750cc Norton Commando Salt Flats Build

This is a thread to document my current project of building a salt flats Norton (AKA Salt Licker as named by my friend Sonny) at the request of a few people on this forum. This is gonna be a bit of a long one to start off with so bear with me. Its about 3 years worth of pictures and progress but I plan to keep updating as things progress leading to the 2024 Speed Week event. Planned on making it for this years event but had some snags in getting parts here.

Originally started out as a conversation between my dad and I in 2017 after finishing up my MK3 850 and watching The Worlds Fastest Indian (surprising no one I'm sure). During a visit to Leo Goff with a friend, Sonny Collier, I decided to bring up the possibility of building a Norton Commando salt bike to Leo and get his take on it. Ended up going with a 750cc engine to get the most possible out for the class. Obviously went for a hi-CR build aiming for maximum top end power(75-80hp as a goal). Now the existing SCTA 750 modified production pushrod gas record is 138-139mph. Final drive ratio was going to be a big factor in this project. After alot of math and searching I came up with the fact that I would need to have a 30 or 31T final drive sprocket. Which of course isn't something that is readily available. This posed another problem but we'll get into that later.

So now to find a donor bike to get this ball rolling. Spent a couple years waiting for the right bike to go up for sale. Didn't want to tear down a numbers matching high quality machine for this. Finally found a 1970 engine and trans that was put into a 1972 frame. While it solid and ran good it was in need of some work soon anyways so this was the perfect candidate. Made a 20hr one day trip to Florida to go pick it up and couldn't wait to get back to the shop and start tearing it down for full inspection.

Got to tearing down the bike and found the motor was in a little more rough shape than I thought (sadly didn't think to take pictures of the teardown like a dummy). On the outside the engine cases have some rough spots from road debris and looked corroded from years of sea air. Internally cylinders had been bored .040" over so I needed to source new barrels right out of the gate. The head had a couple fins missing and some pitting in the combustion chambers as well. Already not off to a good start for using the re-using much of the original motor. Moving onto the transmission it wasn't a whole lot better. Again years of sea air had corroded the exterior as well as some of the interior parts. Layshaft was worn out, all bearings needed to be replaced, and several of the gears showed more wear than I would've been comfortable re-using for an all-out run on the salt flats. The forks, swingarm, frame, gearbox cradle, and hubs were all in good shape. Rims and spokes had corrosion but those were already going to be replaced as part of the plan anyway.

Now the debate of to rebuild the engine and transmission or to just go from scratch with all new parts that are better alloys and better machined? Either way the wallet is gonna be hurting. Started with the transmission. Looked up prices for all the parts I'd need to replace in the stock gearbox and quickly realized that I was just about replacing everything but the cases, shift forks, and the camplate. Which would have ended up being well into the $2000 range. So at that point I may as well spend a little more money and get an better unit. Since I knew that TT Industries over in NZ make some of best AMC gearbox replacements I've heard of I decided to look at what they had to offer for the salt bike. Initially thought I would go with their AMC 5 speed XHD kickstart gearbox given what I was planning to do. After reaching out, their production manager Vaughan gave me several different options given the build. All the options were very impressive between the level of engineering to the weight saving over the stock box. The downside of the two best options they had was neither could have a kickstart option. SCTA rules say that gear ratio changes are allowed, but I wasn't sure if the lack of a kickstart would cause problems. So I ended up going with their standard AMC 6 speed but they made it with magnesium cases to drop as much weight as possible. Next problem is the final drive sprocket. The standard options TT Industries wouldn't quite get me to the speed I was after. This is where they went above and beyond to help me out! They made me a custom lightweight 31T final drive sprocket in a 530 chain profile. I can't give enough thanks to the guys over at TT Industries for this! I did however get told that all this help was under the condition I need to leave Burt Munro's record alone


