Jubilee backfires and runs like crap when you try to throttle it up

[Allischalmersdude]

Did a carb rebuild, tune up, fuel tank replacement and ended up putting an Atlantic distributor in a Jubilee because the bushings were shot and the cap moved around when running, all new distributor, points and condensor, tractor will start and idle fine but the minute you give it throttle it will backfire and run like crap, have run the wires and set the timing a hundred times, its all good, you can move the distributor in attempt to change the timing a little and makes no difference, put an old fashioned timing light on each wire jus tto see fire and it appears #1 lights half the time the other wires do, replaced #1 plug and wire no difference, anybody seen this before? battery is new and engine is charging. All four holes have more then 100psi in compression and within 5lbs of easch other

 

[Tall T]

Sounds like it is just getting enough fuel for idle and when you throttle up, it is getting too much air relative to the fuel demand,
causing a Lean mixture backfire.
• fuel flow to carb bowl?
• float level?

 

[Powered By IH]

Did a carb rebuild, tune up, fuel tank replacement and ended up putting an Atlantic distributor in a Jubilee because the bushings were shot and the cap moved around when running, all new distributor, points and condensor, tractor will start and idle fine but the minute you give it throttle it will backfire and run like crap, have run the wires and set the timing a hundred times, its all good, you can move the distributor in attempt to change the timing a little and makes no difference, put an old fashioned timing light on each wire jus tto see fire and it appears #1 lights half the time the other wires do, replaced #1 plug and wire no difference, anybody seen this before? battery is new and engine is charging. All four holes have more then 100psi in compression and within 5lbs of easch other

Welcome to YT!
Sounds like bad carb to intake manifold gasket or worn throttle shaft bushings. Did you change those?
Have you tried closing the choke and seeing if that makes it better?
Also you could try adjusting your carb too.

 

[Btzj02]

If fuel is not your issue, to me backfiring is usually caused by a timing issue. There are many things that can affect the timing. Considering you worked on the distributor I would start there. Many of us have inadvertently replaced the spark plug wires in the wrong order. Double check that the firing order is 1,2,4,3. Get the shop manual and meticulously follow the procedure to reinstall the distributor. With the rocker cover installed I have always had a difficult time finding TDC. My hack is to remove all spark plugs and then turn the motor by turning the radiator fan by hand. This way I can feel the building pressure of cylinder #1 and slowly creep up to the flywheel timing marks.

 

[Lynn Patrick]

Sounds just like a couple I have had. Both were fixed by replacing the spark plugs (again). I'm guessing you have already replaced them, but new parts does not mean good parts, especially if they come from the Land of Almost Right!

 

[Duner Wi]

Bad condenser can do what you describe. Starts, idles, but won't throttle up.

 

[Allischalmersdude]

Well we foudn the points were burnt after 10 minutes of running, cleaned them and re gapped and so far its running good. not sure how they burnt or if it will happen again but we are running it letting ti cool all the way off and then running again

 

[Jim L WA]

Well we foudn the points were burnt after 10 minutes of running, cleaned them and re gapped and so far its running good. not sure how they burnt or if it will happen again but we are running it letting ti cool all the way off and then running again

A bad condenser will cause points to burn. Sad to say, but condensers can be bad out of the box.

 

[markdtn]

Another vote for bad condenser. If you have a multimeter you can at least test it. There are videos on YouTube on how.

Quick story. I did a full bore and everything rebuild on a Kohler K321 in a John Deere 214 mower in 1993. It got where it would not run well with any load. It was very tired and used oil. It needed rebuilt. Machine shop did a great job. Ordered parts and when I got there the ONLY part that the JD dealer did not have in stock for the rebuild was the condenser. I was young. I thought "why waste money and another 40 minute trip on that, they never wear out". Put it all together and headed out to cut grass. Engaged the deck in tall grass and it started bucking like a Rodeo horse. Changed the condenser and got another 15 years out of that mower before I moved and needed a bigger one. Since then I take them more seriously.

 

[TJ64]

Bad condenser can do what you describe. Starts, idles, but won't throttle up.

you inadvertantly fixed my tractor in a different thread!

 

[Duner Wi]

I take it, that is a good thing.

 

[TJ64]

I take it, that is a good thing.

Been driving me crazy. cleaned tank, new sediment bowl and all new screens, new carb, new governor, new points, took apart the dist cleaned and polished, set timing. Idle, no throttle sputter and die. replaced the condenser and it runs like its 1951! Thanks again!

 

[used red MN]

you inadvertantly fixed my tractor in a different thread!

Dang Fords, always pulling out tricks. Not that the same thing doesn’t happen to other brands, glad to hear you got it running well!

 

[Duner Wi]

Been driving me crazy. cleaned tank, new sediment bowl and all new screens, new carb, new governor, new points, took apart the dist cleaned and polished, set timing. Idle, no throttle sputter and die. replaced the condenser and it runs like its 1951! Thanks again!

The thing is it happens so infrequently condensers aren't considered. I had one failure but it caused me grief. I remembered it.

 

[Doug Wi]

I take it, that is a good thing.

Also fixed my 8N, just reading the posts before starting a new one. This was my problem too and a new condenser solved it Thanks