420 running problem

[theshanmand1!]

hello my friends,

I have been trying to get my 58, 420 running for a while now, I just tore down the carb for the third time and rebuilt it. new float, needle & seat, bushings, seals, etc. put it back on, fired it up, she ran like a dream for 5 minutes, then as the temp was nearing the thermostat opening point it started surging & backfiring until it finally died
I know last time you guys suggested that I do a compression check, and intake leak check, and timing check... but would it run like it did for five minutes if it had one of those problems ?
now I cant get it to even run for 30 seconds, popping and surging til it dies.

I have checked the resistor ballast for continuity, its good, and the coil also.
I am at a loss for my next step of the process of elimination.

any suggestions would be greatly appreciated.

[DukeofDeere]

Check for fuel flow at the carb and work your way back to the tank.
Where the fuel line attaches to the carb the is usually a screen in the elbow. It may be loaded.

Duke

[gregjo1948]

As it warms up, things begin to expand. It ran good for 5 minutes and possibly the intake has a crack that openned up causing the wrong air/fuel mixture. If that's the case, the openning may have stayed apart and now will barely even run. have you installed a new condenser? gregjo1948

[theshanmand1!]

Brake cleaned & blew out with compressed air the fuel line elbow screen
that threads into carb, as i was reassembling the carb on this last tear down.
I am going to try the old starting fluid trick, turn it over & spray either on the intake gasket, if it fires, we have found the problem.
Yes i have replaced "all"ignition parts. However, i am going to put the old points & condenser back in just to see if there is a difference. I also am going to install a inline fuel filter.
Thanks guys, keep giving me all the ideas you can think of, we will fugure it out eventually

[Tigerhaze]

I can't remember if it is you or another gentleman posting that has been having M-S carb troubles also but I had made the suggestion of checking both the ignition switch and the insulators on the distributor housing for the primary coil wire to the points (the small wire to the housing, not the coil to distributor spark plug wire). I had the same issue on my 8N tractor of running fine until it warmed up and then cutting out, and discovered these were weak spots in my ignition circuit.

It's not to say that the intake cracking issue isn't the cause, but it is easy enough to check these two items and replace if needed.

[theshanmand1!]

Thanks tigerhaze,
I will put the old one back on and see if it changes anything.

[Tigerhaze]

Thanks tigerhaze,
I will put the old one back on and see if it changes anything.

Are you talking about switching back the old points/condenser? Changing the points/condenser won't affect damaged insulator bushings or a bad ignition switch. See the referenced thread below that has the parts catalog key numbers (my post in the second page of the thread):

http://www.jdcrawlers.com/messageboard/ ... c&start=15

I saw that the previous 420 discussions were with a different person, so attaching it below may be helpful for you also. Again it still may be an air leak issue as Greg described, as surging and backfiring often are a result of air/fuel mixture issues but can also result from intermittent electrical issues in the ignition. Using a spark tester on each plug wire boot can help pinpoint weak or intermittent spark as well.

[theshanmand1!]

hello men.

since my last post I found that my condenser spade end was touching the bottom plate of the distributor where it attaches to the bushing that goes through the side of the distributor. could that ground have fried my condenser?
also, I cleaned up around the intake & sprayed starting fluid all around the gasket area, hit the starter & no start.

forgot to take the positive batt. cable off & came back the next day and battery completely dead, that's twice it has happened.

pulled the carb, one more time to check & re-check, everything checked out, reinstalled, tried to fire up, nothing , not even a pop.
pulled spark plugs, completely gas soaked/fouled.

now when we re-wired the crawler, re-wire as in wired with new wire because the old wire was cracked and broken. we wired it according to the wiring diagram on yesterdays tractor, 12 volt conversion. as it already was converted to a 12 volt system.

help

[whiteclipse16]

Sounds like a spark issue to me.
Why is the battery going dead if you don't take the positive post off? This doesn't sound correct and could be your problem. If something isn't shutting off it could be burning your points up, hence no spark and no run.
When you rewired, did you put a ballast resistor in for the coil. If not you could be giving it 12V and burning that up.

[theshanmand1!]

Good morning,
Ben, yes i agree, and yes ballast resistor is wired as per the schematic on yesterdays tractor web, 12 volt conversion wiring diagram. Very basic , no lights etc. i am going to change out the condenser, as it might be fried from grounding out. Also i put a new two post key switch in from stiene.
Going to pull the gm single wire alt. off and have it tested, i heard it could be malfunctioning and drawing from the batt.
Thanks again for your helpfull insight guys

[Stan Disbrow]

Hi,

Yes, you need to find the constant load and fix it. If it the ignition circuit staying live, you might burn up the coil primary section of the winding. That would kill the spark for sure.

The grounding of the condenser lug would not harm the condenser, but would keep it from sparking.

I would get new plugs, then leave them out of the cylinders and lay them on the head so I could see the business ends when cranking over. You know, see if they actually spark or not.

Stan

[theshanmand1!]

Hi stan,
Thank you, i will do that, could the alt be draining the battery with the key in the off position? Or could it be a bad key switch?

[DukeofDeere]

Could be both.
When you disconnect the battery you may see a spark at the cable end to the battery. Disconnect the alt and check for spark at the battery again.

Duke

[theshanmand1!]

Ok Duke, i will try that before i remove the alt. for testing
The key switch that i ordered from steiner is the two flat spade, two position, on/off. Said it would fit 420 jd
If there is a better one out there let me know i will pick it up.
Thanks for your help Duke.

[theshanmand1!]

hello men,

I removed the alternator this morn, took it in to napa and they tested it, it is toast! they also said it is not a single wire internal regulator alt. I almost don't want to hear what I have burned up running it this way without a regulator more learning the hard way! I am going to order a new one from Steiner, new plugs, a heavier duty key switch &
wire it again. also I will re-check my ballast resistor for ohms and my coil
for the correct range of ohms.

hmm.... what else? oh yes, load test my battery to see if its toast also.

how bout it boy's, think she might run? hope so...

thanks again for all of your helpful input, I am learning however so slowly.