Tag Archives: YZF-R125

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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Making a new fuel map for bigger injector with PCV & Autotune, on yamaha YZFR125

This video follows on from my last one and goes through the process of building a new fuel map from scratch for my 180cc YZF-R125, the way I do it, using the Dynojet Power Commander V (PCV) and Autotune (with a wideband 02 sensor).

We go through all the various components/electronic gizmos and how they interact to get to the end result of a tuned bike.

I hope this makes sense cos I had to make a bunch of diagrams and stuff for it which took forever lol xD

This video is focussed on tuning using a PCV and Autotune which is a setup that seems to be working well for me, and for this sort of moderate tuning.

I know many of you have PCFC/PC3USB etc which is a little different and can’t use autotune, and the next video will be about what your options are in that case. Thanks for your patience and I hope it’s helpful 🙂

IF YOU’RE INTERESTED IN FUEL MAPPING:

Please check out this interview I did with DynoJet UK – we covered some really interesting ground – especially if you’re thinking of buying a Power Commander (who make the Power Commanders).

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Winter updates

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
Continue reading Winter updates
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How to convert PCV maps to PC3USB easily (and free)

So I just figured some stuff about how to convert Power Commander V (PCV) maps to Power commander 3 USB (PC3USB) so I’ve done a little write up of it.

You can import older PC3USB maps into the PCV, and you can import PCV maps into the PCFC, but you can’t import PCV maps into the PC3USB, and you can’t import PCFC maps into the PCV.

Except now you can…and it’s super easy to do: Read more here

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Autotune – game changer

(for me anyway)

There’s been quite a lot gone on here lately.. I’ve not posted for a variety of reasons which I’ll also get into along the way.

I’m trying to work through the backlog now and will have to post it in parts. This is part 1 – which is a little catchup on the autotune box I added to my bike recently, which we’ll build on for the next part/s.

I also realised that my email subscription thing on here is all messed up so till I get that figured out I’ve added a thing so you can login and comment with a wordpress.com account, as well as google and faceballs and whever other type of accounts. I hope that makes it easier to comment and ask questions etc.



The story so far

Continue reading Autotune – game changer
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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

 

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

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