4 Strike Engine Refuses to Start

Looks like you are making some progress, let's see after setting the valves properly.
 
Well, I was prepared for my first road tests this morning. Thoroughly inspected my carb (float bowl gasket is a bit off) but overall looks great.

Removed the valve cover and, with feeler gauges, I set the intake clearance at .005 and the exhaust at .007. Perfect.

Still no start. Can’t even get a start with starter fluid. It makes no sense.

I dug out my spark tester. Again, touching the block and pull starting I see good spark. BUT, the spark tester shows very weak spark! Tomorrow I’ll check my magneto gap (should be .012) and see if I get better spark. This would explain everything. Just a few minutes ago I ordered a replacement magneto.
 
After several checks and fixes, I still cannot get the engine to start. So frustrating.

Kill switch disconnected.

As for my spark, my plug gap was only .019 - I regapped to .030.

Valve clearances set to spec.

Removed magneto and tested it on my multimeter. 4.6 ohms - right where it should be. There was ZERO clearance between the armature and the magnet. I set the clearance to .011.

I see spark on every pull with plug removed. Plug tester shows about 17kVolts, much lower than what I am used to seeing on China motor CDIs.

I ordered another magneto just in case.

On removal, plug looks dry. My carb is good, with excellent throttle slide movement. Good suction on intake.

The closest it comes to running seems to be with throttle wide open and no choke. I know that compression can suppress good spark but the engine feels right, and sounds right, when pulled. It’s popping one or twice, then dead. I can smell a faint stink of combustion fumes.

If I replace the magneto with new and get the same result, I don’t know what I’ll do.
 
My 3hp flathead briggs is giving problems too it’s on a rupp minibike. Ran fine when I first got it but then refused to run, it has an updraft carb I cleaned it out it back on and zilch. Motor is 30 years old but like I said it was running.
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After several checks and fixes, I still cannot get the engine to start. So frustrating.

Kill switch disconnected.

As for my spark, my plug gap was only .019 - I regapped to .030.

Valve clearances set to spec.

Removed magneto and tested it on my multimeter. 4.6 ohms - right where it should be. There was ZERO clearance between the armature and the magnet. I set the clearance to .011.

I see spark on every pull with plug removed. Plug tester shows about 17kVolts, much lower than what I am used to seeing on China motor CDIs.

I ordered another magneto just in case.

On removal, plug looks dry. My carb is good, with excellent throttle slide movement. Good suction on intake.

The closest it comes to running seems to be with throttle wide open and no choke. I know that compression can suppress good spark but the engine feels right, and sounds right, when pulled. It’s popping one or twice, then dead. I can smell a faint stink of combustion fumes.

If I replace the magneto with new and get the same result, I don’t know what I’ll do.
I know that sounds silly... but did you check for cracks on the cylinder? any kind of leak on it?
 
Well, I was prepared for my first road tests this morning. Thoroughly inspected my carb (float bowl gasket is a bit off) but overall looks great.

Removed the valve cover and, with feeler gauges, I set the intake clearance at .005 and the exhaust at .007. Perfect.

Still no start. Can’t even get a start with starter fluid. It makes no sense.

I dug out my spark tester. Again, touching the block and pull starting I see good spark. BUT, the spark tester shows very weak spark! Tomorrow I’ll check my magneto gap (should be .012) and see if I get better spark. This would explain everything. Just a few minutes ago I ordered a replacement magneto.
Isn't the mag gap suppose to be 20, we used to take a match book cover or a 3 x 5 recipe card and set the gap. Have you also checked the flywheel key? ............Curt
 
Is this the original carb?

Between at first only starting with starting fluid, and now plug being dry after many failed starts, it leads me directly to the carb. Should have been flooding out if you were pulling it like crazy trying to start it.

Pull the bowl on the carb and see if its dry - you may have a stuck float or seat needle that is blocking fuel.
 
Thanks to all for the suggestions. Had to do a brake job on my car last night so I’ll be back at this problem this evening. Very helpful!
 
In my mind, if it won't start on starter fluid then its not a fuel problem. Unless maybe its flooded already. I'd dry out the carb and cylinder, then try running it on starter fluid with out the fuel even hooked up to the carb. If that doesn't make it fire for a few seconds then I would stop thinking about fuel problems. Perhaps get a compression tester and check that. Sounds like you do your own car work too, a compression tester is a worthy investment.
 
Well, I was prepared for my first road tests this morning. Thoroughly inspected my carb (float bowl gasket is a bit off) but overall looks great.

Removed the valve cover and, with feeler gauges, I set the intake clearance at .005 and the exhaust at .007. Perfect.

Still no start. Can’t even get a start with starter fluid. It makes no sense.

I dug out my spark tester. Again, touching the block and pull starting I see good spark. BUT, the spark tester shows very weak spark! Tomorrow I’ll check my magneto gap (should be .012) and see if I get better spark. This would explain everything. Just a few minutes ago I ordered a replacement magneto.
Reading over again i think the valves should be .007 and exhaust should be .009, that's a fairly old engine. The old cast iron blocks was .008 and .0010. You may have to pull the flywheel and change the points, and condenser, points should be .0020
 
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