Sunday, September 27, 2009

Diagnostics 101 for Natasha

So, tried a few things, re-learned diagnostics on boxer engines, learned a few new things about Natasha and while she's not 100%, I think I've got a good idea of what needs to be replaced now.

  • found a bad spark plug cable (it was the cap actually) that read zero ohms between ends, it's supposed to read 5000 ohms. Could not find the right one at the auto parts store so I took an old one from my beemer and made it work.
  • checked the existing spark plugs, found them black and a bit sooty, which means I am running too rich in fuel. Replaced old spark plugs with Autolites, properly gapped to .50 mm per the manual.
  • verified fuel levels in carburetor float bowls are about the same. In the process, found rpoc screws securing the right hand carb float bowl, replaced them with good allen head screws. Left side carb already had those replaced by previous owner.
  • with help of a friend and my manometer, synchronized both carburetors after having to remove the right hand carb to get at the stupid stripped rpoc screw.
  • cleaned out the fuel petcock bowl, had found some cork crud on the bottom, probably from a disintegrated cork seal or something. Verified good fuel flow from both lines.
Natasha now idles great, starts every time with the electric starter or with the kickstart. Of course, it's not a hot day today and I did not go on a long run.

Problem is now that she's got no acceleration power. She just kind of bogs long, slowly creeping up in speed. So while rideable, not exactly what I want in terms of being able to accelerate and keep up with traffic!

I know the carbs are sync'ed and she idles great. I figure it's a timing issue, perhaps the fact I've got mis-matched spark plug cables, perhaps a failed interruptor within the ignition control unit....or a combination of these. I know for a fact its probably not the coil as I first suspected, since it would not hold idle at all if that were the case. So at least, I eliminated the costliest part I was looking to replace (about $100).

I'll be ordering the replacement interruptor first thing tomorrow along with new spark plug cables and new spark plugs. I put some "equivalents" in from Autolite but would like to use the ones recommend in the manual.

5 comments:

cpa3485 said...

I bet that you will have Natasha purring like a kitten in no time.

Richard Machida said...

"found a bad spark plug cable (it was the cap actually) that read zero ohms between ends"

I would think that zero ohms means no resistance and infinity would be an open circuit or failure.

Good luck with the debugging...

Jack Riepe said...

Dear Charlie6 (Dom):

Just when you expect your next bike is going to be "plug and play," the motrorcycle Gods lash out and you find yourself dealing with the "RPOC" factor, or something just like it.

But it seems like you have put these problems into the correct perspective and in a matter of a week or two, should have the bugs in this bike mechanicaly customized right out.

Once again, congratulations on your new job.

Fondest regards,
Jack • reep • Toad
Twisted Roads

Charlie6 said...

cpa3485, she's 99% there as of today. Talked to a great wrench at the wagner's cycle where the PO bought the bike. I re-adjusted the fuel/air mix, blew compressed air through the petcock, lines and carbs and she seems to be running fine in the short test run I just did. Just have to check the timing and see if the interruptor portion of the ignition control unit is loose or not.

Richard-yeah, that's how I understand it as well. I probably should have said it had no reading as in no continuity.

Charlie6 said...

jack, she's 99% back in shape...just got a couple more checks to do for my own peace of mind, timing and check for looseness of a component within the ignition control unit.

re the new job, thanks for vote of confidence...I think I'll do just fine.

I plan a long ride for tomorrow to make sure she's going to stay running well. Got parts on order that'll ensure that for some time to come.