters (Dynasty or aspect).
Preheating is a matter of welding style so I can not give info on that but I assume if not too much input during welding is used i would go up to 100-150 degr Celsius.

If one wants to cheat a little one can use a slightly bigger diameter cup, crank up the gas flow and prekink (with acet torch) the presharpened tungsten in order to reach hard to reach areas without going nutz.
(One of the tricks that the h&d always gladly like to forget to mention on their welding in port statements ;) ha ha ha.
And just because I read it, please no acetylen welding you make treatment wise talking marshmallows out of the crystal structure.

To my memory considering that unfortunately sandy Kosman (used to work there for a while in the early 90's) isn't in business anymore I think that there was in the south eastish San Jose area a very very capable tig-weldor that did a lot for flattrackers and dragster racers to my memory by the name "puccio"

In case there are more questions I'm very happy to help.

Btw I beg you clean the shit out of the ports maybe pregrinding and cleaning with weld prepping Al cleaner in order to get all the crap out of the pores becuz when I welded back then the Norton heads it was quite a messy job due to imho semi indecent foundry work ( oil binder sand?) While I never experienced anything comparable on A65 Heads (supposedly according to literature BSA had a state of the art foundry but what do I know.

Have a nice weekend and tanti saluti dall italia
Christian
 
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Yo fellas,

I have seen first hand right there on the spot about 15years ago the Molnar or was it Bennet (?)manx short stroke heads.
First off the port is as far as I'm concerned a hint more upright and of the very d-style type and the piston has a Xr/Buell style conical somewhat kidney shaped squish.
Port is somewhat more in line with bike axis in order for less low speed swirl and more volume of flow at higher gas speeds due to less friction losses (every tumble or swirl is imho somewhat friction induced and less efficient than the straight dump style port)
Carburetors used were mostly huge Gardner's with matchbox float chambers.
Similar things I have seen so far on some pure sangue Goldie's with no expenses spared ABSAF engines or if I'm allowed to say so on a few of my TT/Sr race heads then of course though with big mikunis, keihins or dellortos.
Valves were due to the short stroke super square engine obviously also larger but I would have to lie if I estimate such a long time later their diameter around 2"ish.

So considering that those repro engines are basically new modern 2valvers I have even higher respect for the likes of Axe, Branch or Augustine, since they achieved that already around late 80ies, having had a blank sheet of paper and just their experience reasoning and surely some good resoning guided by but feeling, but I'm by far surely no historian.
Furthermore after my visit at flowmetrics and having worked myself for a nor cal speed equipment supplier I'm.by far more intrigued by the west coast " who gives a flying "f" let's try it" DIY style, thus I'm a fanboy of the old blue story.

Trivia besides I hope I made my point and explained comprehensively what I saw first hand in the INCA paddocks.

Good evening to you all

Christian
 
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As I understand it, modern dynos operate based on torque. What is the primary calibration for torque based upon - a load cell and a deadweight-tester ?
 
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As I understand it, modern dynos operate based on torque. What is the primary calibration for torque based upon - a load cell and a deadweight-tester ?
On a dynojet dyno, you have a steel drum, I forget the exact weight, but around 450 lbs, that weight is supposed to duplicate the weight of a motorcycle.

Dynojet provides the exact weight, it is already entered in the software, you can change the number, and some dynojet dynos have 2 drums.
I have not read anything from dynojet for a 1000 years, but I believe it is just a calculation on the RPM of the drum and the length of time it takes to get to that speed, which is why it does not matter what gear you are in or the final drive or primary drive ratio.

RPM and Rate of acceleration.

This does have its downside, as when you make the driveline lighter, in any number of ways, chain and sprockets, wheels, tires, you increase the rate of acceleration, and on a Dynojet dyno that reads as a HP increase.

When a load cell is added it does need to be calibrated, here is the link on how that is done. Some models come with the load cell.



HORSEPOWER FORMULAS
For Rotating ObjectsHP =
WhereT = Torque (lbft)
N = Speed (rpm)


���
TORQUE FORMULAS
T =HP x 5252
WhereT = Torque (LbFt)
HP = Horsepower
N = Speed (rpm)
T =F x R
WhereT = Torque (LbFt)
F = Force (Lbs)
R = Radius (Ft)
Ta (accelerating)WK2 x Change in RPM
308 x t (Sec)
WhereTa = Torque (LbFt)
WK2 = Inertia at Motor Shaft (LbFt)2
t = Time to Accelerate (Sec)
Note:
To change LbFt2 to InLbSec2, Divide by 2.68
To change InLbSec2 to LbFt2, Mult. by 2.68
 
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It might be difficult to accurately measure the torque output of a Commando motor with am inertia dyno, when the crank has a lot of inertia of it's own. One thing I have noticed about the heavy crank, is the motor always tends to spin-up at the same rate, regardless of the overall gearing. When you race-change up at 7000 RPM and the crank slows to 5,500 RPM, the energy has to go somewhere. The only way I ever know when I have achieved an improvement, is when after I have raised the overall gearing - the corners arrive quicker and the changes happen slightly further-on on a race circuit. I still don't know what overall gearing my 850 will pull. Every time I raise it. the bike goes quicker
The slowest 650cc Triumph twin of the 1960s was the Saint - it had the light crank.
 
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I'll take West coast USA "f___" lets just try it "any day of the week. Harry Lilly made Rotax motors go pretty darn good for a lot of flat trackers, and I don't think he had a flow bench anywhere nearby. At least I don't remember seeing one. Maybe it was in a different room from the machine shop.
 
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It might be difficult to accurately measure the torque output of a Commando motor with am inertia dyno, when the crank has a lot of inertia of it's own.
Of course it can, the weight of the crank will not effect the measurement.

How much does the crank weight?
 
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