MF 135 Erratic Running

Morning everyone,

I was off Monday and decided to see if I could try and figure out the why my tractor (67 Gas Deluxe w/ Z145) would idle well but cut out at Higher RPM's.

I was able to get the choke all the way in at times but generally I had to leave it halfway out and the throttle lever halfway as well. The carburetor's main needle was set at the manual 1 1/2 turns out.

I got into my field and as I was heading home the tractor cut out and I started to do the idiot checklist. I had an extra condenser so I replaced it, cleaned the sediment bowl, there was some slight crud where the gas flows into the bowl from the tank, removed that and it seemed to run better. At times the RPM's on the tachometer seemed surge to a max of 2200RPM and settle down to 1100-1500 RPMs.

There were two things I did notice, the throttle lever did seem to move by itself. I'm about to order the cork and thrust washer and replace them, the other was that when I re-installed the sediment bowl, I had to let the bowl hang and fill with gas and then tighten the knob. Does this mean that my gas cap is faulty and potentially restricting gas flow?

Here is also some video shot with my phone demonstrating what it's doing.

http://youtu.be/1RKLnM5UN9U

Thanks,

Christos

Sounds to me like you are still starving for gas. You need to pull sediment bowl out of tank. Very possibly plugged right in the neck that screws into the tank. If that"s clear, then pull line and verify it isn"t partially plugged. Also, check at carb. Some have filters where fitting goes into carb and it could be plugged. After all these checks are made, you might also leave gas cap loose or clear off proving it"s vent isn"t plugged. Finally, if no problems found and still same problem, it"s time to pull carb and clean thououghly. HTH

You probably need to clean that carburetor by soaking it in carb cleaner and blowing out all the jets. The tube fitting where you gas connects at the carburetor may have a screen behind it that's also full of crud. Take a good flashlight and look inside that gas tank for any dirt or rust that may be blocking that fuel flow to the carburetor. Open that main jet adjusting Sc/ew some more till it starts to smoke out the exhaust then close it 1/4 turns til it quits smoking. By opening the main jet enriches your fuel mixture. My garden tractor and an old Toro rotary mower that I have has that same feature to get more power from the engine when under load. You don't want to run the air cooled engines with the carb set too lean can cause them to overheat. Hal

Check you spark first. If that is good( FAT AND BLUISH-WHITE). The make sure that you have adequate fuel delivery and tht the vent in the fuel cap is clear.
The friction disk on the throttle assembly may be worn OR the throttle rod may need adjusting. There is a spring near the battery box that keeps pressure on the friction disk and sometimes you can tighten up the spring tension and the throttle will hold.

I have a tractor just like yours, which had the same problem. I did everything that everyone has suggested and it didn't work. I had an old Massey mechanic tell me that the governor was very persnickety. I adjusted it a little and it got worse and I went the opposite way and it has ran great ever since. I know it don't make sense, but it worked.

If you have an automobile gas cap (non-vented) on your tractor, yes, your gas cap is faulty and needs to be replaced...with a gas cap designed for your tractor; no pressure, no vacuum.