Self steering and top speed

Thanks for the perspective. Not sure if a higher balance factor is better from a mechanical standpoint. So you increase the % BF now you need to deal with the greater fore and aft imbalance loading. I suspect that the 83% was more for creature comfort and the 53% dry was a mechanical stress minimum. By the way, I wonder if the wet BF works out to around 50% which would seems like it would be a sweet spot of a mechanical compromise. I am running a Featherbed with a 53% BF and it goes beyond buzzy at speeds; it's brutal.

As for Dave Nourish, we are currently putting together a Seeley Mk2 with a Dave Nourish (73.05mm bore and 88.6mm stroke) 750cc engine - should have it for the Barber Museum and Race weekend in October if all goes well. I do agree with you regarding a very short stroke Nourish and maybe that will be the next build or as a long circuit spare engine.

I originally wanted to proceed with a short stroke Nourish engine in the 500 Premier class here in the states but we decided to go down that very slippery slop of making it happen with a Norton engine. It's been quite the journey and we learned a lot but with hind site I should have stuck with the plan to go with a Dave Nourish 500.

'Dave Nourish (73.05mm bore and 88.6mm stroke) 750cc engine '

Did you make the engine like that, or was it supplied as an option from Dave Nourish ? It seems like it will rev to about 11,000 RPM and be a really good thing. The problem with a lot of this stuff lies with the guys who get paranoid, and start upgrading the rules which then stifles the race classes as far as development goes. There is probably a place in moderns road racing for a motor like that.
As far as the Nourish 500 is concerned, it will always be difficult to develop that engine to be better than a Paton. It depends on how your racing competition are thinking, and how much money it is worth spending on an ego trip. They still have to ride the bike.

No, the engine is an original period piece from 1979 supplied by Dave Nourish. The engine sat beneath the bench at one shop for a decade or more and then sat beneath the bench of another shop for another decade or more. One tear down to replace rubber seals and redo the prelube for start up.

As for 11,000 rpm; I wish. I suspect you transposed the numbers; it's an 88.6mm stroke so unless you are in the hobot lala land of P11's it won't make it there but maybe once for a few milliseconds; then you get an exploded view.

The engine is allowable in certain classes within AHRMA and performance is really more rider dependent than motor these days in vintage road racing.

Yes, the Patton four valve is formidable but not sure if it is legal in AHRMA. There was a great kafufal a few years ago about the four valve that pissed a lot of people off. Basically the Patton four valve walks away from the other bikes of the Premier class.

As for ego, the beast must be fed well!

You are correct, I thought the motor was short stroke, and that's the way it should be if the 4 valve head is to give max advantage. There isn't much use in putting it on an 89mm stroke motor. On Triumphs the Rickman heads did not deliver - a two valve is pretty much as fast. The reason for using the four valve is an increase in BMEP due to the number of valves, and the permitted increase in revs due to the light valve weight. With that you would change the concept and change the cams, inlet and exhaust to move the power up the rev range, the limitting factor is then the long stroke and the bearing loads and crankcase strenghths. With a short stroke the required imbalance is not as much.

One really good thing about the weslake motor with a 4 valve head, is that you are unlikely to drop a valve. Otherwise if you are limitted in revs by the bottom end, it is pretty useless. The Weslake engine is much stronger all over than a commando engine, and as a basis of a torquey engine would be much better. You wouuld save a lot of money going straight there. As I've said elsewhere, I believe you have to choose which path you go down - Weslake type long stroke, or Paton type short stroke. Trying to combine the two makes an expensive grenade.
Have you tried the Weslake using a two into one pipe, and advancing the exhaust cam - then increasing the gearing ?

I always keep a tight rein on my ego. My bank book isn't thick enough, nor is the skin on my backside.

