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JD 620 starter motor turning slow

C

chas036

Member
No matter how much charge I have on my battery , or if the outside temp is 90 degrees, the starter motor always turns the engine real slow when trying to start. My oil is 10-30 so I know it is not oil thickness. I put a brand new battery in last year and it is charged to the max. What else could cuase the starter motor to turn so slow. It has been like that since I bought the tractor 30 years ago.
 
Time to take it out and look at the starter and/or replace the cables, or better run the ground cable out of the battery box to main casting of the tractor.
 

First of all, it takes a good sized 12 Volt battery to replace the original two 5 Volt batteries in series.

I would try a ''31'' series which should have around 1100 to 1200 cranking Amps.

What battery are you using?
 
Battery cables clean at the ends and no bare spots? In the last couple years I have replaced cables that looked good from the outside but were not doing their job. Assume nothing based on appearance.
 
Does taking the PTO drivetrain out of gear (with the lever right of the shift quadrant) make any difference???

Like the others, I'm guessing you have something electrical amiss, like a bad cable, too small a battery, or something not right in the starter itself.
 
Starters (or often just the switches contacts) can go south could be your problem ? but if its not that I would remove, clean brush n shine each n every battery terminal and cable end and insure the ground is to a nice clean bright n shiny frame member, see if that helps. I liked to use good heavy batteries of at least 750 better yet 1000 or more CCA. Has the starter switch ever been replaced ????? as I noted above their contacts can develop voltage dropping burning pitting and carbon. NOTE I forget for sure if the 20 series uses a mechanical starter switch or a solenoid ?? but EITHER has contacts which can get burned and pitted , drop volage and cause slow cranking...

John T Gettin old n forgetful of what uses what grrrrrrrrrrrrrr
 
I just looked at the battery and it is a 700 and the ground cable is attached to a small bolt on the side of the tractor. I think I will buy a 1200 battery as recommended and shine up the ground connection .
 
(quoted from post at 10:38:08 10/02/22) No matter how much charge I have on my battery , or if the outside temp is 90 degrees, the starter motor always turns the engine real slow when trying to start. My oil is 10-30 so I know it is not oil thickness. I put a brand new battery in last year and it is charged to the max. What else could cuase the starter motor to turn so slow. It has been like that since I bought the tractor 30 years ago.
Click to expand...

Got a multimeter??

Turn the multimeter to volts DC and touch the battery post with one end and touch the starter switch terminal with the other end and hit the starter. That will tell you the voltage drop within the battery cable. You can do the same thing for the ground side by attaching to a starter bolt or something. Might be easier said than done though trying to attach the multimeter to the starter switch on a 620 because the switch is on top of the starter behind the flywheel. Maybe an aligator clip jumper wire can work in there?? Been a while since I've worked in that area.
 
If you are still using the original (65 year old) battery cables that is where I would start, replace both with the best quality you can find. I have an AR that is a slow cranker too, new cables improved mine but still not perfect.
 
When I bought my 46 B in 1963 it would just crank tractor over. Turned out that someone had used a too long screw to attach cutut out to generator and dammaged the field winding cover. Just had to have new field wraps put on. Last saw tractor in early 70.s and still working good. Tractor still had orignal Firestone rear tires.
 
I put welder cable on my tractor, with a type 31 battery, crimped new lugs on the cables with heat shrink tubing to protect them. The shorter your cables the better, and if you can run the ground right to the base of the starter or pretty close it can help.

This post was edited by gomi_otaku on 10/03/2022 at 09:36 am.
 
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