Whats wrong with this Mower.

[Steve Webb]

Not mine, but a clients of mine, just got to have a look at it, been running worse and worse over the last couple of years and has had nothing done to it apart from a standard oil and filters service.

Seems to start fine from cold, but then runs rough as a bag of spanners and dies. It also seems to blow a lot of petrol out of the carb and down the exhaust.

When warm its a bitch to start.

I'm gonna try to find the gap settings for the rockers as they seem very very loose and I need to double check there is a good spark. But apart from that does anyone else have any ideas?

Oh and when I removed the rocker cover the oil in there had a fairly strong petrol smell, but that could be because all the petrol sloshing around in the combustion chamber has been washing down (along) the bores.

It does actually start eventually in the video.

Any advice before I get all rock star on its ass and drive it into the lake?


Mower_problems.3gp - YouTube

[1NRO]

Valve sealing problem?

Spark?

Fueling?

[Steve Webb]

Valve sealing problem?

This is where I'm thinking the problem is at the moment, the rocker arm design looks crap and the gap at the moment seems huge. I'm still looking for the specs on the engine (Its a Honda 20hp V-twin) so hopefully I can get them set to something approaching what they should be.

Spark?

Its got new plugs in, and they are fired directly from individual coils that are timed directly from the flywheel. Will check they are both firing tomorrow.

Fueling?

Carb has been cleaned out, fuel puffing out of spark plug hole when engine turned over with plugs removed. This one seems fine.

I'm popping by the mower tomorrow morning so will have to wait and see.

[Steve Webb]

Well it looks like the mower is sorted now.

The rocker arm gaps were well out, Inlet was .25mm instead of .15 and exhaust was .3 instead of .2mm.
The gap from the flywheel to ignition coils was also way larger than the 0.1mm it should have been.

Compression on both cylinders was about 75psi. Not sure what it should be, but they were both the same so thats good enough for me.

Checked on spark after resetting the coil gap, could see spark on one cylinder but not the other. Not sure of this was a grounding issue (engine shielding in the way so tricky to ground the plug on the block) or the bright sunlight.

Anyways, put it all back together and it fired up and ran fine so I'm happy for now.