As for the engine, I knew that I needed to get a steel crankshaft to hold all the added power at the very least. So called up Leo again to get his thoughts on what route to take. He mentioned that the crankcases needed to be strengthened if I wanted to use the originals which would be alot of time spent on a TIG welder and probably wouldn't be as good as new ones in the end anyway. When I told him about the state of the RH1 head he said to just not even bother if the casting was already showing pitting in a street motor that it wouldn't be worth the machining for a race head. Probably had alot of air bubbles in the casting from the factory. Also brought up the fact of new Andy Molnar aluminum nikasil cylinders would save alot of weight and hold up alot better. Looked up Andy Molnar over at MPL/TGA to see what he had to offer. Truly impressive stuff! Now the wallet is already shaking in my pocket as soon as I started looking at his site. And at this point I just told it to suck it up and get used to it cause I was all in. Contacted Andy to see when his next batch of parts were slated to come in. Went ahead and placed an order for new MK2 style crankcases, fully machined steel crankshaft, and aluminum nikasil lined cylinders. So much for my savings account . But I gotta say it was well worth it! Looking back now I don't think I'd have felt as confident in the original cases even after putting in the work to strengthen them. Don't mind the blurry dog in the background. He comes back in focus later lol.


Hit the max file limit for this post. I'll get the rest up as soon as I can. The story continues!

Wow… talk about a cliff hanger ending !

Fabulous stuff you’re doing there.

Really can’t wait or the next instalment…

Looking forward to more of this story. Particularly how you like the engine once put together and running.
I like your parts selection.

I'm using Andy's iron lined barrels and his crank in my 750. Almost got the TGA/MPL cases and built up a larger displacement engine but decided to keep it a numbers matching sleeper. Also ordered the standard 5 speed TTi box from Andy, but don't have it yet.

My wallet has been on fire ever since I pulled my old Norton out of the corner of the garage where it sat for 27 years. Quite a transformation from stock though.

Thanks for posting

Part 2

Now for getting a new head since the original wasn't up to snuff. I called up Matt Rambo at CNW to see when the next group of 750 heads would be available. They ended up being almost a full year in the process. I'm sure at some point Matt got tired of me asking what the status was for the new STS/FullAuto heads (sorry Matt!). But the end result was beautiful. Upon advice from Leo I had ordered one of the CNW dual Keihin FCR intake manifolds for the build to match up with the new head (spoiler for the carb choice later on)


While I waited for all the above parts to come in I went in depth on what kind of cam to throw in this 750. Looked through Megacycle's catalog and landed on their 560-N480 grind. Lots of lift and duration for top end power. Unfortunately Megacycle had a serious problem with their phone lines for nearly a month and I was unable to get in contact with them. So I started looking at possible alternatives and landed on JS Motorsports site. I'd heard from Leo in our very first talk on the project that I would need to get Jims BSA style lifter kit to make the valve train as light as possible. At the time I didn't know that Jim had his own camshafts made for Nortons. And what would ya know, he has one in a very similar profile as the N480. So just decided to go with a one stop shopping and get the whole valve train through JSM. Beehive springs, lightweight lifters and pushrods, BSA lightweight lifter kit, JSM Stage 4 cam, and one-piece rocket spindle covers.

At this point I was still planning on making it to the 2023 Speed Week event, but balancing budget and timeline was starting to become much more of an issue now that I've blown the vast majority of that years budget on a whole new engine from scratch. Still had pistons and rods to figure out. Trying to get as high of compression as possible to make up for the loss in air density at Bonneville posed a bit of a dilemma. Looked long and hard at Jims Ultra-Hi CR pistons and long rod setup to reach 12:1(or 13:1 if running alcohol). But with money running tight and still shooting to make it to Speed Week this year. I made the decision to go with stock rods (new units from Andover) and a set of JS high compression flat-top pistons designed for stock rods. Knowing what I know now about how long the head was going to take to get to me, I regret not saving up a little more and going with Jims Ultra high SR setup (saving that for a future update to the motor after the 2024 event).

