Yamaha YZF-R125 (with 180cc kit) stunt build

Thanks to scubabiker I just found this category now (doh!) so I'll start a build thread here for my daily R125 which I've done a bit of work on

We're already quite a way into things, so this won't be from the beginning. There's catchup posts and youtube videos on my website and youtube channel, but hopfully moving forward I'll keep this up to date..

(blog catchup: https://northcust.co.uk/category/yamaha-yzf-r125/ )

(youtube catchup: HERE )


I have a special attachment to this bike so is not just "any" bike to me, hence perhaps going to unreasonable lengths with it (before anyone says "why don't you just get a bigger/different bike")

This is as she came to me, just over 2 years ago now..







Since then I've done a boatload of changes, generally as I've broken stuff.

I started off with a full stainless system, K+N filter, Power commander V and a dyno tune which was working pretty nicely for quite a long time

I had some problems with the riding position (previous back injury) and subsequent shoulder pain so ended up fitting some stunt clipon/risers, then got obsessed with wheelies and drifting so built a crash cage, fitted motox bars and added a rear handbrake (along with new forks, new clutch, manual timing chain tensioner and allsorts).

The late this summer I blew the engine up and rebuilt it on a 180cc kit and I've just finished running it in now...and now have clutch-slip issues, it doesn't hold the power (upgraded clutch assy on route from malaysia as we speak).

I've been running with the fairings off the last few months while running the motor in because I was doing frequent oil changes to clear debris from the engine failure and I only have so many zipties (for the plastics) but this is roughly how she's looking at the moment:




fully loaded for an overnight trip - out on the road...


At the moment she's on winter rims so is looking a bit more "adventure bike" than stunt bike (esp when fully loaded up with shopping)...



I've recently fitted a wideband o2 sensor so I can get the fuelling dialled in on the new cylinder, but I don't think there will be much happening till the clutch slip is dealt with.

There's a youtube playlist of all the videos for this bike so far here or here:



more as I have it

 

Why did the engine fail? If I recall it was the oil pump or strainer or something?
I think in a couple of years a 125 adv bike will be available by all the big brands..

 

well I guess there is the mt-125 which is heading that way but apparently it's slower or sthing? idk. I like mostly faired bikes though and this is faster The aero makes a lot of difference though with the small engines, as, apparently does a decent clutch

 

> Why did the engine fail? If I recall it was the oil pump or strainer or something?

yeah I'd put the strainer in wrong when I did the clutch which reduced its straining surface area (bc it was squashed flat over the oil pick up hole) so then when I put hard into the wrong gear (over-revved it and shredded part of the cam chain guides), those plastic shavings clogged the oil pickup and resulted in oil starvation. Any of the events on their own would have been survivable but all together nah :-\ Live and learn I guess