Simons for pre 78?

[Davey Crocket]

Alevel 4 scrutineer maRc means if you show up with your abomination of a swingarm of the gods....he is allowed to cut it in half!!!

[motomaniac]

Simo, I'll try and find the notes I made when I did Muz's bike. It may be on an old computer downstairs.

A couple of Nylon spacers under the damper rod heads and I think we replaced the top out springs with shorter ones. he runs fork springs of about 24lb/in and I think it was Motomaniac that mentioned the travel had to be reduced by 21mm, that rings a bell.
Due to the difference in travel between the rear axle and shock I think we put a 14mm thick clamp on the shock shaft under the bump stop.

I don't have the time to make the parts for you but I'll pass on the info, hopefully by the weekend.

And we did measure the rear travel with the axle as far back as possible.

So you lowered the front by 21mm but left the back as it was and, restricted the back wheel movement at the end of the travel by shortening the shaft travel externally...
How did that go?

[tmman]

suzuki rm250 370 had 8.25" according to dirt track u/s in the day so i might have to strech mine out to make it!! wank wank!! if bamford "69" HOW ORIGINAL has been down this road apparently then he should have the ideal solution?? after all were your words not become a scrutineer/clerk n make a difference!! cross up swing arm's are legal if dg etc are!! i'm goin to run a factory optional ally arm complete with original short brake stay!! hopefully this won't end up with me getting banned from another sport..

[bazza]

davey will watch news tonight to see how the Kati Kati Killer/Bomber behaves in Brisvegas

[brent j]

Simo, I'll try and find the notes I made when I did Muz's bike. It may be on an old computer downstairs.

A couple of Nylon spacers under the damper rod heads and I think we replaced the top out springs with shorter ones. he runs fork springs of about 24lb/in and I think it was Motomaniac that mentioned the travel had to be reduced by 21mm, that rings a bell.
Due to the difference in travel between the rear axle and shock I think we put a 14mm thick clamp on the shock shaft under the bump stop.

I don't have the time to make the parts for you but I'll pass on the info, hopefully by the weekend.

And we did measure the rear travel with the axle as far back as possible.

So you lowered the front by 21mm but left the back as it was and, restricted the back wheel movement at the end of the travel by shortening the shaft travel externally...
How did that go?

Restricting the back at the end of the stroke kept the back at the same height when extended. Muz had his fork tubes above the top triple clamp so we slid the forks down by the amount the travel was reduced.
As I said in my first post we kept the standard geometry.

How did it go? He ran second to (I believe) “Johnny O” twice and beat him once for second overall at the Nationals at Conondale.

He’s ridden the bike with the standard 9.8” and the reduced 9” of travel and said he really can’t tell the difference.

[Marc.com]

Alevel 4 scrutineer maRc means if you show up with your abomination of a swingarm of the gods....he is allowed to cut it in half!!!

Mate you almost have to cut it in half yourself to fit shock absorbers to it, adequate spring clearance was not part of the design brief.

But it is true running a tricky alloy arm opens up a whole new bunch of opportunities to get scruted.

[211kawasaki]

Lets get out the rule book in the understanding that the 2012 rule book applies to this years nationals. The overiding consideration is to make your bike fit the rules not try and manipulate the rules to fit because you dont agree.
Its the crap like this that keeps me off this forum
If you have a specific question send me a PM and I will be glad to help.
Shane Fraser is the Eligibilty guy at the nats - its his gig, everyone else is an assistant to his decision making.
211

[Tahitian_Red]

Since we've determine that this portion of the original rule was probably taken from an AHRMA rulebook, a similar method of measuring rear travel may have also been copied.  Here is AHRMA's method:

The field check for rear wheel travel, where applicable, is as follows: 1) Both shocks are removed from the bike, then one bare (without spring) damper unit is reinstalled. 2) The machine is supported in such a fashion that the rear suspension is at maximum extension, and a measurement is taken from the center of the rear axle to a point marked directly above the axle on the rear fender or subframe. 3) With both wheels on the ground, the rear suspension is fully compressed by the examiner with the rider aboard to compress any rubber bumpers; a measurement is again taken from the center of the rear axle to the same marked point above. 4) The measurement obtained in step 3 subtracted from the measurement in step 2 is the wheel travel.

I'm setting up an AHRMA Historic bike for the 2012 season and I'm going through the process of getting the forks to the 9 inch limit and putting a spacer in the rear shock.  It is a '77 bike and came from the factory with more than 9 inches of travel on both ends.  I'm taking it as a challenge to see just what it takes to be in compliance.  I raced an RM125B for two seasons with stock forks and Works Performance shocks, that were the stock length and never thought I could have been protested, but maybe I just got lucky.  Rules are rules, but I don't think 20-25mm of travel would be what beat someone you on the track.  Quality of travel is a bigger deal.  I would take the latest Ohlins piggybacks with 8.5 inches of travel over rebuilt shocks from the era with 10 inches.

