disc brake question

[caps 999]

ive picked up an earily 84 125 disc brake front end for my yz 100 recently an the master cylnder is stuffed i can see to find a peroid one but i have a crf250 master cylinder laying around it would also be good because this would allow me to run the unbreakble leavers my question is about the pre 85 legalities of running the crf mastercylinder

[STW996]

There goes that can of worms again

[caps 999]

haha i can see a discusion coming from this

[Hoony]

short answer is a NO.

if you don't want to race it, then it is a non issue

[caps 999]

sweet i thought this was the case i might let it go till i can find a better master cylinder (pre 85 master cylinder)

[STW996]

Hoony I must ask why? (why not) is it a performance gain (would think not) and if it is then no more then a double leading shoe on a YZ 250 H which can run in evo class because of it's suspension?

It is no different to the other thread on exhaust pipes at the moment, rules are rules you can say and in some points I would agree, but a master cylinder? (and the master cylinder only not brake caliper) could not be that big of an advantage could it??

That is if the bike had a disc break front end to start with?

Shane

[caps 999]

the yz100 dosent have on standarded as the model was discontuned befor the disc brake was bought in but the year after 125 has it im still using the standard caliper and disc and 125 wheel the other main reason i would like to run the crf master cylinder is so i can run the asv unbreakble leavers because  im forever breaking leavers

[STW996]

I did think that but was unsure with Yamaha. So problem will be runing the disc brake in the first place.

[caps 999]

but the parts are still peroid im just switching them between 2 peroid bike

[GMC]

Are you running Honda forks or Yamaha?
Honda had front discs in 84 but Yamaha didn't have front discs till 85
I think Kawasaki had them in 82, not sure about Suzuki

[Maico31]

Suzuki didn't get a front disc till 85 either.

[Maico31]

Hey Shane the performance of a 2008 front disc brake is far better than a '84 front disc brake so i guess you'd have to say that fitting a modern master cylinder or caliper is a performance advantage and probably not legal for pre '85

[caps 999]

your definitly right gmc i thought it was 84 yammys got discs but im happy to be proven wrong im just going to stick to the drums now

[STW996]

Would Agree 100% John if it was the hole brake system and not just the master cylinder. I am of the belief that if it comes to availability, or lack there of it, you should be able to run some later parts as long as it is no a performance advantage like a hole brake system would be, but only a master cylinder is no going to give the extra performance that say a new Ohlins or YSS rear shock would for example and we allow these don't we?  After all it may infact be a dis-advantage in some cases depending on ratio of cylinder. I run a 93 front master cylinder on my RE 500 because I like the feel of it rather then it performing better, but that in itself makes it a performance gain??

But if like the Suzuki the Yamaha was drum brake only in 84 then that is what it should run as I said before with the 79 Honda RZ having to run 37mm forks and single leading shoe in Evo compared to the H YZ with (correct me if I am wrong) 43mm forks and double leading shoe brake with both bikes in stock form.

Shane

[Maico31]

I reckon it should be ok to run a '84 cr500 disc front end in an '84 YZ or RM, or 43mm YZ465 forks in an '79 CR250 cos it's all parts from the same era and i've done it previosly with my bikes. I agree that the later master cylinder is probably not an advantage either, i was basically just saying that it may get knocked back by scrutineers.