750cc Norton Commando Salt Flats Build

I suggest that even with four stroke motors there are Kadency effects. The porting is not only about flow, you can think about it as being two connected organ pipes - the whole inlet, conbustion chamber and exhaust system resonates at a frequency which is in proportion to the speed of sound divided by the revs. Gas flow is about smoothing out bumps, but it doesn't really provide a prediction of what will happen when a motor is running at high revs. The proof of the pudding is always in the eating.

Zachary Brown said:

...Because there is the thought of doing another engine for a streamliner(currently a pipe dream in the design phase)...

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If you do build a streamliner, I suspect it will be to lot higher standard than the one my friend and I built. This was our shot at a budget streamliner. It had a Commando engine punched out to 920 cc and a heavy duty Quaife 5-speed gearbox. We used a lot of bits we had on hand from previous road race bikes. We ran it at the BUB (AMA) Bonneville events from 2006 through 2009, but never managed a really good run. 2006 was particularly interesting. I had fitted a Pingle electric solenoid actuated shifter. It worked fine on the test stand, but would not shift at speed. We did get a measured run in first gear only at something like 60 mph, but since there was no record in the class, that qualfied us to make a return run for a record. After messing around with it for a couple of days, we were able to get it to shift through the gears from 2nd to 5th in a low speed test behind the pits. We decided to just start in 2nd gear, and hope it worked. But it didn't. It wouldn's shift at any rpm much above 1,000 rpm. My friend was driving, and just held it wide open in 2nd gear all the way through the speed traps. I've forgotten his exact speed, but it gave us a two way average of 87.078 mph. That is still the existing record for the 1000-S-PG class! But it's kind of embarasing to claim it. 2009 was the last time it ran with a Norton engine. My friend swapped in a Moto Guzzi engine, added a sidecar, and picked up a couple of records for that class.

I think I posted several threads about our adventures, but my threads on the forum prior to 2009 appear to have been deleted. I'm sure Jerry has to pick some sort of date cutoff for archiving threads, based on the amount of storage he has.

These are pictures of it from the 2009 meet. We never did add the rear body work, and now it's retired. It was fun, in a frustrating way, but we learned a lot, and met a lot of great people along the way. My future plans only include running the featherbed/Commando bike.

This is a picture of it on the cart we used to move it around on the salt.



And this is a shot of it at speed with my friend Eric running it down the salt.



Ken

Zachary Brown said:

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.

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Thanks

Yeah, I understand what the D reversion dam in the exit floor does, just wondered if that smaller exit hole really would be that useful for making maximum HP at WOT for 3 miles or whatever the length of that run is. Kind of a reality versus on paper question.

I'm working on a spare early Commando head and thought it might be interesting to build up the exhaust ports more like a D for the street. Probably won't though. I don't have a flow bench to test anything. Nor do I know what that port looks like on the inside.

I do unfortunately get what I think is significant reversion in my combustion chamber from exhaust ports that are matched to the ID of my 1.5" exhaust. I have never put the engine on a dyno to see how bad it actually is, but it makes my FCR slides rattle at idle.

Schwany said:

I do unfortunately get what I think is significant reversion in my combustion chamber from exhaust ports that are matched to the ID of my 1.5" exhaust. I have never put the engine on a dyno to see how bad it actually is, but it makes my FCR slides rattle at idle.

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All FCR carbs rattle like that. It sounds exactly like its pinging due to a lean mixture.

jseng1 said:

All FCR carbs rattle like that. It sounds exactly like its pinging due to a lean mixture.

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Thanks

I thought it was normal as well. However, I figured something else must be causing it, so I went with reversion. Reason: I mentioned the FCR idle rattle once before on this site and was told "Mine never rattle" by a couple of members. So I hung my head in shame and walked away slowly. My RGM belt clutch is a little louder than the FCR rattle, so I have to listen close now days.

lcrken said:

If you do build a streamliner, I suspect it will be to lot higher standard than the one my friend and I built. This was our shot at a budget streamliner.

