YG 2800i with no spark...HELP!

[CastleRocker]

This has been a great generator for years.  Now I have no spark.  I've read every thread I can find concerning this.  After testing eveything I could think of, I cleaned everything, checked the spark plug cap, replaced the plug, jumpered the oil sensor, ohm'ed out the resistors on the oil sensor circuit board, replaced the ignition coil, pulser coil, and CDI box...still no spark. I've had it apart and back together so many times, that I think I can almost do it blindfolded.  Any suggestions will be greatly appreciated!  

No Yamaha dealers in my area seem to know anything about this generator.  

[Grumps]

Try disconnecting the oil sensor, not jumping it.

[CastleRocker]

Thanks for the suggestion.  The wiring diagram I have shows that as a  normally closed switch going to chassis ground, and yep, I tried that before I made the wire to bypass it.  Still no spark.  Put it all back together this morning to make sure all the connections were good, and all the grounds were good.  Still no spark.  I've NEVER had an ignition problem stump me like this one has.  I keep thinking I'm missing something simple...

[Grumps]

I have a 2400ishc so the engine should be the same. Looking at the service manual you are correct that the oil sensor switch should show continuity when a meter is connected to the lead and to chassis ground. Per the manual if the switch is good and the connections are good , either the TCI unit or the speed limiter is bad. I don't have the test procedure for either of those. Post back with the fix when you find the problem.

I'm sure you have checked the actual run/ stop switch for continuity in the run position ?

[Grumps]

I found another post that might be of relevance. Page 12 from July 2013 by Richard. Sounded similar ended up being an intake rocker broken.

[CastleRocker]

Thanks for finding that!  I didn't take the valve cover off yet, but looking down the intake, and turning the flywheel, I can see the intake valve moving.   Also, I'm still trying to get some spark first... This is maddening!  I'm to the point, that I'm looking for one that runs, and swapping out known good parts, to help me diagnose this.

Thanks again, I'll pull the cover off tomorrow, and check it out.

[CycleRob]

CastleRocker,
 If you replaced all the ignition components, that was an expensive way to solve the problem!!
 The number 1 rule in diagnosing repairs is to make the easy shots first. That would be to Ohmmeter or function test individual components to identify the bad component.
1) Start with the engine kill switch lead in/out wiring for chaffing wear-throughs (short).
2) Test the engine run switch terminals for the required infinite resistance for On and zero resistance for the Off position.
3) Check the oil low level switch wire from the engine for OPEN to Ground with the oil level at the full mark. It should ONLY read infinite, open circuit resistance . . . your circuit diagram shows the switch activated, which happens when the oil is Too Low.
4) Test the ignition coil and trigger coil with an Ohmmeter. Coil primary to coil metal frame ground and secondary to coil metal frame ground, trigger coil between 2 wires and each wire to ground. Ask any Yamaha Service Dept for those numbers.
5) On all the above tests, check the wire terminal's connection to it's wire as rigid and secure.

Those tests find the most common cause of No Spark failures.

[CastleRocker]

Thanks Cyclerob very much for the reply.  In reading this forum, it seems like you are the one who shares the most useful knowledge, and solves the most problems.

 I ohm'ed out EVERYTHING before I started throwing money at it.  As I said in the original post, I even ohm'ed out the individual resisters on the oil sensor circuit boad.  My ignition coil was barely within spec, but still should've worked...albeit with a weak, or intermittent  spark. As I said...I'm at a complete loss.  As far as I know, I've checked, re-checked, replaced, and triple checked every component except the spark plug cap itself. (It ohms out at 4.9 instead of the 5 it says on the cap).  I just don't know...

[PR-AJ]

Is the sparkplug cable good?
I recently broke the sparkplug cable's "head" on the cylinder side on a 6300 unit.
Had to get a Yamaha universal-ish boot... slice it with a razor blade, and rig it into the cable.