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Primer Blub Required For Each Start.


BobHelms's Avatar
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06-15-14, 11:12 PM   #1  
Primer Blub Required For Each Start.

B&S 12H807 1530-21 on a Snapper 21 Self Propelled walk behind. Installed carburetor overhaul kit #498260. Now every crank requires primer blub use before the engine cranks, it has no choke or jet adjustments. This mower sat for a long that so I can't remember if this is/was normal operating procedure. Once it cranks it runs fine. I did not replace the old primer blub, could that have anything to do with my issue? TIA for any help received.
Bob Helms

 
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marbobj's Avatar
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06-16-14, 05:38 AM   #2  
For other than normal operating temps on an engine it will need a richer mixture from somewhere - either a choking system or a primer system.

Does yours have a choke of some kind or is it just the primer bulb? A choke would have two plates in the carb throat - a throttle and a choke plate. The latter would be to the air intake end of the carburetor.

 
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06-16-14, 09:13 AM   #3  
While it is running spray/dribble some carb or brake parts cleaner behind the carb, if the engine tempo changes the carb to intake gasket may be leaking and it is sucking air from there rather than through the carb. Have a good one. Geo

 
BobHelms's Avatar
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06-16-14, 10:48 AM   #4  
This engine does not have a choke. It only has a primer blub. There's only one plate in the throat of the carb, managed mostly by the governor. The breather / carb assemblies have new gaskets. The primer bulb was not replaced. Priming is required to start even when the engine has just been shut off. The owners manual states that it should start on it's own while warm but cool weather may require repeat priming. Thanks for your help.
Bob Helms

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marbobj's Avatar
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06-16-14, 01:09 PM   #5  
The bottom line is the mixture without the primer is too lean to start on.

Not changing the primer bulb may be a problem if there is some kind of air leakage around it.

If what Geo suggested doesn't get you any answers, there could be a restriction in the fuel passages in the way of varnish since it has sat for some time. that can be cleaned out with Sea Foam.

A lawn mower should have an air filter. Make sure that is a good one. It will provide a certain amount of ramp up to the vacuum in the carb throat and get you a richer starting mixture.

The other possibility is a weak spark which needs a richer mixture than normal to fire.

I guess, if it was mine, I wouldn't spend too much money to fix it if I could get it started with the primer.

 
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