Yamaha DT 125R - How do I know if it's been derestricted ?

[Tim_H]

Hi all.

I've trawled bach through the search engine, and can't really answer this.

I have a 2000 'x' DR125R (approx 5000 miles), and am unsure whether it's still restricted or not.

It looks standard, inc exhaust.

It goes quite well though, at 6k it blasts to 8k, then up to 10k if I really want to.

It was probably a bit coked up when I bought it, as it would only rev to about 7k with a lot of smoke.

When you turn the ignition on, you hear the powervalve servo reset, and that's about it.

I've heard that there are loads of ways that Yamaha restricted these, and wondered which ones they've used on my bike.

thanks

Tim

[rizo-sri200]

does it do about 85mph?
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swift kick to the wing mirror puts em straight..
98' Bandit 600 with Slip on

[simon1221]

Or struggle to 70mph?
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DNA50 (sorry) ->> TZR125l >> GPZ500S

[Jebus]

go to this site, they got all the info on restritions https://www.dtr125.net/
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2nd time around CBT: 8/9/11
125 Varadero

[chalky143]

if it struggles 2 reach 70 then its restriced..
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Current bike :: sv650 minitwin race bike
Previous bikes::cbr600 steelie race bike, 1989 Honda vfr750f, 2013 Honda fireblade, 2013 Ducati multistrata 1200s, 2012 Triumph street triple R, 1999 yamaha r6, vfr 800, ducati 600ss, vfr 400x2, ntv 650, bandit 600, cagiva mito 125, aprilia rs 50, honda c90x2, honda hornet 600x2, cbr 600, aprilia rx50, suzuki katana
My bike pics: https://www.bikepics.com/members/chalky143/

[Tim_H]

Thanks for the replies.

It'll do 75 quite easily (but revving the whatsits off it), but i'm not that confident to take it faster, as it doesn't feel that stable.

I think a larger front cog will make for more relaxed cruising, as it's through the gears really quickly.

The only comparison that I have was when I rode a friend's DT, and that seemed to want to pick the front end up in the lower gears. (Dep, power valve etc). Mine doesn't wheelie at all just on the throttle. (I am 15 stone though)

Tim

[element]

Mines a restricted 04. Ive only got 60 so far since I dont wanna push it. Just bought a new front sprocket (+1 tooth, standard is 16t. biggest I know of is 17t and go as low as 13t?) mainly because it does fly through the gears and I want to use it to cruise to work. Think yourself lucky you dont have an 04 model
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04' DT125RE (run-a-bout) // 89' DT125R (rebuilt + supermoto conversion)
SPARES FOR SALE. 2RK TZR // 82 DR125 // DT125R/E .... PM ME...

[Tim_H]

I just bought a 17 tooth front sprocket today. to replce the 16t one on there.

Interestingly the chap in the shop said that DT's used to have a 17t as standard, with a smaller rear sprocket too.

not tried it yet as it's raining, but I don't envisage anything over 80MPH, as that's where the speedo stops

[stevo as b4]

Sometimes it's possible that the manufacturer plays with the gearing as part of restricting the bike, for certain countries power and sometimes speed limits.

Any trailbike is going to have a compromise on gearing anyway, as good gearing for general use including off roading, isn't perfect for road only use, and high speed cruising etc. The KMX125's run a 14t front sprocket as std, and in 24bhp full power form they red-line at 80mph, with this gearing. But they can usefully pull a 15t front sprocket to reach 86-87mph at the same revs for road use, if that's what you want the bike for. The DT is probably the same in terms of the gearing compromise issue!

[element]

just found a site that does upto 19t for my DT. The 17t looks big as it is. I couldnt imagine a 19t fitting in the space there is!
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04' DT125RE (run-a-bout) // 89' DT125R (rebuilt + supermoto conversion)
SPARES FOR SALE. 2RK TZR // 82 DR125 // DT125R/E .... PM ME...

[Tim_H]

Well, I rode it with the 17t front sprocket, and, yes it's a lot less frantic at higher speeds, but slightly slower through the gears.

But, going back to my top post, I still am unsure as to whether it's been deretricted or not.

