Bonneville Daydream

So I just got back from the Motorcycle Speed Trials at Bonneville. This differs from the main event that occurred a few weeks ago, and is motorcycles only. They have a 'run what ya brung' class that lets you run any bike that essentially meets the safety requirements. I have a snail's pace Combat resurrection underway, so naturally I began the daydream. Could I become a world's record holder? Could I be a miniature Bert Munro? Could my bike go from the world's slowest (rebuilding since 1985) to the world's fastest?
I looked at the 2017 records, and there are 3 feasible classes. 750 production is out of the question. The 750 P-P record is a tad over 170 mph. Then there's 750 production pushrod, getting closer. the 750 P-PP record is 129.649, set by a Triumph in 2011. Closer, but I don't think I'll be spending whatever that Triumph guy did to get his 'production' motor to go that fast. Finally, there is a newer class called Production Classic. It's basically the production class but your machine must be older than 1982. The record is presently held by a Honda at 112.283, set last year. That seems remotely feasible, even given the power loss at Bonneville's altitude. If a Combat could pull redline with a 21 tooth sprocket, that would give about 120 mph depending whose calculator you use. A 20 tooth sprocket would give about 115 mph, probably a better chance of getting to redline in 4th. Restricted to stock, a Combat should have the best chance of any Commando doing this.
So it comes down to the rules, (plus our two old friends time & money). I'm lacking a pair of Amals and associated bits as the bike was fitted with a single Mikuni, so that would be the first expenditure. Apart from that, I need to find out about changing handlebars, mufflers, ignition system, etc. The more significant expense to consider would be head work. In a few months I'll dig deeper into the rules, but meanwhile it's just a daydream.
Most of us know how hard it can be to fit in our motorcycle hobby with family and work commitments, and of course there's going to be cash involved. It may never happen for me, but I thought I'd post my thoughts for a bit of entertainment.

What’s the best web source for understanding the classes, and rules, and records, for Bonneville?

Depending on the class for stock they may allow internal modifications that you can't see of the outside. The bike below is faster than a Combat with Axtell copy ports and special internal engine components (I have the porting and other specs if you need them).

Randy Johnson’s land speed record breaker for SCTA 750cc production pushrod motors on gasoline (126mph at Bonneville in 2012 with a best one way speed of 128 mph). Randy also uses it for a street bike.

I went here and downloaded some documents.

https://bonnevillespeedtrials.com/rulesclasses/

The 2018 AMA Bonneville Supplemental regs list the 2017 records at the back, and appears to be the best writeup on rules I've found so far. I think most of my questions are going to be answered here, but need to go back and do more than speed-browse it.

Thanks for the heads up! I read an earlier thread about Randy Johnson's bike, most impressive! His bike could very well qualify for the newer P-PC class and blow that Honda record into the weeds. After I've read the rules, I'm hoping to contact someone through the AMA to help clarify just exactly what internal engine work might be done and still qualify as 'production'. I'm sure I can substitute Amal Premiers for the original carbs, but it would be nice to get a confirmation of details like that. I will go back and try to find more details about Randy's bike and what work he did.

Fast Eddie said:

What’s the best web source for understanding the classes, and rules, and records, for Bonneville?

Click to expand...

The AMA rules are available as Atlas said at the bonnevillespeedtrials.com web site, but as far as I know, the SCTA rules are not available on-line. You have to have the SCTA Rules and Records book to read them. If you belong to an SCTA club, or just join BNI at http://www.scta-bni.org/forms-and-docs.html you get the rule book free. The AMA and SCTA rules are very similar (they used to be the same, back before SCTA and AMA went their separate ways).

The rules for production class are pretty straightforward. For internal engine work pretty much anything can be done, except stroke or bore changes that take displacement beyond the class limit. The requirement is that you keep the OEM cases, cylinders and heads, and that the engine keep stock external appearance. You have to stick with the OEM carbs and airbox, and OEM exhaust, although you are allowed to gut the muffler, as long as it retains stock appearance and the exit diameter remains stock.

Other than engine, the bike has to basically still look original, although your are allowed to change handlebars and sprockets. Tires must meet the speed reqirements for the class, and if none are available to fit original rim sizes, you can change the rims in order to fit legal tires (not usually an issue with a production Commando).

There are some other safety requirements, and details about cosmetic changes in the rule book, but these are the significant rules.

Ken

Thanks for the info! If I do it, I'll have to buy Amals and certain airbox parts that didn't come with the bike. I really hadn't planned on spending any more on this bike than necessary to make it a reliable runner, but the temptation to have the heads breathed on is there. I can justify upgrading to the Amals for resale value. I have the stock mufflers, and sounds like I can use the Pazon ignition I'm about to order.

lcrken said:

The AMA rules are available as Atlas said at the bonnevillespeedtrials.com web site, but as far as I know, the SCTA rules are not available on-line. You have to have the SCTA Rules and Records book to read them. If you belong to an SCTA club, or just join BNI at http://www.scta-bni.org/forms-and-docs.html you get the rule book free. The AMA and SCTA rules are very similar (they used to be the same, back before SCTA and AMA went their separate ways).

The rules for production class are pretty straightforward. For internal engine work pretty much anything can be done, except stroke changes, or bore changes that take displacement beyond the class limit. The requirement is that you keep the OEM cases, cylinders and heads, and that the engine keep stock external appearance. You have to stick with the OEM carbs and airbox, and OEM exhaust, although you are allowed to gut the muffler, as long as it retains stock appearance and the exit diameter remains stock.

