Hard starting & loses prime

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Old 09-01-10, 06:00 AM
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Hard starting & loses prime

Okay, this will probably be my Fall project after grass cutting season is over.

I don't have the exact numbers in front of me, but this is a Craftsman self-propelled with a B&S, 6 horse, I think. It was my sister's, now passed to our Mom to replace her older one when sis moved into an apartment. Has been running okay since I repaired it last year (neighbor helping out cutting sis's yard hit something and bent the crank; it was practically new at the time so I opted to try the repair vice tossing it). Crank R&R went no problems and it ran good. Fast forward to earlier this summer. Now the engine is hard to start, you have to mash the primer bulb about 20 times before you can get it to fire. Once it starts it will run all day with no problems unless you bog it down in tall stuff or shut it off. If you do it takes another 20 or so pumps on the primer bulb before it will fire off. I'm thinking a vacuum problem here - not enough intake vacuum for proper starting - but not sure exactly. I had the carburetor apart for cleaning and inspection, but no help. All gaskets/seals are good so I don't think I'm losing vacuum; my inclination is the vacuum just ain't there. Only thing that comes to mind is rings, but I can't connect the dots on why the problem cropped up fairly suddenly. The patient is about 90 miles away, so its possible the condition was deteriorating previously before I was asked about it. Open for any and all help & suggestions.
 
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Old 09-01-10, 09:25 AM
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Depending on the engine and primer circuit, most of them just force air into the fuel bowl which then forces the fuel up the carb nozzle, if it is a briggs with the primer in the airfilter housing it is usually the gasket between the housing and the carb and you must use 2 gaskets, if it is a Tec the bowl gasket must be replaced. Have a good one. Geo
 
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Old 09-04-10, 03:10 PM
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Had checked the gaskets, but will again when I get it on the bench. I have a rider, so no priming on my usual wheels. Do primer-equipped mowers have to be reprimed everytime they are restarted, even when hot and it's immediately after a shutdown?

It's the one with the primer bulb in the filter housing, just pushes air. Are you saying you have to double gasket the mating surface?
 
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Old 09-04-10, 04:11 PM
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Yes 2 gaskets on the housing to carb, no it shouldn't need to be primed after it is warmed up, while it is running spray some carb/brake parts cleaner behind the carb along the mating surfaces to see if the engine tempo changes, if it does you have an air leak. Have a good one. Geo
 
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Old 09-04-10, 11:14 PM
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I agree. Try a single new gasket between the carb and air filter housing first (where the tiny amount of air from the primer passes through to the carb usually leaks out because of a warped air filter housing) and a new bowl gasket (they can crack and allow that tiny pressure pulse of air to diminish and not pump fuel up through the nozzle). If that doesn't do it, double up the gasket between the carb and air filter housing.
 
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Old 09-06-10, 05:52 AM
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Thanks guys; will let you know how it turns out, but I probably won't get it here for another month or so (grass still growing well down here).
 
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Old 09-06-10, 11:13 AM
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I'd also pull the fan shroud off & check the bolts & gasket where the plastic intake meets the engine... I've seen several loose this year & a couple with the plastic manifold broken, if it's the type I'm thinking of,,, Roger
 
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