Like I said, it seems to hit a lot of power at 6k, and the noise deepens. The power delivery then flattens out slightly at 8k, and will rev to almost 10k.

Is this normal for a derestricted bike, or should it 'whip' round to 10k from say 6k? in the first 3 or 4 gears?

I don't have anything to compare it with, other than that one ride about a year ago, on a friend's 'Full power' one.

[element]

mines restricted and feels exactly as you describe. Im guessing a fully derestricted should have the powerband kick in at 5-6k and stay all the way to red line in each gear. Someone correct me if im wrong.
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04' DT125RE (run-a-bout) // 89' DT125R (rebuilt + supermoto conversion)
SPARES FOR SALE. 2RK TZR // 82 DR125 // DT125R/E .... PM ME...

[stevo as b4]

Yeah from riding a 98 DT125R a few years ago, thats exactly how it should feel. A full power unrestricted bike, has a strong powerband from 6-10k rpm, and yes it should feel like that in every gear during acceleration.

Later DTR's have had lots of different and numerous restrictions, and the 2000> models are much more tricky to de-restrict, and involve more detective work to find out what has been done to restrict them and what parts must be changed to make it run properly in full power form. Even different years and bikes sold in different countries can have several different methods of restrictions and speed/power restrictions that much like some of the Import NSR125's, can be tricky and expensive to work through or change.

[Tim_H]

[stevo as b4]

A 20-25bhp 125 with normal road gearing, just isn't going sent the front wheel skywards just by opening the throttle fully. This does not mean that it will not be fairly easy to wheelie though. It's a technique to learn how to wheelie a bike. It will not just do it all by itself without you actually wanting the the front end to come up.

If the engine note changes at 6k and then it revs quickly up to about 10k i.e. (the powerband) then your bike is full power most likely and there is nothing wrong with it! It should also be making about 20-23bhp at the back wheel, depending on if it's a std or which aftermarket exhaust system you have fitted.

[Tim_H]

- After more reading and thinking.

I believe that with the bike having the P-valve working as standard on a 2000 model, it's restricted by,

Option A) I've read that Yamaha altered the CDI unit, so that as the revs climb above approx 7k, it starts to close the powervalve.

Option B) But, - if you read the DTr125.co.uk blog, he suggests that the P-valve is installed 180' out.

The feeling on my bike is like this. - The power really starts at around 6k, but tails off really quickly (as the p-valve closes?), but will still rev to 9 or 10k, but creeps there.

Q. Is changing the CDi for one from an earlier bike the answer? - or is it installed 180' out? - Please is there definitive answer?

PS, I've just ordered a 'Big One' front pipe.


Tim.

[Tim_H]

Update -

Just fitted the 'Big One' (ex Fresco) front pipe, and left the original silencer fitted.

It's a good fit and at £80 is a lot cheaper than a DEP.


All I can say is - WOW

Let's say it is like a changed bike. The power band has moved up higher in the rev range, and it positively zings round to 10K. - must be much improved breathing.

Ok, and it sounds great too!.

Thanks for all the opinions, and i'll probably leave it alone for a while now.

[Andetover]

I've owned a DT125R since 2004 (now 2020), I'm a mature rider, and the 2 strokes I've owned include a Kawasaki KH250 with a 350cc barrel swap, Yamaha RD350YPVS F2, Yamaha TDR(250), and Suzuki RG500 project bike.

My DT is quite possibly my favourite bike of all time.
It is totally standard, except for the "reed switch" behind the speedo being gently moved to one side and wrapped in plastic to protect it.
When you remove the front section of the exhaust and shake it, you can hear metallic rattling, presumably the factory fitted restricting disc in the header has rusted its welds and very kindly dropped out of harms way.

Unlike a lot of posters on here, I've not only had the bike dynoed, I've also verified its top speed, on standard gearing, with a GPS.

OK, these are the realities:
In top gear, 1000 rpm = 8mph

In lightly derestricted form, it produces a genuine 17.4 bhp at the rear wheel (you can say 20 bhp at the crank).

On a sunny day, when the atmospheric conditions are perfect, top speed was a verified 82mph.
RPM 10,300.
The speedo hit the stop, and was the most accurate I have seen on any vehicle, never more than 2 mph out from the GPS. That was a surprise.

