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Discussion Starter #1



I have an older 420 that has become hard to start. Once I'm able to get it started and it warms up a little it runs ok, maybe a little weak, but ok. When I try starting it, it spits fuel out of the carb, like the accelerator pump is kicking in when it doesn't need to.

Maybe an intake valve sticking? How would I check or what symptoms would confirm? The fact that it clears up somewhat once it warms up kinda throws me.
 

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Kish JD 318/420/430
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Does this have the old style pulse pump or electric pump? When was the last time you did a decarbon and valve adjustment? These should be around 250 hours according to the Technical Manual.
 

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Discussion Starter #3
Does this have the old style pulse pump or electric pump? When was the last time you did a decarbon and valve adjustment? These should be around 250 hours according to the Technical Manual.
This has a vacuum pump. I have never decarboned or adjusted the valves. It is almost certainly way over due. It doesn't look like the valve adjustment is all that difficult. What does the decarbon entail?
 

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This is generally caused by a valve issue. First run a compression check, then pull the head and check the valves. I'll bet you lunch one of the valves is not closing on the compression stroke.
 

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Three of my friends
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It doesn’t have accelerator pump.
 

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Kish JD 318/420/430
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Unless the carb has been replaced, then there could be an accelerator pump on the carb, I know because I got one for my Onan a few years back.
 
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