Starting Behavior on Briggs & Stratton 3.5hp


Old 10-30-03, 05:23 AM
ikleiman's Avatar
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Lightbulb Starting Behavior on Briggs & Stratton 3.5hp

I have an old Montgomery Ward rotary mower with a 3.5hp Briggs and Stratton engine. It runs beautifully when warm and does a great job. However, it has some odd starting characteristics that I'd like to understand. It is harder to start now that the weather is cold and it won't continue to run. When the weather is warm, it does this:

Only starts on the lowest throttle setting; needs to warm up before increasing the throttle; doesn't appear to like the choke at all. It will start up quickly, but once started it falters pretty quickly and often dies, as if it is not getting enough gas or something. Once it is warmed up, it continues running and the throttle can be adjusted to increase the engine speed.

This behavior is exaggerated in cold weather. Harder to start, and once started, the engine gives a good roar; then falters and quits in a few seconds.

Any ideas on what the problem might be or what i should do to troubleshoot it?

Ian K

Last edited by ikleiman; 11-05-03 at 08:26 AM.
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Old 10-30-03, 10:53 PM
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Hello Ian K!

Not sure which carb you have on this, but it sounds like you need to clean it and more importantly change the carb diaphragm. You will need the engine model and type # to get the carb kit you need. Should run less than $7.00 and 30 minutes worth of work.
Old 11-02-03, 02:16 AM
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I saw a problem like that once. Turns out the problem wasn't with the engine at all, but with stale gas. It drove me crazy for quite a while. My nose should have given it away. The gas didn't smell right, but at the time I didn't relate that to my starting problem. Old gas won't vaporize sufficiently in the carb when cold. A little fresh gas added in with the old made all the difference in the world. If you are using good gas I would take a look at the float level in the carb. I'm assuming that you've tried adjusting the high speed mixture screw and that didn't help the problem.
Old 11-05-03, 08:28 AM
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OK. Thanks for the tips. I'm working on it and will let you know how it goes.

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