The exhaust emissions were checked, and it confirmed that in standard set up, carburation is safely RICH at the top end, allowing novice owners to thrash the engine all day.
I wouldn't change the settings. Its not worth it for a brief extra 3/4 mph.

Zeeltronic do a fully adjustable ignition system that also regulates the power valve, in an article in Practical Classics a couple of years ago, they got output up to 19 bhp, and a much snappier mid range.
The trouble is finding a tuner who can fit it and set it up properly on the dyno.
Bear in mind, BIG differences can be achieved by:
Using a NEW, CLEAN, ORIGINAL air filter.
Honestly, if they are clean, they shift enough air.
Also...
Fully synthetic 2 stroke oil... helps keep your plug clean too.

And...
Atmospherics.
There is nothing you can do about this, but bear in mind 2 stroke bikes that use old school carburetors are very sensitive to air density, temperature, humidity and well maintained air filters.
(As well as float height, stale fuel, perforated air inlet hoses, loose hose clamps, clogged fuel filters).

A well maintained STANDARD DT will get about 95 of the performance of a "tuned" version with different pipes, etc... but essentially it should also stay reliable.

If you do want to add goodies, always book a dyno run BEFORE you fit them. Then book a second run AFTER.
Not only will you see if any gains are illusionary, you can also check the fuelling and re-jet if necessary.
And believe me, if your new set up leans off the mixture to any degree, you MUST re-jet or you will end up with a melted engine.

TDRs by the way do about 113mph on @48bhp
RD350 YPVS do about 125 mph on 52 bhp
Kawasaki KH250s do around 83 mph on 28 bhp

Anyone who tells you they can get 100 mph from even a 20 bhp DT is utterly wrong. Maybe they are confusing a KPH clock with mph?
They simply aren't aerodynamic enough.
Bear in mind a TDR does barely 113 or so with an extra 30 bhp!!!

Keep it real, and sunny side up everyone!!

[redeem ouzzer]

A) Holy thread resurrection Batman.

B) I really wouldn't come on here willy waving about how much you know about 2t's and dyno development.
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Be a REAL MAN!

[Andetover]

9 years + must be some kind of record!

The aim was to put some myths to bed, before all us old geezers who've been through the whole (if I put a 21 tooth front sprocket on, will it hit 100? etc) buy, tune, melt piston, and finally afford to get it done properly cycle die of old age or give up and buy a Volvo!

I'm no expert, but, like you I've lived it, and if we don't pass it on, then this generation of new riders won't know what works, and may well give up trying.

Plus you'd need a fecking magnifying glass to see my William, too many years riding in soggy Frank Thomas "waterproofs"...

[Easy-X]

Why tag on to an ancient thread covered in dust?
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Andetover]

I just googled "What is the Top speed of a Yamaha DT125R?"

I was hoping to find some tuning knowledge, or maybe contemporary small capacity 2 stroke enthusiasts. I read the thread, and was disappointed that after much discussion it petered out without any of the crucial questions being answered.

I know these guys are in their 30s now, and probably left bikes behind years ago, so I thought, I can't be the only one who may want answers, why not add some knowledge gained from 16 years of ownership and take some of the guesswork out?

My bike is 2002 model, late registered in 2003, I'm its 2nd owner, it's got 6,000 miles on the clock, and runs sweet as. I actually prefer it to my GSX-R 750K2, because I can thrash it! If I tried to thrap a gixxer, I'd be dead.

[Easy-X]

I don't know whether to be gratified or horrified that Google led you here
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[stevo as b4]

That's how all these fools get here and dig up ancient stuff on the net though isn't it?

[Andetover]

Yep, I must admit I was surprised to see a decade + old thread still popping up on a search, you'd think, legendary bikes like DTs which sold in the 1000s over nearly 2 decades, and which were quite tough little buggers would have people still talking about them.

All the big stuff, RG500s, Kwaka H2s and KR1s, even RD350s/250s and Aprilia RSs have sky rocketed in price, the only stuff left is the small, mass market stuff... and some of 'em are actually a fecking riot!

So I guessed there'd be some people discussing these little gems, and how good they are right now... got that wrong!