I just finished rebuilding the top end of my '98 DR650, and I have this weird carb/jetting(?) issue I can't seem to find an explanation for: when the bike is warmed up, after idling for more than a minute, for example when waiting at a stop light the engine has an hesitation or sometimes just stalls as I try to take off or even blip the throttle in neutral. Sounds to me like running too rich at idle (am I right?). It happens ONLY if the bike idled for some amount of time, like a few minutes. It doesn't happen if it only idled for a few seconds.
I am using the stock BST40 carb with stock components, here is a list of the components I recently replaced (all with brand new stock, OEM parts):
- ALL orings
- pilot jet
- needle jet
- jet needle (6F19)
- plastic spacer under the needle E-ring
- throttle valve (slide)
- throttle valve guide (with equiv. KTM part, as Suzuki doesn't seem to sell this separately)
- pilot screw (currently set to 1.5 turns out)
- fuel enrichener ("choke") plunger
The OEM Mikuni #140 main jet is installed ( I did not replace this one) and also I have a new OEM pilot air jet but I wasn't able to get the current one unscrewed from the carb body, it's stuck and seems to just break instead of coming out.
The needle E-ring is installed in the 3rd (standard) position.
I'm using a GSXR 40F0 pipe, with the stock exhaust header, and stock un-cut airbox, the snorkel is also installed. The air filter is a K&N, just cleaned and re-oiled.
Given the carb is clean and float height adjusted properly, what could cause this rich running at idle? I mean in the stock form, the DR650 is known to run a little bit lean. What strikes me is that even with my bone-stock configuration (apart from the exhaust) I have a rich condition and don't understand why... I'm running out of ideas... any help or suggestions would be highly appreciated.
LE. if it matters, we can't get pure gasoline here in Europe. All gas we can get has at least 5% ethanol.