Ok wow I’ve been working on this upgrade & video for months now – so it’s great to finally get it finished.
This is my step by step journey to upgrading the clutch on my YZF-R125 to the larger, stronger one used on the YZF-R15 (international version, 150cc standard), which is then further upgraded with a clutch boss with 6 uprated springs (vs 4 standard) which claims it can hold 2x as much power as the standard R15 clutch.
[I’m also moving this from the R125forum while there’s issues with it].
Some pics from fitting the temp probe and other randomness…
the temp probe.. it’s in what I believe is the return pipe for the radiator so whilst it’s not quite as good a location for temp as the main temp sensor, I haven’t got a reading from that and won’t have till I have the POD-300 controller/display so this is the next best thing and should tell me if she’s having a meltdown…
here’s my replacement section of pipe to replace the coolant pump return..hopefully it fits in the space.
It’s using a Koso 18mm temp spacer – you can get them on amazon or in kits like this below (which looks pretty good actually and a lot more compact. I may switch to one of those as it’s neater than my sensor arrangement)
You can force it to fit exactly in the normal positions but I felt
happier with the radiator a little more relaxed since it is pretty tight
in there already. The bottom of the rad angled forward a little gives
more room for the hose + sensor but does mean you have to adjust the
holes in the fairing, but it’s ok they’re behind the boomerang panel so
you don’t even see the adjustment.
The mount which came with the temp dial wasn’t going to fit anywhere so I just made one out of ali sheet. Was going to secure it with 3 panel screws but one worked fine and less drilling in my baby’s plastics..
the temp sensor seems to assume you’re fitting to a car where body =
ground.. not the case here so had to include positive and negative.
Easiest way to get a positive connection was this arrangement wiht a
bored-out ring terminal which just fitted over the core of the sensor.
Given you’ve got both + and – in close proximity there and don’t wanna
blow the fuse on the ignition which it’s piggybacked off, I had to make
sure the contacts were very well insulated!
wires wires wires…always wires fs
empty bags but back together and just back from doing a week’s shopping. Rorty and naughty
That rear winter tyre (IRC urban snow M+S rated) is really grippy in the
dry but horrendous in the wet. Could be because of the chunky tread but
the first time out in the wet I nearly went straight in to the back of
someone and I’d left plenty of room to brake and wasn’t actually going
like a nutter either. Have lost the back end a couple of times since in
slight whiff of humidity. Sketchy AF, which is wierd bc the Heidenau
K77 rear (i think that was the model) was *amazeballs* in the wet and
even the frost. Still got the heidenau winter front on and nothing
sticks like it
My account on r125forum.com seems to have been deleted so I’m going to carry on here and transfer the last couple of posts..
I’ve had some work changes going on so been having to deal with that lately.. so not really had time to post about stuff, just do it.
Nearly 1k miles on the new cylinder and I’d been feeling with the old baffle in it was too restricted and losing power, and without any it’s still a bit overpiped and was losing the torque at the top end.
So I got some 2.5″ ali bar off ebay and cut a slice off and then made up some sort of baffle on the lathe, which looked more like the sort of diameter I was thinking might be good. One side is a bit tapered bc I was limited with the lathe bits I had, not really done much boring before, new bits on order will bring new possibilities.
Either way I had it tapered side out and performance was great but horrible clacky, farty sound. Just tested it the other way around today (flat side out) and performance is even better and sound much improved and pretty much perfect. You can go really quiet if you need to stay low profile, but when on it properly she makes all the right noises. Not as many pops and bangs as de-baffled but enough 😉
so just been out for a wicked test ride today – ~30 mins each way, country roads, town and fast 3-lane a-roads too, and she absolutely aced the lot. A-roads are now actually kinda fun. Keeping up with traffic wasn’t a problem at all and she pulled 82 into a strong wind before running out of road again, and that was with a large, flat protruding rucksack on me too, and with the motox bars and cut down screen which are a real hit to the aero.
On standard clipons, without the cut-down screen, without the backpack/sail and in full tuck I reckon 85mph and beyond would be actually fine, and probably pretty terrifying B-)
We weren’t out of revs either – obviously I was focussed on where I was going but I think we were around 9k so plenty more headroom and she was bang in the the “surge”/torque, which seems to come in around 7k and last till just shy of 10k since the new baffle. She definitely pulled all the way to 10.5 one time too so it doesn’t seem to drop off now like it did before.
It’s hard to explain just how happy I am about how she rides now. It’s like running with an excited puppy. Still a puppy but hella fun and up for anything. Keeping up with traffic on an a-road wasn’t a problem, I actually quite enjoyed the fast section, wouldn’t mind a bit more of that. A showdown with literally any bigger bike will not go my way but so what lol.
I need to set up an alternate map since atm I’m just on the one from the wideband, and I thnk the 0% throttle might need to be a bit leaner (big of bogging when you crack the throttle) and i’d like an alternative fuelling (e.g. +/- 10%) for flat out too and see if anything changes there esp now with what’s probably over-scavenging aka “the surge”. The top end could still be a bit stronger but I think the piston is also still loosening up to higher rpm so not looking to rush it, and given we haven’t changed the throttle body, intake or valves I reckon she’s doing bloody amazing \o/
Short video running through installing and testing my wideband O2 sensor to try and get the fuelling right on my YZF-R125 with 180cc kit. I was kinda nervous about hacking a big hole in my nice shiny stainless exhaust but I guess that’s part and parcel of getting into the more interesting tuning stuff…
not a lot to say here really – engine is rebuilt on the 180cc big bore kit, this is just putting it back in the bike..if it runs then we’re pretty much back in business!
This video is me trying to reassemble the broken motor for my YZF-R125, this time with a 180cc big bore kit. Link for the cylinder I bought (which looked *beautifully* machined): https://www.ebay.co.uk/itm/151763913131
Apart from that I only ended up buying the top cam chain guide and one replacement head bolt (which looked like it was going to round off) and a bunch of oil and filters. I’d bought a new cam chain too but hadn’t realised you have to split the bottom end casing to fit it..and you’re supposed to change the main shaft, cam chain and cam gear as a set, so i guess not this time.
Videos I found helpful for preparing the piston, rings and wrist pin etc:
The first step towards getting my beloved R125 running again is going to be taking the engine out to see what went wrong and whether I can fix it or whether I have to replace it.
If there’s any way I can fix the motor then I’m going to try and do that, and possibly slip a 180cc big bore kit in there too since I probably have to replace the cylinder anyway and my very patient insurance folks have said they will insure it if I go ahead.
ok well as regulars might know I’ve been on a bit of a mission lately to repair the wear-and-tear from the wheelies & drifting practice so far, as well as protect the bike for future wheelie activity.
It’s been hard on the bike, and highlighted any pre-existing weaknesses, but I also learnt a lot about what I want and need from the bike in order to do this in a not entirely half-assed way.
I love the clipon risers I’ve been rocking most of this year. My “ideal comfort position” was with them not even on full height, about half height. It added maybe 1.5″ each side in height and the same in width. It didn’t mess with the aerodynamics too much, but gives excellent control from the slightly wider stance, but you can still get down in the corners when you need to. Nice.
However, not so good for standup wheelies. Angles all wrong, doable but feels unnatural. We don’t have lots of power to play with so I need to try and optimise my position as far as I can. I needed to try and push weight back so she comes up more easily, so I added a bit more height to the clipons, which helped but was higher than I’d like and the angle was still wrong somehow, and the brake reservoir hit on the screen constantly which is super annoying.
