DT125R FORUM

Hi there,

Yeah this is quite common these bikes, can be a right nightmare to get loose sadly.

I don't think there is any type of magic, you just have to be patient and keep working it.

You need to ensure that you protect the threads on the swinging arm, so only hit it with the nut threaded on and use a copper mallet.

As you've highlighted, using heat and penetrating fluids here will help.

Try and eliminate the weight off the swinging arm to reduce frictional resistance. So jack the bike up from the center, take the rear wheel off. It's likely that the swinging arm bearings have collapsed and have seized onto the axle.

The next problem you'll encounter (by the sounds of things) is the suspension knuckle will be seized solid also.

The problem being these items are just so exposed to the elements they take the brunt of the dirt/grit.

Sounds like you've had a right restoration on your hands.

These are fetching for a mint on eBay so it's well worth putting the effort in to it.

Pretty sure this lad is dreaming but he wants ~£6000 for that one.
https://www.ebay.co.uk/itm/960133506892?_skw=Yamaha+DT+125+R&itmmeta=01M6GWED4REPT01J3271T1QNZV&hash=itemdf8c6aa74c:g:1tMAAeSwUNhq5MEh&itmprp=enc%3AAQALAAAA0CHNgUiiE%2FjQhlDTaMiAde9fBjbxynqVe44zIMlzHzlVi8pprTTgQy01IHUylvdbeVix%2F7%2BHDt06SNnoJG2cUhXwMoKJhq5j%2F2JCnNU06guM0vbsUkn9reQlxVJSyIoxhKukZZsdYk4OBHSoDixTD1HDmGrkn6if%2BDbkFOA5D0%2FM1R8E%2BKXn769gus91t4FhIB8kMLBGpfKiSKH0Q63rXv4FazZmIleNmmYFxsGBhOroER6Y6R1O1JkvGjuxX0CH1LBepsOV3J8%2BKr2UGPtmifw%3D|tkp%3ABk9SR8LSuZy0aA

Be good to see some before and after photos of this project.

Hi there,

Certainly from my experience it's not uncommon to have a plug left undone. On my RE it was for a factory fitted immobiliser (or so I'm led to believe) that was an optional extra and thus not fitted.

Are you saying that this bike is not running?

With regards to the inline fuse, what's the matter with the OEM fuse box design? There really isn't an awful lot on the DTR that warrants that kind of control. The RE has a starter motor, which draws significant current, but even then the fuse box is sufficient.

Upload the photo to a photo hosting software, grab the URL to the image and ![](www.example.com/image.jpg) put that into your post and it'll render the image. The syntax is called Markdown, it's a very powerful type setting language.

Yeah, it didn't sound great.

If that's the case, you could try duct taping your airbox up to restrict the air flow. This might help richen the mixture and therefore it might idle.

Or fix your problem.

Sadly Imgur is blocked in the UK so I can't see that either.

The gofile is protected so can't see it.

If you spray some WD40 in there, does it then run?

I don't mess around when it comes to fueling. Just buy the genuine kits. I can't guess about how much I have spent on Dellorto odds and sods, but now have a healthy collection of bits should I ever need to jet my bikes I can breathe easy know it's all legit parts.

Due to the exposure that these bearings receive, it's recommended to grease them.

The bearings themselves are exposed to a grease nipple so you should be able to just apply grease through their nipples directly.

I've always found the Mikuni stuff a little harder to locate spares for personally.

The only real change I was aware of for the Yamaha DTR (excluding the very early '88 models that round a 26mm round slide) is the change from 240 main jet on the DTR to 210 on the REs.

With that in mind, I'd say you're probably okay to go with this needle jet kit you've found.

Is it a genuine kit? Or is it aftermarket? If it's aftermarket, then it's almost irrelevant as it won't be perfectly matching to the OEM one anyway.

I would say that both @hannahharris & @joshuaseward look like bots to me.

It's difficult to say whether what they are saying is completely accurate or not, sounds feasible

As far as I was aware the catalytic converter was only on the RE/X and not the early model, for the UK at least, not sure about everywhere else.

