This vintage two-stroke enduro came to us a couple of weeks ago in need of a carburetor. After some research we determined that the OEM carburetor was no longer in production. Since the original was obsolete, we ordered in a Mikuni round-slide carburetor in its stead.
Most of the time we are able to order carburetors that come jetted specifically for the year/make/model of the machine. Unfortunately, due to the age and rarity of this particular machine the distributors were unable to provide us with an exact match. The closest match they were able to locate was a carburetor jetted for a DT 175: the DT 125’s big brother. We ordered that carburetor knowing that it would most likely need jetting adjustments made once it was installed.
After installing the carburetor and starting the machine, we began the process of trial and error in seeing what jets allowed the bike to perform at it’s best. At the end of the day, the main jet sufficed for this application but the pilot jet needed to be larger. We ended up satisfied with the performance of a #35 pilot jet over the #27.5 pilot jet that came jetted for the DT 175.
Initially we were very satisfied with the performance after installing the carburetor and making the necessary adjustment to the jets. After test riding, however, we noted that once the bike warmed up it began backfiring and sputtering. Shortly thereafter, the bike died altogether and would not restart. After further diagnosis we suspected that the coil was breaking down when the motorcycle warmed up.
To verify this theory we let the motorcycle cool during our lunch break and tried to restart it upon our return. Sure enough, the motorcycle fired right up and ran great- until it got hot. After proving our theory, we replaced the coil and are happy to report that this vintage piece is running great again!
