question 420 cutting out

[ggfossen]

I've run my recently rebuilt 420 for about a week. Yesterday, it began cutting out under heavy load. Today was worse.

When at nearly full RPM, and when the govenor is forced to cut in because of heavy load, it cuts out almost to the point of dying. When the load is removed, it returns to normal running.

I'm wondering if maybe these things go through plugs? Timing? Fuel settings?

Any suggestiongs?

Gary

[Lavoy]

Double check that you are not having a fuel starvation issue. I fought a 420 for a long time, turned out there was pieces of tank liner in the sediment bowl passages. Barring that, sounds like you are too lean on the load jet, or float level too low.
Lavoy

[ggfossen]

Lavoy,

OK, I'll check it in the morning. I suspect the float bowl level is OK because it ran well, initially.

I could have some garbage in the line. It's been ejecting rust particals ever since I started moving it. I do have an inline filter, though, so nothing should have gotten into the carb. I will also get out the book and redo the carb settings.

Thanks,

Gary

[russ61]

Just something I did on my 1010 years ago.When I started having rust trouble in the tank,and no time to clean it properly,I stuck a big speaker magenet on the bottom of the tank to help hold some of the rust.Just put it away from the pick ups.Russ

[JimAnderson]

Gary,
I fought a 40c with a similar problem.Found trash in the inlet screen
at the carb fitting.At the time I didn't even know there was a screen there.
This screen is tucked into the fiitting and has little capacity for trash.
Just a thought.JimAnderson

[ggfossen]

Jim,

I've been running the old leaky sediment bowl (I have a new one from Lavoy) simply because it doesn't have the screen, and much garbage has been dropping from the tank. After it's run awhile with no apparent rust, I will go to the new unleaky one.

It has occurred to me, though, in my rather slow pondering, that the inline filter may be partially plugged. I will change that, too.

Today is a tinkering day. It rained so hard, last night, that I dare not cross the newly installed culvert. The muck and mire might put my tracks directly on the culvert, and I don't need that.

Might be time to become a snowbird.

Gary

[JimAnderson]

Gary,
I don't if your machine still has this screen but what I was refering to
is at the carb.The fuel line comes down from the tank into a right angle
fitting screwed into the carb body.Remove the line and unscrew the fitting
and there should be an inline filter less than the diameter of a pencil in
the fitting.Sometimes as old as these machines are someone has discarded this screen but if its in there you can bet it has caught some junk in it.JimAnderson

[JimAnderson]

Gary,
If you have access to the parts manual for your 420 you can see the
screen I am referring to in the parts breakdown.The manual calls this
part an elbow strainer assembly.The part number is 67-523.You can't
see this strainer without taking this fitting off the carb.If you have
one thats clogged there's nothing else you can do that will allow fuel
into the float bowl.I don't know for sure if your problems are from
fuel starvation or even if your carb still has this strainer but it is an
easy thing to checkout.JimAnderson

[ggfossen]

Jim,

No, it doesn't have the strainer at the carb. It doesn, though, have an inline filter between the sediment bowl, and the carb. That should provide better filtering than the screens, and may well be the culprit. I do have a spare, so I will install it, and see what happens. May not be able to put it to the test, though, until spring. The mud just got quite deep, and it's not fun anymore.

Gary

[lastchancegarage]

Gary,
I had a similar problem with my 310 case. It would start up fine and seemed to run fine until you needed real power. It had an inline auto type fuel filter when I bought it and it didn't appear to be clogged. However, after a week of having it die on me I took the carb off and opened it up. The entire bottom of the bowl where the fuel feed for the main jet was clogged with what looked like clay but was actually the very fine rust which made it past the screen inline filter. I assumed the rust got in there before the inline filter had been installed. After cleaning everything out and adjusting the carb again, the tractor ran fine and I replaced the filter to be on the safe side. Two months later it started all over again. Split the carb again to find the same rust buildup. I ended up putting an alternate fuel tank on until I can remove the top sheet metal on the tractor to have the tank sealed. I found the smallest particles of rust will pass through some filters and make their way into the carb. I guess I could have tried a paper type element but I'd probably just have to change the filter that much more often as it would clog up faster than the screen types. Rusty tanks are a pain. The prescreens and inline filters catch the larger particles but the very fine stuff becomes the gremlin. Hope this helps.

Scott

[ggfossen]

Scott,

The inline filter I think is a paper element. It's one of the cheap plastic ones. After I removed it, it was obviouls loaded with rust. That did not, however, fix the problem. I took the carb off, and thoroughly cleaned it. It was running well, but I don't know about under load. It was again raining hard, and turing dark. I may have a chance to try it tomorrow.

I don't know if the governor could cause that problem? I made no changes, and it ran well before, so I think not. I think I will pull the valve cover, tomorrow, to make sure that maybe one isn't sneaking closed.

Gary