Yamaha YZF R125 restricted by CDI unit?

[Bike_craze1]

Does anyone know how to de restrict a Yamaha YZF R125 by the CDI unit?
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Yamaha R125 - Cagiva Mito 125 - Honda CBR 600
CBT passed: 22/07/08 Bike Theory passed: 28/03/09
Bike Test passed: 15/04/09

[Cigaro]

Did you not read the first thread? There isn't a restrictor in the CDI unit. If you're getting 80-90mph then that's bloody good for a 4-stroke 125.

My 250 doesn't go that fast (admittedly it's heavier, of course).

4 stroke 125s are generally not restricted because they don't make enough power in the first place.




Edit: Look here. https://www.bikez.com/motorcycles/yamaha_yzf-r125_2008.php

"14.7hp" it makes.

That's exactly the limit for what you can ride on a CBT.

It doesn't produce any more.

[Bike_craze1]

Who said I was getting that speed?
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Yamaha R125 - Cagiva Mito 125 - Honda CBR 600
CBT passed: 22/07/08 Bike Theory passed: 28/03/09
Bike Test passed: 15/04/09

[veeeffarr]

It's a sports 4 stroke 125, it's slow and crap, you made a bad purchase.

Get over it.

[Wafer_Thin_Ham]

4 stroke 125's are not restricted.

It's only 2 strokes that need to be restricted.

With a 4 stroke 125 it has been built to make the 14.6bhp, and that's all you will get regardless of de-catting, race exhausts etc. etc.

You'll just make it hugely unreliable for a 0.5bhp gain. Don't bother. If you really want to ride outside the terms of your CBT get a two stroke 125.
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[Bike_craze1]

[Xenocide]

[.....]

[veeeffarr]

[veeeffarr]

[Cigaro]

[Yamaha-Tech]

I am a newbie here but I will make this precise.

I am a ex-Yamaha engineer. I was in the tuning dept for a company called Rocket Centre Race Tuning, The RCRT. It since went bust.

The head of this thread however wrong in his approach has been gunned down a bit harshly.
The bike as stock produces 14.6BHP and 12.43NM of torque as averaged by the Dyno systems where I worked.

A 125 usually does only produce what it comes with. You can free up a bit more power by boring it out or modifying the fuelling etc but ultimately thats what its got.

But may I draw attention to a separate bike entirely for a moment as it fits in my arguement here. The Honda CRF150. A moto-cross bike that produces 22BHP at the crank. It is a liquid cooled single cylinder engined bike using an array of good materials. Now 7BHP from 25cc is massive from that what the YZF-R makes.

The YZF-R125 is literally the most advanced 125cc ever made being a liquid cooled single cylinder. It isnt like the Derbi GPR125 4t or similar which are just tuned CBR125 engines. It is derived from its moto-cross counterparts. Hence the long stroke for additional torque.

The Yamaha YZF-R125 IS restricted but was done by Yamaha so that it could fit into the U.K market as a learners motorbike. It is restricted electronically and requires an experience yamaha mechanic to know what he is doing. I can de-restrict the bikes but it requires a lot of work as its electronically rigged. Some places charge as much as £150 to do it.

Ultimately the bike produces 17.8BHP and 14.8NM of torque when de-restricted however it requires a new down pipe without a CAT in it otherwise it still chokes around the 15 mark. Top speed was recorded 103mph with the proper gearing and a engine that runs more freely.
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Yamaha Engineering Specialist

[Yamaha-Tech]

Sorry for posting 2 years on, I thought it best to throw my bit in here. My young lad has one of these bikes and owning a R1 myself I'll tell you it isn't slow.
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Yamaha Engineering Specialist

[pepperami]

Mr Y-Tech.... a very interesting read that last post.

please tell us more..( i have a full license by the way ) cos if this is the case , then a crashed YZF-r125 might make a good project possibly
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[Pete.]

[Noxious89123]

Smells like bullshit to me. 17bhp isn't enough for 103mph. Was the bike on a paddock stand revving out in 6th by any chance? A 33bhp will do about 100mph, give or take a little. 17bhp is about half that, so no a chance unless it was one of those world record breaking streamliner type things...

And it's regardless if you ride an R1 or a CB250... A 4t 125 is slow.

The argument about the bike being capable of making 17bhp sounds relatively believable, but saying it would do 103mph, you lost all credibility in my eyes.
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'06 Honda CBR125RW-6 ~ '00 Honda CBR600F-Y ~ '07 Honda CBR600RR-7 ~ Bikeless
'53 Ford Ka 1.3 ~ '03 Vauxhall Astra SRi 1.8 ~ '52 Vauxhall Astra SRi 2.2 ~ '53 Vauxhall Astra GSi

[Yamaha-Tech]

Consider it weighs almost 40kg less than a 250.
Also consider its tyres are skinny and friction with the road is less.
The bike is very small and carves through the air with greater effect.

The top speed on a track was a recorded 89mph from a stock with nothing more than a Leo Vince exhaust on it. The extra 2BHP doesnt make much difference, its the extra couple of NM of torque which plays a big role here when its derestricted. It then went on and did an indicated 103. Which I have since learned is 98mph true speed.

A Ninja 250 was topped out at 110mph. This of course was achieved with 3 modifications, iridium spark plugs, a racing filter and a full exhaust system.

I understand its incredible to believe, I was just as skeptical. I will outline derestriction and tuning in my next post.
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[Yamaha-Tech]

First of all Noxious, calling Bullshit is fair game but not needed. In future approach things with a more questioning attitude as its best to be enlightened than proved wrong which causes fights. I would prefer this not to be the case as i'm a biker, your a biker. Also I would like to point out the 125 isnt slow. Not this one anyway. Its a matter of perspective, how many 125 4-strokes do you know that pull close to 90mph indicated?!

