Valve retainer GN220

Phak1

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I have a generac 4000xl generator model 09777-2 I bought in 2000, with a B&S engine Model GN220 and broke a valve spring retainer part a1720. It was replaced with a kit with springs, valves, valve spring retainer, oil seals, head gasket and the half clip retainers (Generac part # 0D24890ESV). My first question is, do I need to replace the whole kit or can I just replace the valve spring retainer washer and clips?

My second question is the retainer broke due to an overspeed condition. It happened after I took the carb off to clean it out. When I reinstalled it, I had the idle switch on and when I powered a drill, to check it out the engine started screaming (Over reving). I shut it off immediately avoiding any catastrophic outcome. I suspected the linkage going to the governor so I removed and reinstalled the carb making sure the linkage spring was installed what I was proper and thought I had fixed the problem as I powered my drill several times and it responded by raising the rpm’s and returned to idle when I released the trigger. As it turned out, I needed the generator the next week when I woke up to no power. Confident I fixed the problem, I stretched out a 100’ 12-3 cord, started up the generator and plugged my coffee pot. As soon as I powered it up the generator started to scream and before I could run outside to shut it off, it broke a valve spring retainer washer in half and the generator shut down.

When I cleaned out the carb, I did not touch any part of the governor, only the linkage that attached to the carb. What could cause the over revving condition.
 

Phak1

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I answered my first question myself. Upon looking at both valve stems, I realized that the new stems were designed for the new half keepers and not for the old style keepers. I had to pull the head, lap in the new valves, install the new stronger springs, spring washers and new retainers.
1E568083-2A16-4F6E-80FB-9D301ED057C8.jpeg 4CB3F3F3-081A-4BD9-953A-B90EAFA3EA61.jpeg

The pictures show the old then the new. After reassembling and making sure the linkage was installed correctly it appears to be working fine With no over speed condition. I ran it ten minutes using a fan turning it on and off and it responded perfectly coming down to idle when the fan was shut off and raising to running speed when turned back on. I repeated the test about two hours later when the generator cooled off. Again it ran perfect.

I posted my findings and results to benefit others that may run into this issue.
 

bertsmobile1

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Thank you.\Solutions are always most welcome & very valuable.
 

1121jerry

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do you still have the old A1720 retainer that was good . Mine is broke on the exhaust.
 
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