EVO regs question...

[pmcburney]

The front brake on my '81 KTM 495 is marginal to say the least.


I'm working on improving it, but being only recently completely refurbished it likely needs more time to bed in.

I've been pondering some alternatives at the same time - a couple of questions for the EVO competitors out there:
Would my bike still qualify in the EVO class if I fitted (say) a twin-leading front brake from an IT or YZ?
Is there anything in the regs that prohibit retro-fitting a drum brake with hydraulics - i.e. using a master/slave cylinder arrangement instead of a cable?


Cheers
Paul

[mainline]

Is the part you want to use from an evo legal bike? It's that simple.

[vandy010]

i'd reckon the  std YZ front brake would be legal but once you start hooking up hydraulics, forget it.

[Slakewell]

There are smart ways to fix the cable problem and the 495 front brake can be made to work OK but not Yamaha good. KTM also a twin front brake. There are braking tips on thsi web site to look up.

[JohnnyO]

How do you plan to run a hydraulic drum brake?? Please explain..

[pmcburney]

How do you plan to run a hydraulic drum brake?? Please explain..

Well, I was thinking it would be possible with a normal (modern) disc brake master cylinder connected to a suitable slave cylinder down on or near the drum brake actuating lever.

Then (having figured out the correct hydraulic ratio) set up to push on the drum actuating lever and voila!

I was thinking you could get much more leverage against the brake lever hydraulicly than you ever could by hand via a cable.

Mind you, if it was legal and it worked, well I suppose everyone would do it...

[BAHNZY]

How do you plan to run a hydraulic drum brake?? Please explain..

John,
It's been done before. You use a Magura clutch cylinder mounted to the front brake backing plate then set it up like any normal hydraulic front brake brake assembly. I have also seen a similar thing done to a Husky auto with a drum brake rear end. The rider had two bung (surgically fused) ankles and had the rear brake set up where the clutch would be and had only hand controls on the bike.

Vandy010,
Whether it is legal is a tough one as the GCR's dont clearly define these systems. There are EVO & Pre85 bikes getting around with;
- Magura hydraulic clutch conversions,
- Billett front & rear brake backing plates,
- PD valves in forks,
and most turn a blind eye to these.

Rod

[JohnnyO]

How do you plan to run a hydraulic drum brake?? Please explain..

Well, I was thinking it would be possible with a normal (modern) disc brake master cylinder connected to a suitable slave cylinder down on or near the drum brake actuating lever.

Then (having figured out the correct hydraulic ratio) set up to push on the drum actuating lever and voila!

I was thinking you could get much more leverage against the brake lever hydraulicly than you ever could by hand via a cable.

Mind you, if it was legal and it worked, well I suppose everyone would do it...

Firstly it wouldn't be legal in Evo because it didn't come out on any Evo era bikes.. plus it seems like a lot of work for little gain.
You could legally run a twin leading shoe yamaha wheel and brake from a YZ465 if you wished, i run that setup on my 490 Maico.

[VMX247]

and most turn a blind eye to these.
Rod

time to stop turning a blind eye --why let it go on, when they will just push for the next rule to bend.

Firstly it wouldn't be legal in Evo because it didn't come out on any Evo era bikes..

Best answer yet !! 

cheers A

[Slakewell]

Quality cable (Yamaha) well setup with some shrink fit and good guides plus good controls are all one needs. There are twin leading shoe backing plates on ebay.
You can fit Honda Clutch plates to your 495 which help heaps plus I'm working on casting some new parts to make the clutch work as they should.

[LWC82PE]

Are there any hydraulic slave cylinders that were available back in the day eg pre 85? Ok so a modern magura one is illegal, but what if you built up a system using hydraulic bits available back then? I dont know if its possible to do or if there was any slave cylinders available back then? maybe somethign off a car, road bike, or tractor/ag equipment? I reckon there could be a legal way to do it maybe but like others said, it would be easier to fit a yamaha or Honda TLS brake.

[sa63]

the best cheap fix is to take the wheel and brake to a brake place and get them to do a set of shoes in soft or woven linings arc'ed to your wheel. this will cost you about $40. All brake and clutch in rocklea if you are in Bris. we dont ride the old ones enough to bed in ebc or other after market shoes.
A beefy brake cable and an extended arm on the backing plate will also work wonders
If thats not good enough for you then look at the yamaha hub(the best for sure)

[pmcburney]

Thanks for all the advice...


Ok, so the hydraulic idea probably won't fly. Alright to investigate if I was never going to race it, perhaps.

Say I find an '84 KTM twin-leading setup and adapt it to fit my '81 forks, would that actually be EVO kosher?
The '84 KTM 495 is not an EVO class bike...

Or because YZ Yamahas had twin-leaders in '81, it would pass scrutiny?

[BAHNZY]

Firstly it wouldn't be legal in Evo because it didn't come out on any Evo era bikes. plus it seems like a lot of work for little gain.
You could legally run a twin leading shoe yamaha wheel and brake from a YZ465 if you wished, i run that setup on my 490 Maico.

John,
This is where the EVOLUTION regs fall down. In nearly all cases, the GCR's refer to a specified time in the past, whereas EVO locks in a technology/specification, not an ERA. An example of this is where you have pointed out that a YZ465 43mm front end & brake is a great alternative, yet an almost identical spec 83/84 RM 43mm twin leading front end is not, simply because the RM had a linkage rear end.

Rod

[JohnnyO]

Thanks for all the advice...


Ok, so the hydraulic idea probably won't fly. Alright to investigate if I was never going to race it, perhaps.

Say I find an '84 KTM twin-leading setup and adapt it to fit my '81 forks, would that actually be EVO kosher?
The '84 KTM 495 is not an EVO class bike...

Or because YZ Yamahas had twin-leaders in '8
1, it would pass scrutiny?

The parts have to come from an Evo bike... quite simple really