John deere 70 LP extremely hot exhaust

Dereck Borders · Dec 2, 2009

I have a friend who has a 70 lp JD. He asked me to look at it during the Thanksgiving weekend. A couple of weeks ago according to him it backfired a couple of times and then seemed to lose a bit of power. Now the exhaust turns cherry red after just a couple of minutes run time. Tractor starts right up and is not missing but has a different sound to the exhaust. I pulled plug wires off individually while it was running to verify it was not missing. I seem to think lp gas is being burned in the exhaust but have never run across this before and don't really have an idea. We also pulled the valve cover and everything there seems to be working as it is supposed to. Anybody got any thoughts? Any help is appreciated.

Anonymous-0 · Dec 2, 2009

A broken baffle or other exhaust component causing excessive back pressure can light things up.

Michael Soldan · Dec 2, 2009

.could be timing..its firing early before the valve is closed, firing into the exhaust

plow hand · Dec 2, 2009

Hey BuickDeere this is one for you..

ScottyHOMeY · Dec 2, 2009

Good chance he busted a tooth in the gear train or in the distributor and jumped and retarded his timing. With the timing retarded sufficiently, the fuel isn't finished burning when the exhaust valve opens. Less power and hotter running, with fuel burning in the head and exhaust.

Jon Hagen · Dec 2, 2009

Nothing will turn the exhaust system red hot faster than late ignition timing.

I would inspect the point gap and distributor advance weights to see if something is stuck or broken.
If the advance mechinism is free and working, you should be able to grab the rotor and rotate it in the direction of normal rotation, about 10-15 degrees against spring pressure.
when you release the rotor, it should snap back to the original retarded position.

teddy52food · Dec 2, 2009

Please explain that one!

buickanddeere · Dec 2, 2009

John Hagen beat me too it with the late timing.
The other possibility is a lean mixture.Low regulator pressure or something out of calibration with the funky LP metering rod system in the carb.

Owen Aaland · Dec 3, 2009

Either too rich or too lean can cause excess exhaust temperature on LP engines.

With LP it is much more important than with gasoline to have the correct mixture since going either too lean or too rich slow the burn rate of the fuel in the cylinders so that the fuel mixture will still be burning when the exhaust valves open.

John deere 70 LP extremely hot exhaust

Dereck Borders

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Anonymous-0

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Michael Soldan

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plow hand

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ScottyHOMeY

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Jon Hagen

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teddy52food

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buickanddeere

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Owen Aaland

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