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Symptoms.... Large Pilot, Lean Idle Hang : My Resolution!

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I wanted to share my findings with the rest of the Thumper Talk community. I have in the past seen a few posts by frustrated people with the same exact symptoms that i had and the subjects sat in their various forums with not real response. This is what i did to resolve the issue. It may not be the right thing for all cases but this is what i found and it worked for me. If you are experiencing the same symptoms, it does not take long at all to check if your slide is at the proper height.

............Large Pilot Jet, Hanging Idle...............

My problem ended up being that my carb slide was adjusted too far up in the "0" or idle position. basically, all the tinkering with my idle and swapping pilots my slide was adjusted further up than the recommended 1.5 mm's.

When i was in the thick of things trying to resolve this issue, nothing made any sense. I am by no means the best at tuning carbs but all the fundementals that i knew seemed like they did not apply anymore. My A/F meter was telling me that i was a little to alot rich but my idle was still hanging like it was lean......

The symptoms where like i had an air leak, that is the only way i could rationalize it. At idle, i had no response from my fuel screw. Closed would not choke the engine down as it once used to. Every PJ i tried had the same results, no reprieve from my lean hang, that is until i was 3+ out on my screw. I was like this makes no sense at all !!! I popped in the largest pilot i had, a 48, and still the same thing. Lean hang on on throttle chop.

I really started to get irratated. i checked once more for air leaks with everthing from WD 40 to propane with no results. I bought and installed a new engine side carb boot and clamps, no change. As i was about to back over the thing with my truck, i got lucky..... I noticed on my A/F meter that as i slowed my idle speed down, the circuit leaned out a bit, not a big suprise there, but what did get my attention was that at a lower idle, i got a response from my screw again. So, i started working my way back down through the Pilots and finally got to a point to where a 42 was magic again. Then i started digging through the manual and checking specs and i figured that it was the slide height.

I guess it all makes sense to me now, with the larger slide opening, air does not pull fuel from the pilot circuit effectively and causing the problem that i was experincing.

Since then, i took a road trip to the local home depot with my trusty calipers and bought an assortment of rod stock to properly guage the throttle slide opening on all of my toys.

I would have to say that this was biggest headache that i have ever experienced with the FCR. But it is the tough problems that give you the biggest feeling of satisfaction when you resolve them. I do not fully understand all of the mechanics involved here, maybe someone else can enlighten us on the finer points, but this i do know, the little graph thingy in the manual that shows the slides effective range...... Pay attention to it, it has more effect than you would ever think it does!

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Congratulations on solving a knotty problem. You can also use a #56 drill bit when setting the slide height.

Thanks for posting your thought process too.

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