OutdoorKing Repair Forum Forums Repairs and Maintenance Question on Digging Equipment Trenching Machines Dingo

Not sure if this in the right spot but best spot I could find.Dingo with a Kohler twin motor is fouling one spark plug. What is strange is the way it is fouling the plug. The end ring of the plug is very clean, almost as new but in the core of the plug it is full of carbon. Can't say I have ever seen a plug like this, if it is going to carbon up the plug will usually be black. Motor has very slight smoke from the exhaust, no more that I would expect,not sure if a fuel or oil problem. First pic is looking directly into the end of the plug. Any thoughts?

G'day Norm,

Looks like that plug is running too cold - i.e. the centre electrode isn't getting hot enough to burn off the carbon deposits. As it should do.

This can be due to two things; most likely is a manufacturing fault in the plug - the other is that that plug is the wrong 'heat range' for that engine.

As you'd know, if it was just that one cylinder is burning oil, the complete end of the plug would be covered in deposits.

Hi Gadge,
That seems like it could be the problem and then as soon as I pull out an NGK plug it always puts doubts in my head. It is the correct plug for the motor. I have never really studied plugs to the point of the heat range numbers on the plug and how they rate the numbers between different brands. This plug is a BKR5E and the Champion is a XC12YC so do you think the Champion might be a hotter plug going by the numbers? As for it being a faulty plug apparently this plug was recently replaced for the same reason, so I am expecting it to come back with the same problem shortly. This could also be an ongoing NGK problem so the next thing is to change brands and see how that performs

We always used bkr's in kohlers and vanguards, never really had a drama. Did you do a compression or leak down test? That usually finds any mechanical problems with twins.

Also is it a single throat or dual throat carb? The dual throats could have a tendency to run rich or lean one side. Single throat carbs could also run rich one side if there is an air leak in the manifold.

And here I thought Norm has gone from possum problems to Dingo problems. Oh well not the case.

Hi Nath,
I didn't get time to do anything except change the plug he brought, he wouldn't have had a plug spanner he could get in there, as you know motors are produced, plonked in some machine with little thought to servicing without special tools. He said he would bring it back for me to go over after he finished the job he was doing.
Hi AVB.
Possums are still a bit of a problem but greatly reduced and no I don't want a Dingo to chase them away

G'day Norm,
Nope, they'll be the same heat range - the plug makers all use different systems, for their heat range designation. For NGK's, lower number = hotter plug.
I'd think it unlikely - I've had much better experiences all round with NGK and Nippondenso plugs, in comparison with Champions.
Bosch plugs have been good too, except in LPG fuelled cars.

As nath says, it would be well worth having a look over the fuel system - I do know that uneven mixture distribution is a pretty common issue with any multi-cylinder engine that uses a single fuel metering device.
Whether that be a carby, or a single-point fuel injection system, such as the low-end EA Falcon 3.2 and 3.9L I6's had.