My 2k2 DS recently started coughing back through the carb.
It doesn't happen at idle or higher RPMs but when I slowley increase RPM (and then hold it at about 1200-1500) it starts to backfire through the carb. Sounds like it's coughing.
It goes away as I get on the throttle. No stalling.
I tried adjusting the air/fuel mixture screw and it doesn't seem to help.
I'm running the stock Carb, stock Pilot Jet, 175 Main Jet, K&N clamp-on filter (no Airbox) and a full race Big Gun exhaust.
I cleaned & reoiled the K&N w/ no effect.
Due to hard starting. I recently had the valves adjusted by my dealer. It starts fine now, even when cold but the coughing is really evident.
I recently switched to regular fuel vs high test.
I'm thinking either;
1. The dealer improperly adjusted the valves
2. Fuel is to low in octane
3. My DS has the Flu

Any ideas?

 

Opps - It's a 2000 model.
Also, I put new plugs in w/ no effect.

 

It sounds like your experiencing a lean condition in the transition circuit. Drop one clip position (raise needle) on the needle and see if this helps the problem. This could also be caused by a vacuum leak at the intake manifold or boot.

 

AZDUNNER
mine did back fired the the carb to, do a search on backfiring, what I came up with is the 2000 carb spring that opperates the big slide was made of a smaller diameter not as strong than 2001(letting the slide flutter and letting to much gas in at certian rpms. so I upgraded to the 2001 and all back firing stoped. also the pilot was up graded from a 37.5 to a 45 and the sleeve around the main is longer on the 2001 and newer.
Sam
[img]i/expressions/face-icon-small-smile.gif[/img]

 

Thats the same thing that is happening to mine. Like you said, it sounds like it is coughing and mine didnt want to hold an idle very good. I played with the air fuel screw and got it to idle great. The only problem i have now is that it coughs at about 3,000 rpms. When i gun it, its fine, but if i have to putt around at 3 grand she'll wanna cough and die. I checked all the boots that connect to the carb and filter. Should i richen up the main one and/or richen up the needle? Temps dropped about 30 degrees since i jetted it the first time.

Thanks,
RoughRider01

 

You have some kind of crap in your Fuel Bowl! Take it off and clean it and your fuel circuits out real well. Trust me on this!

 

Ok, I cleaned the fuel circuits out and the carb. Used a whole can of carb cleaner.
I checked the pilot jets and there are two correct?
One jet (looks like a regular jet) and was a 32.5! I changed this one to a 41.
The other jet is longer (has a stem w/ holes in it) that I couldn't find a larger size for in Phoenix.
I can't see and don't know the size of this jet.
The DS is still coughing but not as bad. Do you think I need to change this one as well?
No junk was found in the in the bowl and the floats are correctly adjusted.
It fires right up but still coughs at around 2000 rpm. It goes away when the throttle is increased.
I also cut four coils off the spring and it seems to rev quicker.

 

Hey AZDUNNER....
I would try to stay away (they suck), but az motorsports on Country Club
has them.

 

It sounds like the part-throttle circuit is lean which is controlled by the needle. Raise the needle one groove at a time until it runs good in that range. To raise the needle, you need to remove the slide from the top of the carb, remove the needle and move the clip toward the pointed end of the needle. I doubt you will have much luck by replacing the jets.

 

It would be best to put the stock snorkel tube back on with the open air filter. The stock vac diaphram carb does not like having the air box removed, either, but a direct air filter off the back is really causing it to be confused on air signal. Running a big gun with no air box lid or tubes requires a 190- 195 main jet and the needle one notch up from stock position. Running without a box altogether...?bigger? But the stock carb loses peak hp without the lid. Pump gas is good, the flu is possible, and chances are the dealer did not change the valve lash - the valves are not adjustable - you have to reshim if they are not correct, but I've never seen a stock ds get out of spec enough to cause a problem.
Keep trying, you'll get it there!