DT125R FORUM

Well the best thing to do is to check to ensure that the thermostat is working correctly. You can remove it and place it into a sauce pan and check to see if it correctly opens at the right temperature when left to boil.

If your daily commuting the bike, then leaving the thermostat in is advisable. Yamaha know what they're doing.

If you start tuning the bike and pushing it beyond its original specifications, then you may want to consider removing it.

The thermostat isn't just there to aid heating up of the engine, it also has a role in providing pressure in the cylinder head to avoid pocket stagnation of gases. So it's actually important it's fitted.

I just noted that these engines do run warm and removing the thermostat allowed my bike to run at a more consistent temperature when under load.

DTRs do seem to run very hot in my experience. Always have, wouldn't worry about it.

My Aprilia RS usually sits around the 60 degree mark, I run a Vapor Trail Tech unit on my DTRE and it's ready 110 before!

To combat this, I removed the thermostat and now it sits around the 60-70 mark, just note you do really need to be careful when warming them up to ensure you don't cold-seize the engine.

Yeah okay, well that sounds like you've ruled out all most of the basic things.

I've had this before with a faulty ignition coil. These can still be bought brand new from Yamaha and I highly recommend going for genuine coil over an aftermarket one. The aftermarket one I had led me on a wild goose chase trying to figure out the intermittent fault.

You can measure the coil to see if it's within tolerance, what I was finding was that from cold it would work a treat, but once under load and warmed up, it would fail to fire above 4k RPM.

So it could be a worn out ignition coil, however unlikely that may seem.

Other than the stator/pickup, there really isn't a lot more to these engines to get them running.

The side stand sw and the whole interlock chain should be good. I even bypassed all of that by grounding the blue yellow wire to the CDI directly

If I had to guess, that's probably your issue.

I see this time and time again with the side stand switch. My brother had a similar problem on his 2001 DTR many years ago now. My advice would be, if you're struggling to figure out a problem, get it as close to factory as possible, otherwise you're going to be chasing ghosts.

No a mechanically unhealthy engine wouldn't necessarily affect spark, but given how you described riding the bike and it cutting out, indicates that you had spark.

Okay, well it's good to know it's unlike to be water corrosion But still check those connections anyway to make sure they haven't vibrated themselves to pieces.

Ensuring good connection between that block is essential.

As I said previously, triple check the neutral switch, clutch switch as well. If they are vibrating loose they will cause intermittent problems.

Oh that's frustrating.

There really isn't an awful lot to these engines. I've never heard of a stator go bad. I've had a bad ignition coil and I've had an aftermarket (bike sadly got stolen from me) ignition barrel disintegrate and cause this problem.

A common one is the side stand switch, similarly the neutral switch and the DTRE has the clutch switch.

Check the plugs from the ignition barrel to the wiring loom as they can have a tendency to trap water and destroy the connections.

Did you say whether the engine is healthy or not? Is it making a good PSI? Are the intake and exhaust pathways clear?

What specifically do you mean by cut? The Tachometer is mechanically driven on the DTR. So you need to replace the tachmeter cable back into the gearbox and the clocks.

If you mean the lights etc, then there are many wiring diagrams already uploaded to this forum.

Workshop manual is pinned: https://training.dt125r.co.uk/files/Yamaha_DT125_Workshop_Manual.pdf

@hensmaxim Just contact him directly via Facebook or something, he did my pipe for me silly cheap.

Hi there and welcome.

What a great machine, they're becoming rarer and hard to find in unmolested condition, so definitely bear that in mind before tou do anything drastic and keep all the original parts.

I super moto'd my DTRE using Yamaha WR450F Forks and Aprilia RS125 wheels just because.

But the simplest way, to my knowledge, using the stock DT200R would be to grab the DTX setup as that should be a drop in replacement, may need to machine up some rear spacers for the swinging arm, or just grab a DTR rear swinging arm.

If your bike uses the ally arm then it's just easier to get spacers made. PCBWay will make them for £40 no dramas at all.

Sounds great though, I always wanted a DT230 Lanza personally.

I'm not familiar with the market, but a cylinder piston combo with all the work ready to go has got to be £300+. Any more than that then I wouldn't understand why someone wouldn't go for a brand new Athena 125 kit, or a little extra for the 170 kit.

The Zeeltronic, new they're around £240, so with the programmer I'd say £160ish is what I'd pay, otherwise I'd just go new.

Hope that helps.

Oh how annoying! I've seen this before when people have incorrectly set up the YPVS servo and stripped the teeth on the gears.