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Ken,
I wouldn't go saying things like that JUST yet. This is my first experience building any form of race bike, let alone one to go for a land speed record. Built my own MK3 Commando from the ground up and it had its own set of issues(some caused by me). God willing I'll have a much better set up shop by then but we'll see how that plays out. This whole build is just one big test for what I know as a mechanic, what I've learned from countless hours reading all the info I can get my hands on about Norton race bikes, and at least the same amount of hours spent trying to better understand engine performance as a whole. You guys put forth a great effort just in what you've shared here. I would love to build a 1000cc streamliner Norton. But for now it would start off with the 750cc motor I'm building for the current project.

jseng1 said:

All FCR carbs rattle like that. It sounds exactly like its pinging due to a lean mixture.

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This just saved me alot of future tuning headache! Thanks guys!

Just got back up from the garage. Took some time with a wire wheel all the weld points on the old frame and they all looked good! No visible cracks or inclusions that would give concern for frame integrity. Think I'll be getting into tearing down the front forks in the next few days. In the mean time I would like to pose a question to anyone with experience about lowering the front suspension. I'm not looking for much more than 1-1.5". I'm going to be replacing the stanchions regardless due to wear/corrosion. I'm thinking Featherbed length stanchions & springs (23.25" Commando vs. 21.875" Featherbed/Atlas for stanchion length). Anyone have thoughts on this?

I hesitate to interrupt the flow of this wonderful thread but I must say it is fascinating to an old line mechanic who just tried to keep the customers bikes rolling, while looking longingly at some of the race prep done by The Boss. Mostly flat-track bikes and scramblers. This land-speed-record stuff is a whole different world .

Keep writing. I'll keep reading.

Thomasa said:

I hesitate to interrupt the flow of this wonderful thread but I must say it is fascinating to an old line mechanic who just tried to keep the customers bikes rolling, while looking longingly at some of the race prep done by The Boss. Mostly flat-track bikes and scramblers. This land-speed-record stuff is a whole different world .

Keep writing. I'll keep reading.

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I plan on writing everything possible on this. To paraphrase Paul Dunstall, "People may think I've kept a few secrets, but if you follow what I've done you could do the same". Had to look back in the Dustall tuning manual I've got just to be sure I wasn't far off. I meant to give another chapter today beyond checking the frame but it's been a busy time with the US holiday weekend. I'll post a better update as soon as I can.

Very nice build. I noticed in Post #15, you have the stock oil junction block. Will you be using original oil lines?
Wondering if you saw Minnovation Racing's billet machined oil junction block:
"Billet machined Norton Commando oil junction block; a neat little addition to your bike, it does away with soldered-in pipes and gives provision for Aeroquip type fittings if required."

wonder if there may be improved flow as well...

and another...
Oil junction block https://www.tga.co.uk/products/oil-union-junction-block/

RGM do tig welded stainless oil junction blocks ...that are very durable

Zac
A very well scripted story , Keep it coming

colin davie said:

Zac
A very well scripted story , Keep it coming

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Agreed - following this with much interest.

YukoNorton said:

Very nice build. I noticed in Post #15, you have the stock oil junction block. Will you be using original oil lines?
Wondering if you saw Minnovation Racing's billet machined oil junction block:
"Billet machined Norton Commando oil junction block; a neat little addition to your bike, it does away with soldered-in pipes and gives provision for Aeroquip type fittings if required."

wonder if there may be improved flow as well...

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Its a new Andover piece my parts guy happened to have so I just put it on. I'll be looking into the other junction blocks to weight the options. I'm going to be making a custom aluminum oil tank so the original oil lines are not being used. All options are on the table at this point.

Thank you all for the kind words and advice!

