DT125R FORUM

@Calum @raceraidan Interesting thread. I once owned a 1998 DT125RE French import which looked identical to a DT125R the same year (pic 1). It had a larger battery and separate toolikt compartment as well as the electric start wiring. [image: 52481614948_a84fb86893_b.jpg] During this time I was fortunate enough to source a Yamaha service manual for this exact model, I still have this and here are some pictures of the wiring diagram. I believe KTM also used this engine/electrical platform for the LC2 125 which they sold a lot of in Germany (I bought 2 or 3 3MB CDI units marked LC2 125 from German breakers, and also some NIP 3MB YPVS servos which had both the Yamaha and KTM part numbers on the packaging (sadly now all sold). During my ownership I tried all these items on the bike and they all just plugged into the loom (same connectors) and worked. I'm pretty certain the (inverted) flywheel and stator were both stamped 3MB. As you can see this model also has a clutch switch which IIRC, with the clutch pulled in, allows you to start the engine in gear even with the sidestand down, but cuts the ignition when you let out the clutch to try and pull away. If you've already looked at the sidestand switch I'd locate this and give it a dose of WD40 etc. as a starting point. Also the two relays (items 12 and 13) are worth a look although I'm not sure how you'd go about testing these. It might be of some help to just get some more and plug them in and try them. Here's a link to the KTM parts fiche; search Google/eBay etc. for the KTM part numbers as well as Yamaha France and you might get lucky with a European breaker as they can be quite diligent with posting up used parts for sale including the original numbers: https://www.trevorpopemotorcycles.co.uk/index.php?main_page=ktm_fiche_finder https://ypec-sss.yamaha-motor.co.jp/ypec/ypec/b2c/html5/app/en_GB/parts-search/index.html?ver=bd30d8f2-88bf-45bf-81ba-b46167a61f3c Here are some pics of the wiring diagram, not sure if the Gilera SC125 used the same electrical platform but hope this helps: [image: 53464155671_38fb444afb_b.jpg] [image: 53463243007_9a4dea8951_b.jpg] [image: 53464293058_21dae26cab_b.jpg]

@matt0084 Yeah, I only say that as it is a known issue where the cables get mis-installed and the servo doesn't operate as intended. I find that the alignment hole in the cylinder doesn't allow the valve to sit flush in the port. I always align the valve with the exhaust off to guarantee alignment.

Hello @matt0084 and welcome to the forum. Amazing, what a choice for a bike at 17. Thanks for taking the time to say hello. Yes, you always have to start somewhere and the DTRE is a great bike to start with. That's where I started out learning about bikes/mechanics all those years ago and then the passion for bikes just spiked!

@ChuckSR86 Do you have a DTR or a DTX? [image: yamaha%20dtx%202006.jpg] or [image: yamaha%20DT%20125%20R%201991.jpg] I must admit, if it's light greenlaning, then you can get away with it on supermoto in the summer? Anything more hardcore then some knobbley's would be ideal. For simplicity, I'd be lacing a set of hubs with ally rims for knobbleys. That way you only need to swap the wheels and not the brakes.

RD and DT LC are the same block, but gear ratios differ. RD has a close ratio gearbox and DT has a wide ratio. Close ratio is not ideal if you want to go offroad IMO. Primary drive with clutch and 'middle shaft' length differs in the the LC engines I compared. Definitely get a LC YPVS engine if you go that route, -more usable power than without power valve. I have a DT LC YPVS close to stock, I reshaped the head and installed a Zeeltronic and put in 0,3mm carbon reed petals, the rest is stock. Goes well and has really good midrange torque for a 125. I think the DTR and TZR engines are the same block too, but there is probably the same gear ratio difference, and possibly more I have not tried dropping in a DTR engine in a LC frame (have only one DTR engine and many LC's), but have thought about it. Let us know if you try it!

Hey @rhodes5150, Nice early example which should hopefully be full power. Best thing you can do with these is to start by getting them full stock. That's a derestricted CDI (yours sounds like it should be), then making sure you've got a working YPVS system which is setup correctly. If the engine is sweet, then leave it alone for the time being. If it's aged and worse for wear, then getting it rebuilt is the way to go. These engines are incredibly simple and easy to rebuild with no specialist tools required. Can drop the bearings in by using a conventional oven heating the cases up. Checkout Yamaha DT 125 r derestriction to see what's needed for your bike. Once you've got the stock motor running sweet, and you still want more power then here are a list of mods I'd do (haven done most of what can be done, experience tells me this is the best order and bang for buck). Exhaust System Full DEP system Really perks up the mid-range punch Cuts out significant weight over the stock system Zeeltronic Ignition System Over my DTRE/X (pretty restricted CDI) really punches up the midrange Carbon Reeds I run VForce4 Reed block on my DTR But generic carbon reeds can help Mileage may vary I'd struggle to tell the difference Porting work Making sure the head/squish is correct is where you'll get the most gains Cheap to get someone to do and can make or break a two stroke Having the cylinder done can be more expensive and mileage may vary on this Athena 170 I've grown to appreciate the 170 kit It doesn't compare to RS 125 big bore kits or other extreme setups Massively increases the mid-range (reducing overrev) Makes the ride much easier to live with Of course this can also be ported to make additional gains here. You can do other mods, such as skimming the flywheel. This doesn't give you any more power per se, but allows the power to be obtained faster. This can drastically affect the overall performance though, so sometimes it's best to leave it alone.

