# 3.5 HP Briggs Engine Surging



## techymechy (May 3, 2013)

I'm new to these engines, so please be patient with my question....

I purchased a used McLane Edger with a 3.5 HP B&S engine. The edger seemed to run OK at the guys house and seemed to have descent power under load. When I got it home, I had a devil of a time starting it and when it did run, it misfired more than normal and the govener seemed to hunt a lot, especially at high rpm's. I drained the gas tank and installed a new spark plug. I did not gap the plug. The engine is running a whole lot better but the govener still seems to hunt, mostly on unloaded running at high RPMs and it still seems to back fire more than I would like. I held the throttle shaft and the engine ran smooth and quit back firing. I think that the engine will back fire from the govener hunting. The engine seems to have enough power to stall the McLane 9" blade and slip on the belt. The belt seems to have the right amount of tension. The engine seems to hunt less when under load.

The engine is a L head 094202-0117-E1. It was made in 1999.

OK....Questions and observations:
1. Is hunting and back firing expected on this engine at high RPMs and no load?
2. I shut the engine off when it was warm. I could not get it restarted, but I'll I can start under full choke and throttle 1/2 it when it's cold.
3. The guy I bought it from said that he had stale 10% ethanol gas in the engine, but he took it to the shop and they fixed it. I think that he tried to fix it. He had put this "TruFuel" in it with TF3 additive package. The stuff comes in 32oz cans.
4. When I drained the gas, the gas tank had some varnish in it, but it generally looked pretty clean (no particles).
5. I've had conflicting information on the plug gap. The manual says 0.030", but the guy at the local shop said 0.025". I have installed the Champion RJ19LM spark plug.

What should I do to stop the hunting and back firing? I haven't changed the oil yet, but I doubt it would have any effect. Should I regap the plug for .025"? 

Thanks for your help.

Dave


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## techymechy (May 3, 2013)

Looking at the engine a little closer....

I read that hunting was due to an air leak somewhere.

The jet pilot was screwed in tight. I unscrewed it and it looks clean. The carb looks clean down the throat by the choke. I checked the bolts that tighten the carb to the main block - they seem tight. 

The engine just hunts or surges. I don't know...it just isn't acceptable for me. 

Is the jet pilot the same thing as a needle valve? I read somewhere that you should start at 1 1/4 turns on the needle valve and then adjust it just until the engine rpm starts to go lower.

I'd really like to figure this out myself....I sure appreciate some help.

Dave


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