Yamaha YZF-R125

Removing the flywheel on YZF-R125

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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

Yamaha YZF-R125

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

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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).

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
Continue reading Winter updates →
Yamaha YZF-R125

Big Bore Problems? Thoughts on 180cc fuelling issues

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Yamaha YZF-R125

How to convert PCV maps to PC3USB easily (and free)

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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

Yamaha YZF-R125

Autotune – game changer

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(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 →
Yamaha YZF-R125

YZF-R125 injector swap

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So there’s been a few discussions on the forums recently about different injectors, and I happened to film when I swapped my injector over so figured it might be useful.

It’s a pretty straightforward process…as long as you don’t mess it up.

At which point it would become very complicated. So really don’t do that.

I have a theory – that on a stock R125 which has perhaps a slip-on ((or full exhaust) and a K+n filter, that a 120cc/min injector would make a really cheap, convenient upgrade.

When mine was tuned like that the fuel map was adding about 20% across much of the map. Not all of it but enough for it to potentially make a difference where it matters.

And here’s the link to the 120cc/min injector. As far as I’m aware stock is 100cc/min, so that would give you a 20% bump across the range.I’ll just leave this link here: https://www.aliexpress.com/item/32921…

My problem currently is that I don’t have a stock bike to test the idea on…though I’m hoping i’ve found a volunteer. Watch this space 🙂

Yamaha YZF-R125

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

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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 →
Yamaha YZF-R125

Fitting an extra temperature gauge to the YZF-R125

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[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 →
Yamaha YZF-R125

Baffled again..Exhaust tuning with custom baffle

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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 →

YZF-R125 tuning, Stretching scooters, welding & fabrication, customising, custom parts.

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