Disc brake lever

I replaced the brake lever on my '74 after having dinged and bent the original in a fall. The shape of the new one (purchased from Old Britts) is different in the area where it pushes on the M/C piston. I had to grind down the nub, else it wouldn't fit without the brake being 'on' full.

So, first - how many different levers are out there and when did they change?

I picked my part from Old Britts' excellent web site by the correct year. Was the MKIII lever different? I don't understand why a new one wouldn't fit. The difference is subtle if you just look at them - it's the spacing between the pivot bolt hole and the business end of the lever.

Secondly, how do I determine the correct play in the lever? I have it set so the brake doesn't bind, but I've had the experience of it locking up on a really hot day in the past with the old lever, and I don't want to aggrivate that. The M/C is sleeved 13mm if that matters (also by Old Britts).

Of course I didn't notice this mis fit until after I'd had the lever chromed. Now it'll probably peel. Grrr.

The M/C is sleeved 13mm if that matters (also by Old Britts).

Likely this is the problem rather than the lever. Any stack up length difference for the piston and other internal parts to the master cylinder will cause what you describe.

As far as I am aware there are only two standard levers for disc brakes.

Pre MK3. part No. 063241

MK3, part No.065604

There was also a "racing lever" produced which I believe was a lot straighter in the "finger area" than the MK3 type, but don't know the how it compares to the earlier type.

If you have sleeved your m/cyl, I believe that there is an adjuster on the outer pivot point, which will give varying distances of reach for your fingers. There is on the RGM type, but don't know about other conversions.

maylar said:

I replaced the brake lever on my '74 after having dinged and bent the original in a fall. The shape of the new one (purchased from Old Britts) is different in the area where it pushes on the M/C piston. I had to grind down the nub, else it wouldn't fit without the brake being 'on' full.

So, first - how many different levers are out there and when did they change?

Click to expand...

850 Mk 3 lever:

L.A.B. said:

maylar said:

I replaced the brake lever on my '74 after having dinged and bent the original in a fall. The shape of the new one (purchased from Old Britts) is different in the area where it pushes on the M/C piston. I had to grind down the nub, else it wouldn't fit without the brake being 'on' full.

So, first - how many different levers are out there and when did they change?

Click to expand...

850 Mk 3 lever:

Click to expand...

Ok, now put it back on your bike. :mrgreen:

swooshdave said:

Ok, now put it back on your bike. :mrgreen:

Click to expand...

It's a spare

btw, the instructions with my sleeve kit mentions there may be several lever variations than can cause "issues". So I assume it's know problem.

If the original isn't too bent you can straighten it. I know you wont find it recommended officially anywhere but if you get the lever to right temperature you can bend them OK, the old soap trick is pretty handy to get to the right temperature.

My original lever has road rash at the ball end. It was also chromed (years ago).

LAB thanks for that pic, but without a pre-MKIII next to it it's hard to tell what's different.

Keep the shiny side up folks... replacement parts can be funky.

I have one of the sleeved MC and replaced the lever after a spill. The new lever Old Britts was different too and did'n't release enough to open brake fluid return completely and when brakes heated up the rotor would lock up! I warped a couple rotors before figured out what's happening. And now it leaks too!

Th real issue is as the fluid heats up it expands so the plunger piston the lever touches must be ground back enough to let the relaxed lever allow master cylinder piston to retract enough to relieve the thermal pressure. i found this out the hard way after 12 mm resleeve in cool spring climate that worked a treat - until 1st ever 1000 mile rally trip with my buddy and 45 miles out we stopped in direct sun and when I started to leave brake locked and I fell right over- cargo and all. Realized the cause -after some time- took piston out and rubbed it on side walk a few times till hot brake fluid did not activate brake w/o my permission. I had RGM race lever on and still loved its extra easy leverage, on top the resleeve ratio increase. I took off minimal amount to function but was still pretty pensive so placed a cap over master cylinder to shade it when stopping the rest of the trip till confidence built up again. The only thing that saved me not continuing on this trip after the lock up tip over was I'd put on a foot rest across the fork brace and it took the impact not the bar ends and lever and mirror.

I rebuilt my master cylinder using the Kawasaki seals, 1/2 inch custom turned bore (stainless) and piston (bronze). Thing of beauty. Stops great.
I was also a bit concerned about stack height since I adjusted all the specs found online, but so far it works fine.

Hobot, since the brake lever holds the "stack" in place, why wouldn't you relieve the internal pressure by removing the materal off the working end of the lever? Unless the locking up issue is lack of alignement of the piston seals with an internal bleed port, which is what I am thinking is really going on here.

Stephen Hill
Victoria, BC

Well I suppose you could also relieve lever pad and heard of mods to put a set screw in lever to adjust slack that way. At side of hwy the plunger was easier to file down on cement 'evenly' than lever. Might pre-empt my fall down method by setting bike in hot sun or use light bulb or hair dryer to heat area up about too hot to touch and see if still releases safely.

Same here with new parts that have to be modified to work as intended. I had to file the lever knob down where it touches the piston, not real good especially brake parts. Isn't chroming alloy frowned upon as it weakins it and is prone to cracking?

Aluminum alloys chrome very well. They flash it with copper first.

So I've had to grind the lever where it pushes the piston and the brake is working fine, but It'll always be in the back of my mind that I didn't grind enough and the bugger will lock up on a hot day.

Time will tell.

Chromed Al is frowned on in structural stuff like wheel rims d/t hydrogen belittlement but fine for decorative and light load items like levers. I've heard more tales of chrome flaking off Al than other metals if that matters long term.

Its a bit of a opinion call-guesstimate on how much to relieve plunger spacer or lever pad as too much nullifies some of the levers pressure stroke, but not enough drags or locks tire.