Part 5
So there hasn't been a ton in the way of progress recently, but I figured I'd at least share whats been going on. Still currently waiting for the trans cradle to come back from the fabricator which is holding up getting powder coating done and starting frame assembly. However, I have been taking the time to work on some smaller aspects of the build. Decided to lighten up the Z plates by removing material from inside the factory radius. Got out the blue Dykem and the scribe tool. Made a little jig to keep it as accurate as possible. Now dummy me forgot to take pictures of the process but after laying it out with the scribe tool, I used a 1/4" drill in the drill press to put holes along the layout line leaving enough to clean it up. After putting the holes in, got out the coping saw and cut the webbing the drill left. Probably 5 hours with a dremel and different files later, I ended up with a decent looking pair of modified plates. Alot of work for what ended up being 5oz per plate lighter! Ah the things we're willing to do for speed. There's still some work to do and they're not CNC perfect but I feel pretty accomplished using a drill press with a cross slide vice. Half tempted to do this to the Z-plates on my MK3. Got a spare set in the old parts bin to play with.


Figured while I was in the shop/basement already might as well start working on the front forks. Drained the old fluid which looked like caramel with metal flake. Starting to feel really bad for this poor bike and how it was treated before I got it. Pulled the stanchions out and there was alot of wear on the brake side stanchion towards the bottom. Not sure what caused it because the inside of the slider didn't look worn. The springs didn't look too bad but there was some pitting on the bottom part of both springs so they'll be getting replaced along with the stanchions.



Finally got the damper assemblies out to clean the sludge out and check the valve for wear and found something I've not run across after rebuilding several Norton front ends. The damper rod was bent! I'm sure its been found before but this is a first for me. The really odd thing is the bent rod wasn't from the fork with the heavy wear. Added a straight edge to the picture to show how bad it was bent.

So now I've got yet ANOTHER parts list burning a hole in my wallet. But at least I've got a spare set of springs to play with finding the sweet spot for spring length to lower the front end.

Schwany said:

Thanks

Yeah, I understand what the D reversion dam in the exit floor does, just wondered if that smaller exit hole really would be that useful for making maximum HP at WOT for 3 miles or whatever the length of that run is. Kind of a reality versus on paper question.

I'm working on a spare early Commando head and thought it might be interesting to build up the exhaust ports more like a D for the street. Probably won't though. I don't have a flow bench to test anything. Nor do I know what that port looks like on the inside.

I do unfortunately get what I think is significant reversion in my combustion chamber from exhaust ports that are matched to the ID of my 1.5" exhaust. I have never put the engine on a dyno to see how bad it actually is, but it makes my FCR slides rattle at idle.

Click to expand...

The 750 that I raced against with my MK3 Slug has the D exhaust ports as well as some other performance modifications.

Glen

worntorn said:

The 750 that I raced against with my MK3 Slug has the D exhaust ports as well as some other performance modifications.

Glen

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Yikes! What that tells me is D exhaust ports on a 750 make no significant 850 whipping difference, or the tune on the 750 wasn't particularly well suited for "Dyno Hill", or your friend just didn't want to ring the engine's neck.

Your 850 is no slug though. It sounds perfectly tuned to me.

His bike did outpull mine when I held on from 6000 to 6800 in third.
That's not surprising as my stock cam is all done at 5900. I should have shifted at around 6000-6200.
When I did that first to second and second to third we stayed even.
I expect those D ports do help at the top if you are building a top end type engine. It might not be a great amount however, maybe a couple of hp or so?
We ran on a flat section and I would say we both gave it a pretty good go.
Being a top end type race I expected to lose badly but the MK3 did surprisingly well.

Glen

Going for records, which = high rpm, certainly higher than a Commando likes, I think you are very wise to deep six all of the original Commando stuff in favour of strengthened parts.
These race classes must allow all new engines?
I ask because Alp built and ran a Vincent at Bonneville awhile ago in a class that required original crankcases be used. The engine was burning Nitro and he managed to go past 190 mph if memory serves. That was quite a feat with original cases and very risky to life and limb!

Glen

Vincent 666 at 193.6 mph. Nice looking piece it is. I'd need a Swedish nut enlarger to swing a leg over something like that.