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.
 
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.
Click to expand...
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.
Click to expand...
.010 seems quite too tight, no room for the slightest deflection...
 
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.
Click to expand...
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.
750cc Norton Commando Salt Flats Build
750cc Norton Commando Salt Flats Build
750cc Norton Commando Salt Flats Build


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.

750cc Norton Commando Salt Flats Build
750cc Norton Commando Salt Flats Build


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.
750cc Norton Commando Salt Flats Build
750cc Norton Commando Salt Flats Build


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.
Click to expand...
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.
 
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.
750cc Norton Commando Salt Flats Build
750cc Norton Commando Salt Flats Build
750cc Norton Commando Salt Flats Build


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!

750cc Norton Commando Salt Flats Build
750cc Norton Commando Salt Flats Build


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.
 

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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.
 
Time for a LONG overdue update for the project. Been busy between job swap and starting to build my own bike/machine shop to get the ever growing number of bikes and parts out of the basement. Trying to decide if I'm gonna open up my own side business for this or not. But that's another story

Mostly been more aluminum fabrication (really getting the TIG practice in!) First part was to make up a battery tray/holder. Had enough scrap aluminum angle bar left to weld up a pretty nice enclosure. Bent a section of 16ga steel to act as a hold down using 1/4-20 stainless screws to hold the Shorai unit in place.
750cc Norton Commando Salt Flats Build

From there moved onto putting together a tach mount for the old but freshly rebuilt Smiths to be front and center. I had an old beat up instrument mount laying in the parts bin. Took it to the saw an removed the original mounting lug that was bent. Smoothed all the edges out with a file before mocking up some new ears to fit on the fork nuts. Grabbed some 1/8" plate and cut out a few strips to work with. After many hours getting everything lined up just so, marked up, and welded I ended up with this. Also decided to add on an oil pressure gauge as well. Had to make a couple little pieces to to move it from the intended mounting location to avoid the new tach mount. Went ahead and snagged a new twist grip, clutch lever, and killswitch to finish up the controls. I have a Brembo master cylinder that came from the original bike that just needs a new coat of paint before installing on the bars.
750cc Norton Commando Salt Flats Build
750cc Norton Commando Salt Flats Build


Most recent new development was completed today. Fabricated a primary cover and seat. Took a little time at the slip roll getting the outer parts for the primary cover radiused properly but otherwise straightforward. Didn't want to get to complex with the seat (which will also double as the number/ID plate) so it looks a little boxy. Not exactly my greatest design choice but I think it'll work fine. Not going for streamliner class with this one so not to worried about it.
750cc Norton Commando Salt Flats Build
750cc Norton Commando Salt Flats Build
750cc Norton Commando Salt Flats Build

Forgot to grab pictures of both sides but also got the foot controls roughed in for the custom rear sets. Next on the list for completion is to fabricate the mufflers. I've already laid out the blanks I need. Now to make the time at the cutter and slip roll to form everything up for welding. The gas tank is currently out for paint. Really hoping to have it back by first of next month. Engine is still on the bench awaiting the final tweaks to the head before putting it in the frame. After that I will finalize the suspension height on the front and rear. Wanted to wait until I have all the major pieces in place weightwise to calculate ride height.
 
Zachary Brown said:
Time for a LONG overdue update for the project. Been busy between job swap and starting to build my own bike/machine shop to get the ever growing number of bikes and parts out of the basement. Trying to decide if I'm gonna open up my own side business for this or not. But that's another story

Mostly been more aluminum fabrication (really getting the TIG practice in!) First part was to make up a battery tray/holder. Had enough scrap aluminum angle bar left to weld up a pretty nice enclosure. Bent a section of 16ga steel to act as a hold down using 1/4-20 stainless screws to hold the Shorai unit in place.
View attachment 118140
From there moved onto putting together a tach mount for the old but freshly rebuilt Smiths to be front and center. I had an old beat up instrument mount laying in the parts bin. Took it to the saw an removed the original mounting lug that was bent. Smoothed all the edges out with a file before mocking up some new ears to fit on the fork nuts. Grabbed some 1/8" plate and cut out a few strips to work with. After many hours getting everything lined up just so, marked up, and welded I ended up with this. Also decided to add on an oil pressure gauge as well. Had to make a couple little pieces to to move it from the intended mounting location to avoid the new tach mount. Went ahead and snagged a new twist grip, clutch lever, and killswitch to finish up the controls. I have a Brembo master cylinder that came from the original bike that just needs a new coat of paint before installing on the bars.
View attachment 118141View attachment 118142

Most recent new development was completed today. Fabricated a primary cover and seat. Took a little time at the slip roll getting the outer parts for the primary cover radiused properly but otherwise straightforward. Didn't want to get to complex with the seat (which will also double as the number/ID plate) so it looks a little boxy. Not exactly my greatest design choice but I think it'll work fine. Not going for streamliner class with this one so not to worried about it.
View attachment 118143View attachment 118144View attachment 118145
Forgot to grab pictures of both sides but also got the foot controls roughed in for the custom rear sets. Next on the list for completion is to fabricate the mufflers. I've already laid out the blanks I need. Now to make the time at the cutter and slip roll to form everything up for welding. The gas tank is currently out for paint. Really hoping to have it back by first of next month. Engine is still on the bench awaiting the final tweaks to the head before putting it in the frame. After that I will finalize the suspension height on the front and rear. Wanted to wait until I have all the major pieces in place weightwise to calculate ride height.
Click to expand...
Looking good! When do you think you will start testing?
 
jan nelder said:
have a look at the Norton monocoque racer, especially the rear tail: the whole buke was wind tunnel optimised for airflow over the crouched rider.
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I love the workmanship on that bike. Sadly since I'm going for the open class I believe they would frown on that much aero work being on the machine. Seeing the tail section makes me feel better about what I ended up with though.
 
Last edited:
I notice the cranks has a lightened flywheel. I suggest that might be a backwards move. When I built my Seeley 850 I never believed in it. When I first raced it, I had the standard gearbox with wide ratios, and a single disc front brake. It was absolutely hopeless, but I did not know what I was dealing with. If I raised the overall gearing, it accelerated faster. I bought the Manx 4 speed racing cluster. With close ratios the bike was much faster, once it was mobile - it was better everywhere. With the Commando, you are playing with torque, not horsepower. The two things are related by the revs the motor is doing when it develops its power. A motor which develops a lot of power at high revs sometimes has no guts. The last time I raced, I kept up with the lead bunch fairly easily, but I was not getting good starts. In the last race, I revved the heavy crank to about 6000 RPM on the start line and was right up behind the leaders at the second corner. I rode under and past the three of them easily, and was well ahead when the fuel line under the tank came adrift and the motor stopped. It was no big deal but a bit disappointing.
After that meeting, I knew I would probably never race again but I sold a TZ350 Yamaha and bought a TTI 6 speed close ratio gearbox just to complete Seeley 850. One day I took the Seeley to Winton to ride it with the 6 speed close box. When I rode the bike around the pits, it would not accelerate, So I gave it a big rev and rode the clutch out. The bike took-off like a jet and I almost stuffed it through a fence.
My message is that with the heavy crank, you do not know how fast your Commando engine will accelerate the bike until you raise the gearing. The TTI box I bought had the wrong shift drum in it. What I thought was 2nd gear was probably 5th. - When you use the heavy crank with close ratio gears, you use the crank inertia to advantage when you accelerate, and also when you need engine braking. On an upchange with a wide ratio gearbox, you tend to lose too many revs. With a close box, you get a boost with each upchange.
 

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