750cc Norton Commando Salt Flats Build

savingclassicmotorcycles said:

Thanks for sharing Zachary great thread always been a dream of mine to run a bike at the Salt Flats something for the future for sure, fun fact for a while Burt Munro's Grand daughter was our next door neighbour epicly awesome family she always used to pop her head over if I had the 650ss in the garden working on her

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That's awesome! When I ordered the TTI gearbox for this project I got the following response from the TTI design group "We're willing to help you. We just request that you leave Burt Munro's record alone." Haha

milfordite said:

Curious as to why you are using the Norton rear wheel. Is that in the rules? I used a Suzuki GS550 rear wheel on my race bike because it was lighter, has a better cush drive, and you could change sprockets.

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It's not in the rules from everything in the SCTA book. It's just the route that I decided to take. Really wanted to keep it as much Norton as possible. Not to concerned with a lightweight wheel since I'm just going in a straight line and not going for extreme acceleration. As for changing the rear sprockets I'm not to worried about that with the TTI 6-speed wide ratio gearbox. Now I may be way off base and be proven wrong when I finally make it out to Bonneville (sadly won't be this year due to financial and time restrictions on the project)

Zachary Brown said:

That's awesome! When I ordered the TTI gearbox for this project I got the following response from the TTI design group "We're willing to help you. We just request that you leave Burt Munro's record alone." Haha

It's not in the rules from everything in the SCTA book. It's just the route that I decided to take. Really wanted to keep it as much Norton as possible. Not to concerned with a lightweight wheel since I'm just going in a straight line and not going for extreme acceleration. As for changing the rear sprockets I'm not to worried about that with the TTI 6-speed wide ratio gearbox. Now I may be way off base and be proven wrong when I finally make it out to Bonneville (sadly won't be this year due to financial and time restrictions on the project)

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Hi Zachary I have read a great deal on this site but never posted ever before.
Your build story is excellent. I am building a very similar engine but 828cc for drag racing here in NZ. Will put a bit of info up when I get a chance.
I have Molnar cases and using a JS3 cam and found the cam tunnel clearance in cases to be ~ 0.010" and have been unable to find a suggested clearance. I note that you have come up with 0.035-0.045". Is this based on a recommendation or what looked good. Appreciate any comments.

Jim said it should be 40 to 50 thou (at 6.00 mn in the video )

CUin11.2sec said:

Hi Zachary I have read a great deal on this site but never posted ever before.
Your build story is excellent. I am building a very similar engine but 828cc for drag racing here in NZ. Will put a bit of info up when I get a chance.
I have Molnar cases and using a JS3 cam and found the cam tunnel clearance in cases to be ~ 0.010" and have been unable to find a suggested clearance. I note that you have come up with 0.035-0.045". Is this based on a recommendation or what looked good. Appreciate any comments.

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Your build sounds very interesting, please do post some details, maybe start a build thread ?

CUin11.2sec said:

Hi Zachary I have read a great deal on this site but never posted ever before.
Your build story is excellent. I am building a very similar engine but 828cc for drag racing here in NZ. Will put a bit of info up when I get a chance.
I have Molnar cases and using a JS3 cam and found the cam tunnel clearance in cases to be ~ 0.010" and have been unable to find a suggested clearance. I note that you have come up with 0.035-0.045". Is this based on a recommendation or what looked good. Appreciate any comments.

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.010 seems quite too tight, no room for the slightest deflection...

marinatlas said:

Jim said it should be 40 to 50 thou (at 6.00 mn in the video )

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Thanks for the link.
I am more specifically after the clearance between the crankcases and the lobes rather than to the tappet block. I guess they should be a similar number though.

Fast Eddie said:

Your build sounds very interesting, please do post some details, maybe start a build thread ?

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My frequent song...

CUin11.2sec said:

Hi Zachary I have read a great deal on this site but never posted ever before.
Your build story is excellent. I am building a very similar engine but 828cc for drag racing here in NZ. Will put a bit of info up when I get a chance.
I have Molnar cases and using a JS3 cam and found the cam tunnel clearance in cases to be ~ 0.010" and have been unable to find a suggested clearance. I note that you have come up with 0.035-0.045". Is this based on a recommendation or what looked good. Appreciate any comments.

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Glad to see I'm not the only building one these days! Truthfully I don't remember where I got the .035-.045" figure from at the moment. Don't have all my notes in front of me. I'd be willing to bet that figure came from a friend of mine Leo Goff or I got it as close as I could by hand without taking to much from the cam tunnel in the cases. We've had many phone conversations about this project and sadly I can't keep track of all the notes from them like I should. I really hope to see how you're build for drag racing goes!
I'm currently waiting for the frame and other parts to get back from powder coating. Should be next weekend when I get them back and a good assembly done. Would like to have the complete engine assembled before putting it in the frame but we'll see if that happens. Still waiting on the head to come back from porting/polishing.