Not many I would suppose so in the general scheme of things its a fast little bugger. Also it out turns the bike in your picture if thats a CBR600F like the one I had back in 2000 . So faster through corners and faster than all 125 4-strokes that are road legal. Though its down to my old F having quite soft suspension.

The bike is restricted at the C.D.I. The rewiring required simply isnt worth derestricting it. The extra gain just gives you a bit more acceleration and a top speed it at best... Crawls to and loses it with so much as a head wind.

If you however buy a salvaged one with an extra £1000 spare... I can help you. Replace/add the following.

170cc Malossi Kit with C.D.I - Very reliable and I can reccomend it
Leo Vince race exhaust - Best for this bike
Iridium spark plug - Reccomended for the 170kit though have a mechanic check the gaps are correct for it.
Racing air filter - Any will do, you need the extra air for fueling
Sprockets - Add 2 the the front, take 2 off the back. Or 4 though it doesnt behave very nicely in that setup
For those who choose the lesser sprocket sets...
150/70 tyre over the 130/70 at biggest. A 140 will do the trick better I think but others have disagreed.

Job done, Power was measured out at 24BHP and 18NM of torque (I got hold of a pal who measured it).
So extra 45cc and right C.D.I with the racing kit. 9BHP increase and 6NM torque increase.

The gear box can take it. In asia the R15 has the same engine with a 150 top end. Does 95mph stock and makes 18BHP but its a work horse bike. Its heavy, taller and wider. Not a good combination with only 25cc extra.

Hope this helps people.
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[MarJay]

[Kickstart]

[Yamaha-Tech]

Again, these speeds were indicated.
And RS125 at 33BHP and similar weight to the Yammie has been recorded indicated 123mph and a true speed of 115. Before anyone starts I still dont believe this to be true. I still am convinced it was rigged as I had a £20 bet it wouldnt reach 110mph true speed as i mistakenly believed it used the same calibration on the clocks as the old one was poor.

So the Yammie reading 110mph though not actually possible for such a small bike true speed will be remarkably close to what you have stated kickstart. Given that clocks are off by up to 10%.

So to put it short I am in complete agreement with you. Well, at least give or take a mph

The 103mph reading will put true speed around 90-93mph at best I would say. But may I say the power it produces after C.D.I derestriction didnt include the new air filter and iridium plug I put on all little bikes like these just for smoother running and a bit more top end. The power could be higher by at most 1 horse power though each one makes a difference on these bikes.

In regards to Malossi Marjay. If you think Malossi are a bad brand, you are correct. In fact, this kit they sell is actually just the 170 variation out in Japan. They just sourced the parts and stamped their name on it.

Good chat, Im sorry for any confusion. I will try to source some extra information on the matter but it is small and far between as Yamaha are very grouchy that the bikes are being derestricted.
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[Kickstart]

Hi

No way will an RS125 manage 115mph true. Road tests got them to 100mph give or take a gnats (and they made about 28hp). I have had mine to an indicated 115mph (185kmh), but realistically it was a long way short of that.

Speedos can legally be more than 10% out. Legal limit is from accurate to 10% +8kmh over (so a true 100mph could be an indicated 115mph with the speedo still being legit), and the accuracy is only tested at 2 speeds. For an accurate idea of speed they are pretty useless.

Also found that with my 1200 Bandit, its inaccuracy isn't even that consistent when compared with timing lights.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Yamaha-Tech]

The RS I am referring to was a track day model derestricted. I assumed 33BHP was as high as an RS125 can go with the one I personally owned never getting above 31 with every race part in the catalogue to which my 97 RS I had for weekend use topped out somewhere in the region of 115-118 by the analogue clocks so close on yours.

The recording device for the speeds is a satellite aided device. It must be at full signal before we take a recoreded speed as a legit score and is 2% wrong at most. Usually it gets them going too fast but it is far more reliable than the clocks.

I am surprised you got so much out of yours with 28bhp. was this at the wheel or crank?

I can ask a friend right now actually regarding the RS that topped 115 true speed.
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Yamaha Engineering Specialist

[Kickstart]

Hi

Mine is an early full power one (never restricted). Never dynoed it but the highest figure I have ever seen in a magazine test is 28.5hp (seen a dyno run giving 36hp, but then in small writing a 1.2 correction factor so really in only made 30hp).

What is the GPS system you use? I have a driftbox I have used on the bike. Also just got a video vbox to play with this year. Normal GPS is way too inaccurate as I am sure you have realised (according to normal GPS my YSR50 has managed 70mph!).

115mph is going to need something like a true 36hp at the back wheel.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Yamaha-Tech]

Im amazed you use the Driftbox. Is this for normal use? as at the track we use those along with a Novus Alpha which is intended for road use and camera alerts but works almost as well as the Driftbox. We have also used Blackbox's which were custom made using the Driftbox's technology but it would average speed over a set distance so you could see average times around tracks using the rough mileage to a decimal point.
Very tricky and if you mess it up you just threw £800 down the loo.

I have confirmation from my friend John. The RS I saw was a track day racing model putting out 42BHP. It was still miles off the motogp bikes but more importantly the guy who took my money Sol made the condition that a 33bhp rs couldnt top that speed. There will be words...

Regular GPS devices are catching up in terms of reading speed. They are getting more and more accurate but they are still 2% out or so at last check. I use the Tomtom Rider as the Garmin is a lot further out. Sorry for the consumer advice but if you use any satnav make it a tomtom on the bike.
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