MF 135 - Throttle Issues, Backfires, Power Issue, Dying

[slhilbert]

I have been fighting issues with my 3 Cylinder Perkins Gas M-135 for a few years now. I finally broke down and bought a new carb for it a year ago and it has helped. However, I am still having a few issues that I would like smarter people than me to help figure out.

1. When throttling up, it starts to increase RPMs than hesitates before continuing.
2. When throttling down, lots of back fires.
3. Under higher RPMS (plowing, etc) runs for a while and then starts to die.
4. Seems like it is starving for gas after a minute or two of use, but gas is flowing well through the line.
5. In high gear seems to have much lower performance than when in low gear.

I took a video trying to show what I am talking about. Hopefully it helps!

I appreciate your thoughts!
Stuart
Indiana

 

[Roadworthy]

You may wish to check your timing. As points wear the gap changes, which in turn changes the timing. If you have flyweights in your distributor they could be sticking and not allowing a smooth advance, too. Look for a crack in your distributor cap or possibly a plug wire breaking down. You may have a number of ignition issues ganging up on you. Have you checked valve adjustment lately?

 

[murphy1244]

You may wish to check your timing. As points wear the gap changes, which in turn changes the timing. If you have flyweights in your distributor they could be sticking and not allowing a smooth advance, too. Look for a crack in your distributor cap or possibly a plug wire breaking down. You may have a number of ignition issues ganging up on you. Have you checked valve adjustment lately?

I agree it is in the ignition system.

 

[Jerry/MT]

I have been fighting issues with my 3 Cylinder Perkins Gas M-135 for a few years now. I finally broke down and bought a new carb for it a year ago and it has helped. However, I am still having a few issues that I would like smarter people than me to help figure out.

1. When throttling up, it starts to increase RPMs than hesitates before continuing.
2. When throttling down, lots of back fires.
3. Under higher RPMS (plowing, etc) runs for a while and then starts to die.
4. Seems like it is starving for gas after a minute or two of use, but gas is flowing well through the line.
5. In high gear seems to have much lower performance than when in low gear.

I took a video trying to show what I am talking about. Hopefully it helps!

I appreciate your thoughts!
Stuart
Indiana

There could be too problems it could be ignition and/or fuel mixture. get the ignition checked out first.

For a spark ignition to perform properly, you must have a strong spark at the right time and the fuel/air mixture must be correct for the operating rpm and power requirements.
Do you have a blue-white spark, the color of lightning? Is the timing correct? Is the carburetor adjusted properly? What color is the exhaust while running? Accelerating? Any black smoke indicating an overly rich mixture.
Do you have a factory operators manual? The instructions on how to check all of this are in it. Don't start throwing parts at it without finding out the root cause of you problems

 

[super55]

Could possibly be running too rich on the hi-speed air mixture screw but I am leaning with others in it sounds like your timing is a little off. If you already went through the tune up kit routine then it sounds like it could possibly be the weights on the distributor.

If you have access to a timing light this could be very beneficial. The white mark you put on the main pulley should advance once you give it more throttle. If it doesn't then distributor isn't functioning properly. Good thing is I don't believe they are terribly expensive for the 135.

 

[rslaughter88]

Curious if you have solved your issue here. Mine, also a MF 135 3CYL, is doing the same thing

 

[Joe Hickerson]

Curious if you have solved your issue here. Mine, also a MF 135 3CYL, is doing the same thing

Not an expert or mechanic here, but the video from the OP sounds like it's only hitting on two cylinders......

 

[big bubba]

don't overlook valve lash adj as well, could contribute to backfiring

 

[rScotty]

I fixed one old tractor like that. I couldn't figure what was wrong. .... rebuilt the carb and fuel delivery & that helped.... but didn't fix it.
The problem had to be ignition but I couldn't find what part was wrong. I finally decided to just buy all the ignition parts - high & low voltage parts - points, condensor, coil, everything in the distributor, auto advance , and even the spark plug wires & caps - I was particular about replacing the old carbon fiber plug wires with stranded copper racing wire. Everything I took off looked and tested OK. The hardest thing to find was new spark plug and distributor caps for the stranded copper plug wires.
All the parts were bought on line - a couple hundred dollars.

I'm still not sure what part fixed it but simply replacing everything made it work right again.
Years later and it is still good as can be.

rScotty

 

[toolslinger]

There's a point when that's just simply the answer... I hate just throwing money at a project, but then I remind myself that the machine I'm working on has been on the planet longer than I have, and really, having a few hundred bucks in new wiring, or parts, really isn't a waste. It will likely be a lifetime repair, if done correctly, with quality parts, and then you can get back to more usual maintenance of just finding the part that went bad, if it happens. My 135 could use a refresher, though it's ok, but I really should just bite the bullet, and completely redo the 202...

 

[rScotty]

In the case of old - vintage - gasoline ignition parts it's not just throwing money at the problem. I don't like that approach either. But with vintage electrics we aren't really doing that. What we are doing is fixing problems that have become cumulative with age and were simply not anticipated back when the machines were built new.
For example, it was thought that since metallic conduction was forever, so was insulation. But not so.

The type of bakelite used for the ignition insulation on the rotor, distributor cap, and points bushing breaks down over time and allows both low and high voltage leaks. We know that now. It's a known problem due to age. Carbon tracks form conductive paths. On a dark night you may be able to see it happening.

Likewise, the "ignition suppression" spark plug wires and caps were designed to do their job by using conductive carbon fibers instead of copper. Those carbon fiber conductors aren't forever either. They do crack with time and vibration. Even the insulation around the carbon becomes "leaky".

The springs on the auto advance get weaker and bushings wear - so it advances too much at progressively lower and lower RPM ..causing knocking and eventually backfiring. If we ****** the distributor to compensate, it will backfire the other way.
Then there is the phenolic gear problem.... Some of the old Brit motors used a phenolic drive gear on the lower distributor shaft where it meets the cam. I don't know if yours did, but it is worth pulling your distributor out to check that the drive gear is not torn up and the push pin that holds it on is still tight. Doing so gives you a chance to dust off the old timing light not used in 30 years and get reacquainted with what used to be a necessary tune up tool.
I just found my own old timing light the other day in the bottom of a tool drawer I hadn't looked at in years. Make that decades....

rScotty

 

[bearthebruce]

I just found my own old timing light the other day in the bottom of a tool drawer I hadn't looked at in years. Make that decades....

I don't own one any longer... A guy was cleaning out his garage to sell the house and gave me a timing light. I tossed it.

If I needed one, I wonder if you can buy one. <pause to look on Amazon> Huh.. they still sell them. Who'd have guessed.