Hi all,

after having restored my DT 400 from 1976 I‘m getting confused because the bike does not run smoothly.
Especially in the half gas position it runs out of the round, does not go up smoothly with speed.
I checked the carburettor (changed with a alternate one), the ignition point (Vape 2.9 before top dead Center), the oil pump - still the same ….
When I bought the bike 20 years ago it was dissambled from two bikes (Dt 400 and dt 250). Today I was thinking about the exhaust, I have two of them, looking totally the same, but what if I took the 250one instead of the 400one? Does it lead to the problems I described above? How can I differ between the exhausts - I could not find a number or something similar….

Best regards 

Jan

Try running it, for a short distance, without the air filter lid and then without the air filter and see if that makes any difference.

I'll also pre-empt RT325 here and suggest chucking the exhaust on a bonfire, in order to clean out the exhaust.

CMSNL online parts list indicates that the DT250 and DT400 for 1975 and 1976 all used the same exhaust, although there might have been a slight tweak between the years (ie part number has -01 suffix).

Thanks a lot for your prompt reply - I will do the next days and will post some feedback,

And of you and neighbors around can handle it, a short rip without the muffler on…

Needle jets wear out & makes them blubber around 1/3 throttle & overlapping further up. Can you swap exhausts to prove that point if one tuns ok. Can you swap carbs for the same reason. It's a pain when you have two bike essentially the same but one doesn't play ball.

… still the same symptoms after taking the air filter away  next trial I will leave out the muffler…