Other than engine, the bike has to basically still look original, although your are allowed to change handlebars and sprockets. Tires must meet the speed reqirements for the class, and if none are available to fit original rim sizes, you can change the rims in order to fit legal tires (not usually an issue with a production Commando).

There are some other safety requirements, and details about cosmetic changes in the rule book, but these are the significant rules.

Ken

Click to expand...

Ken, if I read your understanding correctly, one could build a short stroke motor (even with different bore / stroke to Norton’s own short stroke motor if desired) and so long as it’s below 750cc, that is within the rules.

Am I right?

It appears that this ‘day dream’ is contagious...

Fast Eddie said:

Ken, if I read your understanding correctly, one could build a short stroke motor (even with different bore / stroke to Norton’s own short stroke motor if desired) and so long as it’s below 750cc, that is within the rules.

Am I right?

It appears that this ‘day dream’ is contagious...

Click to expand...

I think you are correct, Nigel, although you can never be totally certain that the SCTA tech guys might not "interpret" the rules differently, based on the "spirit of the rules". The rules for "Production Engines" do not specifically prohibit using a different stroke crankshaft, as long as the engine displacement is still within the limit of the class, which is determined by the original size of the engine. That is, if it started as a 750 Commando, it has to run in the 750 Production class, and an 850 has to run in the 1000 Production class (although it can be taken out to a max of 1000 cc, if you can manage that).

Ken

For those who are interested, these are the pages from the 2017 SCTA rulebook on Production class bikes. There are also several pages of general safety rules that have to be met by all bikes, but they aren't really germane to this discussion, so I'm not posting them. As mentioned earlier, the comparable AMA rules are available on-line.









Ken

That's great information..... While I get my bike put together with hopes of hitting 115 mph to take that 750 P-PC record, Fast Eddie will show up with his short stroker and pull 130 while spraying salt all over my dream..... (sniff)....

Anyway, it's clear I can use my electronic ignition and can maybe get some head work done. My budget won't let me go much further than that. I would/will have to spring for a new pair of Amals as the bike came with a single Mikuni. The Combat cam is not a bad choice for trying to pull redline with a 20 or maybe even a 21 tooth sprocket at Bonneville's altitude, roughly 115 or 121 mph....
Hmm, another little challenge. I'm getting a new right knee in early December. I guess I'll have to get an extended kick start, or I might have to carry a passenger who can start it for me.

Thanks a lot for posting that info Ken.

And @ Atlas Commando, calm down dear, I’m the least of your worries I think...!

10-4 Fast Eddie. My only worries are the laws of physics, lack of ambition, knowledge, skill, budget, time and of course physical capability. Oh, and I'll need to bring a good coffee machine too, not much available out on the salt.

Reading the rules, I note the part about all OEM bodywork and fairings must remain in place.

Hmmm... fairings...

Given the importance of streamlining on top speed, a fairing might make a big difference me thinks.

If so, perhaps a JPN replica is the ideal Cdo for a production class LSR attempt ?

Production Racer would be a far better idea than the extremely overweight JPN.

Additional weight may be an advantage for LSR attempts on the salt. Power, aerodynamics and traction should be the focus.

Atlas, JUST DO IT (screw Nike, they don't have a lock on that expression)

Yes, it takes money. Yes, it takes time. Yes, it takes a lot of work.

To think you MIGHT even have a shot, unless you REALLY set your mind and wallet to the task, is dreaming.

Even if you come up short, it is an experience you'll never forget.

Something happens to certain people once they've been there. Some keep coming back, some go broke, some set records, some don't, some die, some get divorced, some get strange (hence, divorce).

I set the original BUB class record for Production Heavyweight (different rules back then, AHRMA's classes, basically), and had the time of my life. Kinda doubt I'll ever be able to get back there, even if I fall into a truckload of money; I still have 2 school-age kids, and will for 11 more years when I'll be 72. But, I JUST DID IT.



Didn't even "do the ton", but it was basically just a fun run and taking it easy. I still had 4 races left in the season, and didn't want to mess up the engine holding it pegged for 3 miles. Also, I had the wrong speedo gearbox and it said I was going 70. If I knew I was going 90, I would have wicked it up and done 100 easily. I was geared for roadracing and didn't compensate at all for the altitude. It really was just for fun.

I happen to be friends with Phil Hawkenz, who was the photographer for Triumph USA, and later, Norton USA. He took a ton of photos of me, which was pretty cool. I met Sir Alan Cathcart and poured him some of my coffee, saw the Vincent streamliner and heard it fire up (they were having unforseen issues related to the altitude, who'd a thunk it?)

Yeah, go for it.

These guys were having fun. They used my starter rollers to get the high compression Commando to fire off. They came slipping and sliding past my pit, trying to push start it...

grandpaul said:

Production Racer would be a far better idea than the extremely overweight JPN.

Click to expand...

A good point GP. Any comments from anyone on which of the two (JPN vs PR) is likely to be more aerodynamic?

I’ve never got up close and personal with a JPN, are they really that much heavier? If so, and if the weight is the faring and associated components (all up high) it may not be so good for high speed stability I imagine.

And, any thoughts on whether or not a ‘Prodcution Racer’ would be allowed in a production class by the STCA (or whoever is in charge of such things)?

A proper PR would be out of the question cost wise, but creating a good replica out of a good donor bike shouldn’t be beyond the wit of man...

PR was just a few bits bolted to a standard Commando. I don't see how it would violate the rules. Apart from being too cheap to buy a set of header pipes, this was not hard at all...