Alright its finally looking like a motorcycle! All the parts came back form powder coating. Spent a day getting the new bushings, bearings, and isolastics installed. Followed by getting the frame put together.


Next day was all about fighting with the rear wheel and hub. Guess between powder coating and welding in the new gussets it shrank up just a bit on the inside width. But everything came together and now there's a full rolling frame including the TTI gearbox! Took a little time this afternoon to get that put in place too. Waiting to put the engine in place until I get the head installed and degree in the JS4 cam. Threw the old gas tank on with the modified Z plate just to get a little better idea of how everything was gonna look in the end.



Got plenty of clearance for the massive final drive sproket as well. I may end up ordering another lower teeth sprocket (maybe 25T? depending on what TTI stocks) to have as well. Should help with testing and tuning when the time comes.


At this point all install hardware except for the new ARP bolts pictured is temporary. I have new units coming from Andover and John Heely. Including the end caps for the swingarm. The old ones were to rough to re-use on the new O-rings.

Zachary Brown said:

Alright its finally looking like a motorcycle! All the parts came back form powder coating. Spent a day getting the new bushings, bearings, and isolastics installed. Followed by getting the frame put together.
View attachment 114769View attachment 114770View attachment 114771

Next day was all about fighting with the rear wheel and hub. Guess between powder coating and welding in the new gussets it shrank up just a bit on the inside width. But everything came together and now there's a full rolling frame including the TTI gearbox! Took a little time this afternoon to get that put in place too. Waiting to put the engine in place until I get the head installed and degree in the JS4 cam. Threw the old gas tank on with the modified Z plate just to get a little better idea of how everything was gonna look in the end.

View attachment 114772View attachment 114773

Got plenty of clearance for the massive final drive sproket as well. I may end up ordering another lower teeth sprocket (maybe 25T? depending on what TTI stocks) to have as well. Should help with testing and tuning when the time comes.
View attachment 114774View attachment 114775

At this point all install hardware except for the new ARP bolts pictured is temporary. I have new units coming from Andover and John Heely. Including the end caps for the swingarm. The old ones were to rough to re-use on the new O-rings.

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You may have already heard this or know, but powder coating the cradle without a lot of masking can cause you problems. I love powder coat but never powder coat cradles even though I can do them in-house. Unless you're going to remove the powder coat at each nut and bolt location, you need to check them often at least for a while once you're running to be things have not come loose. The same, to a lesser degree is primer, paint, and clearcoat on the cradle. I use KHT Roll Bar and Chassis paint in gloss black. No primer needed, high temp, strong, and easy to do while keeping the thickness like the original.

This might be better- pick on somebody your own size ? -

Alright. Finally more off the checklist. Spent the last week fabricating a new aluminum oil tank thank would allow for the long intake runners. Decided that it would be best to have one that mounted slightly lower and transverse. Opted to put a few cooling fins on each side to precipitate more heat dissipation where possible. Made two mounting brackets using 1" aluminum angle bar. The excess ended up being perfect to drill for the frame mounts behind the Z-plates. Now before going seeing the pictures, its important to know that until last month it had been over 10 years since I TIG welded aluminum lol. I spent some time practicing on some scrap I had on hand and got the feel back, but this is by no means the prettiest welding out there. Especially the fillet welds for the fins

Here's a couple for the general overview. The hoses were in preparation for leak testing.


And here is a couple with it in the bike. Exact mounting to be determined. And yes the filler cap can be removed with it in the frame. Made many measurements to make sure of that during fabrication!



Current game plan is to use the forward ends of the brackets for mounting the battery tray (also to be fabricated) give the carbs allow for enough room. The measurements I took with the old motor says yes, but I'm not going to make that call until I can confirm with the new engine in place and the carbs mocked up.

I was wondering about the gearbox. Whether it would be better to accelerate faster from start up to the measured area then hold speed, or accelerate slower from the start and continue to accelerate at the same rate through the measured area. With wide ratios the acceleration rate is slower. Is acceleration versus wind resistance linear ? - I think it is a curve. Once you have got the bike to it's maximum speed at the start of the timed distance, it might be easier to hold that speed, than accelerate from a lower speed through the timed distance to a higher ultimate speed and have an averaging effect.

From my understanding its better to hold your speed over the measured mile. I believe you're right that wind resistance does run on a curve. I've run the bike setup through an engine simulation ALOT. Given approximate figures for head flow rates, machine/rider weight, and overall drag coefficients, it takes roughly 23-25 seconds to reach the record speed from a standing start.