ride on mower engine issues

[Jonnym_here]

Hello all

I have an Atco gt130m I got it recently from an estate of a chap who had passed away.

The engine, a Briggs and Stratton 3130 powerbuilt is making me want to treat it to a petrol and match bath.

First the engine has too much compression, I've already replaced the starter from my other ride on and I'm spinning it using a heavy duty jumper direct to the starter from an old but good and then a new car battery.

It's not hydrolocked, the oil is the right level, dry plug and fuel is disconnected.

I checked and adjusted the valves to 5 and 6 thou.

I treated it to a new cam shaft as I assumed the pressure release mechanism had fallen off, as that's what they tend to do. But no it was all OK and working fine.

When I first changed the cam shaft it did spin up once or twice but I still need to block the air intake just to get it spinning. I did confirm good spark.

I didn't replace the valves as they looked good, that's my next move.

Anything I've missed before I give it a viking funeral?

thanks all for any help
Jon

[Metric Max]

can you spin it over Ok with the spark plug out?
I don't think there is such a thing as an engine with too much compression.
It sounds like your starter is weak, either knackered or bad connections, maybe earth?
With the plug out and the piston not at the top of it's stroke squirt a little carb cleaner/ easy start/ petrol down the plug hole. Replace the plug and try it, you should get at least a cough from it.
Most unlikely that the valves have suddenly decided to cause a problem. In all likelyhood its the Ethanol in the petrol causing blockages in the carb. With any of these small engines that are going to be left for more than a few weeks run them dry first

[jb2410]

When setting the valves, did you have the piston at slightly past rather than at tdc?

Just checking as on my ride on I was told the was a fault with the compression release, but the valves had been set incorrectly as they needed to be done with the piston at about a quarter inch beyond tdc for the compression release to work.

I reset them myself and it fired straight up.

[Metric Max]

Just noticed that the OP has replaced the camshft which makes me wonder whether he got the valve timing correct. If its wrong various things might happen including the piston hitting the valves

[Jonnym_here]

The starter is fine as I've swapped it for the one off my other ride on so known to be good, infact the original one is still staring my other engine no problem, the bigger puzzle is on my three available 12hp single Briggs and Stratton engines the one which isn't working is not the hardest to spin by hand.

The earth straight to engine and live straight to starter so not a connection issue. The timing is perfect, this is not the first small engine I've rebuilt, and very hard to get the timing wrong.

Yes I set the valve clearances just after top dead centre, good catch as not to many people know that.

The engine turns over fine with no spark plug in there.

Finally the valves, I do agree unlikely to just go wrong but nobody can remember the mower being run as the chap had died and the garden had returned back to nature. So it may have been parked up due to an issue. I'm clutching at straws a little as I've never had this kind of trouble with any of my engines, and I've worked on a quite a few.

Thanks all
Jon

Edited by Jonnym_here on Friday 28th March 18:52

[richhead]

Are you sure the carb is working properly? that would be where i would look first, is it sparking at the right time? there cant be too much compression if the valve timing is good, and the exhaust isnt blocked, why did you change the camshaft?
Those sort of engines are very simple, just remember a 4 stroke is a very simple thing, suck squeeze bang blow, but they all have to be at the right time.

[Jonnym_here]

I changed the cam shaft as these engines have a decompression mechanism on the camshaft. They are held together with good luck and a prayer. You mostly find them in the oil pan. It makes the exhaust valve just pop up a millimeter to allows the engine to loose compression when turning over on the starter, then as the engine spins up it flattens out. Usually this kind of issue is caused by this missing, or hydro locked engine, after you have ruled out all the simple stuff.

The decompression mechanism wasn't missing on the original camshaft, but I suspected it could be a weak spring so swapped it. It had no effect and made no difference. I usually remove the oil pan anyway on these to clear out the smoo, as these engines loves to collect it there.

As I said I've rarely been beaten, but this one is kicking my arse.

Thanks again
Jon

Edited by Jonnym_here on Friday 28th March 21:03

[Jonnym_here]

I've had the carb off and it's working OK, but that shouldn't prevent the engine spinning up. I haven't checked the exhaust yet. I will take it off in the morning and fire her up. Good idea.

Edited by Jonnym_here on Saturday 29th March 11:46

[Jonnym_here]

Here is an image on the decompression release

[Jonnym_here]

richhead said:

there cant be too much compression if the valve timing is good, and the exhaust isnt blocked

The exhaust isn't blocked unfortunately. There is too much compression for the starter as explained above. Next new valves, as I have them. Then I will confirm the new cam is still in tolerance as I've read about them insta failing, but it's unlikely, then head off I guess.

[oakdale]

Does the starter motor turn it over with the spark plug fitted but not connected?

[Jonnym_here]

No the plug is currently disconnected and the same issue
I've got the engine out on my bench currently.

I'm back to the original can shaft now I stripped it just to check the timing marks etc. My current thinking is it might be the piston rings leaking oil. I'm going to take the head off later

Or I have an old car starter which I may be able to Frankenstein in to it .

[Jonnym_here]

Thinking about it I'm going close up the valve clearances to lower than tolerance to make sure the compression release is working. And there isn't something too worn.

Then I must do something for mother's day. Apparently staying out the way isn't a good enough present .