So finally ended up with all the engine parts in hand minus the head. Time to get the rods polished up to remove any stress risers on the surface. Spent many an hour on the bench with a dremel tool and fine grit sand paper to get where I was happy with the result. Probably had 10hrs into both the rods when all was said and done. Now to get the rotating assembly balanced. I knew it needed dynamically balanced for the best results. Hard to find someone willing to dynamic balance a Norton twin in the US. Or at least it was for me. Finally found House of Balance in Maryland. After sending in to get a quote, a man by the name of Douglas Simms gave me a call back and talked it over with me. Gave him the parameters of what I was looking to do (7k rpm, iso frame, ect) and he had confidence that he would be able to get the crank set right. Also told me that he had done some things for the salt before so I left the details of determining balance factor to him. After about a month I got the call that he had finished the crank and was ready to ship it back to me. He determined that an 80% BF was the number for this project. Also told me to let him know about the engine performance once its all put together so he could have some feedback. So if you're on this forum for some reason Douglas, its still in progress. I haven't forgotten! Here's a shot of everything after it came back from balancing as well as the balance card.


Still more to come but I'm short on time for now. Maybe I'll get the rest of it put up this evening. Part 3 coming soon!

Fascinating build. Definitely using a good combination of parts for a landspeed engine. It will be fun to see how you do. I assume you are now planning for the 2024 Speed Week.

FWIW, neither SCTA nor AMA care if you remove the kick starter assembly for the MP classes at Bonneville. I ran a Featherbed Norton with 750 and 920 Commando engines, using a Quaife 5-speed gearbox with no kickstart provisions, in MPG and MPF classes at Bonneville, at both SCTA and AMA events, and never had a problem with tech inspection over the lack of a kickstarter.

I am a little curious about your choice of a 31T countershaft sprocket. If you are running the stock 2.19 ratio primary, standard 42T rear sprocket, and something like an Avon 130/650-18 rear tire, a 31T countershaft will give you a theoretical tops speed of 170.9 mph at 7000 rpm, and 183.2 mph at 7500 rpm. That's seriously tall gearing when running against the current 137.872 mph gas and 138.491 mph fuel records. Even after accounting for some wheel slip, I doubt if you will be able to get high enough speed in 4th gear to be able to shift to 5th without dropping off the torque curve. But that's assuming you are using close to the stock gearing and tires for most of the drive train, and you might be planning something else entirely.

In any case, I look forward to seeing your updates. I think you have a package that definitely has record potential.

Ken

FABULOUS...
So that's what a raised floor exhaust port looks like,,,

BTW, don't worry about being long winded, most here prefer the Looongggg version....

lcrken said:

Fascinating build. Definitely using a good combination of parts for a landspeed engine. It will be fun to see how you do. I assume you are now planning for the 2024 Speed Week.

FWIW, neither SCTA nor AMA care if you remove the kick starter assembly for the MP classes at Bonneville. I ran a Featherbed Norton with 750 and 920 Commando engines, using a Quaife 5-speed gearbox with no kickstart provisions, in MPG and MPF classes at Bonneville, at both SCTA and AMA events, and never had a problem with tech inspection over the lack of a kickstarter.

I am a little curious about your choice of a 31T countershaft sprocket. If you are running the stock 2.19 ratio primary, standard 42T rear sprocket, and something like an Avon 130/650-18 rear tire, a 31T countershaft will give you a theoretical tops speed of 170.9 mph at 7000 rpm, and 183.2 mph at 7500 rpm. That's seriously tall gearing when running against the current 137.872 mph gas and 138.491 mph fuel records. Even after accounting for some wheel slip, I doubt if you will be able to get high enough speed in 4th gear to be able to shift to 5th without dropping off the torque curve. But that's assuming you are using close to the stock gearing and tires for most of the drive train, and you might be planning something else entirely.

In any case, I look forward to seeing your updates. I think you have a package that definitely has record potential.

Ken

Click to expand...