Restoring and racing these great old machines is much more fun than arguing over 25mm or dealing with jerky comments.  I'm going to be 51 yo soon.  My father past away when he was 52.  That fact and the posts here about Magoo make me realize how trivial some of this stuff is.  Get your bikes into compliance and then together figure out how to change a bad rule.

Life is short, have fun!

[Lozza]

That method assumes the spring would not go coil bound before the full stroke is taken up.

[TM BILL]

Since we've determine that this portion of the original rule was probably taken from an AHRMA rulebook, a similar method of measuring rear travel may have also been copied.  Here is AHRMA's method:

The field check for rear wheel travel, where applicable, is as follows: 1) Both shocks are removed from the bike, then one bare (without spring) damper unit is reinstalled. 2) The machine is supported in such a fashion that the rear suspension is at maximum extension, and a measurement is taken from the center of the rear axle to a point marked directly above the axle on the rear fender or subframe. 3) With both wheels on the ground, the rear suspension is fully compressed by the examiner with the rider aboard to compress any rubber bumpers; a measurement is again taken from the center of the rear axle to the same marked point above. 4) The measurement obtained in step 3 subtracted from the measurement in step 2 is the wheel travel.

I'm setting up an AHRMA Historic bike for the 2012 season and I'm going through the process of getting the forks to the 9 inch limit and putting a spacer in the rear shock.  It is a '77 bike and came from the factory with more than 9 inches of travel on both ends.  I'm taking it as a challenge to see just what it takes to be in compliance.  I raced an RM125B for two seasons with stock forks and Works Performance shocks, that were the stock length and never thought I could have been protested, but maybe I just got lucky.  Rules are rules, but I don't think 20-25mm of travel would be what beat someone you on the track.  Quality of travel is a bigger deal.  I would take the latest Ohlins piggybacks with 8.5 inches of travel over rebuilt shocks from the era with 10 inches.

Restoring and racing these great old machines is much more fun than arguing over 25mm or dealing with jerky comments.  I'm going to be 51 yo soon.  My father past away when he was 52.  That fact and the posts here about Magoo make me realize how trivial some of this stuff is.  Get your bikes into compliance and then together figure out how to change a bad rule.

Life is short, have fun!

Red i think all people want to do is comply  but how can you comply when no body in officialdom will tell you how travel will be measured  Thankyou for your AHRMA system description but what the potential competitors at the Aussie Nats would like to know is what is the official MA measuring system ?

It was an MA scrutineer who made the big statement, but the best he can come up with is sacasm and a forum name change 

Yet he wont come forward and explain the official measuring system  is it really that difficult 

[Tahitian_Red]

Lozza,

The whole mess is imperfect.  I was just trying to give the probable method for those that were waiting for something from the higher ups.

Someone has to decide if it is a "Spec Class" or an "Era Class".  If you could look down the start line in September 1977 (or whichever month was prior to the 78 models being in dealer showrooms) and see the bike you are inspecting, then it should probably be in the Pre-78 class.  If you want to limit bikes to 229mm travel, then it should be called the "229 Class" and 78-79 bike owners, who are willing to limit their travel, can run the class if they choose.
  
The rules are what they are right now and if I were going to a great expense to travel to a National I would have my bike in compliance.  I would also piss and moan to anyone who would listen in order to try and get the rules changed for the following season.  Give the under 178mm bikes their own class and a bike with just less than 255mm doesn't look so much like a Cheater Bike.

 

[Marc.com]

That method assumes the spring would not go coil bound before the full stroke is taken up.

I guess if you coil bind then that is the natural limit of travel, but the bare dampener unit would be the starting point. I assume without having a copy that the MA provides some such procedure. I mean finally as a rider you also have some rights to the correct information and guidelines from the MA....they are quick enough to take a bite out of your entry fees. You pay them to provide a service which includes adequate information before you turn up.

[JohnnyO]

That method assumes the spring would not go coil bound before the full stroke is taken up.

99% of off road shocks built by the manufacturer won't coil bind. Shock suppliers i've dealt with always make sure the spring has more 'travel' than the shock absorber.

[motomaniac]

That method assumes the spring would not go coil bound before the full stroke is taken up.

99% of off road shocks built by the manufacturer won't coil bind. Shock suppliers i've dealt with always make sure the spring has more 'travel' than the shock absorber.

That right , probably more than 99%.If anyone is riding with springs that coil bind best of you fix that unless you have a death wish

[Lozza]

Then all you need to do is measure by the AHRMA method. That method is simple enough to do.