It's probably easier to just buy another YPVS servo sadly than trying to find the individual cog.
https://www.ebay.co.uk/itm/307114030022?_skw=Yamaha+DT+125+R+YPVS+servo&itmmeta=01M0T0CTAKVKYBVERW4KK9HKJQ&hash=item47816c33c6:g:QqIAAeSwkVdqdvO2&itmprp=enc%3AAQALAAABAGfYFPkwiKCW4ZNSs2u11xDV5F88zNLFmQlOj5cc4%2FxlPVfMrS0CX9zdgmCMx0exrIiMBYEnl2C70gEhZcvwr3BYq%2BewLJHyMjxf%2BATBLTUnAq5B4Os%2FAuVyeOUNpVSRYxblUNuwL%2BjqWn0F95mbpkEWkXEDU%2F4blrRDuajNXDPVd8py1aTbWsSecsyFqwFQqqWjrgMG65s52PTjh2LPZ%2FOmWbQsy4dMVcVkq6VX2lCX6cdUUBN6SMPZHm3xNkDwYsJXuOa1TCyyOEaSwcuLKfJrQwb9YP1PtVMNdQS0UqCxAXfBI4hQNMZjPJwu4V6qdKAjffzCnESPO3DSoS0%2FsfE%3D|tkp%3ABk9SR9als8CGaA

If you have access to the a 3D printer, or are capable on CAD, you might be able to 3D print a new set of teeth, setting the TPU to 100% fill should be strong enough to cope with the demand. My 3D printer is pretty darn accurate so it would probably do a fair go at it to be fair.

@elan-n Too much to list.

I've done basically most things to it, the thing that's impressed me the most is specifically the Zeeltronic ignition system. I have like 5 of those CDI units now as they're excellent! I fit them to all of my bikes. Single biggest bang for buck.

I've done everything to it: https://www.youtube.com/watch?v=jZ1C_xCmqWg&pp=ygUbVGhlIGxldmlhdGhhbiBQcmplY3QgZHQgMTI1 (build video).

I've ran TZR R 4DL Belgarda setup, to ported Athena 170 kit. I'd say, if you dampen your expectations, then the Athena kit is next inline (after exhaust setup). This is because, whilst it's not rip roaring tear your arms off performance, it gives you more low-end grunt and that suits my setup better.

I have my RS for all out smoker power.

I have had my Romeu for 13 years, it's been absolutely solid for me.

My DTR is wildly tuned though, so it's hard to say precisely what the pipe was responsible for.

I got mine originally from a local Yamaha dealer.

But nowadays either TheTuningWorks or just go to PJME

It should rev to the redline.

Depends on where you get your Zeel from, I paid £200 for mine, but that was like 12+ years ago.

Did you try the powervalve trick I just told you about?

I know that the restrictions on the UK models differ from overseas models, so I am not familiar with what restrictions there are on other regions.

Either way, grabbing yourself a Zeeltronic ignition system will make all of these problems disappear and you'll gain a noticeable midrange boost.

Clutch could be stiff for many reasons. I run uprated clutch springs on my DTR so it is stiffer.

The clutch cable comes off very simply, just slacken the adjuster nuts on the clutch arm on the engine, then remove the cable from the engine. Route it through the frame and disconnect from the clutch perch.

You can then run some lubricant through the cable. I suspect though it'll be the clutch springs.

If the bike is falling flat on its face at 8k, then I'd initially say Powervalve.

Easy way to tell. Take the exhaust off, switch the ignition on and off (you'll hear the servo do the cleaning cycle). Once the powervalve turns flush with the exhaust port, switch the ignition off. Disconnect the powervalve servo from the main loom and ride the bike.

The bike should lose all bottom end, so basically gutless below 6k, but should rev to the limiter.

If this is the case, you've identified it's the powervalve. If this is not the case, then you know the problem lies elsewhere.

I don't support image hosting sadly as it's very costly.

That's a tidy looking DT you got there though.

Best thing you can do for derestriction is to get yourself a nice Zeeltronic ignition system for it. That was the best bang for buck I can think of.

Hey All!

Due to personal circumstances I will be needing to suspend the DT125R Forum for an indeterminate amount of time.

This is an advance notice to say that at some point, in the not to distant future, I will be switching off this forum.

My intention is to relocate the forum/database hosting as the current situation is no longer economically viable.

It is unclear at the moment as to what the future will be for this forum, but rest assured it will be back online in the fullness of time.

I appreciate each and every one of you that contributes to this forum so there is a BIG thank you from me.

Take care & keep smoking!

Calum

Aww that's awesome.

Glad you're getting out there on this motor and it's giving you some success

Such an iconic livery set on there as well. Looks great