YZF R125 Derestriction by West London Yamaha

[TomB]

Apparently West London Yamaha have pioneered a way to "de-restrict" the YZF R125, and are charging £150+vat to do it.

It consists of fitting a specially modified secret part and a new sprocket,

Now common theory is the bike is not restricted any way, so firstly I imagine this is tuning.

The second thing is there is supposed to be an article by Liam from MCN floating around somewhere, where he had the work done...
I cant find this and wanna see what he had to say.

I just dont seem entirely convinced, expecially as they claim that you dont need any kind of fuel management system fitting.
Can anyone shed any light on this as I am having real trouble finding anything out!

Thanks
____________________
WR125x......

[Pete.]

Course they are not restricted - that's why they hit the power limit almost exactly

I think that 'restricted' is perhaps not the best terminology. Almost every production vehicle out there can be modified to go faster, so effectively everything is 'restricted'. My opinion is that if you get 'across the board' gains in power and torque without changing out moving parts then you could deem that to be a 'de-restriction'.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[TomB]

That does seem to be the general consensus, and I totally agree.

I just want to try and get a bit more of an insight into what they could do other than change the sprocket (I assume its the front one)

Apparently they are the only place in the UK that knows about it and have developed a bespoke part.
But are keeping tight lipped.

I'm just wondering if they change the sprocket and tell you they have fitted something else, as I have read that the YZF is not geared optimally out of the factory.
____________________
WR125x......

[Pete.]

It would be a trivial matter to have it done then look on the bike to see what part they have changed - if you had £150 to burn. TBH I would wait a week or two, it'll be common knowledge soon enough. One thing you can count on is that WLY never developed the part - they will have sourced it from Japan or somewhere.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[TomB]

It seems like they have been doing it for a while no, so it's quite surprising someone hasn't done exactly that.

There are plenty of mentions on various forums yet noone simply saying, I've had it done and all they did was..................
____________________
WR125x......

[BenR]

www.yamahar125.com/forum
____________________
Current bikes: suzuki RG125UN wolf. Yamaha MT-07

[TomB]

I've had a look through that site, but couldnt really find what I was lookin for.
____________________
WR125x......

[Pete.]

They might be fitting a different camshaft that pushes the engine's output up at higher rev ranges, and fitting a 1-tooth larger sprocket to take advantage of the extra power. Would come at the expense of some mid-range probably. Since fitting it would be a simple excersise I guess that £150 &vat would cover it.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[bradh511]

Umm i wonder if the replace the cdi as this will do the engine management? Then put it a tooth down on sprocket?

[TomB]

I dont think this engine uses a CDi as its fuel injected?
____________________
WR125x......

[TUG]

It is CDI, and they cut the cat out of the exhaust pipe to "derestrict" it in normal means. If they change the CDI and sprocket thats just like buying a power comander for a generic 600 sports bike.
____________________
Haz ER-5, innit!

[TomB]

Interesting ideas, however I dont think they cut the cat out.

As they recommended fitting a Leo Vinci system to get the best out of the mods.

Something else mention on other threads was a 5 position CDI?

Its all really confusing and there seems to be no concrete evidence.

I have never expected to get anything much out of the bike, however if some improvements are to behad then i'm willing to give it a go.
____________________
WR125x......

[TUG]

I take it you have the WR? which is the same engine, Everytime i see a piped R125 it has had the cat cut out of the main pipe, Its fuel injected so to get better power from the induction side you'd need a better flowing airfilter and a different map on the CDI. Final drive gear ratios will affect the bikes acceleration/top speed but you need to sacrifice one for the other. Its not hard to understand, its more complicated and costs more on modern bikes and 2t's as alot of it comes down to how good you are at working out the numbers.

Wish i had the cash to buy the WR250 supermoto, man i love working on them.
____________________
Haz ER-5, innit!

[TomB]

I have seen people who have chopped the cat out, I am wasiting on a Gianelli aluminium system that has a de-cat front pipe.

My main concern is with chaning the exhaust and filter, is that of fuelling.
I am not sure that the standard eci can adjust enough to compensate?

When I spoke to WLH they were adamant that with the mods they do, yopu dont need to change the fuelling.
Maybe this is beacause they use a modded/different CDI unit then?

I was considering the WR250 as my next step up, but have read its a bit lacklustre in performance, not to mention I cannot undertand why they gave it that ugly front headlamp unit???
____________________
WR125x......

[TUG]

The bike is injected so changes its fueling in a certain adjustment to compensate for how hot it runs, how much air its getting, how much CO2 is in the exhaust etc etc but only has a short range, the CDI is the brain of your bike, if you unplug it it wont work. Sounds to me that if what they say is true, they do alot of mods.

WR250 lack luster? It will spin the back wheel under heavy acceleration and wants to wheelie, if its speed your looking for then your barking up the wrong tree, so to speak.
____________________
Haz ER-5, innit!

[G]

Maybe they 'chipped' it

[TUG]

Does the job imo, I test ride them in the yard and they're fun to ride, like i said...
____________________
Haz ER-5, innit!

[G]

I often find under-powered stuff fun to ride, however I'd certainly be disappointed if I paid for it at the current prices.
If I was a new rider, I'd be quite happy with it I suspect - until I had a go on a friends semi-proper supermoto.
A lot of DRZ buyers soon come on here asking how to make them faster, so I don't see this faring much better.

[Pete.]

[Kickstart]

Hi

If they are charging only £150 then I doubt there is much they are doing. Might well just be something really crude like a resistor in a temperature sensor circuit to make the ECU think it is cold and so richen the mixture a bit.

Wouldn't be surprised if what they are doing is ripping the cat out. Suppose possible that the throttle doesn't open fully as standard and they just change the pulley wheel the cable operates. Could be loads of other things though.

As an aside, personally I would say derestricting is removing a deliberate restriction on power put in to keep the bike at a certain level below that which it was designed to produce. As I don't think it was designed to make more than 11kW I would call it tuning.

All the best

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

[ms51ves3]

After a quick Google about it I came across one guy who claims he does them saying that you have a choice of either more top speed or more acceleration. Sounds as if they are just changing a sprocket.

[Pete.]

A de-catted exhaust would be easy to spot. I know of one that's been done with little effect. It could even give the impression of better performance by making a hole in the mid-range.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[TomB]

To be honest the WR125 will get up to around 72-74mph with no major struggles, but it must have different gearing/sprockets to the YZF as people are regularly claiming around 80mph.

I just wish they werent keeping it so much on the down low, either they have something to hide or genuinely have found a way to improve the performance.

The guy on the phone did mention that the YZF in standard form does not make good use of 6th gear, and with the mods will pull right through 6th.
But again, this could just be down to the sprocket...

These bikes have been around for a while now, why is it so difficult to find any concrete facts????
____________________
WR125x......

[G]

The WR will be significantly less aerodynamic. For top speed, power is most important to overcome air-resistance.
See another thread recently with links to 125s doing well over 150mph when air resistance is massively reduced.

[TomB]

Thats a very good point, I hadn't considered the drag.

I'm sure the WR is set up differently though, it mentions something about it in the sales brochure,
____________________
WR125x......