Briggs and Stratton Carb.

[joegrgraham]

Afternoon everyone,
Just looking for a ‘fresh pair of eyes’ really.

My ZZ engined Trusty has been playing up of late.

Today I stripped, cleaned and replaced the carb, after a couple of swings, she started and ran pretty well for about 20 minutes, then it stopped whilst ticking over, restarted no problem, ran for a few more minutes then faded out and stopped, refusing to restart again.
I suspect the carb is the problem, I believe it is over-fueling/flooding as the engine is very smoky when the revs increase, and you have to be very gentle opening the throttle, open too quickly and it simple stalls. Also, after just todays running it has sooted the plug up quite badly, the pistons rings are in good order and it doesn’t use oil.

The carb was rebuilt with a genuine B and S kit, probably less than 30 running hours ago, I’ve checked that the float is not holed and set right, the fuel flow needle opens and shuts/seals as it should etc. The jets are set to a recommended setting, and it has run perfectly happily at that.

Also, there are no issues on the magneto side of things.

Hence my suspicion of an issue with the carb.

What does anyone else think?.

Thanks

Joe.

[charlie]

I had a problem with my Trusty Earthquake, started and ran well then started stopping and playing up. I suspected fuel, checked flow from tank to carb, that was OK. Took carb off and found water in fuel in float chamber. Cleaned float chamber, problem solved.

[andyfrost]

Joe , it’s difficult to say without actually “being there” , but I am from the school that taught me that the vast majority of carb issues are more often than not electrical.

Andy.

[joegrgraham]

From day one with this machine, the carb has been ‘difficult’.
Looking at the american websites, the FloJet carb has a pretty bad reputation, the alloy casting of the body is pretty poor (it is a wartime machine) and none of the needles and butterflies fit snugly, everything flops about a bit, I think a number of small innaccuracies make for one big problem!.
I remember reading somewhere of an alternative carb that can be fitted, just cant remember what.
Next step I think is to measure the port and bolt centres, and start searching for an alternative.

[sidevalve44]

It might be worth considering an Amal Motorcycle carburettor. I guess the ZZ is about 500/600cc which means the jetting for an old BSA M20/21 would be a good starting point. Spares are easy to get from Burlen Fuel Systems or Hitchcock’s Motorcycles.

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