My 95 Savage (with Dyna muffler) runs perfectly with the Choke out, but as soon as I put the Choke in, it coughs and sputters, and backfires.  It feels like you are running out of gas, even though the tank is full.  Any ideas on where to start?

If it idles ok w/o choke, I would go for a partially plugged main jet.
I have not done it, but if I remember correctly, the main jet is easily removed w/o removing tank or carb.

clean carb if seafoam in tank doesn't work

4forths wrote on 10/22/09 at 05:44:11:


Probably late, but I'm guessin' pilot jet is dirty.

Try closing the throttle slowly coming down from higher RPM'

If you havent messed with the white washer, maybe its time. But, before anything else, Id suggest getting the air mix screw set. Do it twice, or 3 times. Count in to stop, open back out & go 1/4 turn past. Ride it. See if you can operate the throttle in a way that keeps it from B/firing.  Mess w/ that mixture screw ( 1/4 turn) & listen to the engine, ride.

You can also open it till it starts to sound "wrong" & close it till it starts sounding "sick" again & go in the middle of that & see how it acts.

Digger wrote on 12/16/09 at 19:35:22:


Digger is right.  If it is only at the idle point or just off throttle it is the pilot circuit (this is provided you don't just have your idle set too low).  Usually the pilot jet gets plugged.  It has the smallest hole of all the jets in your carb.  One way to confirm is if you can get going on choke and once up to 1/2 throttle it runs fine with the choke in then it is just the pilot circuit that is bad.  Now if you find the pilot jet perfectly clean then there is a little known passage that feeds from the pilot to the throat of the carburator just down stream of the butter fly valve (or slide depending on CV or VM carb).  It allows the gas into the airstream when the throttle is closed.  This one requires squirting carb spray into the pilot jet opening (or manytimes you can find the air passageway at the front of the carb throat and squirt in there) and you should see a little tiny squirt of spray come out of the tiny hole I described above in the carb throat.  The hole is on the botton of the throat.

Generally the it is just the pilot jet that causes your issue but I have cleaned carbs where that passage gets gummed up to.

Tony - It starts well with no choke? Runs well normally? Count yourself lucky. You're pretty much as perfectly tuned as you're going to get unless you're rich at speed. You might be a bit rich in general but if you start well and run well I wouldnt mess too much with a good thing.
If you're curious get a new plug (or 3) and test each circuit. Idle a while, pull the plug. Good? If not are you lean or rich? Readjust if needed. If you had to readjust try it again. If you're good go ride around at more or less half throttle for 10-15 minutes, pull the plug. Good? If not are you lean or rich? Readjust if needed. If you had to readjust try it again. Go WOT up hill and hit the kill switch while you simultaneously pull in the clutch, pull the plug. Good? If not are you lean or rich? Readjust if needed. If you readjusted try it again. Over and over again until you get it all right.

If a WOT plug chop seems too much for you go WOT for a 10-15 seconds (assuming the idle and mid range is correct). Now let back on the throttle. If you get a boost when you let off the throttle your main jet is lean, go one size up and try it again.