K8 Two-wheeled tractor (rotary hoe)

[farmboy9]

I use a two-wheeled Kubota diesel rotary hoe for our veggie patch. K8 8.5 hp Kubota single cylinder diesel. (This is very similar to the current TVCS Kubota diesels).

I have a problem when the engine is hot and under load. Power fades and it struggles towards a stall until the load is taken off, then it speeds up and runs fine. Maybe once every twenty minutes, and after running for twenty minutes. I have cleaned the fuel tank, the filter, blown out the lines, dumped all the fuel and put in new but the problem has come back (it seemed better for an hour). I don't have a lot of money and would like to fix it myself. I have now put in a double-dose of Nulon injector cleaner. Clearly the injector or the pump is likely to be the problem. The engine doesn't make smoke, either starting or running, and my guess would be that it hasn't done two hundred hours in total. The oil is new and the air filter has been washed, dried, etc, looks good as new.

Can anyone help? I will be grateful for any suggestions.

 

[KennyV]

I’m not familiar with your engine but it sounds like a cooling system problem… You have pretty much cleared any fuel related problems. What type oil are you running in it?
If nothing else this should bump your question back up to the top and someone that knows your engine may have a better guess. KennyV.
PS. I see your new to this forum, welcome to the group…and post back with what you find…

 

[farmboy9]

Hi, KennyV,

thanks for the welcome to the forum.

I am no closer to a solution yet but I appreciate your suggestion about the cooling system. I had ignored that but I should change the coolant (I don't know that it has ever been changed) and check the operating temperature is about right. But how does one check the operating temperature? I have seen engines cooked and usually the burning oil and smoking hoses let you know that what is wrong (I have a sad smile of memory) when the engine stops working because the head gasket is burst. There isn't any smoking or obvious signs of heat but that isn't to say that the engine isn't too hot.

Any idea how I would tell whether the diesel engine is operating at normal temperature?

 

[KennyV]

The head, especially around the exhaust valve will be a good place to check… Under load the exhaust valve will get very hot… when the load is removed, fuel is reduced but air flow stays the same, so the exhaust valve and that space around it will cool quickly…
If there is any build up in the cooling system around the valves, you will have a problem with heat exchange… anything you can do to help dump the heat that builds up during a load, will help. Using synthetic oil will cut down on heat build-up…
If your coolant has not been changed you should do that and flush the system then use a quality antifreeze, it helps move heat better than water. KennyV.

 

[farmboy9]

Hi, KennyV,

thanks for that. I checked the engine, particularly the exhaust valve/ manifold area, under load and it didn't seem too hot. I bought some more coolant but I used the hoe for an hour before changing the coolant and while I was using it, the answer dawned on me. When the machine started to labour it was doing what it had been doing for the last hour, hoeing up and down in gear one (of six) on the speed and high speed on the tines. But this time I pulled up on the handles and I couldn't shift it, it was as if an elephant was sitting on it. Bingo. It turns out I had turned over the topsoil and got down to my heavy layer; the tines were now sticking into the heavy layer and with their shape, trying to pull the whole hoe underground. I adjusted the depth setter (which, I have to admit, in three years I have never touched, except to put the back wheel on the ground coming and going from the garage) and the poor unit stopped labouring. I feel a bit stupid -I did, after all, strip the fuel system down- but I am relieved that there isn't a problem.

Thanks for taking the time to try and help me.

 

[KennyV]

Well it’s good to hear you do not have any mechanical problems… and you got the chance to do some fuel and coolant changes…
sounds like you have some tough clay, where are you located? KennyV.

 

[farmboy9]

HI, KennyV,

I am 50kms north of Palmerston North in the North Island of New Zealand. We live on a stretch of farmland known locally as "the golden mile", the Kiwitea Loam soil is highly fertile former forest floor over a layer of clay and alluvial soil. One could grow anything here. We own a farmhouse, a six bedroom place the oldest parts of which are 100 years old, and a couple of hectares and are surrounded by a six square kilometre farm that belongs to a family of professional farmers (they own seventeen farms and milk 8000 cows) and I have our garden and the run of the rest of the farm. They also let me use ( in return for some work or other favours) their 80 and 100hP tractors so I won't be buying my own anytime soon.

 

[KennyV]

Small world… Isn’t this internet something. KennyV.