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John Deere 400 - Lack of Power

4895 Views 9 Replies 4 Participants Last post by  Sandpiper
Hi Guys,

We are helping our Uncle out with his 1982 John Deere 400. It runs and drives fine but when the mower deck is engaged and starting to cut grass it lacks of power and you have to crawl through the lawn so it won't die. Any help is greatly appreciated.

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I had that problem on my 400 it ended up being the points where out of adjustment a little. Also check the carb might have a little dirt in it I've also had that happen and the problem was the same as yours.

That will be a start. He is currently out of town now for work but I think he is bringing it over so I'll take a look at it.


Make sure it is firing on both cylinders. Those opposed twins will run on 1 cylinder, even if a rod is broken. Saw one come in to the dealer with a "low power" complaint and the rod on one side was broke, and had been for a while from the look of the bore once the head was removed.

A simple test of removing both spark plugs and feeling for air will tell you if both pistons are moving.

Could also be valve related on one cylinder.
I second Scott on the points, that's the only issue I have had for power on my 400. You can have your main jet screw out by a mile and they still run decent, but points off or slightly corroded, feels like a 3.5hp briggs under the hood. Plugs are key too, but bad plugs seem to causes 'popping' under heavy load and hard starting when hot.

Sorry, meant to say "Scott, I second Mark on the points"

The plugs have been already changed to Champion H10's(I think thats what JD recommened). We will adjust those points. What are the points set to on this motor? Also does Kohler have a service manual posted online as they do for the K181-? Can't seem to find one. We will be trouble shooting once it is here.

Thanks Again,


The points are .020 if it's like mine it will have to be exact or it runs bad.

Scott, as Mark said, 0.020. If you must err, err fat. They are ignorant to set. Once you think you're at 20, leave the feelers in the gap and rotate the engine by hand to make sure you are at the widest opening. If you're not, the feelers will fall out when it gets there and you'll need to re-adjust.

Really tricky spot! As for the manual, I think someone here said before it is, but I have a paper copy of it and the 400's so I have never looked online. (try for a K582, seems to me I have seen it and apart from displacement, is the same beast).

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