jd 50 running rough

[farmerjim]

i have a jd 50 and its running rough seems to skip a bunch. did the basics plugs /cap/points/condensor. also wash/clean carb/fuelbowl. nothing still the same, then noticed it sounds like there is an air leak coming from the head or exhaust manifold. i think its the exhaust because it doesn't seem to have any white smoke when you give it some throttle.what would be a good way to check for a leak in this area, thought about spraying something there to see but don't want to use anything that is flammable near the hot exhaust. she could use a rebuild which i had planned to do next winter after this years hay. any help would be great thanks again jim.

 

[BobG_in_VA]

Quick way to tell if you have an intake leak is take a propane torch, don't light it, but open the valve and point the nozzel at the intake: if its "sucking" air it will clear up the miss while you are putting the propane to it. If its an exhaust leak you wouldn't be missing, just popping (more so than a Johnny Popper does normmall..lol) Also, you can lightly turn in the carb screw adjusters to bottom and turn them back out. as sometimes dirt/stuff gets caught at the needles, this may get rid of the "stuff". Good luck. BobG in VA

 

[hudr]

We have a 720 LPgas that had similar symptoms. We had also been planning an overhaul for some time (hey, it was built in '57). Turns out it had a burnt valve. Don't mean to be a doomsayer, but it may be time for that overhaul. Hope it is something simpler though.

 

[farmerjim]

w/ all the rain we've had i had some time to do the maintainence on the old jd 2010 and finally got around to the 50 as well. finally figured out what the problem was, leaking exhaust manifold gasket. also gummed up carb again, this time took carb all the way down and got it soaking in some kero, also got a new screen for the fuel bowl and a carb kit. should be up and running good as new soon. next winters project is restoring the old 50, motor overhaul and a fresh paint job.

 

[farmerjim]

w/ all the rain we've had i had some time to do the maintainence on the old jd 2010 and finally got around to the 50 as well. finally figured out what the problem was, leaking exhaust manifold gasket. also gummed up carb again, this time took carb all the way down and got it soaking in some kero, also got a new screen for the fuel bowl and a carb kit. should be up and running good as new soon. next winters project is restoring the old 50, motor overhaul and a fresh paint job.

 

[hudr]

Had the same prob(leaky exhaust gasket) on our 720LP. Cause of the burnt valve was probably from water leaking into the cylinder. After a rain we would crank it up and it would run on one cyl until it pumped all the water out. IT ran for several years like that. Its not hard to find a dead miss on a 2 cyl.
We have a 40, a couple 50's and several 60's lying about that sure need some attention. What I really need to do is find someone interested in B model Macks. /forums/images/graemlins/grin.gif

 

[hudr]

Had the same prob(leaky exhaust gasket) on our 720LP. Cause of the burnt valve was probably from water leaking into the cylinder. After a rain we would crank it up and it would run on one cyl until it pumped all the water out. IT ran for several years like that. Its not hard to find a dead miss on a 2 cyl.
We have a 40, a couple 50's and several 60's lying about that sure need some attention. What I really need to do is find someone interested in B model Macks. /forums/images/graemlins/grin.gif

 

[Soundguy]

</font><font color="blue" class="small">( carb all the way down and got it soaking in some kero)</font>

Good luck. I have not had great luck with cleaning carbs in Kero or Mineral spirits. Sometimes laq thinner.. or varsol / chem dip is the only way to get the bad gum out..

Soundguy

 

[Soundguy]

</font><font color="blue" class="small">( carb all the way down and got it soaking in some kero)</font>

Good luck. I have not had great luck with cleaning carbs in Kero or Mineral spirits. Sometimes laq thinner.. or varsol / chem dip is the only way to get the bad gum out..

Soundguy

 

[Chuck_Lind]

I remember my grandfather's "B" and Model 50 never had any carb gum-up problems. But in modern times, gasoline composition has changed.

Is it the modern gasoline that is causing the problem? I know on my "50", I have to drain the fuel from the tank and the carb bowl if it's going to sit for a period of time.

Comments or experiences anyone?