Briggs 19.5 hp motor won’t operate past half throttle / overly rich

And the 793880 camshaft only has one tiny piece plastic on the ACR. The lobes and the rest on the camshaft is all metal. I know as I replaced enough of them for failed ACRs.

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What was that old wordage? If it backfires through the carb it's ignition timing? Backfires through the exhaust it was cam timing? Where's the Chevy guys at?

slomo
 
StarTech said:
And the 793880 camshaft only has one tiny piece plastic on the ACR. The lobes and the rest on the camshaft is all metal. I know as I replaced enough of them for failed ACRs.

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Great so we have a steel cam. Nice find StarTech. Hopefully it hasn't jumped time?
 
Still sounds like it's overly rich. You said the float was closing proper. Put a fuel cut-off valve in the fuel line. Start the engine and close the fuel valve. See how it runs. Should run for 20 or so seconds and begin to sputter. Fuel valve closed should stop the excess fuel from coming through the carb when the engine is running. If in fact this is an excess fuel issue??

You might have a valve seat not where it belongs holding a valve open. You said you can hear air leaking out on leak-down. Head gasket or valve seat maybe?

slomo
 
Question. I don't know if this engine has a plastic cam but if it did, would the valve clearances at TDC always be correct like they are?
 
Slomo, not sure what you mean about the shut off valve but I do have a remote tank hooked up to bypass the fuel pump and it has a shut off.

But even if the carb was rich I would expect to see black smoke but would I expect to see mist and feel pressure coming back through the carb inlet?
 
You need to find out why, according to leak down test you did, the intake valve is not sealing. What I see is blow back. It also can be cause by a worn exhaust valve cam lobe but you said failed the leak down test on the sealing of the intake valve. It going to require to remove the cylinder head as the intake seat may be loose and not allowing the intake valve to close properly.

I just recently repair a Ariens Zoom 34 where the exhaust was nearly worn completely round and the engine was running like your engine but the engine did not fail the leak down test; just very little movement of the exhaust rocker arm.
 
Baymee said:
Question. I don't know if this engine has a plastic cam but if it did, would the valve clearances at TDC always be correct like they are?
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StarTech found you have a normal steel camshaft. Forget about a plastic camshaft.

You might be 180 degrees out on your valves or a flat lobe as StarTech said.

slomo
 
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