Briggs & Stratton 3HP 125cc Model 80202 side valve

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Re: Briggs & Stratton 3HP 125cc Model 80202 side valve

Postby Plugsnpoints » Mon Jan 14, 2019 10:19 am

That makes sense! The pipe from the valve chest operates the diaphragm on the carb! It works by the difference in pressure and 'flaps' the rubber diaphragm on the inlet side and 'pumps' the petrol at the correct time. If you make sure the pipe isn't sucking in air it will improve it. This is crucial.


As I said in an earlier post, the diaphragm needs to put under a little tension as you tighten the screws between the carb halves. I take it the carb is spotless inside and out now?


Andy :)

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Re: Briggs & Stratton 3HP 125cc Model 80202 side valve

Postby 56G80S » Mon Jan 14, 2019 5:35 pm

Been at work all day today. "screws between the carb halves"

Oh dear, I think I'll start with gettng an exploded diagram.

Or I may just settle for explosion.

Johnny B

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Re: Briggs & Stratton 3HP 125cc Model 80202 side valve

Postby Cjay59 » Mon Jan 14, 2019 6:10 pm

I would start by checking if it has a fuel filter, that could be dirty and blocking the fuel line, then on to a dirty air filter, then air leaks, then take the carb apart, all the Briggs & Stratton stuff is fairly bullet proof from my experience.

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Re: Briggs & Stratton 3HP 125cc Model 80202 side valve

Postby 56G80S » Sun Feb 10, 2019 8:46 pm

Thanks for the useful advice.

All running fine after head off, remove valves, lap in, replace, dismantle carb, thoroughly clean, seal the joins in the tube to the diaphragm, replace diaphragm, replace other seals, redo the linkages that were connected incorrectly then clean and reset plug gap.

The linkages still aren't right but I can get it to start. idle and go smoothly up to working speed. I thought my torque spanner went down to 11 ft lbs but doesn't so did the head old fashioned; it's hardly F1.

Thanks again.

Johnny B

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