Small Engines (Lawn Mowers, etc.): 18hp briggs, troybuilt, jumper lead, jumper cable

Question
I am almost at the end, I have a rebuilt  mower, 18hp ovh. it lags when trying to start. rebuilt the starter, tried bigger gauge wire, changed the solenoid, twice. now there is no power. going past the solenoid, to the starter. the key switch is a live wire only when key is on. getting frustrated can I get some help, before I blow.  

Answer
 Hello Tim:

 I'm Not Sure, But Check the Valve Clearance. Set the Engine to Top Dead Center and Set the Exhaust Valve to .008in - .010in and the Intake to .003in - .005in. for OHV Engine. If Not OHV Engine, then Set the Intake to .007in - .009in and the Exhaust to .016in - .018in. As for the Solenoid, you May have Burnt it Out or the Starter May have Burnt up. Check the Solenoid by Using a Jumper Cable Set. Take the Positive Lead and Attach it to the Positive Post of the Battery. Take the Other End and Touch the Large Post on the Starter Side of the Solenoid. Does the Starter Turn? If Yes, then Touch the Small Post on the Solenoid with the Jumper Lead. If the Starter Turns, then the Solenoid is Good. Send me the Model Numbers Off the Engine and the Mower, Please. With these Numbers I can Locate the Proper Manuals and Better Assist you. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.