DT125R FORUM

Hi Folks,
Thought I’d introduce myself to the forum. Slowly getting around the site. Starting to realise theres quite a bit of knowledge out there and before I decided to buy strip and rebuild “For the Bairn to pass his test on” French import DT I should have looked on here 1st.
But it gave me something to do over the winter and now I’m just waiting for UK plate to come back from her majesty’s finest admin dept to get him out on the road.
In between then I bought myself a 1984 DT200R. Apparently it’s a Japan only spec bike with Kmh clocks and only exported to Aus NZ and Canada. But found it’s way to the UK.
A good old stroker to revitalise my youth and something I can go out on with my son until he gets bored finds his feet and his own scratching roads and trails. Now this is where my problem lies the DT200 is running 13/49 on 520 chain and far too under geared for the road. Hitting the red line in every gear, wheelies for fun in 1st and 2nd off the throttle. Fine for the 18 year old outside the school gates, but a pain in the arse for the mature 50 something who doesn’t want to attract the attention. Can anyone recommend/ supply the correct gearing in the UK ? I’ve seen loads of variations for the 428 but very little in the way of sprockets for the 520.
Thanks Scootjockey

@Calum
What year is the Belgarda ? This option is for the TDR I have, and think the carb mount is straight unlike the DTR which as you say is angled to the side.

@HOTSHOT-III
Great info and drawings too !!

@SpookDog
I know what you mean about the WR250/400. There’s no substitute for big CC’s and a torquey motor. My problem is I just love little 2 strokes !
But it’s been a while since I’ve got my hands dirty and stripping and rebuilding the DT125R for my son has been fun, as we all say I just wish I knew last year what I know now …! The problem I’ve got to remember it’s his and when his done his 28 weeks training he’s going to want it back.

@SpookDog
Ha ha ! I passed my test some 30 years ago and owned a TDR250 as winter bike when I didn’t want my Gixxer 750 to get dirty. I’d love another one now but all of the ones I’ve seen recently have either been abused or will cost a fortune to get back to some sort of normality. Spare parts are like hens teeth and French love them that much they don’t want to sell the ones they’ve got ! Least not for a premium … I’ve seen some lovely ones go for a song in the sales in Japan but It costs a fortune to share a container at the moment so it’s just not worth getting one. But my biggest problem is the room at home. I don’t have much of it !

Still we’ll see how next year plays out I can always loose the dining table and have another bike in the lounge

Before I go down the rabbit hole spend needless amounts of cash what’s the best route to get more reliable power from a TDR125, I’ve seen 170 big bore kits advertised, crazy BAracing kits from Portugal which really hit the spot. But you just know it’s gonna go bang if not kept in top fettle. Will a WR200 engine drop in ? No autolube ?? 230 Lanza hard to find do these run the autolube ?? And did I say I want to keep the autolube. I want the bike to be a sleeper and want 200cc plus performance if possible. And if it’s available 30-40hp.
A decent road tune and pipe to match. A bike that’s quick enough to get you in and out of trouble but not quick enough to get you banned. Well not 30 over the limit on a motorway. But close enough. I don’t mind spending the money but I want it to be well spent. The TDR125 is a big heavy bike imo and the 1st thing to loose weight will be with the wheels. Subtle changes new rear shock should save a Kg or two and loose the 24 year old bouncy wallow. Rims n spokes will replace the cast alloy items. Has anyone done this ? I love the excel rims talon hubs combo but want to retain the speedo drive and standard clocks. Brakes will need a look at. The front is a dual piston item which is ok but are they better bolt on items ? Any ideas will be gratefully received,

Cheers Gaz

@markus-w

Hi Markus I thanks for the info, you may be right with the LC and not an R as I am struggling for bits when I search with the year. I’ll check with Yambits as I’ve tried Fowlers, the chassis and engine is a 37F ****.

@SpookDog Hi the new oil pump done the trick with the bike running much better and not splattering everything behind it in oil or smoke.
So I took it for a run to put some extra miles on it respectfully trying not to lash it and only letting it run up to 7-8k to do a plug chop.
Only for it splutter and not go past 8k then when it did get there it died as if the throttle was part closed just for it to drop out of the power. Down a cog and came back to life but it didn’t like going upto or past 8k. The drive back got me thinking and I give it handful to see if it would pull past 8k but it just wasn’t having it.
Got home checked the plug and if anything it was rather black running more rich than the coffee colour I was hoping for. Only one thing for it carb off and have a look.

