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720 carburetor

B

Bob seND

Member
Carb overhauled by Poppin John, but tractor surges. It
will not idle unless choke 1/2 way out. Then the surging is minimal but not 100% gone. It smokes black when the governor opens up on the surge. Before the overhaul it used to start at zero degrees with no choke, now full choke to start.
It also surges driving wide open without the choke partially on. It only rarely backfires.
 
Have you talked to Mike about it. He has been doing many for me over 22 years and always makes it right , if its a carb problem.
 
Sir, we have researched our daily log book back to December, 2015, and can
find no record of doing a 720 carburetor for either a Bob or a Robert
from North Dakota, which your handle seems to suggest.
If you care to call us during normal business hours, we will be happy to
answer any questions you may have. (845)626-5870 MikeS.
 
Mike, looking back for my emails, I believe it was between May and Nov. of 2014, and that is the gist of my question. Could it have plugged up so soon? or is it likely non carb related. I know it
wasn't doing this when I first got it back. I'll give you a call Monday.
 
That's three years ago ,trash from tank can get back in carb the same day, and a jet has gotton stopped up again, It wouldn't have anything to do with his rebuild. Mike is the best carb person I know but I don't know anyone who would give a 3 year warranty. Gas today is also not what it use to be . theres your problem GAS.
 
Yes, I was in no way casting aspersions on Mike or the quality of his overhaul, I brought it up so as to define the quality of what has been already done to the carb. I understand about trash getting into the fuel supply, but my impression of the problem these carbs get is varnish/gum plugging the small passages over many years, old fuel, etc. Does this current fuel do that much sooner? or again would these symptoms be less likely due to the carburetor and from something electrical.
 
A bit of additional trouble shooting, there is a good pencil stream of fuel coming out of the hose entering the carburetor. There is also a good stream out the sediment bowl drain.
The tractor surges equally on each cylinder with one plug wire pulled off. I have autolite 386 plugs clean and gray after running.
When I first set the idle screws, I used Clooney's method of shorting out one plug with a paper clip, rubber band on the throttle at low rpm, and adjusting each low idle screw to best rpm.
I would not be able to do that now as it won't idle without the choke on, and even with the choke partially on it won't run at the slowest idle speed. Running wide open in road gear it misses, but rarely will backfire.
 
throttle rod is 1/2 hole short.
Here is a video:

https://www.youtube.com/results?search_query=720+surging
 
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