Doug38
Model #:54160
Serial #:4938394
Total run hours: unsure, but has been installed several years
Fuel source: NG or LP: LP

Here's my saga any help appreciated...Generator was working when I bought a house 1 year ago.  Started for the weekly run most times.  Infrequently, it wouldn't start and give an overcrank error.  I replaced spark plugs, old ones seemed ok though, but it seemed to help with starting.  Then months later I got an overspeed error.  I determined the stepper motor gears went bad.  I replaced the stepper motor, but when disassembling, i broke the intake airbox getting it off, so i replaced that as well.  I ensured the ng/lp was on lp, cycled a few times.  Engine won't start.  I took airbox back off, even removed the ng/lp slider to ensure it was not blocked, reassembled, won't start.   I purchased a manometer, tested gas pressure at the regulator ports, have 10.5".  I had a service tech come out.  He stared it with a spray of starting fluid and it ran.  He concluded bad fuel regulator.  I purchased a fuel regulator, install, still won't start.   Tested the pressures again, all are 10-11.5".   i checked the valves and appear to be .0025 which is in spec.  I tried to start it today by putting my fingers in the venturi's and cranking on manual and it starts right up no problem, runs normally.  I looked at the choke and it appears to move like it should when it is cranking, opens fully at speed.   The the chock plate seems close to the venturi's not sure how to adjust to get it tighter and still allow it to move.   I"m at a total loss on where to go from here.   One other weird thing, I placed it in auto and set the exerciser, when it started cranking I put fingers in venturi and it started, but the choke is staying closed and it is not running at proper speed so I'm not sure what that means.  If I start it in manual (with fingers in venturi) it runs just fine.
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Peddler
Last first, the controller is set for low speed exercise so the choke would be closed and it is running at about half speed, totally normal.  As to the starting.  I normally set the valves at about .004 because the springs don't have much pressure and it is easy to actually compress the spring while sliding the feeler gauge under the rocker.   Also in replacing the airbox did you re silicon the rubber seals in both inside and out?  Any leakage here can cause hard starts.  Also on the adapters that screw into the demand regulator make sure they are tight.  In 20 years of working on Generac generators I have only found one demand regulator that needed to be replaced.  Lastly and the most likely problem is the coils, they have been a weak spot for years and it is my first concern when I'm having hard starting issues.  The  starting fluid sort of tells the story, much more explosive than LP and weak coils would light off on it more quickly.  If you hear any popping, even very slight, while cranking with the air box cover off then it is most likely coils.  It is a timing thing with the old coils not lack of fire. 
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Peddler
You need the choke to be flush but free moving.  To adjust you have to remove the solenoid and take out the allen head cap screw and pull the choke up to adjust the choke flap.  It should have been fine from the factory if you ordered a correct new airbox.
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Doug38
You da man Peddler.  It turned out to be the rubber seals from the airbox to the intake tubes, siliconed them up and put it back together and started right up.   Thanks so much for your words of advice, this one's had me stumped for quite a while.  
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