To my disgust the carb was filthy the float and bowl covered in yellow silt. Striped the jets to find the main jet must have spent its life in the bottom of a tool box it was that battered and bruised I couldn’t make out what size it was. Naive as I am I still knew over the years Yamaha will have changed the carbs and fuelling and the Haynes manual confirmed this. The magnifying glass tool on my iphone confirmed 125 main jet with 5J25 Needle on the 4th step. Ahem that should be 210 main jet not 125 ! Or it’s the wrong carb ?

A visit to the local MX shop made me £12 lighter and got me some nice shiny brass in the shape of 200,210,220,230 jets. I hoped I didn’t need them all but it’s better to be safe.

Cleaned the carb and fitted the 210 main jet and took it for a run, once up to temperature it ran like a dream. I know it sounds ironic but even the engine tone sounded happier more powerful and deeper….. Pulls well in all gears and no splutters or flat spots up to and past 8k. Quick plug chop later and conformation of the nice colour I was looking for.
So all is looking good and it just needs a few more miles on it and hopefully my Son will be abusing it and annoying the neighbours just like I did all those years ago.
So job done another DT back on the roads and not some industrial estate or school field being chased by the Feds.

Hi Callum I’ve changed the oil pump and it’s running much better. Looks like the return spring has stretched or jumped past the stop once or twice. But when I had a close look either something has snapped inside and made its way out of the oil input connection or something has forced its way in, possibly deliberately? I don’t know but you can rotate the cable pulley and it will just sit where it likes. The new one snaps shut and has a strong spring mechanism.

https://www.flickr.com/photos/196470812@N07/52348117734/in/shares-rBVx80AG4a/

Thanks for all the suggestions. Gonna take it for a run and see if it runs without spluttering. Hope fully I’ll be able to get some miles on it then do a plug check

Dunno if this will work but the Japanese exotica arrived last month

@primal-carnage Do you have a multimeter or tester to help you ? Potentially you have several issues and it’s a process or elimination.
Start simple do you have a fully charged battery ? And does this only happen when the bike is or isn’t running ? Are you running LED indicators and have you replaced the flasher relay (Standard) for an LED compatible version ? Or are you running standard lamps and relay ?
I’ve yet to see LED indicators work with standard relay. The relay doesn’t like them full stop. But standard lamp indicators will work with an LED relay but not for long. LED indicators draw minimum amounts of power and standard lamps don’t and eventually you will burn the LED relay out if used with standard lamps.
It may be coincidence that your LED back light has stopped working. But I would remove it connect positive and negative to a known 12v power source ( A fully charged battery ) and see if it works. If it does work, you may have a bad earth connection. Or bad negative to use the correct term. If it doesn’t work it’s knackered. Same for all of your indicators. Remove them and apply voltage individually.
An existing old school lamp is not generally polarity conscious and will work positive negative reversed. But LED lamps and indicators are polarity conscious. But most of them will just not work if voltage is reversed. If it doesn’t work and your not sure which is positive and negative reverse the voltage and they should work. If not they may be knackered.
Indicator relays don’t last for ever and get noisier as they fail and longer to energise. Did you notice a longer than normal delay when they were working or have they just stopped ?
If all the lamps/LEDs work when you connect them to a known power source you may have a wiring fault or switch fault. Are all the connections clean and not loose ?
If a lamp blows the relay unit usually will flash twice as fast on the working side. If an LED stops working it will prevent the whole circuit from working.

Hope this helps and I’m sorry to ask more questions than give answers but try and keep it simple, one task at a time and remove parts individually. It’s a process of elimination until you find the dodgy part or parts.

@SpookDog
The servo motor is ok isn’t it ? For the powervalve to be gummed up and it’s not opening is a bit suspect, as the servo can apply quite a bit of force and if it’s not it might on its way out. ? Then again is the battery ok and alternator charging ok ?

@Hybrid_Theory01

Of what I’ve seen from 80’s 90’ to 00’ Yes they have changed the engine casing numbers in line to match the frame numbers. In size and font. Not that I would ever advocate such an illegal and treacherous action but I have seen where the engine casings were blasted and polished and painted to such a degree that the numbers (all original by the way) were put on using a rub on letraset. Then clear lacquer coated coz the paint filled the original numbers.

@SpookDog
Loose the mirrors hand guards rear foot pegs change or loose the indicators for a smaller LED style loose the nobly tires for more road orientated and a recon you’d get an extra 2-3mph and on set of DT clocks that’s easily 5mph ! Lol