Ruff running engine, help plz

Saberr · Post by **Saberr** » Fri May 26, 2017 8:45 pm

Finished my 64 m38a1, but its started to act weird. It's started to run ruff, and and only runs evenly when choke pulled out. But it drives fine, great power and no choking going up hill or straight, hit 55 in it and just sang along, not a hiccup when going. Once warmed up put choke in and it will idle forever, but you can hear it surging at idle. This all yells vacuum leak, and I've checked all the connections, and even smoke tested the whole thing, NOTHING. The fuel pump was rebuild by then and now, a company rebuilt carter ys, and i even rebuilt it again with Midwest's kit. Pull idle screw out and it kills engine, but the idle with out choke has to be higher than should be. Have checked the float and its at 5/16. Fuel lines new and tanks is lined and vented. Great compression on all pistons. When i put my hand over air horn, it revs up, and i noticed, the windshield wipers have slowed down as well. It screams vacuum leak, but there are no leaks to be found, even smoke just traveled through all the lines. Totaly confounded.

4x4M38 · Post by **4x4M38** » Fri May 26, 2017 9:09 pm

Do you have any fording ventilation piping installed?

Have you checked for a leak between the carburetor and intake
manifold?

Saberr · Post by **Saberr** » Fri May 26, 2017 9:53 pm

All fording has been restored, and is working, smoked the whole engine nothing. Even sprayed carb cleaner everywhere and no change.

Post by **wesk** » Fri May 26, 2017 11:59 pm

1 - I don't see a set of compression readings taken after the engine started running poorly, nor do I see any fuel pump pressure and flow numbers, nor do I see any recorded vacuum gauge readings tied to RPM readings! What RPM are you setting the idle at now?

2 - Is the fording knob full in and both valves full open?

3 - Is the fuel tank filler vent and tank vent both open? Tested to insure not plugged?

4 - Does your wiper "T" have the restrictor installed on the leg that feeds the distributor vent?

5 - Is the accelerator pump discharge check ball and weight in place?

6 - Are both diaphragm springs located correctly?
If you rebuilt your carb using the TM 9-1826A the illustration on page 114 is erroneous.

Original Illustration has BB in wrong location

In this illustration I edited BB to it's correct location.

7 - Do you have the correct spring in each position? They are different!!! Do you have the correct metering rod for the YS950S?

8 - Are you certain you have your carb adjusted to the correct specifications?