I wish I had known that last year! Would have made the transmission selection so much better. But good to know going forward. Because there is the thought of doing another engine for a streamliner(currently a pipe dream in the design phase) As for the countershaft sprocket, originally I was looking at the AMA record which is around 158-159mph if memory serves and I wanted to over shoot that on the drawing board by a good amount, Because as we all know, drawing board figures vs. real world are totally different things. I'll give a full breakdown for all the specs on the build after I get current on all the progress on the project posted.

MichaelB said:

FABULOUS...
So that's what a raised floor exhaust port looks like,,,

BTW, don't worry about being long winded, most here prefer the Looongggg version....

Click to expand...

Just wanted to give as much detail as possible without writing a novel. Hard to do with 3+years of progress and details though haha
Alright. Now I'm gonna start typing up part 3 to this.

Maybe you'll have a tail wind to help with that 31T gearbox sprocket.

Part 3

So got everything in hand to start putting together the bottom end. This is where I got out Jim Schmidt's race manual and went by the book. Got out an old (but still workable) set of FAG main bearings and ground down that ID and OD of the press fit portions to slip on and off of the new cases and crankshaft. Put the dummy bearings in and measured the crank end play. Ended up being pretty spot on at .007-.011" and decided it was close enough to put the brand new FAG C3 bearings I got from my friend and parts Norton dealer Sonny Collier.

Heated up the cases after putting the outer races in freezer for a few hours. Took a little coaxing from a hammer and aluminum drift to get them home but both sides went in perfectly. Checked it again after letting everything cool down to room temp and ended up with a .008" end play. Perfect! Geralt my shop wolf kept his eye on me the whole time to make sure I didn't measure wrong lol


Time to move on to the rod bearing clearance! Took the crank out of the cases and installed new bearing shells in the brand new rods. Grabbed the trusty plastigauge kit and started checking. First two times the rods and crank rolled while torqueing the nuts down but on the third try I got .001-.0015 on the timing side and .0015-.002 on the drive side. Felt super lucky to hit tolerance (or extremely close) right out of the gate and not need to correct the rods with honing. Cleaned off the plastigauge from the journals and the bearings, put a drop of oil on each, and torqued them all down to 25 ft-lbs. Next came time to check for clearance between the conrod bolts and the cases, and cam tunnel clearance. The new cases from Andy are definitely beefed up over stock cases. Cam tunnels needed alot of clearing to fit the monster JS4 cam. Set up both halves of the cases with the pistons as guides and checked the rod bolt clearance. Turns out there were several spots that the bolts were hitting the inside of the cases. Time to breakout the carbide bits and 80 grit slap wheel for the die grinder. I taped off all the bearings to keep them metal free during this process. Once again MANY hours spent carefully removing material. Went with .035-.045" clearance for the cam tunnel to the lobes and after alot of reading came up with .060"+ for the rod bolts to the cases. I didn't want to remove all the material from the cases and weaken them. So after removing what I estimated to be enough material from the cases (did a couple check assemblies to see how close I was getting), decided it was time to start taking from the rod bolts and nuts to finish out the clearance. Took the crank out of the cases with rods still attached, got a thick plastic bag over the crank assembly and put two holes just bit enough to get the rod bolts and nuts through. Carefully put an angle on them to give me the clearance I was looking for. One ended up being a little more than I was shooting for but it all came out pretty good in the end I think.

Finally time to put the bottom end together! Got the cases all cleaned up and free of debris. Prepped the cases with a light coating of Permatex, set the crank in place, and tightened up the case bolts to 30ft-lbs (3/8 bolts) and 25ft-lbs(single 5/16 bolt). Now its finally starting to look like a solid motor!

Also forgot to mention that I also got all the case bolts and barrel studs from CNW as well. Hard to beat ARP hardware!

Hoping to get part 4 posted tomorrow evening and that should have everything pretty well caught up for now on the project.

