Another carb question

Chief1942 · Post by **Chief1942** » Wed Mar 07, 2007 4:01 pm

After much fiddling I have finally got my carbs to idle OK at the prescribed rpms, after a complete rebuild. The problem I am now having is the "return to idle" rpm after tapping the throttle. It revs and then holds the rev and very slowly returns to idle. Is that an accelerator pump adjustment problem? I put everything back as before after the rebuild so I'm fairly sure I have the accelerator rod in the right hole on the linkage but was wondering if I should experiment with that in an effort to solve this prolonged return to idle issue. The return springs on all the linkages are also plenty strong, so I don't feel they are the problem. I suspect the accelator pump but am looking for some input before tearing into the carbs again. Thanks.

Jim LaGuardia · Post by **Jim LaGuardia** » Wed Mar 07, 2007 5:13 pm

Check the carb lnkage rod ends for wear and binding, the rear rod goes onto the bellcrank first, then the front one.
Make sure the bellcrank bushings are free, also check the hand throttle for binding.
Check with sync tool to verify full idle return. before re-installing air cleaner components

lindenengineering · Post by **lindenengineering** » Wed Mar 07, 2007 8:08 pm

Here's several other aspects to consider.

Excessively lengthened push rods for the accelerator pumps can give you this symptom
Also
With the engine running at a high idle and warm operation (ie your sticking problem) switch off the engine. Without touching the gas pedal restart the beast. Does it return to the same high idle or does it run at a lower speed that maybe you have set it to. If so, then raise the revolutions top say 3000 and see if it drops or is slow to return.
If its slow or doesn't return to idle then attach a strobe light to number one wire and again without touching the pedal start it up and verify your base timing, now rev to 3000 and observe the advance curve. release the gas pedal and watch the advance try to return to base. If it won't suspect a sticking or partitally seized adv. The is a prevalent problem when using Petronix conversions and the adv/diz shaft is worn.
By the way the fixing screw for the Petronix perception head can be a tad on the long side and will jam the ADV weights if there is reduced clearance.
Dennis Bin Had That
Best of luck
Dennis

pinzinator · Post by **pinzinator** » Thu Mar 08, 2007 10:40 am

I had the exact same problem, nothing seemed to work. Then I had the cards syncronized by a good mechanic with an exhaust gas analyzer, and have not had a problem for 3 years now.

Chief1942 · Post by **Chief1942** » Fri Mar 09, 2007 5:39 pm

Thanks all for the recommendations. I can see I have my work cut out for me. Off to the garage