Tag Archives: YZF-R125 engine rebuild

Removing the flywheel on YZF-R125

This is just a quick little edit i’ve put together because I know that at least one of my viewers is about to do the same process, so wanted to show a little what to expect (and see for myself!) what wonderful mysteries line beneath the stator cover etc.

This is working on my “B-motor” which is a motor i got as a non-runner, hoping to just put a new cylinder on and get it in the bike, but then whilst removing the seized wrist/gudeon pin the bearing surface on the little-end got scored, which means now I have to pull the crank out, get the crank separated, fit a new con-rod and then re-assemble. So since i have to split the casings and whatnot I might put a forged con-rod and fresh bearings where I can, though in general this motor is a lot less shagged than my current one .

I’m not looking to do a mega-rebuild on this, just get it back to working, stick a 180cc cylinder and a stage 2 cam on (both of which I have already), and then get it into the bike so I can start work in rebuilding my ‘A-motor’, which will be getting The Works (with a view to forced induction)…so this is a bit of a trial run.

With a bit of luck this build should see us comfortably into the 90-95mph sorta territory, given we’re already knocking on 90’s door on the current (very knackered) A-motor.

I’ve not had one of these motors apart to this extent before so please don’t use this as a “how to”-video, it’s likely to be more useful as a “here’s some mistakes to avoid”-video (like losing the woodruff key, as you’ll see), and perhaps might be useful to see what special tools are needed to actually take these beasties apart.

STUFF YOU MAY NEED:

replacement woodruff key in case you lose it like I did:
https://www.ebay.co.uk/itm/GENUINE-YAMAHA-WOODRUFF-KEY-90280-03X00-YZF-R125-WR125-R-X-CW50-AEROX-JOG-RR-TY/114045590439

set of box wrenches including an 8mm which should fit in the tight hole indicated in the video (though this is only needed to split the casings):
https://www.ebay.co.uk/itm/7PC-BOX-SPANNER-SET-PLUMBERS-TUBULAR-NUT-WRENCH-MONOBLOC-6-17MM-TORQUE-BAR-20B/331623284582

cheapo ebay flywheel puller (requires additional bolts in order to be of any use (see below):
https://www.ebay.co.uk/itm/13-PIECE-HARMONIC-BALANCE-CRANKSHAFT-GEAR-PULLEY-PULLER-FLYWHEEL-BALANCER-TZ/324497829601

Additional/longer bolts needed to make the cheapo ebay flywheel puller work (get 3 of M8 x100mm ):
https://www.ebay.co.uk/itm/M8-8mm-PART-THREADED-BOLTS-HEX-HEXAGON-HEAD-SCREWS-STAINLESS-STEEL-DIN-931/383682199386?var=652081107590

#YZFR125 #BIKELIFE #BIKEWIFE

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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

 

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

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

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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

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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

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