DT125R FORUM

@Marillionado Hi, welcome to the Forum!

Not very familiar with the 3RM but on the earlier 3NC and 3MB bikes you do need to remove the powder coat where the coil attaches to the frame for a really good earth connection. It's also where the loom earths to the frame (the black ring terminal) and IIRC this attaches at the rearmost (i.e nearest the shock) coil mount. Lastly, only one mounting point on some of the coils is an earth so it's important you mount the coil the correct way, it should look like this:

As title, Lidl have just got these in, cheaper than most but I've always been impressed with their tools. Useful for all the small stuff on the DTR like coolant drain bolt (10Nm), oil drain bolt (15Nm) and fork and handlebar clamps (23Nm). If your 1/4" drive socket set has a universal joint you can use it to do all all 5 cylinder head nuts with the engine in situ as well:

https://www.lidl.co.uk/p/crivit-bike-torque-wrench/p10026677

@Calum That kit looks ace, I've never seen one of those before.

Spare a thought for the man somewhere in Europe on one of the TDR250 Facebook pages who tried to make it 340cc using two Athena DTR 170 kits. Barrel stud locations slightly different on the TDR crankcases so he filed them out to match, and then he noticed they were too wide to mount side by side. His solution? Just machine off the offending water jackets from the inside of both cylinders, then plug the holes with a whole packet of JB Weld. This was a few years ago so not sure where that bike is now...

@SpookDog Yes you could install grease nipples on the swingarm and linkage, might be easier because all you'd really need is a set of M6 taps. It would work exactly the same as the one in the roller bearing bush as you say.

I never got any of those sleeves drilled as every time I did the rear linkage job on a DTR I always found the sleeves aren't very prone to wear, two or three times IIRC I measured the OEM ones that came out with a digital vernier, found them to be almost exactly 20mm OD and just re-used them and replaced the bushes.

I always just used NLGI2 Lithium grease off eBay, it's the same spec as Silkolene Pro RG2 but a lot cheaper (it's also the same colour which kind of points to where Silkolene get it from lol).

@SpookDog There is a complete linkage repair kit on eBay that reconditions all 3 pivots but this is the one I was saying you'll need to get the long tubes drilled in order to grease them externally. Apart from that it's excellent quality and fits very well:

https://www.ebay.co.uk/itm/273964244490?_skw=dt125r+linkage+repair+kit&itmmeta=01JNS8GP47RXBRY3388JTDD77P&hash=item3fc98a9e0a:g:QeIAAOSwejlmIRnp&itmprp=enc%3AAQAKAAABAFkggFvd1GGDu0w3yXCmi1ewok0zvqvvsjaaesI%2B3AqBrNzJsMtN%2ByfXZjyUIUUXfj6QoCMC13skvVzLiqG%2FH%2F9tbxdIjH%2B4atRlor7FzTWzGMpxOzPLgwpWCAZ%2BsYD23e%2FVBR3dWDx4fm4J8E8GmosgW9fdd67Bv%2BTCogYvcKlITQftiOe0zTVTJE1LT3aL5vS0qIojINIgvTN26rq%2FHC1mQgSUVuPxjHprHzZZZLrHBay7eg6unKoC1l1ZETeZwamUAwvHK0789UP%2FcuJuCq8d%2FeKNbtq%2Bu1J%2B%2BxqoY5EHFq87Q0cyo76L7apLVo80bDYNTtniwioOGYH0%2BlqLdDs%3D|tkp%3ABk9SR7jiwqiuZQ

Only other thing you might need is the bolt/nut where the linkage joins the frame; this is no longer available but as long as you can get it out it's solid enough to clean up. Just try to resist whacking it as there's a good chance it will knacker the thread, the studding method gets them out clean. Long linkage bolts are still available but special order from Japan:

https://www.fowlersparts.co.uk/parts/4163783/dt125r-3rmj-2000-050-a/rear-arm

@SpookDog Hey bud, didn't think I'd seen you on here for a while

You can remove the relay arm without taking the swingarm out, and at both ends of the dogbones there are just plain bushes (the needle roller bearings go where the relay arm attaches to the frame). However at the upper end of the dogbone the bushes are in the swingarm so if you have the time, I personally would take it out which will make the job a lot easier, and it's also a great time to replace the swingarm bearings and set the swingarm side clearance if you haven't done this already.

This guarantees perfect chain/sprocket alignment and without the rear wheel/linkage fitted, you can get the arm to fall under its own weight with <1mm side-to-side play even with the swingarm pivot bolt fully tightened. A lot of the "specialist DTR restorers" on Facebook etc. miss this step but it makes a huge difference to the bike's handling and chain/sprocket life.

From memory I think I always just drifted the linkage bushes out with a hammer and punch, and pressed the new ones in in the vice using a socket. Same goes for the needle roller bearings except I pressed these out as well, and be sure to take out the grease nipple first otherwise the outer cage of the roller bearing will vandalise the protruding end of its thread as it goes past.

