74 JD 400 Dies

[davidjd400]

So I bought a 1974 JD 400 340cc sled and while it ran fine at first, after replacing the recoil I broke on the third try, I have noticed that the sled dies down a lot when the headlight is on. I do not know why this happens. It isn't equipped with a battery so it is powered by the engine running. Anyone have an idea?

[Liquifire84]

How low is the idle? It may need a slight bump up.

Brice

[davidjd400]

When the light is switched off the idle is around 3000 but when I turn the light on it drops to about 1300 and has turned off a couple times from going so low.

[400brian]

The lights shouldn't affect the idle at all.

[JDT]

Actually it is possible for the lighting curcuit to slow down an engine at idle.

I have seen this before and thought it not possible. But you learn something every day.

What would cause this is a very heavy load (probably a short) in the light curcuit that is only on when the headlight switch is on.

Time to look at the harness and headlight/taillight curcuit with a keen eye and an OHM meter.

[davidjd400]

Yes I did not think this was possible either but it's the only thing I can come up with. I figure there is a ground from the headlight wire somewhere but I haven't had time to trace it yet. Been working on getting it started since the plugs seem to foul out pretty fast.It runs for a bit then kind of just dies out. The person I purchased it from told me it was a 20:1 mix but this seems like a lot of oil and it does smoke a lot. Also should I use premium gas instead of regular unleaded? Just some things I read on other posts.

[JDT]

Bingo! Premium fuel and 40:1 ratio.