I suggest your choice of 6 speeds close ratio with high overall gearing is a good one. With the Commando motor, it is difficult to know if it is not giving it's best. With close ratios, you will not be so dependent on throttle response as you change up through the gears. When you test ride the bike, you will need to notice when the bike is fastest if you wind the throtle on slow or fast. If the gearing is too high, you usually move onto the richer part of the needles, that slows the motor slightly. So two things can compound the situation - you haven't got the revs to be up far enough into the power band and the mixcture is too rich.
The heavy crank can actually be used to advantage. Each up-change in the close box, should give you a boost due to crank inerta,

IMHO, FWIW, AFAIK, ETC…
I would get more sprockets made / sourced. Along with chains pre cut to the required length.

You have no e start etc, so with the right tools, changing the gearbox sprocket isn’t a big job especially if you have the pre cut chains ready to go.

I’d suggest doing this and taking a selection with you. I’ve no experience with LSR but your gearing sounds too high to me.

Don’t forget, a purpose built 750 has more revs to play with than a strict 7,000 limit, so you do have some flexibility to play with there.

Single row primary chains are lighter and so is an earlier Norton clutch. That setup has been used on many drag bikes over the years, and is unlikely to fail, if you lube the chain prior to events. I use floating Jawa speedway engine sprockets, which are available from Andy Smith in the UK, and they are cheap. The splined Jawa sprocket carrier will probably fit the Commando crank taper. The taper is 5 degrees. - I had one made,
I think I bought 4 engine sprokets at aboiut $10 each. They are changed by taking the clip off the carrier. I usually carry a chain breaker. The TTI box also came with 4 sprokets. My rear sprocket is about 36 teeth, I think the clutch is 48. If I have to change the gearing, I usually change the engine sprocket, but overall gearing does not matter much, as long as it is high. Nothing will slow the Commando crank when it is spinning above 6000 RPM. If I change up at 7000 RPM, I lose 1500 RPM. With a wide ratio box, that would probavly be 2500 RPM - regardless of the overall gearing

Fast Eddie said:

IMHO, FWIW, AFAIK, ETC…
I would get more sprockets made / sourced. Along with chains pre cut to the required length.

You have no e start etc, so with the right tools, changing the gearbox sprocket isn’t a big job especially if you have the pre cut chains ready to go.

I’d suggest doing this and taking a selection with you. I’ve no experience with LSR but your gearing sounds too high to me.

Don’t forget, a purpose built 750 has more revs to play with than a strict 7,000 limit, so you do have some flexibility to play with there.

Click to expand...

I do plan on having at least two other sprockets to work out there that are shorter to see if i can get the most out of the machine. Just wanted to get the bulk of the project put together before trying to add more pieces. I knew I would have some wiggle room with a 7,000rpm limit given the new components and being purpose built. Still wanted to play it as safe as I could first time out on the salt.

acotrel said:

Single row primary chains are lighter and so is an earlier Norton clutch. That setup has been used on many drag bikes over the years, and is unlikely to fail, if you lube the chain prior to events. I use floating Jawa speedway engine sprockets, which are available from Andy Smith in the UK, and they are cheap. The splined Jawa sprocket carrier will probably fit the Commando crank taper. The taper is 5 degrees. - I had one made,
I think I bought 4 engine sprokets at aboiut $10 each. They are changed by taking the clip off the carrier. I usually carry a chain breaker. The TTI box also came with 4 sprokets. My rear sprocket is about 36 teeth, I think the clutch is 48. If I have to change the gearing, I usually change the engine sprocket, but overall gearing does not matter much, as long as it is high. Nothing will slow the Commando crank when it is spinning above 6000 RPM. If I change up at 7000 RPM, I lose 1500 RPM. With a wide ratio box, that would probavly be 2500 RPM - regardless of the overall gearing

Click to expand...

I'm going to be using a belt drive primary from CNW. The transmission is a wide ratio box but if memory serves the first three are where its are wider. Past 4th it gets back to a close ratio. I'll post the full details when I get current.

