YZF-R125 CLUTCH IMPROVEMENTS AND rear HANDBRAKE PROGRESS

I don’t even know where to start so I’ll just chuck some pics in and hopefully it will make sense along the way

And the quest for wheelies continued…

Ok so i beginning there was the normal clutch lever, then we went shorty two-fingers (which was better) and then slipping off once too often when pulling up with two fingers I realised why they all have 1-finger levers…

Love these lovely CNC’d numbers but wheelies say you gotta go

The 1 finger lever (ebay link) is actually bizarrely comfortable like I’m thinking why the hell did we have all that other nonsense before. The movement is pleasantly smooth and precise. Also the lever has 3 positions where you can hook the cable in which slightly change the feel and cable orientation to suit your hand. There’s a wee bolt to set the resting position of the lever too so you can get it set up exactly how you want. So much fun with one finger…anyway.

hello shorty 1 finger lever

I actually didn’t use the funky cnc’d cable adjuster it came with because it didn’t have a cup section to hold the cable and I wasn’t happy with it just sitting as it was, but the adjuster off the oem lever fitted and worked perfectly, and then even the rubber boot fitted over and it all sealed up like factory (because rain and muck).

You do end up with a connector left over which I shorted and sealed up, otherwise you have to be in neutral to start the bike which is not ideal.

I only did the 1 finger lever for better wheelie control but now having ridden with it for a few days I kinda love it for the feel and precision of adjustment. It’s like I don’t really have to think about it anymore and maybe we could feed in the power better like this. Weird but nice.

But handbrake plzzz..

Well I was on my way towards this anyway but then upon advice from other wheelie enthusiasts, I realised that a rear handbrake is probably a good plan if you wanna learn standups (which I very much do), so here we are.

I’ve been vaguely working towards this for a while, and by now have a few different brake and clutch levers of various sorts to choose from, but obviously more options are good. I’d been seeing this type of lever (below) on various youtube stunters’ bikes – namely using a brake cylinder oriented at 90 degrees to the handlebar rather than along parallel with it like a normal cylinder – should use up less of the precious space on the bar, right?

I happened across one on ebay from the “Adelin” tag, and dug from there. Apparently there’s a brembo one from a honda CBR1000 (?) which is similar design but better but also costs like £250+…so we have this one for proof of concept.

As it happens it doesn’t fit with my current clip-on arrangement (haha, obviously) but nice try. Would probably fit nicely on motox bars, and the brake cable placement is arguably better than a regular cylinder for my application.

So we ended up back with the first set I bought, this is the right-hand brake lever, somewhat upside down, with the microswitch removed (since it’s not going to connect to anything anyway) and all packed as tightly as possible so I don’t have to widen the bars any more.

I started off trying out where I’d want the levers if no constraints and then worked towards that. I tried a *load* of different positions and configurations and tried hopping about on the bike a bit to see how it might be in practice, whether I could reach things etc and this seemed to be about where I’d want the levers to be (as far as I can tell). The clutch is pointing a teeny bit more skyward than I’d have it normally but it’s not even inconvenient, and the brake lever is comfortable to grab with any fingers I choose, or you can do both staggered (though not sure my brain can do both yet).

I ended up grinding down the head of the clutch position adjustment screw to get the levers to butt up against each other more tightly. Now it’s just adjusted by hand and held in place by the lever clamp pushed up against it…but with that done both levers fit perfectly alongside the map-switch, and i only had to widen the clip-ons by about 5mm so shouldn’t really affect filtering . Having to move the bars out a tiny bit meant the map switch didn’t really have enough bar to grab onto the other side of the pillar, but it happened to just fit perfectly in the leftover space this side of the pillar \o/.

*tightly packed*, but it all somehow magically all *just* fitted without really needing to widen the bars

Hopefully that brake lever will be happy living somewhat upside down….I mean I think it should all seal properly, but yeah, there’s still some “grey areas” to figure out. Still, progress…

The rear caliper

Since nobody seems to particularly stunt R125s (that I know of) there’s not exactly a lot of precedent as far as handbrake setups go, but my plan is roughly this:

Cut and weld along red line

I managed to snag a brand new caliper and caliper mount on ebay which I’ll take my grinder to and cut so that it fits flush like in the pic above. Getting it all clamped in position is probably going to be a bit tricky but should be doable as long as I take my time and make sure it’s all aligned correctly.

When I change wheels on a paddock stand I take the axle out and drop the wheel down vertically (since that’s all the chain allows anyway), so having the extra caliper on the back shouldn’t make changing the wheel much more difficult. Refitting will be a bit more annoying because there’s an extra set of pads to clear but shouldn’t be a major issue.

Drag from the extra caliper could be an issue but I guess it works for everyone else who has one?

Once both parts are fitted to the bike and I’m happy with them, I’ll measure up and order a braided cable to length.

This very much may still not work

There are still definitely numerous ways which this could not work, the main ones so far:

  • It’s possible the second brake caliper doesn’t like being oriented back the way it is in the pics, or it becomes a bastard [tm] to bleed.
  • or maybe the brake lever/master cylinder thing doesn’t seal properly or like being oriented somewhat upside-down… e.g. might leak or not hold pressure or whatever.
  • it could be the caliper carrier is some weird carbon steel and doesn’t like being welded with the mig
  • thermodynamics and metallurgy in general
  • anything else I haven’t thought of

I’m hoping neither of the first two will be an issue, there’s probably solutions for both – e.g. motox bars would mean I could use the adelin lever, and [open to ideas] on the caliper orientation. I saw someone messing about with a triple caliper setup and they were doing stuff with a spare brake disk for all the calipers to grip on whilst not in the wheel, so perhaps that’s just where we’re at now.

If the caliper carrier is some sort of carbon steel which maybe doesn’t like being welded (with the mig) then it can still be welded but it’ll need doing with the “The Magic Lightning” aka tig which is a royal pain in the ass to set up, but will weld pretty much anything, including carbon steel. I should know more after the first attempted tack weld (which I would prefer go fabulously if possible).

EN24 carbon steel outer welded to a mild steel inner (collar) using 312 filler (iirc?)

  • Test the brake lever/master cylinder to see if it seals properly in current orientation
  • Do a test weld on spare spare carrier or the section to be removed – does it weld?

I can probably do a test weld on the caliper carrier on the section I’m going to cut off anyway or the spare (spare) carrier, and test the brake fluid thing on the lever before committing to welding the additional caliper carrier on. Both of those seem like they would probably be a good idea…let’s see if that’s how it works out…

Motivation:

Been loving the Russian stunters and their attitude – This dude – stunting the hell out of his CBR125 and the guy rocking stunts on a TULA. Stuntexru is suddenly one of my most watched channels:

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