Case 444 , backfires ... any thoughts

Dutchman · Mar 20, 2016

Will I been working on a Case 444 for over a year { see post below } anyway was hoping to get some ideas what I should do about "backfiring "....
I can start it up [ sometimes at takes a little to get it going ..] once it's running it seem to run good for a short time , then it will "backfire " .. a flame will come out of the muffler 12 - 18 inches and it's loud ...

I'm not the best with carbs. so I'm trying to learn .. on top is the power screw around 2 turns out .. on the side is the ideal screw . 1 1/2 turns out ... this is a Kohler 14hp , model K321A ....

Where do I start , and do I need to replace something ???? fuel pump or something else .. the carb. is brand new , did a tune up on it new points, condenser , plug, and wire from coil ...

I'm not sure what to do next ..... THANKS for ANY advice you share with me ... mark

THERE is pictures in post below .....

I'm just not sure .... what to try next ...

T.R.K. · Mar 20, 2016

If it backfires out the muffler when running, usually 1 of 3 things are going on:

1. The spark is happening when the exhaust valve is normally open. Don't know which is yours, but the plunger that operates the points can stick on the early K-series kohlers.

2. There was no spark at the proper time and unburnt fuel went through the cylinder and blew up in the muffler. Fouled plug? or dirty points? did not make a spark, or no or intermittent primary ground through the points. (The wire from the coil to the points is grounding before the points or is broken and sometimes the circuit is open)

3. The exhaust valve is not closing. Either carbon holding it open, sticking in its guide or else no valve tappet clearance when hot.

Of the three above, I would probably put a jumper wire in place of the wire between the coil and the points, I have seen that intermittent or no-ground problem twice in recent years on 40 year old Kohlers. Then I would probably do number 3, probably pull the head and lap the valves before I adjusted them.

Dutchman · Mar 20, 2016

THANKS .. tomorrow I will check the wire to the coil and check points gape and leave the cover off and see if the points are sparking all the time ...

THANKS ................. mark

Dave Sherburne, NY · Mar 20, 2016

Also, engine timing could be off It's not a hard job but you probably would need a manual.
Or check the condenser do you have another engine you could take a condenser to substitute. Don't count on a new Chinese condenser being any good. I never change condensers anymore if an engine is running good when I change the points.

jacks · Mar 20, 2016

Also, the pushrod that drives the ignition points gets worn down over time. Probably many of the old K series engines have never had the pushrod replaced. When the rod gets too short due to wear, the timing and dwell will be off in spite of having the point gap adjusted properly. I have seen Kohler OEM tuneup kits that had a new pushrod included. You should check the timing with a timing light while it is running. If it is off, try a new pushrod and tweak the point adjustment until the timing is set properly.

Bob · Mar 20, 2016

Fortunately, the manuals are easy to come by.

And for the OP, you will find troubleshooting info in them, including for backfiring.

K321 Service Manual
http://www.kohlerengines.com/onlinecatalog/pdf/tp_2379.pdf

K321 Owner's Manual
http://www.kohlerengines.com/onlinecatalog/pdf/tp_1346_c_all.pdf

Dalex · Mar 21, 2016

The point adjustment is very critical on this engine , just a few thou's will make it go from laboring to very smooth .I just went thru this on a Cub Cadet.

joe csuti · Mar 21, 2016

If you haven't done so already try replaceing coil,when a coil starts going bad it will make eng hard starting & once coil gets hot it can cause backfiring/stop working all together till it cools down.

Connect a spark tester to plug & leave it connected to watch spark or loss of same when eng gets hot,many times a coil/ign problem will act like a fuel system problem.

Case 444 , backfires ... any thoughts

Dutchman

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T.R.K.

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Dutchman

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Dave Sherburne, NY

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jacks

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Bob

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Dalex

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joe csuti

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