OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Old flathead stuck on compression stroke

Hey Guys,

I have an old flathead in a Greenfield that was starting and running fine (after a new solenoid) but now won't crank past the compression stroke.

Model: 28N707
Type: 1130-E1
Code: 0108092D

Between working and not working I replaced the blades which involved turning the motor by hand na lifting the mower.

So things I have done/observed:

Obviously cranks fine when no spark plug fitted, tested voltage drop on the starting circuit and the earth and it all looks good.
Tried jumping with a 640CCA battery that starts my ute with the same result.
Tried hitting the starter motor, think it cranked slightly better but could be wishful thinking.
At one stage the key got stuck there was a little pop through the carb and it started cranking well, stopped it tried again no good.

My thought is possibly starter motor, or a small engine dude who is coming to look at it thinks it might be a sticky/stuck valve bit I would have though that would cause low compression.

I can re power with a 13.5HP Briggs or 13HP Honda for less than $1000, or a chinese motor for $600

Should I try to fix or just get a new one?

Thanks Brains trust.

Phil.

Well I think you got an incorrect model number posted based the type and trim codes. It is either a 28M707-1130-E1 or it is 28N777-1130-E1.

First You don't never, never strike a permanent magnet starter motor. It is a sure way damaging the motor by breaking the magnets or knocking them loose. Plus that L-head engine not really all that old being that is a 2001 engine; although, might be depending on your age.

Now the starter may worn out brushes or bushing wise causing the starter to drag but as said beating on the motor is only going to damage it farther. THis thought is because the engine spins freely when the plug out so there shouldn't be a valve binding.

Now it could also be a worn camshaft lobe as the camshaft has automatic compression ramp or bump ground on one of the camshaft lobes.

AVB,
not sure how Phil can test if it is starter or worn cam compression ramp. If it is the cam ramp what are your thoughts on fitting a manual decomp valve in the head?

Thanks you gentlemen,

On closer inspection (the plate is very hard to read) it is probably a 28M707-1130-E1.

Oh and when I say hitting, it was more of a robust tap in frustration. As a fitter there is a modicum of mechanical sympathy.

A manual decomp is intriguing

Phil.

Well that can be problem for an individual but for a shop it shouldn't too much of a problem as the engine uses a fairly common Briggs starter and a known good could subbed temporarily for testing. Personally I would think it is more likely a starter problem but that is just experience here considering the engine is 19 yrs old.

Well that can be problem for an individual but for a shop it shouldn't too much of a problem as the engine uses a fairly common Briggs starter and a known good could subbed temporarily for testing. Personally I would think it is more likely a starter problem but that is just experience here considering the engine is 19 yrs old.

Not about a manual decompression valve, I suppose it would work but I have only seen them on chainsaws and old ATVs here.

This could also be a starter solenoid or wiring issue. if you use a thick screwdriver and short the terminals on the solenoid, will it crank? other thing you can do is jump from a good battery straight to the starter motor lug, see if it cranks then. failing that i would as suggested try another starter motor or pull yours apart and have a look at the commutator/brushes. if it still has a problem i would be checking the valve clearance (unlikely to be really wide on an L head though) as that will give you big compression

Thought I would give you an update.

I have a lawnmower dude come who didn't really shed any light on the issue, he suggested a possible bent pushrod which he has seen before.

Anyway needing a mower I bit the bullet and installed a 16 HP Jono & Johno engine (Locin) and she is trucking along.

However after the first proper mow of the yard I stopped and the starter motor was whirring away until I disconnected the batter, the solenoid was stuffed as I think the key had gotten stuck in the start position. New key and a new solenoid and away we go.

This also got me thinking that the original starter motor could be dead rather than the motor, anyway I now have a quieter, more efficient and more powerful engine. And something to play with when I have the time.

Thanks for your help,
Phil