The linkage bolts with grease nipples shouldn't be worn at all because assuming they're done up tight with the linkage assembled correctly, they, the bearing sleeves and the dogbones form a rigid sub-assembly and so should never move relative to one another.

If you've bought the eBay linkage repair kit, unfortunately the long inner sleeves (i.e the tubes which fit between the linkage bolts and bushes) lack the 2mm holes necessary to allow greasing of the pivots via the grease nipples. It's well worth getting these drilled as it makes a massive difference to how long the bushes last if you keep re-greasing them. I say get them drilled because I think they're case-hardened; I once tried doing it myself on a pillar drill and even using a cobalt drill bit set that cost me 50 quid in Screwfix, I couldn't make any impression on them so this needs doing by some engineering firm somewhere.

If you have double-lipped seals from Simply Bearings etc., another hack you can do when assembling the linkage/relay arm is to flip the seals so the garter spring faces outwards away from the bearing; the lip without the spring is just a dust wiper so you can then cut small sections out of this with Swiss Army Knife scissors (best/sharpest scissors I've ever used) or one of those leather punches so when you re-lube the linkage bearings with a grease gun, the hydraulic pressure is less likely to force the seals out. The grease is free to pass through the gaps in the dust seal lip (now on the inside) and lift up the lip with the garter spring in its bid for freedom! The sprung lip then retracts, retaining enough grease inside the bearing and keeping dirt out.

If like me you're ham-fisted with the grease gun, it will still try and force out the seals so you can also hacksaw a section out of an M20 x 3mm washer and insert it in the gap between the tiebars and the arm during greasing to prevent this (with the linkage bolted together and the seals where they should be, you can actually move the tiebar/sleeve assembly 2-3mm side to side; useful after you've greased up everything as you can move it fully each way to make it splodge the excess grease away from the bearings/seals, then clean it all off thoroughly to prevent any getting on the rear tyre).

Lastly I'd also replace the lower rear shock bushing as this usually wears before any of the actual linkage bearings. It's held in the shock by two of those PITA C-clips and IIRC I destroyed a Lidl precision screwdriver set getting them out (mind your eyes as the speed one of mine flew out, I think explains why the Northern Lights were visible over Dorset that time). This one fits the DTR:

https://www.mandp.co.uk/products/29-5027-lower-rear-shock-bearing-kit-605946

All sounds like a lot of work I know but being able to externally grease up the rear suspension is one of the greatest features of the DTR, done like this you can just ride the bike week in week out, 10 minutes with the grease gun every week or two and you'll probably pass next year's MOT without even having to look at this again.

Happy New Year everyone, agreed it's important to keep the Forum alive as the DT125R is IMO one of Yamaha's greatest achievements, I'll be here in 2025!!

@Calum Merry Christmas and a Happy New Year!!

@Camugica No worries

The DT125R TM28SS uses a mixture screw instead of an air jet, it's the brass one on the left of the carb body just in front of the carb-to-airbox rubber (below the idle screw). Normal starting point with a healthy engine is around 1.5 turns out from fully screwed in. Screw it in further to richen the low-speed mixture or unscrew it more to make it leaner. There should also be a spring, washer and O-ring on the screw (in this order) so it's well worth checking this if you're having low-rpm running problems. The screw is prone to seizing on the DTR carb so whilst it's removed smear some copper grease on the threads.

Some other Yamahas use the TM28SS with an air jet instead of a mixture screw like the TZR/TDR250 and DT200R 3ET (I think).

@Camugica 15.5 - 16.5mm on the TM28SS.

@Calum Shame this has happened to you buddy. I once saw an Aprilia Tuareg 125 Rally (twin headlights/massive fuel tank/centrestand for fast enduro wheel changes) parked outside my local Lidl in a manner that would suggest it was owned by someone working there whilst doing their A-Levels etc.

https://www.motorcyclespecs.co.za/model/aprilia/aprilia-tuareg-125-rally-90.html

It was literally falling apart; quite upsetting as I always wanted one. Italian 125s are night and day ahead of Japanese ones on spec/performance but you really need to give them a wallow in WD40/copper grease from new to protect them from British winters and that is beyond the understanding of most teenage owners.

That being said, I bet if you had a holiday in southern Italy you could pretty easily locate a corrosion-free ETX125 frame or two, bring them back and get them straight down the powder coaters...

@Calum Ace build mate, I don't really know anything about On One bikes but that frame looks beautiful. And I've always liked eXotic, I ran a set of those rigid forks in a 26" fitness/road MTB I built a few years ago.

@kieran-hutchison Lots of ways of doing this but my preferred method is to get the caliper off the bike (but leave the hose connected for now), then gently pump the piston as far out as possible just using the brake pedal. Stuff some cardboard between the piston face and caliper body just in case the piston pops out suddenly and try and resist the temptation to grip the piston with mole grips etc. as this is a sealing surface. Keep an eye on the reservoir level as if it gets too low and air gets in, you might need to do a brake bleed just to get the piston out. And cradle the entire caliper in an old towel etc you no longer want to contain the spilt brake fluid. I've also used a foot pump before by stuffing one of those plastic airbed adaptors in the threaded hole where the hose attaches, this works well but you really do need to be careful and pump slowly as the piston will pop out suddenly, so you really need more than cardboard to stop it being damaged (and wear goggles ideally). In both cases it's better to pump the piston as far out as possible without it popping out, then edge it out with your fingers when it's almost free if you can.

