carb help.

[jsandy]

so my carb has a stumble in it one hard acceleration, mostly sure that it is the accelerator pump not squirting. so is there an easy or simple fix for this? would like to avoid pulling the carb for rebuild

[csuggs]

so my carb has a stumble in it one hard acceleration, mostly sure that it is the accelerator pump not squirting. so is there an easy or simple fix for this? would like to avoid pulling the carb for rebuild

FYI - I just had my carb rebuilt and it would stumble on the hole-shot. Not enough fuel. I installed a larger primary squirter and that seemed to take care of it - but I haven't had too many hours on it since then . . . Don't know if that helps.

[cadunkle]

First make sure your squirter is squirting out of both nozzles. They're actually called accelerator pump discharge nozzles. If it's only shooting out one side of the discharge nozzle, remove it and clean it. There is a washer on top and below the nozzle... Do not drop these into the intake.

If there is an overall weak (or no) shot out of the nozzle, pull the primary fuel bowl and replace/clean the accelerator pump. You likely have a ruptured diaphragm.

If the shot is delayed from when you start pushing the throttle (it should be immediate), you may have slack in the linkage. Try moving the arm that rides on the accelerator pump cam and pushes on the accelerator pump. If there is any slack, loosen the bolt that presses on the accelerator pump arm just enough to take out the slack so there is no free play.

If the shot looks good from both sides and responds immediately to throttle movement, try stepping up to a discharge nozzle 2-3 sizes larger. If that fails, you can try another 2-3 sizes larger.

If that fails, you may be looking at a incorrect accelerator pump cam or a worn one, not giving enough shot or the correct curve for enrichment. You may try different cams that give a larger shot sooner if the stumble is immediately from a stop/idle or if it's at higher RPM/cruise going to WOT you may try one with more shot left in at later in the throttle opening.

Also note if this carb is vacuum secondary, too weak of a secondary diaphragm spring may result in secondaries opening too quickly or too soon and giving a leak stumble. This situation should be corrected with a stiffer secondary spring so the secondaries open slower and later.

If you have a double pumper please let us know, as tuning that can be a little different.

[jsandy]

wow cadunkle is like the Carb guru. would like to say that i did all this and it fixed it but no. turns out the supra must have fixed itself cause we went out today and it did fine.

[DAFF]

Make sure you change your fuel filters every season. Clean fuel makes carbs happy!!!

[rludtke]

A low primary float chamber setting (or a stuck needle) could also cause a stumble.

Most of the tweaks and adjustments that cadunkle wrote about can all be performed with the carb bolted to the engine. In some cases the float bowls need to come off, but that is no big deal. The fabric washers or seals under the float chamber bolt heads can handle several removal cycles before leaking. The overhaul kits that I have seen always provide extra seals to allow for these extra removals. Don't be afraid to overhaul your carburator. This too an be accomplished in the boat, no need to remove the carb. The overhaul part replacement is very simple.