Zachary Brown said:

I do plan on having at least two other sprockets to work out there that are shorter to see if i can get the most out of the machine. Just wanted to get the bulk of the project put together before trying to add more pieces. I knew I would have some wiggle room with a 7,000rpm limit given the new components and being purpose built. Still wanted to play it as safe as I could first time out on the salt.

I'm going to be using a belt drive primary from CNW. The transmission is a wide ratio box but if memory serves the first three are where its are wider. Past 4th it gets back to a close ratio. I'll post the full details when I get current.

Click to expand...

The cNw belt is great. It is only standard gearing though (or very close to) whereas Maney or Norvil ones are raised. Norvil actually do quite some options.

Part 4

Rotating assembly complete. On to the pistons and rings. The JSM hi CR flat-tops are beautiful units the I got Jim to ship with rings for the nikasil bores. Took the barrels and pistons to a local engine machine shop to have the deck surface cleaned up and cut the squish band step into the piston tops. Also had them double check my piston clearance before working on the ring gaps. The machine shop got the deck cleaned up in .003" from where they started and the piston clearance was between .00325" and .004" (recommended clearance to nikasil bores was .0035"). Dancing all over tolerance so time to get the rings gapped. Started with the top rings and worked my way down to the oil rings. Checked top rings for .012" gap. Both top rings would need filing. Got out my ring filing tool and started working. Finally got the top rings done at .012". Second rings didn't need any filing, so moved onto the oil rings. Since they're so thin it was alot harder to check gap. Specs said that they needed at least a .015" minimum gap and by my best measurement they were anywhere from .014-.017". Since they were so close to minimum spec I opted to leave them be. Didn't want to chance damaging them on the fairly course filing tool. Cleaned of all the sharp edges on the top rings with a fine machinists honing stone and got ready to start put the pistons in the cylinders. Put one drop of oil in each ring groove and spun them around to distribute the oil to the whole ring before setting the gaps in their correct position. Got out the trusty ring compressor, got the pistons in their bores, and set the barrels down. Gotta say it really looks beautiful!

Just realized I forgot to mention I had already worked on the cylinders to install the JSM bronze BSA lifter blocks and lifters before putting the barrels in place. Didn't want people to think I was letting the cam work on magic At this point I've gone as far as I can with the motor. Leo Goff currently has the head and is working his magic on the new STS/FullAuto piece. Cam timing was set to standard for the time being until I can get the head installed and set timing for the JS4 cam correctly based on the valve lift. Hoping to get it all put together by the end of the month so I can have the engine completed. There's still plenty of other things to attend to in the mean time. Rims & spokes, tires, front fork rebuild/modifications, frame check and modifications, ect. One of the main things in the works now is getting a whole new gearbox cradle made to allow for the large 31T sprocket. The swingarm mount is having to be relocated rearward .625-.75" to clear the swingarm pivot. Now using a smaller sprocket would make this a pointless venture, but I'm still toying with the idea of maybe doing some streamlining with this build in the future

A rear hub that supports changing rear sprockets = fast overall gearing changes.

That 750 engine you're building should do 8K RPM to help with the tall gearing shifts. I don't know if it will run at 8K RPM for 2 miles without backing off some though. It probably could. My guess is you will find out trying to break a record. Once you get that thing singing above 7500 RPM you'll want to push it more.

The Molnar crank is 3lbs lighter than the stock 750 crank. You will not miss the heavier stock crank inertia with those pistons. You'll be amazed at how quick this engine you are building can spin up even with taller gearing.

Have fun with the two nuts up front on the barrels that go on the studs coming down out of the head. I had to do some work with a Dremel around that opening (before dropping the barrels on for reals) and use a dental tool to get those nuts started.

