Surging

**cathal** · #1 14 May 2008

My '91 Tenere has started to idle irregularly. One minute it's ticking over fine, blip the throttle and it cuts out. Start again, idles fine then it might do the same or it might tick over at 3000rpm, also happens when riding. Either it won't cut back or there's a slight lag when you open the throttle. It's not the cables. I've cleaned both carbs.Inlet rubbers are fine, I tested them with easy start. Any new ideas or similar experience?

**aukeboss** · #2 15 May 2008

1. Remember, the last part of the travel close to idle has only a very little spring force available - a cable sticking a littlebit might just be the problem
2. Is the lever of the primary slide well fixed to the shaft - no play? Check by removing cover of primary carb
3. Fuel arriving in the float bowl as it should - check per procedure in earlier post(s)
4. Slide of 2nd carb moving really free? Should return in closed position smoothly when you push it up
5. Throttle valve of second carb not sticking in open position?
6. Idle speed setting (bog screw) correct? Idle speed set not by cable but by screw!
*. Ignition OK? Another chapter ....

Good luck!
Auke

**bruken** · #3 22 May 2008

Quote:

Originally Posted by cathal

My '91 Tenere has started to idle irregularly. One minute it's ticking over fine, blip the throttle and it cuts out. Start again, idles fine then it might do the same or it might tick over at 3000rpm, also happens when riding. Either it won't cut back or there's a slight lag when you open the throttle. It's not the cables. I've cleaned both carbs.Inlet rubbers are fine, I tested them with easy start. Any new ideas or similar experience?

If you blip the throttle and it cuts out you are too lean

this is where it gets tricky though... Make sure your primary carb slide is the prescribed height (or you will be trying to balance two sets of variables) when reaching the throttle stop (or as Auke says..Bog Screw). Then adjust your idle jet. Lean the motor out until you get optimum revs then start backing off (richenning)

tell tale signs if you dont have diagnotic tools and doing it by ear.
Burbles with hesitation on blipping the throttle - too rich
starves and dies on blipping the throttle - too lean
when riding when you back off the throttle after hard on and the motor starts popping - too lean
When you come off the throttle and the revs stay high for a while and then gradually drop - too lean
When you come off the throttle and the revs drop low and then pick up - too rich
A long idle that dies slowly - too lean
A idle that is difficult to cut (dead stop) wayyyyyyy too lean

PS. These bikes like to run rich. Dont be afraid to richen the mixture as far as it will go before it starts degrading performance.