Farmall Cub Forum -- Questions and answers to all of your Cub related issues.
Wed Jan 09, 2013 3:24 pm
OK, need help! Katrina started and ran fine last fall, crank start, magneto all same as last time. Sat over the winter, now when I crank it over get a loud backfire thru the exhaust !??? First reaction was it is out of time but nothing has been changed since the last time it ran?? Suggestions on where to start??? Thanks, Dusty B
Wed Jan 09, 2013 3:34 pm
Not an expert, by any means, but I would suspect moisture in the distributor cap. Wipe it out good and see if that makes a difference.
Wed Jan 09, 2013 3:45 pm
what about an exhaust valve that mey be stuck open?
Wed Jan 09, 2013 3:52 pm
Do you get a good loud click out of the impulse coupling each time it should fire? A sticking coupling can cause some bad timing behavior.
Wed Jan 09, 2013 3:58 pm
check and make sure the distributor cap is dry inside also
Wed Jan 09, 2013 4:10 pm
Ditto to what 64/67 said, exhaust valve not closing properly/sticky valves
Wed Jan 09, 2013 4:36 pm
All 3 of the aforementioned scenarios very possibly causing your grief.
If the impulse snap is late, so will be your spark. This is the easiest to check, all visual by looking at the timing marks and listening for the magneto snap.
Next check that distributor cap for moisture or other defects.
Thirdly, a quick compression test will determine valve operation or lack there of.
I think your diagnosis is correct but the timing affected in a slightly different manner.
Wed Jan 09, 2013 6:47 pm
lW/check cap tomorrow! Then on to compression. Thanks, Dusty
Wed Jan 09, 2013 7:26 pm
Borrow her Ladyship's hairdryer it's great for drying out the distributer cap etc
Wed Jan 09, 2013 8:23 pm
Points gazed over; just guessing, but possible. clean them up, and try again.
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