Briggs & Stratton 3.5hp Engine Will Not Start with Air Filter Bolt Installed

My 1968 B&S 3.5 HP lawnmower engine (92902, pulsajet carb with two fuel pickup tubes) will not start unless I remove the air filter; nor will it start with just the air cleaner bolt installed without the air filter. I have serviced the carb and replaced the gasket. I have checked and am certain that the bolt is not interfering with the movement of the manual choke.
Anyone experienced this problem?
Davy
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Davy wrote:

Never anything remotely like it.
Its not shorting a wire or summat is it?
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On Sun, 10 Jun 2007 22:13:05 +0100, Davy wrote:

Just what did you service?
Yes I have seen similar carbs that wouldn't run with a cleaner. The added vacuum sucked too much gas. Spark plug wet when it won't run?
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Gotta be a blocked jet somwhere or a gasket covering a hole.
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I second that opinion. I suggest that you dismantle that carburetter again, and clean it thoroughly in clean petrol (having thoroughly cleaned the outside first with Gunk, paraffin, or petrol). Preferrably, blow through all the jets with compressed air. As as been suggested; some gaskets can be fitted the wrong way round, thus covering a fuel or air jet. BTW, I have no experience of that particular carburetter.
Sylvain.

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That's an oldie but a goodie. My first sense is that you have the mixture screws out too far, and it's running rich. Turn in (clockwise) till very lightly seated, and back them out 1 1/2 complete revolutions.
--

Christopher A. Young
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Christopher,
you might have a point about being too rich. Looking again at the carb, the filter retaining bolt goes through the centre of the choke butterfly. When the bolt is removed then it leaves a hole in the middle of the choke and the engine is less choked. I was on the wrong lines, as in "what does the bolt interfere with"; rather I should have been thinking "what is different with the bolt removed" thanks
Davy

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Pure guesswork here. A very rich mixture needing lots of air to start. Removal of filter allows more air. Does the bolt also allow even more air when removed? Presumably when you can start it it subsequently stalls when it gets hot? Phil
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Phil,
I will try to start it with the filter and bolt in place and not full choke. thanks for the ideas. Davy

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Following on from the theories mentioned in this thread, I tried to start it with the air filter attachment bolt in place but with less choke - no success. Incidentally I now find that I can start the engine with the air filter box attached provided I remove the attachment bolt - then starts first pull. Davy

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Sylvain VAN DER WALDE wrote:

Thats the sort of state I got my wifes peugot handed to me in, after it packed up halfway up the A1..it was obvious it was running way too rich. I looke for the airbleed adjustment, and discovered it had been removed in order to try and fix it.
I left it a a garage who wanted me to replace the airbox and the computer.
Then I phoned a friend, talked it over, he sent me a spare airbleed screw, and we decided to change the water stemp sensor.
Its resiatnce never varied in a pot of boiling water, from cold. So I spent 7.50 on a new one and screwed it in. Problem solved.
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