philhill

Hi, just to update and round of. I fixed the leaky exhaust which entailed a trip to my local engineer to remake the flange on the front of the exhaust as there was just a fraction remaining! With the exhaust now sealed into the barrel I worked my way down from a 130 main jet (book setting) to eventually a 115 where it is now working great. I was amazed at how sensitive the engine is to air restiction. With no filter I could run a 125, with a K&N type it runs as set up but with a standard oiled foam filter I would have to go lower again. I have a new problem now, the engine is very loud and attracts unwanted attention. I have an old Fresco end can fitted, can anyone recommend something quieter for road use or can the Fresco be made quieter ?, it has fiberglass cloth wrapped round the removeable tube at present. Also does anyone have the original paint code for a 1982 DT125MX red. I am also having the graffix re made, if anyone is interested I could get some extra made up. Phil

hi Paul, speed not that important to me other than a guide to how well it's performing in comparison, though i would like to be able to take it on the motorway for short hops on my way to visit a mate in Sheffield. The 125 prob not up to that but there are other routes I can use. Your probably not that far from me, are there any green lanes, off road areas out your way? Phil

Hi again, CDI i think, the main jet and holder unscrew (hexagonal pieces) then there is a rubber 'O' ring and then the needle jet tube. It would probably knock out with a smart tap, I tried a light tap and nothing happened and didn't want to risk breaking/bending the top, U shaped looking from the top i.e it has a cut away. looking up from the bottom of the carb there appears to be a brass peg and possibly a grove/cut away in the jet tube to ensure it is fitted the correct way round. No holes are apparent in the tube but then it is very difficult to see without taking it out. The flat spot is definately improved now but not gone, dropping a gear and keeping the revs high it will whizz through the flat spot without much notice but still want it right if possible. What about the speed, I seem to remember that my old one went faster but I may be wrong. If converted to 175cc what can you expect? Thanks Phil

Hi, have remeasured and adjusted the float height according to your instructions, still got a problem at 5,000 revs. Not sure what to do next other than wait for the exhaust gasket to come through the post. Does it matter what 2 stroke oil I use, I have gone for the most expensive synthetic. Are you able to use less oil when using synthetic, I believe i have read somewhere that you can use a lesser concentration with this stuff and if so are you able to alter the amount that is pumped out into the carb? Thanks Phil

Hi, checked the Clymer manual and it didn't make reference to measuring from the base, in fact the diagram showed it being measured from the lip! But I will bow to your greater knowledge of these things. Did it my way with the 125 jet and top notch on the needle and it is getting better but still stumbling around 5,000 revs, so will go with your method of measure to see what happens. I suspect the exhaust leak may be having some influence as we get nearer to spot on. What speed can I expect, i have been getting 55 to nudging 60 top wack? Phil ps needle jet didn't want to come out easily so have left it hoping its ok.

Hi, thanks for the info, aware of most of the above but I haven't measured the float height correctly. I am not sure you are correct measuring from beneath the gasket as this will be hard to do, I will check with the manual, i measured from the top of the lip with the carb upside down. the clynes manual does say that I should measure with the needle uncompressed, just touching as you describe, which i didn't do and which i will correct. I thought i had ordered an air filter to go into the air box but was sent a K&N type which i have twisted and contorted to fit with the airbox, the box is still fitted because otherwise no support for the battery and i want to use the original type later. The filter may be slightly restricted due to the twisting. The exhaust is standard as far as I am aware but the silencer is marked FRESCO. There is also a slight leak from the exhaust gasket and I have a new one on order. Thanks for the input, I will get there eventually. Phil

Hi Paul, have cleaned the screen and bowl, loads of muck in there but have taken it out for a spin again and still same problem, flow rate appears good from the tap.... more than it can be using! Will try to lower the foat hight a little to see if any difference. Phil

Hi Paul, the no is 4J300. Going to clean the screen and see what happens. Thanks Phil

Hi, have been trying to get the fueling right on my new, old DT125MX. I have used the Haynes manual data sheet main jet, a 130 and adjusted the float height to the recommended 21mm. On the 2nd from top needle notch the engine was bogging down still around 5,000 revs, have gone down to top notch this morning and much better but still slight bogging down so will try a 125 main jet and lowest notch on the needle ( am I doing this right? ). Now that I am able get into the high rev range, couldn't before with the 140 jet fitted it came with, a new problem is occuring. I am only able to sustain short periods of high revs, the engine will die and i will have to wait for what feels like the float bowl to fill, or fuel to get through. The flow from the tap appears ok, but I have just filled the tank and will have to drain it to remove the tap and clean, I don't think this is the problem though as it feels like the carb is the problem. Is it likely to be the needle valve and how do you test it? Phil

Hi, can anyone recommend recommend a dealer for DT125MX parts? Phil

Hi, thanks for your reply, I managed to get the lights working this morning before work. I don't think they were working before as I had to clean up the connections from the dynamo as they where furred up, working nicely now though. I have also noted that the exhaust is leaking from the joint at the cylinder which could be robbing power so will need a new gasket. I have seen two choices ali or copper. which do you recommend? One of the fork legs is weeping oil and they are knocking slightly on the rebound (full extension) so I am wanting to change the oil and seals. I have got some oil seals but do I also need some dust covers/seals and will I need anything else to sort? I also don't know how to remove the steel top cover at the top of the fork legs. The Clymer and the Haynes don't appear to cover this models forks. Chap at Redrose said to insert a screw driver and gradually work round twisting the blade, have tried this but scared of damaging the metal at the top of the fork leg! There are two small holes on the side of the cap, are these for removal using a tool? Also can you suggest where I can get some fork gaiters that fit this model. One more thing, I am planning to convert to 175cc at some point will I be able to use the carb I have got and change jets or will i need another? Oh and one more thing where can I get an original rear mudguard. I think thats it for now. Looking forward to answers from you. Phil

Hi, I'm a newbie to this site and I have just recently bought a DT 125, 1982 registered. I have got 2 problems with it. The first is the headlights don't work. I have been working on it all yesterday and a bit today studying the wiring diagram to try to get the headlights to work. Question 1. Are they supposed to work off the battery or only when the engine is running as they won't do either! Any help here would be great. Also the engine won't run at higher revs and coughs and splutters, but starts, idles and low/medium revs ok, dropping the needle a notch and breathing unfiltered air helps a little. The main jet is a 140 and I think it should have a 130, carb is marked 4J300. Is the jet swap likely to do it and is there anything else I should consider? Also Alans Performance R&D has been suggested as the place to go to get the jet. Also I had one of these bikes when I was 19, many years ago obviously, and I remember getting a Gianneli exhaust for it that seemed to make it run much better, maybe it was just louder, anyway can you still get these anywhere? I have emailed the company and translated my request into Italian but have heard nothing for a week. Over to you any ideas? Thanks Phil