More on that 23hp Vanguard in my skid steer

Bret4207 · Jul 8, 2019

Pulled the Nikki carb apart and cleaned it out. Not much to be seen in the way of dirt or grunge. Stuck it back on and the machine started right up. Moved it up near garage into my wifes parking space (mistake!!!) and let it run and get nice and warmed up. Fiddled around for 10 minutes or so and she died and went right back to the same semi backfire mode. I'm thinking bad ignition now. So I guess I'm going to have to pull the engine out. Got it moved to a better place with a tractor and the 420 crawler.

BTW- that Nikki carb is nowhere near as scary as it looks in the diagrams.

Mike M · Jul 8, 2019

Have you tried new spark plugs ? Years ago I worked on a guys lawn mower with a Briggs single cyl. It backfired out the carb. like one would think a stuck valve would do or a sheared flywheel key ? Turned out it just needed a new spark plug ! I have no idea how but something in that old plug must of been making it throw off the timing ? Sure a weird one to me.

4520BW · Jul 8, 2019

I have a Briggs and Scrapiron on a fertilizer pump that acted like that, so I added some Seafoam and now it run fine. Have to add the Seafoam every time I add gas.

Steve@Advance · Jul 8, 2019

Mike, I agree, replace the plugs just to say you did.

I wasted $100 and many hours frustration on a Kawasaki mower engine once, all it needed was a plug!

But as to why they will backfire like that, the plug was bad enough it wouldn't fire under compression, but would fire on the overlap stroke. Since the plug fires every time the magnet goes by the coil, it fires on overlap, and will set off residual gas in the cylinder when the intake valve is just starting to open, giving a pop out the intake and sometimes out the exhaust.

Geo-TH,In · Jul 8, 2019

Bret,
I seen bad plugs go bad after they warm up.
On a few occasions I've seen valve seats get hammered into the head. When it warms up, the valve doesn't
seat properly a few minutes after of run time. Check the valve clearance. Sometimes the valve clearance is
only .005 inch. on some briggs with OVH.
I've also seen ignition modules go bad after they warm up.

Then I've heard of and not seen Gremlins that you'll never find unless you're lucky.

Bret4207 · Jul 11, 2019

Thanks for the thoughts gentlemen. These were new NGK plugs or the correct designation, but I will likely try another set just to be sure.

More on that 23hp Vanguard in my skid steer

Bret4207

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Mike M

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4520BW

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Steve@Advance

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Geo-TH,In

Well-known Member

Bret4207

Well-known Member

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