It might be the case that a previous owner rebuilt the caliper with an aftermarket piston and seal kit. I bought an eBay DTR rear caliper rebuild kit once, cleaned the caliper completely including the seal grooves, put it together and bled it and there was a small dribble of brake fluid on the back of the pad on the piston side. Wiped it off and it came back several times, so I cleaned up the (old) genuine piston/seals and put them back in as I wanted to go for a ride that evening and it cured it, no issues for a couple of months whereupon I bought new genuine ones. Compared the seals, the eBay kit seals are slightly smaller in cross-section than genuine which is what causes them to leak.

@Calum Thanks bud

@tfsv8 Exactly the right thing to do holding off from fitting the big bore kit until you've sorted this, I'd start off taking a look at your jet sizes and compare these to what the Yamaha repair manual says they should be (Haynes managed to get their VM26SS '88 carb mixed up with their '89 onwards TM28SS so it's well worth getting a genuine Yamaha manual online).

I once bought a sub-5000 mile French import DTR in excellent condition which ran awful, on stripping the carb I found:

270 main jet fitted (stock TM28SS is either 210 or 240)
Float height about 5mm out ensuring the float bowl was constantly pretty much empty
One of the float bowl breathers blocked with silicone sealant
It also had a pattern coil which cause all kinds of running problems on DTRs, and the air filter element hadn't been cleaned in what looked like years (this went straight in the bin; a well-maintained £10 Yambits one is easily as good as a genuine Yamaha item)

It ran OK at low rpm but was asthmatic as soon as you tried to rev it and was pretty much unrideable as it was set up so a basically empty float bowl was trying to supply that fire hose main jet. As soon as I put the jetting/float height back to stock and fitted a genuine coil/new air filter it became well-mannered and went really well like a well-sorted DTR should. These are the kinds of modifications "Biwt me own bowek" type characters make to try and make 125s faster before heading off to Bike Night to brag about how the manufacturer didn't know what they were doing when they designed this bike so they had a few beers, went into their shed and finished the job.

@kieran-hutchison The waterpump drive gear could be broken as @Calum said, it's worth checking this.

The DT125R is a little prone to getting hot during serious off-roading. Compared to the twin radiator setup on the DT200R, the single rad with 2T oil tank opposite design is aimed more at youths messing about around town with perhaps a little bit of dirt riding occasionally. Near where I live there's a green lane which runs along a high ridgeline; to get onto it you have to go up a long steep unsurfaced hill where the farmer has added a lot of concrete speed humps to slow 4x4s down (which appears to have the opposite effect on dirt bikes). On three different DTRs I could literally watch my temp gauge go from 1/3 to 2/3 when enjoying myself up here, then when I reached the top where it was flat I'd go along in a high gear at low revs for a bit and it would quickly come back down.

If you're getting serious off-road it's worth looking at one of those Chinese pattern radiators which are about twice the thickness of the stock rad and look to bolt straight on. Also make sure your thermostat is working well (Haynes tell you how to test this) as one of it's functions along with the waterpump is to keep the water jacket around the cylinder pressurised which increases the coolant's boiling point (some competition bikes have restrictor plates in the cooling system to do this).

In the 1st instance I'd have a good visual inspection of your stock rad as the DTR is a bit prone to clumsy people bending the fins over when doing plug changes etc. which can reduce airflow by a fair bit. You can carefully use a thin screwdriver to straighten these and in extreme cases it can make the bike run cooler.

@mbmO8 This explains the YEIS box between the carb and reed valve better than I can:

https://global.yamaha-motor.com/stories/history/stories/0019.html

When working around that area it's not that difficult to remove as long as you have a decent pair of pliers to squeeze the clip on top of the reed block, just stuff a rag in the hole until you refit it. The one behind the carb on later bikes, I've never owned a DTR with one of these fitted so maybe someone else can help out explaining this? I see a lot of people blank these off with the lid off a Coke bottle.

@89dt125nick No worries bud When refitting the CDI to the oil tank, be sure to apply plenty of copper grease to the mounting bolts and brass inserts to prevent them corroding together (this is also a good idea for all the captive threads in the airbox) as if this happens it's almost impossible to get the bolts undone because they just spin round in the plastic. Common problem on MX bikes where the rad shrouds attach to plastic fuel tanks after a lot of pressure washing.

@89dt125nick Judging by the throttle cable splitter box and reg/rect (and your CDI being mounted on the 2T tank) I guess your DTR is a '99 onwards. The migration to the later electrical system wasn't completely smooth, for example I once owned a low mileage original French '98 4BL with 3NC electrics (CDI under the tank) but the two brass threaded inserts were present to mount the CDI at the front of the oil tank. Here are the cable routing diagrams for the '88 DTR, you might need to get a bit inventive with some items but hope this helps: