Ok so I’m quite excited about this. It’s been in the works for coming up to a year now but till we reached a particular point where we were both happy, I’ve had to keep things kinda under wraps.
Several years ago, sparked off by a conversation with Legend of Legend’s Garage (who used to do a fair bit of R125 stuff), I learned about Tuneboss ECUs, which seem to be quite popular in the R125 racing community (in europe anyway).
I got in touch with Tuneboss but since the previous ECUs were a limited run there were simply none to be had.
3 years pass and then I get an email asking if I’m still interested in buying a few ECUs. At the time I was just looking to buy 2 or 3, mostly for my own usage but perhaps for a few other friends if they were interested.
Either way, we got chatting and things escalated and whilst the UK/EU market is small compared to the Asian market, they wanted to have a presence here.
So I’m not 100% sure where I’m going with this but I’ve been chatting to a few folks who race R125s in actual race series, and have recently helped tune a couple of them too. Oddly enough both the bikes I helped with are from a fairly similar part of Australia…not sure why that is, maybe they just have good taste 😉
Either way till recently I wasn’t even aware that there really *was* anyone using R125s for any sort of racing, but was obviously *delighted* to find out I was wrong.
So as you may or may not know, so far I’ve come up empty on what the current speed record for an R125 is, so I figured if there isn’t one, why not try to set one (with proof – pics or it didn’t happen!).
Even with many things in my favour, it turns out this is quite an expensive undertaking. It’s a long way to pretty much anywhere from Devon so fuel and entry fees are enough of a problem to be a problem, especially when trying to ensure a working bike too.
In this video I start off riding for a bit while I give a bit of background about the dyno, why, how etc, and then we do a few runs with my mint, bone-stock 2019 R125 to try and get a feel for how to actually “do” power runs (I’m not a dyno engineer, just a nutter with a welder and little respect for my own mortality) as well as *hopefully* somewhat calibrate the dyno’s readings to match the expected power output of the bike we’re testing (2019 Yamaha YZF-R125, which should have 14.7hp).
After that i ride for a bit more and try to draw some conclusions from the tests and figure out next moves. I also have a bit of a catchup on other stuff that’s been going on, and what might be going on in future.
So as usual, the reason I’ve been quiet is not because I’ve been idle, but because I was working on something and didn’t want to show it till I was reasonably confident it was going to work.
Some recent developments and projects have highlighted how useful it would be to have a dyno to test and tune on. I’ve always wanted one but didn’t really have the space before and hence was going to do an engine dyno, and never quite got around to it. Here I’ve got a bit more room to work with and with the help of one of my sponsors/partners, was finally able to take the plunge and attempt building one.
It took about a month working intermittently in the rare gaps between rainstorms, and because I kept having to wait for stuff to arrive as I realised I needed this or that from ebay. But eventually it all kinda came together.
[UPDATE: unfrotunately I was notified by the organisers that the 28th even will be cancelled, and apparently there will be no more drag events at Dakota for the rest of the year. When I asked why the carefully worded response led me to believe someone got hurt (or worse) at one of the events, but that is purely my speculation. Santa Pod have a whole series of dates in October so I will hopefully be running at one or more of those. I was already planning to be at the October 19th one but given Dakota’s cancellation may add another date in, depending on what I can manage].
I am looking for additional sponsors: If you have a Thing to promote and are interested in sponsoring my looney bike racing adventures and getting views on youtube then there is sticker space to be had on my personal bike, which is currently the fastest one and the one likely to be setting ‘records’ (if any) for the moment, so that’s probably where you’d want stickers anyway. Ideally I’d need assistance with entry fees and fuel costs getting to and from the events (since it’s a long way from Devon). If your target market is CBT/L-plate/young riders, and anything R125-related (other than ECUs) then that is exactly my audience and you can just drop me an email and we can work something out. This is all pretty informal and laid back and we’re not talking huge sums of money here, but I only work part time (because bikes) and racing is expensive, so every little helps. Decal space for small decals can be had starting from £20 per event (see I said it was reasonable didn’t I?)
