Motorcycle Repair: yamaha beartracker ignition, spark plug gap, continuity check

Question
hi, i am an outdoor power eqipment mechanic by profession and work on motorcycles as a sideline, i recently purchased a 2000 yamaha beartracker yfm250xm with little hours but wont run and has weak spark. the previous owner was frustrated with it and sold it to me, he had taken it to a dealership when it first satrted missing and quit last year, prior to quitting he said it would start with rope only even though the starter was turning the engine fine it would not start, he said the dealership replaced the stator/pichup coil assy. and the cdi module and battery, the machine ran great for a couple of houirs and started missing and quit on him, frustrated, he decided to sell it. he brought me the old stator and pickup coil but did not get the cdi back when he picked it up from the dealership. the neutral light is not working and it has spark but will barely jump the electrode gap, i have taken some readings of components and compared with another 4-wheeler and they are similar, any help troubleshooting would be greatly appreciated, thank you for your time, i have never asked a question but have refered to your advice on multiple occassions
scottstinsons@bellsouth.net  

Answer
Hi Scott,

Welcome and thanks for the compliment.

Check cylinder compression to learn the condition of the engine in general. Perform a leak-down if necessary. Check and adjust valve clearances.

Look for wiring or connector defects that may cause the neutral light problem. Check neutral position switch continuity. Check neutral bulb and socket, etc...

It's a tough call on the ignition problem. Are the symptoms actually fuel related? Consider checking fuel in carburetor and fuel tank for evidence of varnishing.

As long as the arc at the spark plug gap is blue, you have a healthy ignition. The size of the arc is minute with some digital ignition systems.

Ensure that the battery is fully charged and in good condition. Check battery voltage with your multimeter. Check specific gravity of each battery cell with a Hydrometer designed for use with motorcycle batteries. Charge or replace battery accordingly.

Get a copy of the service manual. Follow the usual procedures.

I'll send a few tech files to your email.

Respectfully,
Mark Shively