Either way, there is definitely some great points being raised here with cutting the window option, any debris that get sucked back into the engine could be disastrous.

You don't need a battery but you'll want a battery.

Yeah, looks a bit of a basket case that bike and you're asking us to make wild guesses when it could be anything.

You've not running a snorkel, that engine does not sound crisp at all, you can tell it's swamped with air and it's struggling.

Without a battery you're relying on the generator making sufficient power to do all the lights and make 20'000 volts at the spark plug lead, coupled with the poor wiring, bad earths and the second rate coil, it's no wonder it's not running right.

You need to get yourself a battery.

Sort the wiring out
Get a genuine coil on there
Get a genuine snorkel fitted

https://ebay.io/m/cHVjjv

Make sure you got good grounding from the chasis to the negative terminals.

Search on this forum for the wiring diagrams as there are many different grounding points, different for different years, so ensuring you got the wiring for your model will ensure you capture the grounding points.

Ultimately there is not a lot to these engines, but you have to have the basics done right, otherwise we're stating into the abyss trying to help you.

I never could get my DTR to run on those shite orange coils.

https://www.cmsnl.com/yamaha-dt125r-1999-3rmd-germany-293rm332ga_model39887/ignition-coil-assy_3rw8231010/

There is a genuine coil brand new stock there.

I found that the bike would idle but refuse to rev and cut out. Rode it back from Wales like this back to Cheltenham, couldn't rev past 4k, was a nightmare.

So lesson learned on that one sadly. My brother had EXACTLY the same problem with these type of coils on his RD350. So it could be something as simple as that.

Make sure you've got good earths to the frame as well. Has the frame been powdercoated recently or anylike that?

Probably worth mentioning, as you can see in the background of this photo, I have managed to acquire a fully supermoto setup for this machine as well.

These come off the Aprilia MX 125. Since I'm running an MX rear end, that should be simple enough to swap out, but the front end shows some challenges.

The MX125 front wheel uses a digital speedometer, so swapping out the front end means losing the speedo.

Instead, I managed to find a brand new old stock MX front rim, and I've also managed to source an RX125 front hub, so I will look to lace the RX hub onto the MX rim, thus retaining the original speedometer configuration. The rear wheel is in poor condition, the hub has snapped in several places, but I managed to find a brand new old stock MX rear hub, so the plan is to lace both wheels and have an easy to swap out setup for both road and trail riding.

Slow slow progress on this...

It's really not far off completion, I have been addressing the wiring harness as it was completely torn to shreds. It's all starting to come together now and it's good to see the lights come on after it being sat in the dark for 4ish years.

I really feel as though it's getting close to rideable.

There have been a lot of problems with pretty much every component, but brakes are now bled, radiators are plumbed in and it's almost ready for some fuel and it's first start.

I mean....

As I say, I can't see how this doesn't affect performance!

Only use genuine coils. The cheap orange ones simply don't work so make sure it's a genuine one.

@Yaya97422 Vert/noir

From my experience, the catalytic converter was so restrictive that I cannot fathom how it possible could not have an adverse effect.

I do think, leaving your pipe standard is really ideal, especially as these bikes are appreciating classics. Instead, just grab yourself a DEP pipe and be done with it, the weight saving alone is worth it!

Do you have a powervalve fitted or is it fixed?

It's in my experience that my DTR never started without choke, so that's normal. It needs to get to temperature and then you can remove the choke.

Sounds like you need to strip and clean your carburetor, based off what you've just said.

It could be float level height if it's just shutting the fuel off before it's even getting a chance to get into the bowl.

Strip the carb, removing the atomiser and properly clean the carburetor in and out, being careful not to damage it as the components are brass and delicate.

The engines are very basic and provided you've got compression, spark and fuel ,it'll run.

If you can confirm that it's got spark and fuel, then check the compression for the engine, should get around 140PSI. Anything below 90 PSI and your engine is going to need an overhaul.