Is there any AHRMA 500cc four stroke class in which this could be used ? :

http://www.motorcycleclassics.com/class ... tx500.aspx

Keep in mind that so far as I know there is only one cycle fielded that looks forward to the sudden stand up hi side crash into opposite new direction on purpose. What is trying to be so avoided-feared by the rest of the world is big part of the wonder of an isolastic Commando and Roadholders, with some taming devices added. The wildest part of this type handling is right where everyone else crashes with more power added, ALOT more power is needed instantly to induce it in Peel. A lot of what is felt in the forks ain't coming from the forks but its too confused to feel that clarity in too rigid or too flexy chassis.

acotrel said:

Is there any AHRMA 500cc four stroke class in which this could be used ? :

http://www.motorcycleclassics.com/class ... tx500.aspx

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Bearing in mind I am no expert on Yamaha twins, that bike looks like it has a lot in common with the UK market XS500 twin. There is a guy developing one for the air cooled 500cc post classic class in UK CRMC racing. He is not having too much luck so far, but that seems to be the story of his life at the moment (I know you use the CMR Forum Alan, look for posts from Nige Collier, his avatar is the bike in question).

As far as I know the first thing he did was dump the balance shafts! but I guess its the 4 valve head for very little money he was looking for.

Steve

You might not be aware of the Suzuki SEAR engine (Special Engine Auto Race) - comes in two sizes - 600cc and 500cc :
http://www.youtube.com/watch?feature=en ... UybQg&NR=1
We need these in Seeley frames with 6 speed CR boxes:

You might not be aware of the Suzuki SEAR engine ( Super Engine Auto Race) - comes in two sizes - 600cc and 500cc :
http://www.youtube.com/watch?feature=en ... UybQg&NR=1
We need these in Seeley frames with 6 speed CR boxes:

How they are used in Japan :
http://www.youtube.com/watch?v=EDYvPlmI ... ure=relmfu

Speedway without shale, and auto racing without autos!

Have seen video of this sport before....understood it was more about gambling than bikes

500 singles racing used to popular in the '80s, the CRMC air cooled 500s provide an opportunity to revive some of those 4 valvers, in monoshock frames of the period that may or may not be better than Seeley frames.....only a couple have decided to go twin with 8 valvers, the Yamaha you mentioned earlier....surely there are just a lot fewer parts in a single, and suitable candidates for that too

A Jawa four valve motor on alcohol would be hard to beat. But the SEAR motor looks really good.

Acotrel,

suggest you get a copy of Tony Foale's book (latest edition) on m/c chassis design. He goes into great length about the effects of rake and trail, with lots of experimental data. It's the best book out there on m/c chassis design.

Ken

Ken, Have you heard of the expression 'potential well' ? I've found an acceptable solution to the stand up and turn problem so anything else takes more cash, and I need to climb up to get it. I've ordered the book 'motorcycle dynamics' from Amazon. Thanks for the info about Tony Foale. I think Colin Seeley must have known a bit, but the original Seeleys used slightly more offset than TZ350 yokes give. I've read that they had 'neutral' steering. I use the self-steerring of my bike to advantage, I'm just a bit apprehensive that it might step out and hi-side me if I get more power out of it.

acotrel said:

Ken, Have you heard of the expression 'potential well' ? I've found an acceptable solution to the stand up and turn problem so anything else takes more cash, and I need to climb up to get it. I've ordered the book 'motorcycle dynamics' from Amazon. Thanks for the info about Tony Foale. I think Colin Seeley must have known a bit, but the original Seeleys used slightly more offset than TZ350 yokes give. I've read that they had 'neutral' steering. I use the self-steerring of my bike to advantage, I'm just a bit apprehensive that it might step out and hi-side me if I get more power out of it.

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Alan, as far as I know, Seeley, Rickman etc used 2.5" offset and TZs 50mm. And as you say for Seeleys this delivered 'neutral steering', which very few complain about, quite the opposite. Looks like the set up you had used too much offset and what you have uses too little, which to me means the 2.5" is going to be about right!

I would not have thought the yokes you need were that difficult to source, worse case is a set of Commando yokes, bad only due to the weight on a race bike.

Lots of people CNC lighweight yokes for these bikes in the UK, a couple do it with more traditional workshop machines and Dick Hunt casts them!

The original Seeleys used Metal Profiles forks. We are talking 1966. I was quoted $500 to make a set of yokes, and I didn't know the offset I needed. I just happened to have a set on a TZ350 frame in the back yard. Turns out they are magic, but after the experience when the bike stood up and turned, I'll always be apprehensive until I've raced the bike regularly for a couple of years. The seeley frame has a head angle of 27 derees and uses 18 inch wheels. The TZ uses 26 degree head angle and 18 inch wheels. It stands to reason that Yamaha will intentionally err on the side of safety when selling production racers to unknown punters.

