Message Board - Machinery: Briggs and Stratton Carb' Problems
23 Feb 2010 by Chris Thornton
Hello,
I have two B&S engines both with carb problems which I need to fix in the next couple of weeks.
The pic shows them both and whilst I don't think the solution is difficult I am a bit worried about stripping them due to the various springs involved.
The 375's (Black mower) carb' will prime but will not run. It will run as long as one keeps pressing the primer bubble So I think the problem is with the diaphragm ???
The 40's engine will not prime but i know it does run. Perhaps the pipe is blocked???
So can anyone describe to me how to take the Carbs to bits without springs flying off and not getting put back right?? Also can you suggest what is wrong with each Carb'????
Thank you, Chris.
"He not busy being born is busy dying"
23 Feb 2010 by Sumomosr Last edited 23 Feb 2010
Diaphragm has stretched and is leaking air at the edge closest to the engine.
Remove air filter and long screw with it.
Remove 7/16th bolt at front of carb/tank.
Remove 1/2" bolt securing tank to engine and watch for spacer behind tank. It should stay in tin plate shield but keep an eye on it.
Pull carb/tank outwards and rotate to release governor linkage from throttle arm. Leave all springs where they are.
Undo 5 screws holding carb body to tank and seperate the carb from tank. diaphragm should stick with carb body. A spring and cap sit above the diaphragm. and these are what stretches the diaphragm to create the air leak, You should be able to see the slight pucker at the edge where the seal has failed.
A fine mesh screen cap covers the main jet. Carefully remove and blow through the jet. Clean mesh in petrol. Refit mesh. Clean fuel tank pick-up tube mesh screen also. Don't try and pull tube/pipe from carb body.
Flush out tank.
Reasemble by holding carb body upside down.
Put spring in recess it came out of.
Put cap ring over spring.
Put diaphragm on top.
Compress diaphragm and spring with a 10 thou feeler gauge blade flatwise.
Put tank over fuel tank pick-up tube. making sure all screw holes line up!
Turn the whole assembly over right way up while holding carb body and tank together with feeler gauge still squashed in between.
Fit 5 x Phillips-head screws and tighten lightly until you can just pull the feeler gauge out and tighten fully in cross pattern.
Put some fuel in tank and check primer action.
Offer tank to engine and twist to engage governor linkage to throttle arm. Push carb gently onto inlet manifold tube until O-ring seats easily.
Insert 1/2" bolt and then 7/16th bolt.
Oil foam air cleaner after washing in petrol.
Refit air filter and long screw. Tighten gently.
Prime engine and pull rope.
It should go.
Diaphragms last about 150 hours.
If your reading this and yours is younger - Remove air filter and tighten the scews a bit. Factory fits them just snug. It may last a bit longer. Refit air filter.
Second carb has blockage probably. Same procedure as above.
Primer bulb can perish sometimes. You can replace it by prising out a plastic retaining ring like an internal circlip but with 2 prongs.
GOGGA
23 Feb 2010 by Sumomosr Last edited 23 Feb 2010
It may pay to fit a new spark plug as it has been running rich and can fail as a result. They're not expensive. NGK B2-LM or Champion J19-LM.
GOGGA
23 Feb 2010 by paul kelsey
Job done Chris just print it off and away you go it looks a top explanation.
23 Feb 2010 by paul.
Yes i have not had to rub Sumo`s lamp for a bit ,but it nice to know he`s out there!
Brilliant, long may it continue!
Paul
23 Feb 2010 by Sumomosr
Forgot to say, Use a NEW diaphragm. Once stretched they're a throw-away.
Cheers Paul & Paul.
GOGGA
23 Feb 2010 by Chris Thornton
I didn't want to take Sumo for granted but "kinda" knew he would send a good explanation. Thanks mate!!
Can't say that I'll be able to reciprocate but if ever you are in North Lancs I'll buy you a J2o or two!!
Chris
"He not busy being born is busy dying"
24 Feb 2010 by ticky21
LOL @ my mate Sumo...........without putting too much of a smutty twist on his reply....ive told my missus to use a new diaphram.....but ...nope...hence our son......hahaha
Ticky supports British farmers...!!
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