d4 pony running bad

[crazylegs]

The pony on my d4 used to run really good Idled great and ran superb and top end but I could never push the throttle in all the way because it would start missing.

Well it set for about six months and when I started it up it would not Idle right like it was missing on one cylinder. As you start pushing the throttle in it runs better and better and at full throttle it runs great but if you keep pushing it in it will start missing again till it just don't have the power to start the diesel.

has anyone run into this problem before if so what can I do to help it out.

thanks
Ben

[SJ]

From setting that length of time possibly the fuel system and carb. needs a good cleaning from the tank down and including the carb. Also might check the mag. to make sure it hasn,t got moisture in it and points set right and also that the plugs and wires are good.Might not hurt to change the wires if they are getting old and the plugs too. Don,t use resister wires or plugs but the old wire type wires.Many on here doesn,t recommend Champion plugs anymore for these older starting engines but I can,t remember which brand OM on here recommends.

[crazylegs]

I am sorry I was not thinking this morning when I posted this I should have went into detail on what I have done to try to correct this. I suspected plugs so I put new autolites in changed wires cleaned points inspected cap and rotor and visually checked mag. No help. removed and cleaned carb checked everything out reinstalled and set needle back to where they were. I started the engine and tried adjusting high speed air adjust needle but it did not seem to affect to much so I put it back were they were. I can not set the idle air adjust because it will not idle right so I did not mess with it. I am missing something and I don't know what right now.
thanks
ben

[SJ]

Try adjusting the high and low speed adjustment screws as they might not be right now from where they were set.Many times just a little adjustment makes a big difference in their running.

[Old Magnet]

If your not getting response to adjustments you still have a passage/port problem. Autolite 386 plugs are fine or the NGK A6.

Also check/reset float level.

[SJ]

I have rebuilt 100s of carbs. and to adjust the float I always put the float on the cover and turned the cover up in the air horizanilly float on top with float attached in place and then adjust it so it was parallel with the cover and they always worked perfect with that adjustment.

[crazylegs]

I will pull the carb back off hopefully next week and take another look at it they are pretty simple so I don't know how I could have missed a port but anything is possible. I am wanting to repair a couple of things in there anyway there is a fuel line that way broke and repaired with rubber and the exhaust manifold developed a hole in it that is going to have to be welded so maybe I will have time to fix those two things while I am in there. it is gonna be turning cold in a bit so I want this thing running good before that.

Turning the adjustment screws made it worse but never any better.

[bruce oz]

hello crazylegs,if the fuel line has been replaced with a rubber hose,make sure the inside is not being draw closed off ,if it not proper fuel line it may become soft or parted from the outer rubber ? ,bruce oz

[ol Grump]

You might do a search for rebuilding the carb. .there was a fairly extensive thread about that subject that included destructions for drilling out the plugs at the bottom of the float bowl and cleaning those passages. If those are plugged they affect both high speed and idle passages and you'll never get it running correctly.

[SSsssteamer]

Symptons of pony missing on one cylinder at an idle but hitting on both at higher RPM brings up these suggestions: Running too lean at an idle for combustion. (carburation?) Too low of compression at low speed for combustion. (Intake leaking to bad cylinder, poor rings, poor valves?) Points on the mag not set properly. (too close?). Old gasoline. Poor spark plug wires. Deffective condensor, coil, or possibly cracked mag cap. (carbon tracers?). Any other ideas?