Engine loosing power under load

[PeterJones]

Hi,

I have a Scag Cheetah with a 29HP Briggs Stratton Professional Series engine. I was cutting grass a couple of weeks ago the engine became rough as. I powered down and towed it back to the workshop.

Eventually I had the covers off the motor and noticed an electrical wire to the base of one of the armatures had come adrift. I refitted the wire and the engine started ok and seemed fine however, when I started cutting again, the engine basically died (nearly stalling) when it hit long grass, grass that it would normally cut with ease. Anyway back to the workshop and a closer inspection of the armatures revealed a crack in one. In the hope this was the problem I bought and fitted two new armatures and set the air gap at .25mm. Tested the mower and no change, i.e. engine runs ok but seems to have very little power.

Any clues as to what may be going on.

Cheers, Peter

 

[ILENGINE]

I would start by making sure you have spark on both spark plugs. If that checks out then remove the valve covers and make sure all 4 push rods are in place and not bent, or in the case of the Intek style engines that one hasn't migrated into the engine crankcase via the oil drainback hole in the block.

 

[PeterJones]

Thanks for the info. Spark plugs are fine so I'll get to the valves tomorrow. Hopefully its not too big a job.

Cheers, Peter

 

[mcdonell]

Could be the amount or quality of fuel. Sometimes we get clues and focus only in that area. You might try a new fuel filter and some fresh gas.

I would also check the engine temp while it is running. Poor piston cylinder lubrication can cause the lack of power too.

Good luck.

 

[PeterJones]

Thanks for the replies, I'm afraid my news is grim.

Before looking at the valves I decided to change plugs and fuel filter. The engine started ok and I made my way to the grass to see if the engine still lost power under load and then there was a very loud mechanical bang!

Off with the engine covers and confirmed it had siezed. So maybe the problem started life as a bent valve but it ended with a seized engine.

Currently waiting for a new engine and hopefully back in work next week. I'm not too sad about the outcome - from day one this engine had leaked oil from the sump gasket which was repaired under warrenty. Then is started leaking again and I had it repaired at my expense and it still leaked. Didn't bother after that - I just kept adding oil as needed. Hopefully the replacement will be better.

Cheers, Peter