Tag Archives: YZF-R125 big bore kit

Yamaha YZF-R125

Winter updates

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been a while since last post…so this will be a bit all over the place while I catch up. Apologies, please bear with me, there’s a lot to cover and some really exciting stuff to follow. Details on that as soon as I know for sure 🙂

Sooooo… the B-motor investigation didn’t go so well, scored bearing surface on the little end (wrist pin) bearing on the con-rod, which means new con-rod, which means bottom end apart and basically new crank which comes with free con-rod (or separate/re-join crank which will cost about the same as replacement). Ran out of budget on that so that’s been paused for the moment.

very expensive scratches
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Yamaha YZF-R125

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

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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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Yamaha YZF-R125

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

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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!

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Yamaha YZF-R125

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

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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…

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https://www.patreon.com/northcust

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