Makes sense to me Alan, I paid £300 for mine, roughly translated as $500AU!

Don't know about Yamaha taking the safe route Alan, TZ are more 'manouverable' than most things, which sort of suggests a level of instability, my obnservation is that more people get spat off TZs when the power kicks in than they do off Seeleys, regardless of engine type!

Seeley themselves carried on into the '70s with the same yokes and there is a huge number of manufacturers making Seeley/Rickman/Norton copy stuff still using the same offset, could be they got it right first time?

I'm just a bit apprehensive that it might step out and hi-side me if I get more power out of it.

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Tony Folate is still looking for the best set of forks geometry to fit on various cycles and you might be bored waiting for his comments on 'self steering' solution. If ya got the urge to run around faster than ya have before, then rest assured any cycle can and will hi side at some point of skewed power loads conflicting at either end. You have pressed your nice combo up to a energy transition point, so just need a bit extra energy-speed-power-balls to cross into the fling up or flung down behavior. I call this and sense this as, "control reversals". If you never discover when that crossing over happens then you are about topped out on further progress. If you are not getting any head shake tank slap reactions up to this point then likely can creep up on the hi sides to know what to expect. Just short of the tire-chassis jump up it feels like magic as bike uprights its self like a horse heading for the barn w/o holding the reins There is ancient accepted tradition that states when in doubt-trouble, NAIL IT. in these close to transition rates, when the rear fails to out power-control the front forks-tire road following effect, Weedoggiedoo, unexpected transition onset. This happens to me when either running out of power band or out of adrenalized bravery to stay on hi power. With a really Neutral set up you finish sharpest turns by a power chop then hold on tighter for the whiplash upright just in time or even further into a new direction, but planted on both tires so ready to nail it out of there. Only way I could conquer this type behavior was to work up to losing traction on purpose, at either end, first by leaning, then by over powering, then by turning forks too much,then all of em at once. WeeeDoggieDoo!

What I like about my current setup is that you can get loads of power on early, and the bike doesn't try to hang you up on the outside fence. I've wicked it up pretty hard and it doesn't hang about, yet it has never stepped out. I might ride a bit differently to some others. I came up through the era when we only has T1 compound triangular tyres. My brain is always at the rear tyre contact patch, and I usually increase my speed until I start to get movement. I am now using Bridgestone Battle Axe tyres, and never seem to get there. I believe better tyres woulkd be wasted on me. As a kid, I rode my old short stroke Triumph 500 on T1 Dunlops and led a field of Z1s and H2s for a lap off the start of a race. I blitzed them all around the tight stuff on Winton, they got me down the straights. That would never have happened if I had been riding my Seeley - the motor is fast enough to conquer, and the bike handles much better anyway. With my old Triumph, I was a lways fighting to stay away from the edge of the bitumen. The Seeley usually ends up in the centre of the track coming out of turns, even when I am hard on the gas.

Is the Triton still extant , or History ? .The twisty tracks was were the Nortons did well . We couldnt all afford Gilleras .

Savoring your descriptions and trying to translate acotrel.
Nothing beats staying in good traction for continuing laying on accelerating power tight as you need. Anyone not giving full attention to rear patch over all else ain't really pressing fully on it yet. I got forced into learning rear looseness on my P!! then again on Commandos in THE Gravel. I can't trust me or cycle until I get a sense of what it takes to spin or skip out some, in various ways, on my terms. If nothing weird scares me then work up short drifts, if still calm then can slide some, first crossed up then w/o crossing up, either of which tend to end with a pop up on its own, thank goodness. Peel could come out a turn keeping rear spining enough not to hi side while laid over at same angle as earlier in turn til scubed off speed of exit direction as it converts that energy into a new direction.

Main reason to try to get loose on purpose is to lean that tire's limits when its going to happen and what happens next, which usually ain't hard to control, then either don't do it quite that hard or play with the tire and traction waste when practical. This skipping and leaping about stuff mainly only applies in chicanes, but once that gets routine then the longer sweepers get boring, so more fun to break up into series of short WOT straights punctuated by brief instants of mania.

I think isolastics can hook up better than solids and 360' power pulses also seem to hook up on edge better than others. Only leaves mysterious balance factor for me to explore with nothing but rear patch reaction as the measure of its worth.