Pre '78 Front Brake

[firko]

A friend is building a C&J framed Honda XL350 for the pre '78 class. He's an old time vintage motocross racer who's been away road racing for a few years but is returning to the VMX fold. He's emailed me with the following question regarding front brake and even though I have my opinion on his brake choice I thought I'd throw it into the mix and see what you guys think..

I intend to use 38mm Yamaha forks (gold valved etc.) & front wheel & brake, mainly cause I have some but I was wondering if it is ok to use a twin leading shoe backing plate. I have found out that Yamaha used a twin leader on a works 77 model 125 (OW 27 I think) it was featured in a VMX magazine sometime ago. It's appearance is similar to some of the stock Yamaha ones produced a few years later but not identical. Is this legal to use for pre 78?

[shorelinemc]

i would think no

[Nathan S]

The short answer is no. The slightly longer answer is that you could try your luck.

The typically verbose Nathan answer is:
I think you could mount a fairly strong argument that says the later production part is a replica of the works part.
BUT I also think you'd be pushing pooh uphill because almost everyone says "No later parts" and ignores the contradictions that exist.

If an 80-model front brake is accepted, then watch me fit a 79 model production alloy swing arm (which is a replica of the 77 works part).

[firko]

My friend shares the same philosophy as me regarding his bikes in that he likes 'em trick but within the correct period framework. My short answer was no too and not knowing how close the works part is to the 80 model item I couldn't make a judgement call. The other part of his enquiry was whether billet triple clamps would be kosher...over to Ken  again............,

Also I want to machine up my own triple clamps, is it legal to make these up how I like or do they have to replicate something from the period (pre 78). Obviously I want to make the bike as trick as I can & a little different to mainstream thinking, a special I guess you would call it. Anyway, any help or advise is more than appreciated. Just for your interest, I have a couple of other projects going as well, one is an XL125 which will look just like a big version of an XR75 & a '77 CR125 with a 4 stroke motor. Anyway all the best, hope all is well with you. Look forward to hearing back from you.

This is one of my pet subjects . I maintain that custom triple clamps should be exact replicas of period parts, not like the shrines to CNC art that seem to be allowed in the AHRMA rules. I reckon that billet replicas of period items are indeed kosher such as the billet replica Pro Circuit Husky clamps that are available. So, my advice to Ken is a no and no for both items...What do you reckon?

[JohnnyO]

I think with the front brake it has to be what was available on production bikes of the era and that was single leading shoe for pre '78.
The '77 OW125 works Yamaha also had watercooling but that's not legal in pre '78 or Evo so whatever a works bike had in the day is irrelevant to our rules..

[firko]

I agree wholeheartedly John. He misses out but it's not a big deal. I suppose if he really needs to use a twin leader he could modify one from a road bike or from an early Monty but they're so heavy it'd cancel out any advantage. 

[Nathan S]

I think with the front brake it has to be what was available on production bikes of the era ....

The rules say nothing about production vs works parts, just about what was available.
 

The '77 OW125 works Yamaha also had watercooling but that's not legal in pre '78 or Evo so whatever a works bike had in the day is irrelevant to our rules..

Watercooling is specifically prohibited, and was available as aftermarket parts in the day too (not just as a works part).

I see the points you're making, but there's nothing written in the rules to support them.

[090]

The rules say nothing about production vs works parts, just about what was available.

Works bikes were not available (to the public). Its a no in my book. For both.

[DR]

Here we go..how 'bout this..

a factory 'works' bike, say a 1974 RH250, now this bike is allowed in pre'75 is it not? The replica parts from this model are deemed to be quite desirable also and so far as I know (not a lot) no-one has ever made protest about replica or ridgy didge 'era' works bits.

 Why then can't someone use twin leader from a works bike even if infact it's a replica? For all intents and purposes it apparently looks the part.

Where's the line drawn and who draws it?

Have all the guys who've purchased or fabricated RH replica airboxes, billet brake pedals, machined fork lowers or any non original part made their bike illegal? Factory or works bikes are allowed. Joe Blow who builds a bitsa can fabricate pretty much anything he likes so long as it remains within era yet this bike is a 1 off and never was it ever produced for the public.

In my eyes if the part looks the goods then where lies the problem? It's all about proof..you need to simply prove it existed within the era. Even if it is a works item or a replica thereof I can't see what grounds there could be for dispute if infact it appears correct

[mx250]

I'm with you Doc. I think the rules could be a lot more liberal - it's not a museum.

It would be a more interesting world if they were.

[JohnnyO]

A '74 RH250 still has to comply with the pre '75 rules. It still only has 7'' & 4'' of travel.
Everything on the bike is pre '75 legal.
A '77 OW125 is not legal in pre '78 for many reasons and you couldn't go out and buy one in '77...

[vmx42]

I'm with you Doc. I think the rules could be a lot more liberal - it's not a museum.

It would be a more interesting world if they were.

Now light the Blue Touch Paper and stand well back… 

[LWC82PE]

My opinion

NO, but if you can get a genuine works OW 77 plate/hub or can replicate it perfectly/exactly then maybe i might say yes. Using any 1978 onwards model brake is not allowed if your in pre 78 class unless as per the parts book the part is exactly the same part number. Eg if there is a 1981 brake plate that is exactly the same part number as brake plate in a 1977 parts book then that would be ok i reckon.

Triple clamps, YES because you could have machined a set back then, but try and keep the maching and looks basic to how a machined set back then could have looked. Try and get inside the head of a machinst back then to think how a machined set would have looked then and then i reckon you would be right. Dont just try and make the coolest modern looking triples you can. Also look at some billet triples from back in the day to get an idea of how they were done then. So im meaning no fancy angles, grooves, scollops etc. Keep it simple.

[Nathan S]

Works bikes were not available (to the public).

OK, poor wording on my behalf. Change "available" to "existed" and try again.
(NB: I'm not really offering my opinion right now, just what the rules say).

[micks]

firko the mountain man ken should know better it`s the same as historic road race.if he used a period brake eg ds7,xs1 etc ok but to use a it/yz of 80 period no no.
if he was to build adjustable offset tripple clamps i think it would be a no no, but straight up tripple trees should be ok.
cnc art ken couldn`t program one but his work is fine art.
i can understand why he what`s to put 125 4st into the cr frame but he is up against the 2st.to make them compete with the 2st we should allowed to run up to 150cc.