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carb_problems 2013/10/26 12:33 current
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 +From:  ricksbro
 +
 +Please accept this as constructive and not critical. Not to be to simplistic but, have we all forgotten the basics? The 151 engine is 1 step up from a Model A (with a fording valve)in operation. The engine needs fuel in the correct mixture & spark at the right time to operate correctly. This can be verified with simple tools in simple order without randomly replacing parts. 1) Verify fuel flow & pressure at carb inlet. 2) Verify ign. timing. Any poor run condition that is corrected by the application of the choke usually indicates a lean fuel mixture. While this can be caused by improper float setting and carb adjustment it is most likely a vacuum leak downstream from the carb,especially if it is intermittent. You can track this down with the application of propane (stick a hose over the end of a propane torch...UNLIT) and probe joints/gasket surfaces while engine is running (FIRE HAZZARD)Don't forget to man handle the carb/manifold etc. while doing this. If the engine speed increases while doing this you have found the leak. <br>I know we like to do everything for maintenance but if you can come up with the correct ignition adapters from a LVCT kit it may be worth a trip to an old service station that has a "antique" engine analyser to check the ignition secondary. In less than 1/2 hour they can verify correct operation of the distributor (cam, advance, point dwell, coil output), wires, plugs, timing and fuel mixture, compression balance etc. Happy hunting.
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 +From:  arhhhbuckooo
 +
 +I swaped a rebuilt zenith carb for my old one today on my 72 M151A2. When I was tuning up and test driving,First I set the choke butterfly to as far open as it
 +would go with the cable pushed all the way in.I found that I had some hesitation when accellerating.I pulled the choke cable out just little and it ran
 +perfect.When I looked at the butterfly I found that if it is tipped up a couple of degrees from full open it's centered in the venturi making the smoothest air flow into the carb.I reset the cable so full open has the butterfly centered in the venturi and now it it accellerates like a bat out of hell, smooth and strong.
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 +From:  j_w_whitten3
 +
 +My National Guard buddy who runs one of the nearby maintenance shops told me that they were told to set the chokes on MUTT carbs a little off of "all the way in". His procedure was to set it normally, then slowly pull it out until it ran the best, then to hold the butterfly lever, loosen the screw, and push the knob all the way in and retighten the screw. That way "all the way in" actually ran "a little choke" all of the time. In other words, he was taught to do exactly what you just found out works the best!
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 +From:  gbpmi
 +
 +You have not adjusted your choke cable correctly. It's as simple as that. If you check in the -20, you will find that 1/8' adjustment is supposed to be pre-set. If you do not adjust the cable as such, you will find that you need to pull just a wee bit of choke to get her to idle nicely.
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carb_problems.txt · Last modified: 2013/10/26 12:33 (external edit)
 
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