Ride on mower slows

[jblessing]

My belt-drive mountfield 1430 ride on mower has recently developed this fault:

As my normal practice, I put it in top gear and it pulls away fine, but after a minute or two it seems to lose torque (the engine is still producing plenty of power), so much so that it slows to a halt on the first bit of difficult going, and I have to drop back to 3rd gear to keep moving.

The belt tension looks fine. I'm wondering if perhaps I have been over-exuberant in my recent lubrication and gotten some spray-on grease on it (although the belt doesn't feel greasy).

Any ideas?

 

[munchingB]

quite possibly its a fault with your governor spring and the engine isnt powering through when under load. the governor adjusts the throttle according to the load and if the governor(a spring) is weak then it wont adjust the revs automatically when needed.

take the spring and bend one end of it in a manner that will shorten it. put it back on and try it out and buy a new spring if that is the cause.

 

[Burnerman]

That does sound like a reasonable diagnosis but of course the same effect occurs if the belt is too slack.
Is the belt a good 'Vee' shape, so it fits in the pulleys? The top edges mustn't be rounded or the belt too thin.
If the belt is a 'double vee' in other words it has to drive on both flanks, a genuine Mountfield replacement is essential.
Next thing, check that any belt tensioners aren't at their maximum extension, preventing the belt from being tightened anymore.
Please be sitting down when you price up a new belt if you need one
John

 

[jblessing]

MunchingB: Where would I find the governor? Is it near the throttle linkage?

 

[kbdiy]

Whilst the governor theory could well be correct I would be inclined to thoroughly investigate the obvious first - being the belt tension and the fact that you have been spraying grease around. Quite easy for the grease to have contaminated the belt or coated the pulleys sufficiently to cause the problem. Eliminate that then work on the governor I would suggest.

 

[Burnerman]

This motor (usually a Briggs 13.5 hp side valve, but others have been fitted) has a flat out speed of around 3200 RPM, governed, no load. With the blades connected and in drive, the governor should maintain this, and you can tell if the engine starts to slow down......does it appear to be doing this?
Its unusual for the governor to need adjusting if its been left alone.
John

 

[jblessing]

No, the engine maintains its revs so I guess it must be down to the belt - greasy or worn. I have a can of degreaser spray - probably some nasty solvent - would it be ok on the drive belt?

 

[Burnerman]

There are proprietary spray solvents for belts, but I'd give yours a go.....chances are, a new belt will cure your woes.
Maybe the Vee of the belt is touching the bottom of the pulley?
Also look for any visible fibre strands on the side of the belt.
John

 

[Mursal]

Can be hard to get a replacement belt for some of those decks with the correct profile, unless you get the genuine one.

1/2" original profile and the 13mm replacement is just that bit to big

They can be expensive

Tensioner working OK, not at the end of its travel?

 

[munchingB]

the governor spring is the longest wobbliest spring that looks like it has been made from a spiders leg. on the long straight end with the paper clip fold give it a bend so that it 5 mm shorter.

obviously as the other replies have said it might well be a slipping belt but upping the revs-or putting back up to normal is well worth a quick go and is completely reversible if you have no result.

id try running it without the air filter also as a blocked filter will stop your engine running completely and yours might well be on its way out.

even a dirty carb could be the cause of your symptoms with the engine underload pulling in more dirt than normal.

if the belt runs ok then try without the air filter, then tweek the governor, try cleaning the carb...and if all that fails check if you have any oil on the plug and in the combustion chamber as worse case scenario is going to be a piston ring or bore failure and a lack of usable compression.

 

[jblessing]

Thanks for all the replies, I'll probably get a chance to look at it over the weekend and try your suggestions.

 

[jblessing]

After using it several times this weekend, it has gradually improved and is pretty much back to normal, so I think it must have been grease on the belt. Thanks for all your ideas though.

 

[Burnerman]

That'll do nicely......!
Keep the idler pulley on the deck tight and it will reduce the noise from the deck, I've found.
John