Zachary Brown said:

I wish I had known that last year! Would have made the transmission selection so much better. But good to know going forward. Because there is the thought of doing another engine for a streamliner(currently a pipe dream in the design phase) As for the countershaft sprocket, originally I was looking at the AMA record which is around 158-159mph if memory serves and I wanted to over shoot that on the drawing board by a good amount, Because as we all know, drawing board figures vs. real world are totally different things. I'll give a full breakdown for all the specs on the build after I get current on all the progress on the project posted.

Just wanted to give as much detail as possible without writing a novel. Hard to do with 3+years of progress and details though haha
Alright. Now I'm gonna start typing up part 3 to this.

Click to expand...

Yeah, that 159.903 mph record in the AMA 750-M-PG class is pretty tough. It was set by Canadian Tom Mellor with his very trick Triumph triple in 2008. One of the issues with going for that record, is that the rules for the amount of streamlining allowed behind the rider, i.e. the seat shape, were different then, and Tom took full advantage of them. That's no longer allowed in the (unstreamlined) M classes, making it more difficult to compete against his record. That's one reason I stopped running in that class at the BMST (AMA) meets, and switched to the 750-M-PF class, where the record is only 130.369 mph. Just doing a little cherry picking. Unfortunately, I had mechanical problems the last time I ran in that class in 2019. I'm still hoping to try again in 2024. Tom ran the bike with more bodywork in the 750-MPS-PG class, also in 2008, and set the record for that class at 180.317 mph. I suspect that both those records will hold up for at least a few more years. Those are pretty high goals.

The 750-MPS-PF record, currently at 146.351 mph, also looks reasonably achievable. I set the record in this class with my Norton at 126.461 mph at the 2006 meet. It was admittedly a bit of cherry picking, and didn't last long. I wasn't running fuel, just the normal event race gas, but the existing record was low enough that I couldn't resist running in the fuel class.

There's a good description of Tom's bike and his record runs here:


This is a picture of Tom's bike as he ran it in the 750-MPS-PG class. He ran the same bike, but with the front fairing removed, to set the record in the 750-M-PG class. You can see the advantage he got from the massive rear streamled tail section.



Ken

Zach, if you're interested, here are links to some threads I did about my experiences with nitrous oxide on Commando engines at Bonneville. I don't know if you will find anything of use there, but it makes interesting reading. I've posted some other threads about running Nortons at Bonneville, and I'll post links here if I can find them.




Ken

Zachary,

Could you ask Leo what he thinks about the D exhaust ports in a 750 head for land speed record breaking?

Schwany said:

Zachary,

Could you ask Leo what he thinks about the D exhaust ports in a 750 head for land speed record breaking?

Click to expand...

So this was a topic we covered in a previous conversation. Leo says the D shaped ports flow better with the floors being raised up. Don't have my notes in front of me right now but I believe it has to do with keeping exhaust gases from flowing back into the chamber (reversion). The advantage isn't even just for land speed racing.

lcrken said:

Zach, if you're interested, here are links to some threads I did about my experiences with nitrous oxide on Commando engines at Bonneville. I don't know if you will find anything of use there, but it makes interesting reading. I've posted some other threads about running Nortons at Bonneville, and I'll post links here if I can find them.

Norton Ready for Bonneville Speed Trials

Having trouble accessing Putfile, so no pictures today, but I can do a status update. The weather has been iffy. I managed two runs yesterday with good and bad results. The bad is that on the first run the engine quit running just before the timed mile, but it was just a lanyard kill switch...

www.accessnorton.com

Return of the Nitrous Norton (2016)

That looks the business Ken. Good luck.

www.accessnorton.com

920 Race Engine Teardown

I had to tear the 920 Commando engine down after going to Bonneville this year, because it developed a crack in the crankcase. I thought it would be a good opportunity to post details of how the iron cylinders were sleeved, for those who haven't already seen them. These are the cylinders that...

www.accessnorton.com

Ken

Click to expand...

Thanks for the links! Tried to read all I could before going all in on this but there's alot out there and not enough hours in the day. I had read about Toms bike and heard about the rule change which made me decide to run at the SCTA event. Hopefully I'll run into you out there in 2024!