I started a thread on the forums a little while ago but meant to mirror it here. I may add in the old posts here if i get time but otherwise this will have to serve as a little photo-catchup. please refer to the forum thread for the full story. I’ll try and update both moving forwards..
Whilst not pictured here the cylinder and head are loosely on now while I set up the timing chain etc. Hopefully in the next few days it should be ready to fit.
[EDIT: pics updated, engine fitted and runs!]
Biting the bullet here and using the ebay hydraulic pless to separate the halves of the crankshaft and replace the con-rod etc. This is getting serious now..
going further down the crankshaft-rebuild rabbit-hole and getting on with the crankshaft rebuild for my new motor…
In this video we’re looking at trying to calculate the balance factor for the old 125cc setup vs with the big-bore kit, to see if that maybe explains why it’s run a little differently since going big-bore.
The logic is based on this video from 2StrokeStuffing (thank you!): https://www.youtube.com/watch?v=0hoE_…
B-motor crankshaft rebuild progress in pictures…
what we’re starting with..
This is me attempting to replace the inner camshaft bearing on a YZF-R125 cylinder head.
I’ve not done this process before and it involves extracting a bearing from a blind hole. I’ve found how it’s meant to be done but this is a test to see how well that goes to see how difficult it is, and to help me decide whether it’s something I want to try doing on my main engine.
The bearing puller I’m using is pretty much the default ebay one, just search on “blind bearing puller”.
This is the second attempt at removing the lower timing gear and the captive bearing on the crankshaft of my spare “B-motor”, which I’m trying to build up for my bike.
Idk if this is how it’s supposed to be done but I’m working with what I’ve got.
Whether this turns out to be a good approach or not long term remains to be seen but for now let’s see how far we get with it…
This is the first of my “descent into madness” series of videos where I’m trying to rebuild this spare R125 engine.
I bought the engine as broken and when I took the cylinder off the bearing surface of the little end was damaged, which means the crank needs to be pressed apart to fit a new connecting rod.
So basically I have to take the entire engine completely apart just to get to this one dumb piece to replace it.
The videos are out of sequence but I have such a backlog and there was going to be a plan and it all went to crap. Every expert I was hoping to get to help me with this basically just disappeared or didn’t follow through, so I’ve finally resolved to buying the kit and figuring out how to do it myself.
Even though the engine in my bike has issues (from when I messed up a couple of years ago), despite that it’s done another 5k on the 180 cylinder (even wiht the timing chain issues) and I have not gone easy on it 😉
I’ve had a few people asking me to rebuild engines and do upgrades etc which is very cool, so it seems like it’ll be worth learning how to do it.
Hopefully this all ends with an engine dyno and building mad engines as was always the dream/plan 🙂 I’ve added this video to a new playlist for the B-motor rebuild so I can add all the other videos to it as I work through them. Thanks for watching and thanks to SXparts.com for sourcing hard-to-find components like the lower timing gear.
UPDATE: I said in the video (at 2:08) the lower timing gear wasn’t available, well it turns out i was wrong on that and you can get it here. Thanks to A for the link 🙂 https://www.cmsnl.com/products/sprock…
Ok well you probably know how I feel about facebook products but if anything’s going to get me to cross that line it’s bikes. And it did..Actually so far I quite like it. Lots of nice picsand seems like lots of similarly bike-obsessed ppl but less noise than fb. Biker twitter has decidedly less outlaws than I was hoping for so perhaps Insta is a better place.
Either way..if you’re on there, of if we’ve seen you whilst out riding, please do follow + say hi 🙂
Let’s see if insta is a better outlet for my photos…
https://www.instagram.com/north_cust/
Also: this just happened:
For about a year I’ve been looking for a cheap frame to mount the turbo motor in, kinda because I was hoping it would be easier than making a motor stand..You sometimes see written off frames o ebay for peanuts and I was hoping to get one and perhaps cut out what I needed if it couldn’t be put onthe road anyway. You can get clean frames with paperwork from italy and germany but they’re usually £500+ and that’s a bit much to spend on somethign wich may never even make it to he road…but then at long last I found this one the other day in Germany.
Continue reading I’m on Instagram – NEW R125 FRAMESo as you may have seen the last few videos have been focussing on fuel mapping with the Power Commander.
Till now the videos have been focussed on the Power Commander V (PCV) since it’s the one I have, but it seems like the Power Commander FC (PCFC) and Power Commander 3 USB (PC3USB) are more widespread, perhaps due to their lower cost.
In the last video we went through the process of how I build a map for my bike using the PCV + the attached autotune box which links to a wideband O2 sensor to adjust the fuel map on the fly.
But as far as I could tell there was no way of doing that with the PCFC or PC3USB. They don’t have the onboard CAN bus (a messaging protocol which car devices use to talk to each other) so there’s no way to link them to a wideband, and if that’s not how you tune.. how *are* you meant to tune them?
Lots of people talk about “chuck a power commander on it and get a bit more power” (aka “Common Knowledge”) but I never found anyone willing to go into more detail on how to go about doing that in a slightly more scientific way, or why you should have one box over another. Or at least I couldn’t find anyone *who knew what they were talking about* who would do so.
Mechanics are often better at doing than explaining which doesn’t help feed this “pool of common knowledge”, and they arguably also have a financial incentive to not tell you how to DIY since that potentially deprives them of future business. That’s just capitalism though, and also not necessarily how my brain works, so here we are.
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.
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