I’ve just booked my 180cc bike into the RWYB at Dakota on the 28th sept. With the new RPM increase and some other changes I have yet to make I’m really curious (and excited) to see whether we can finally break 90 (i think yes), and if so how close we can get to 100mph.
Currently she’s capped at 11k which should put us at a geared max of 96.7mph, but so far I’ve not really seen the power band finish yet even with the 11k limit, so I’m thinking of adding another 500rpm and just praying i don’t melt the engine, which would potentially get us geared to 101.1mph.
Whether she’ll have the power to push that far I don’t know, whether I’ll end up melting everything and be left with no local transport and lots of new bills, I don’t know either. There’s gonna be a lot of “i don’t know”s in this experiment, some of them potentially quite expensive if they go the wrong way, but hey, life is risk, right?
So far with the local riding I’ve done she’s felt really good right up to the limit but I’ve not had chance to actually see about top speed, only in lower gears so far.
Also Dakota is an old runway and from the look of it is large blocks of concrete and definitely a “no prep” track/event. Apparently “they sweep it sometimes if they feel like it” which is very different from the fully-prepped (smooth as glass and glue on track for extra grip) Santa Pod which is the only other strip I’ve raced driven on.
Personally find no-prep more interesting/fun/dangerous since you have to actually take into account the track surface, lane choice etc rather than just twist the thing as hard as you can, so it’s actually more about rider skill than just who has the most ponies and money, but I suspect that it being less-than ideal conditions will affect achievable top speeds.
There do look to be a lot more small-cc bikes there so I’ll hopefully not stick out and feel as much of a wally there as I would on my little R125 at santa pod among the scoobies, skylines and superbikes.
Tbh if we can convincingly break 90 I’ll already be pleased, but if some of these new ECU tweaks pan out as hoped I think we might be able to do a little better than that.
Bear in mind this is still a 180cc with a stock head and valves, so we’re still using the small valves from the 125cc but trying to squeeze 40% more air in and out (80x/second!), and I’ve done *nothing* at all to the intake tract yet – stock throttle body, stock airbox etc, and no valve timing adjustment either, and all of those could make considerably more power.
So if we don’t hit 100mph this time, we’re certainly not out of things to still improve to get there, and if we DO get there, then we may well be able to push further than I’d ever hoped. And that’s before we even start down the road of forced induction, whether NOS, supercharger or turbo.
Given the rough surface at Dakota I think I won’t be switching to the “track” wheels with the sport demon tyres on and will just run my current combo which is a dualsport/all-terrain tyre on the back (Heidenau K60 Scout 130/80) and a winter tyre on the front (Heidenau K66 100/80). Somehow Heidenau tyres are unbelievably sticky but really hard-wearing. I don’t know how they do it. Both tyres have incredible grip in sketchy conditions, and ngl I sorta like the idea of rocking up to a drag strip on what are essentially dirt tyres on a somewhat “farm use” looking bike 😉 (especially if I’m then somewhat fast).
I was going to get all the newly painted plastics out of storage, and even had the boxes open and was looking at them, and whilst I’d love her to be in the right colours, looking as intended rather than the mishmash of random panels she’s wearing currently, the environment here is pretty brutal for a sportbike and until I have the facilities to repair/refinish them, I’d rather not trash my nice new panels amid the muck and gravel where my workshop is based, so I guess for now, patchwork bike on farm tyres ftw ¯\_(ツ)_/¯
Fastest R125-based bike?
I don’t know what the world record is for an R125-based bike (whether 125cc, 150cc or 180cc) – the fastest similar bike I know of is the Tuneboss Thailand one which has a turbo (but still somehow only makes 24hp??). They looked to be hitting 180kmh (111.8mph) but that was on a dyno with no wind resistance, so whether that would be the same on track I don’t know. Some dynos can calculate wind resistance and factor that into their power calculations but we didn’t see that, only the speed reading on the speedometer, which showed (an indicated) 180kmh.
