Having trouble with my dt125r



  • New to this
    Ive a 2000 yamaha dt 125r dep pipe ( has been welded ) and silencer, the reed switch took out of the back of the clocks ( didnt notice any difference by doing that ) and think it may have different reeds in it ( they are not metal, they are like a yellow plastic type maybe hy-tech).

    Any way, she seems to bog down but then takes the throttle when you snap it open. you dont notice this too much when you are driving just when it is on the stand. idle is difficult and its in the low revs were she bogs or hesitates. plug is a nice brown in colour though?

    Its a tm28ss carb with the standard jetting, 240 main and 25 pilot. ive tried adjusting the pilot screw but no luck. Bought a 250 main jet and a few bigger pilot jets but that not helping with the bog.

    Anyone have any ideas?



  • Plastic reeds are standard.

    Sounds like there is no snorkel in the air box.



  • She's slightly rich then. Clean your Air filter and see what that does. You would be surprised the difference it makes to any 2stroke really.



  • @Calum

    The air box doesn't seem to have been touched small black bottle on left is there but wasn't tightened right but made no difference. Snorkel there nothing seems to be missing. Bike will idle now but when you give it the boot she hesitates.

    Am I right in fiddling with the pilot circuit to try and cure this problem?

    Cheers for the help been at this a few days now and not getting anywhere...



  • @Darty

    I blew the air filter out with compressed air but I'll wash it and leave it to try over night and try it again tomorrow .

    Newish plug in it too.

    Thanks for the help



  • To find out where the problem lies is trivial. You want to expose the bike to two extremities to find out which exacerbates the problem, and which improves it.

    If you don't know whether it's rich or lean then you need.to test scenarios that make it better in one way another, and take note of the results.



  • Put in the washed air filter with the 27.5 pilot and 240 main and at 1.5 screws out on pilot seemed to have the least amount of bog even a little screw either way didn't seem to cure it?

    I put all the standard jets in (240 main and 25 pilot) but no good seemed to be the further screwed in the better.

    When I bought the bike it didn't seem to do it but started now. There was a small cable tie wrapped around the choke so that it held it up just by a mill or two. I put one of them back on with the 25 pilot in and it take the boot no problem but then top end seems to suffer a little.

    Starting to give up on this



  • Have you tried adjusting the needle position yet!?? This will adjust your Mid-High RPM running significantly first.

    Change the Needle clip, get a feel for it. then attack the Main Jet.

    Check your plug gap, 0.6-0.75

    I ran

    Standard 5J25 Needle 3rd Position
    250RD Main
    25 Pilot
    1.5-2 Turns Out Idle screw.

    We have the same bike essentially. I ran Standard set-up, Air box, Snorkel, Air filter, BR9ES Plug, No boost bottle using older 3BN rubber(won't effect the jetting noticeably). And she ran perfectly.

    Adjusting the pilot jet on the standard engine should not be necessary.

    +Check the choke for leaks, there is a seal in there and rebuild it with the correct spring on the lever to be sure.



  • I got the bike going today by using a 30 pilot and the rest standard. She takes the throttle no problem but the plug is wet and oily. I might try lowering the needle to lean it a little to try and get the nice brown colour it used to be.

    I will check the choke just to make sure and then I will be able to rule that out. I'm running br8es which hardly make much difference?

    Its awful hard to get a constant sign from this yoke so I've a new coil ht lead and a cap coming, new air filter and I might get reeds too.



  • Yea tried the needle position when all was standard but the leaner I put it the worse it ran the richer the better but still didn't cure the hesitation.

    Thanks for the help.