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JD 755 rebuild to rebuilt
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I have newly rebuilt John deere 755 it has a 20hp diesel yanmar in it. It sounds great and runs good but it smokes a little even when warmed up. its a lighter gray/blue smoke like oil. The manual says it should smoke when cold. This is the first diesel I have actually owned myself. I have been around my share but none this small. I have probly less then 8hrs on it since the rebuild.

Should I stop worrying? Or what should I look for? Thanks for the help.
 

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Try running it on kerosene. If the smoke is reduced, you have a fuel system/injector/timing problem. If it is not reduced, it could be burning lube oil.
 

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Try running it on kerosene. If the smoke is reduced, you have a fuel system/injector/timing problem.
Interesting suggestion. First, let me begin by stating that I am not questioning your recommendation or knowledge. I am a curious guy and like to understand not just what works but also why. Can you explain the reason this technique may work? Does running kerosene create a lean effect? Are there detrimental effects to running kerosene for short or long periods?

JN
 

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Kerosene is lighter and cleaner burning. It also contains less energy. Try running a low pressure atomizing space heater on kero and then diesel fuel, you'll see the difference. The diesel fuel will have a distinct odor, and may be harder to ignite. I would use this as a troubleshooting aid only, not as a steady diet, as it may not have the necessary lubricity for continued use.
 

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Try running it on kerosene. If the smoke is reduced, you have a fuel system/injector/timing problem. If it is not reduced, it could be burning lube oil.
Are you suggesting he empties the tank then fills with kerosene or making a 50/50 mixture? I'm just asking so he knows what route to take...:thThumbsU
 

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Are you running it at high rpm's or just idling it? If you're just idling it, try bringing up the rpm's to at or near the governor maximum and working it for a while. Diesel's don't really like to idle. They run better when they're worked hard.
 

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I would say straight kero, as its effect, if any, will be more pronounced than a 50/50 mixture. You don't necessarily have to drain the tank, just run the machine off another fuel supply and let the return flow go to the main fuel tank. Another characteristic of a fuel system problem is that the exhaust will burn your eyes. Oil consumption will not tend to do that, but you can smell it.
 
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