It sure takes off though and as far as I’m aware, that’s currently the fastest…whether it’ll stay that way, remains to be seen.
If you know of another fast R125-based bike then please do let me know.
The only other thing I could find re fastest R125s was this video below on youtube which also shows the TuneBoss one as the fastest but also has another one which looks pretty spicy:
But those two are the fastest I can find and whilst I don’t think mine makes quite as impressive flames (though tbh I’ve generally been focussed on where I was going at the time so don’t actually know) I wonder if we might be in the running for at least being in the top 3 fastest R125s in the world, which would be awesome.
I was chatting briefly to a guy in france (or belgium, idr which) who had an R125-based bike apparently with hp in the 30s. He’d managed to squeeze a 250cc cylinder in there somehow but apparently he had to do quite a lot of work to the crank cases to make the cooling work (I’m not surprised!), but he wasn’t super communicative so I don’t really know much more about it than that. Pics or it didn’t happen.
Either way, I’ve just spent money which was earmarked for urgent drainage pipework for my workshop/living space, to go drag racing instead, so it’s pretty clear where my priorities lie ¯\_(ツ)_/¯
p.s. I just found this guy (Abhinav Bhatt) the other day and whilst he’s having the work done rather than doing it himself, he explains what’s going on really well and he’s doing some really interesting things with his later R15 which has the VVA engine and a 180cc kit. There’s a really good video of the (top end) engine build for that bike. With ~25hp it would also have to be in the running for fastest R125/R15 and he’s had quite a lot done to it. Check out his channel 🙂
So my bike keeps topping out at 89mph at which point we’re still on power but bouncing off the limiter.
Today we’re attempting to fit another OEM ECU, but which has been tweaked to increase the rev limiter to 11k.
If it works, it should increase our potential top speed to around 96.7mph – which would be a significant improvement, and also makes me wonder whether 100mph might actually be possible.
Will it work though, or will it result in fiery engine death?
ok so we’re about 1200miles down on the rebuilt B-motor with rebalanced internals and right the way through break-in miles I felt like the clutch was slipping. I sorta expected this because on the previous motor it slipped from too much power so didn’t really think much of it. Every now and then it did seem to “catch” properly and would dig in and take off but it seemed to be random. For those times it happened though.. wow.
But then at the end of break-in miles since i had to change the oil anyway I put the upgraded clutch (R15 clutch basket with 6-spring boss + uprated springs) from the old engine and it still wasn’t quite hitting the speeds I was expecting. It would get to about 85mph but not any further and given this engine has the power band back in the correct place and screams from about 8.5k right thru the limiter this was unexpected behaviour.
I had been expecting the map to take a while to adapt to the new engine but really it ought to have done that by now. I had recently done a 2hrs each way run which was all main roads so we were in the 8-10.5k range most of that run which meant the autotune had plenty of time to do its thing and sort the map.
The other week I thought I’d just try it on the 14t front sprocket as a test and weirdly it was still not catching right…so I dug into it a bit more and discovered I’d put the clutch cable in a different position from how i’d had it before to see if i could lighten the pull, and then forgot I’d done that. It’s a 1 finger stunt clutch with 3 cable positions so you can vary the travel/pull-weight and as it turns out in the “lightest” position where I had it (which gives the least clutch movement) it was never fully engaging the clutch….
So then I switched it back to the middle position back to the somewhat heavier pull and holy chickenballs what an instant difference.
Since the “A-motor” has been removed from the bike now, I need to strip the upgraded clutch I built a while back off it, since the newly rebuilt “B-motor” is already slipping on the stock clutch and the upgraded one needs transferring to that engine when I do the “end of break-in miles” oil change.
