Small Engines (Lawn Mowers, etc.): john deere Stx 38 Yellow deck, belt tension, transmission belt

Question
QUESTION: I bought a stx 38 as a project mower with my dad and it had a starter solionoid problem, which was an easy fix. then, it wouldnt start, so i took apart the ignniton switch, and eveything was in place, but all i would get is the solinoid click, while um sitting in the seat and have the clutch pressed down. it only works when i hotwire the switch, but automaticly engages the transmition (clutch depressed).
I want to get this mower runniong towards summer, so i can mow!
thanks!

ANSWER: Do you have a hydrostatic or manual transmission?  
Eric

---------- FOLLOW-UP ----------

QUESTION: It is a manual, and i noticed today that the last owner had hotwired the seat-switch around, so i will check if that is the problem...
thans you!

ANSWER: The transmission belt tension should be adjustable using the cluth idler arm pulley.  Since the first thing is to get the engine to start you can remove the belt from engine pulley so the mower will not try to move when you attempt to start the engine.

Is the transmission belt the correcte JD OEM belt?

Eric

---------- FOLLOW-UP ----------

QUESTION: Yes it is, and after a few alterations, i have fixed most of the mower exept the starting key-hole switch, i have to hotwire it in order to start the engine, but other than that, the mower work perfectly! it is not the switch itself, but the wiring.... and i cannot find any wiring diagrams anywere, only vaugly touched at http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.H. could you please help?
thank you!

Answer
Unfortunately most mower manufactures do not provide very good wiring diagrams.  The Briggs site below has a decent schematic but you still have the JD safety switch configuration to figure out.


http://www4.briggsandstratton.com/miscpdfs/RNT/alternator_replacement.pdf

I'd check power to the key switch (B), 12 volts DC.  With the mower in neutral, clutch depressed, blades off...the mower in the start position, you should have 12 volts DC on the (S) pin.  This voltage feeds the starter solenoid to engage the solenoid plunger connecting the battery to the starter and turning the engine.  If there is no power on the (S) pin then you will not have any power on the solenoid exciter post.  Check to be sure.

If there is no power then one of the safety switches is probably the problem.  You can start a the key switch and trace each wire to the safety switches.  I use a 12 volt test light or continunity meter to check to see which switch is causing the problem.  It's a painful process but this is the best method I've found to trouble shoot safety switch problems.  The other method, and a good cross-check, is to ohm/continunity test each switch.

Let me know if this helps.
Eric