Category Archives: Yamaha YZF-R125

Cooking Clutches – R15 clutch upgrade for YZFR125. Attempt #2

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.

Continue reading Cooking Clutches – R15 clutch upgrade for YZFR125. Attempt #2

Fitting an extra temperature gauge to the YZF-R125

[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.

Continue reading Fitting an extra temperature gauge to the YZF-R125

Baffled again..Exhaust tuning with custom baffle

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.

Continue reading Baffled again..Exhaust tuning with custom baffle

Wideband O2 sensor on YZF-R125 with 180cc kit, for street tuning

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…

links:

LDPerformance wideband O2 sensor: https://ldperformance.co.uk/product/wideband-controller-for-bosch-lsu49/

carbide grindy bits:https://rover.ebay.com/rover/1/710-53481-19255-0/1?ff3=2&toolid=10044&campid=5337039155&customid=1&lgeo=1&vectorid=229508&item=254299095337

motorcyclespareparts.eu (clutch diagram & parts): https://www.motorcyclespareparts.eu/en/yamaha-parts/2008-yzf-r125-motorcycles/clutch

6-spring clutch boss conversion from MOTOGAGA (untested, mine hasn’t arrived yet): https://motogaga.com/clutches-clutch-housings/567-6-spring-sports-clutch-conversion-yamaha-r15.html

 

My links:

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Patreon (support the channel): https://www.patreon.com/northcust

Twitter (realtime updates): https://twitter.com/northcust

Refitting the engine on the YZF-R125, now with 180cc big bore kit

 

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!

My links:

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Patreon (support the channel): https://www.patreon.com/northcust

Twitter (realtime updates): https://twitter.com/northcust

YZF-R125 engine rebuild (180cc big bore kit) – can I fix it?

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:

wrist pin fitment (this was super useful):
https://www.youtube.com/watch?v=siG5W…

measuring ring gap:
https://www.youtube.com/watch?v=zHK1M…

installing rings:
https://www.youtube.com/watch?v=rgu5v…

My links:
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Patreon (support the channel):
https://www.patreon.com/northcust

Twitter (realtime updates and nonsense):
https://twitter.com/northcust

YZF-R125 Engine tear-down & failure analysis – what went wrong?

Engine out on the YZF-R125

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.

Continue reading Engine out on the YZF-R125

Fitting the motox bars to the YZF-R125: success!

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.

Continue reading Fitting the motox bars to the YZF-R125: success!