Motorcycle Repair: 1967 HONDA CT90, honda shop, permanent magnet

Question
Hi,
I have a 1967 CT90 that wont start after a top end and tune up.  Before ripping into it, I put oil and gas in it and after 15 minutes of kicking it over it started up and I rode it up and down the street. I then took it apart and did the topend, valves, and tune up.  Now that it is done it is very very hard to start. It has new points, condensor, plug, battery (now weak)and top end.  It is getting gas and spark.  The spark seems weak though.  My question is:  I have had the coil tested at a Honda shop and checks out fine.  Can it be bad under load and test good off the bike?  The spark does seem weak.  After the top end was done it has ran for a few times for only about a minute each time, this is after A LOT of kicking!
The only other thing that I can think of is that the timing is 180 degrees off?  If that is the case, would it have even started in the first place? Could the cam chain have jumped a notch?
Thanks for you help, if you need more info let me know.


Answer
DO.... First, if the cam timing or the ignition timing was off 180, it wouldn't run. If you timed the cam properly on installation, the chain doesn't usually jump. The tensioner is kind of hydraulic, so unless it is stuck, it is probably okay, although the camchain could be stretched out in extreme cases.

Check the mechanical spark advancer to be sure that it is functioning properly. If it is stuck, then the ignition timing settings will be off and it will be hard to start and/or will run bad once it is finally started.

The ignition is BATTERY operated! Weak battery = weak spark. Although the permanent magnet charging system will eventually build up enough juice to get the engine started, the voltage output won't be sufficent for decent running. Charge the battery, recheck the cam and ignition timing, check the spark plug cap for excessive resistance 5K ohm or so. Use a fresh plug once you have made all of your checks and adjustments.

Check the compression to see if it is sufficient for startng and running. Cam timing off will give low readings, as will a bent valve if you got the timing off more than a tooth...

Bill Silver