js550 wont turn with plugs in engine

G

goatse

Hello guys, warm season is around the corner and i need to get my project running. I haven't messed with it in a while but i gave up and the problem is still here. Well i bought a js550 with lots of AM performance mods. Initially it had a bad e box, but i replaced it with one from my junker and i got spark. The problem is that the starter struggles to turn the driveshaft. If i remove the plugs (less resistance without compression) it turns and so does the driveshaft, and it turns with ease. But if i return the plugs, it barely nudges. I have to bump the starter button to barely get a revolution. I replaced the starter with one that was in my junker and its a good starter, it was turning the junker's engine just before installing. I have 3 batteries which all turn my high compression js650xs so i know it isn't the battery. I'm lead to believe it is something in the engine since it turns with ease, including the driveshaft, when the plugs are removed.

As far as i know, the previous owner poured some oil in the sparkplug sockets (without turning the machine over) "because the motor sat for a couple years, to ensure the pistons moved with ease". No i don't think that was a good idea. But i don't think it is hydrolocked because i removed the plugs and ran the starter to remove the excess oil (as you would do if you got water in the engine)

Any ideas? Thanks a lot
 
screaming440

screaming440

The Old Skool Professor
Location
KC/Lake of The Ozarks
you have a voltage drop to the starter motor or a bad starter. do voltage drop tests with a DVOM if you know how otherwise check and clean ALL your connections and retest. if that does not fix it there is a good chance the starter is bad.
 
Wil5on

Wil5on

Location
T-Burg
Judging by what your saying I would say starter as well. I had same problem once new battery and starter and good to go.
 
Tyler Zane

Tyler Zane

Open Your Eyes
Location
Panama City Beach, FL
Just to expand on screaming440's post... Which I think is right...

If a voltage drop test seems intimidating then I would like you to take a voltage reading directly at the starter (neg lead on a clean portion of starter case and pos on the starter post, not the crimped end on the wire) and then directly at the battery (again, on the post, not on the crimped end on the wire). Do this with the plugs in and dont have a battery charger on it. Let us know your results.
 
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