£300 is a good price. Get them respoked with some stainless steel spokes and powdercoated hubs etc. I ended up running RS 125 wheels on my Yamaha to get it supermoto. But again, that wasn't cheap. By the time you've refurbished them, sure I paid more than £300 all in.

I saw a another post about someone who made a model of it (the original rubber airboot). But he has not been online for over a year :(. I have a 3d printer so its cheaper to print a new boot than but one.

Aprilia ETX Suspension Bushes Bearings Part No Dimensions Description Quantity AP8121815 12X26X12(16) GE12PW -SPHERICAL BEARING 1 AP8110037 18x24x12 HK1 812-MB Major Brand HK1812 Drawn Cup Type Needle Roller Bearing with Two Open Ends 6 AP8110067 22x28x16 HK2216-MB Major Brand HK2216 Drawn Cup Type Needle Roller Bearing with Two Open Ends 4 AP8120809/AP8110068 18x24x3mm Nitrile Rubber Rotary Shaft Oil Seal Springless Design VC Style 6 AP8163318 - Aprilia MX Shock Absorber 856715 - Aprilia RX/SX Shock Absorber AP8135848 Aprilia RX 1995 Swinging Arm AP8121121 - Swinging arm pivot bush AP8105132 - Swinging arm pivot bolt Uses same suspension linkage & swingingarm pivot bolt. The swingingarm pivot bushes are the same and are also used in the Aprilia RS 125.

@HOTSHOT-III Does sound interesting, for my long-term Aphrodite project I definitely need to set this up properly. So either I'll be taking it somewhere, or I'll be learning the ins and outs to get it in the right ball-park.

No you don't need to open up the engine all the way. It's just a push rod system, if the clutch cam isn't engaging with the push rod then it might be because the push rod has fallen beneath the cam arm so you're not able to position the cam behind the push rod. I've never had this happen to me personally, I don't recall this being an issue, but the design is very simple so there is very little to go wrong. What commonly happens is that the ball bearing inside the engine can get misplaced, which presents itself in a similar manner as you're describing. But this is not possible without dismantling the engine. In essence what you have can be pictured as below: |_._ The | is the cam that you slot from the top of the engine. When the cable is pulled, it twists the cam which acts on the first pushrod denoted here by _. This is space separated with a ball bearing, denoted by . which pushes a further push rod denoted by _. What might be possible is that you've ended up in situation where you've pulled the cam out and now the setup is like: | _._ The cam is now resting on top of the push rod and is no longer engaged with it. So when you pull the lever, nothing happens. I can't remember whether this is even possible, but if it is then you'll notice the cam is sitting a lot higher outside the engine and would be obvious. I am not sure if the pushrods are under load, but if they're not, then leaning the bike over towards the clutch may cause the rods/ball to move allowing the cam to be lowered appropriately. If that doesn't work, then no it's not a full dismantlement. It's just a case of taking the clutch cover off, and taking the clutch pressure plate off to expose the push rods. Extracting them (by leaning the bike over careful not to misplace the ball bearing) and then inserting the cam in first. BUT I REALLY don't think that's what is happening here. It's probably more likely that the clutch just needs adjusting. I'd recommend referring to the Haynes manual for this.

@HOTSHOT-III damn just did enduro on sunday and the bike shut off instantly its having electric problems im having a very weak spark the bike doesnt turn on at all tried bypassing the killswitch and the kickstand switch no result and now i want to check the pickup coil from the stator im not that good with electrics but im trying my best to find the problem

@Calum ok, thanks, and what about electronics?

I’ve had someone listen to it as in person is obviously way better then a compressed video and think it may be the piston rings

@gary76 i do have the meter but i dont really know how to use it could u help?

That's normal. All DTs are like that. [image: IMG-20251011-114625.jpg]

@HOTSHOT-III Hopefully the issue gets resolved as I don't want to lose the data they're hosting. The important stuff I ought to host here to guarantee it isn't lost.

@HOTSHOT III Thanks for the reply bud yea all good on that front it’s the long pedal travel I don’t like it’s just me and how I like things

PS Same issue, bottom of gasket is dry and the top has oily wet channels…