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Message started by Sandy Koocanusa on 06/06/08 at 18:21:16

Title: On reading pipes and plugs
Post by Sandy Koocanusa on 06/06/08 at 18:21:16

I had my spark plug out today, and was a little surprised at what I saw. Then again it doesn't take much to surprise me. Maybe someone can clarify a few things for me.

Here's how I read the symptoms (good and bad):
1.) Exhaust shows about 2 inches of blue at head/header joint, fading to a nice gold color which runs to about the front foot peg (getting lighter all the way. By then, and from then on, the exhaust is chrome colored.
2.) The muffler pops and gurgles on decel, but never blasts unless I slap the throttle shut, and not even all the time then.
3.) The muffler gives a quiet little fart sometimes when I shut it down. More and more often the higher it is idling at shut down.

All these things I would think indicate that the bike is running just on the lean side of perfect.

But my plug (gapped at .034) is dry and black and starting to get fluffy. This I take to mean the bike is running too rich. It's a newish plug. (1000 miles?) NGK.

I rarely run WOT, but most of my riding is at 65, 70 mph. Do I need to run it harder once in awhile, or what?

I haven't opened the carb on this one yet, but to my knowledge it's running a 155 main jet. I think that was stock, and I have every reason to believe the bike was pretty much unchanged until I got my grubby little hands on it.

Any ideas?

Title: Re: On reading pipes and plugs
Post by Reelthing on 06/06/08 at 18:54:44

that a 86-88 ?

a good way to find what range is rich/lean is to start with about half dozen of cheap champion plugs - go through the plug/chop cycles -
where you'll the engine at a steady speed, pull the cluch and turn the engine off - pull the plug and have a look - helps if you either leave the cover on the leftside off or leave the rear bolt out.

takes awaile but you'll know what's going on

Title: Re: On reading pipes and plugs
Post by serowbot on 06/06/08 at 19:13:12

Here's how I test main jets...
Get going at a gentle lope in 4th gear, say 40mph, then go full throttle for about 3 seconds...now very slightly roll a tiny bit of throttle off... If the engine slows a bit, you're good,... if you feel a little increase in power, you need a bigger main.
Don't judge your jetting by the pipe color, This bike has a double wall pipe, but it is a thin one and will blue, if you drive in heat, or do mountain rides, etc. Too many variables.
From the look of you're plug I'd say you're rich at some point. i.e. idle,pilot, spacer or main.

Title: Re: On reading pipes and plugs
Post by thumperclone on 06/06/08 at 19:28:32

jmo:
you can not perfectly tune (afish)a carb..humidity changes= tune changes, temp changes=,altitude(less O2)changes= etc etc
best you can hope for is a happy medium..that said you should be able to tune out any shut down howitzer booms.

Title: Re: On reading pipes and plugs
Post by Sandy Koocanusa on 06/06/08 at 19:44:21

Well, I guess I'll leave it be for now. I wasn't worried about it, just curious. I opened up my exhaust some more today, so I'm sure that will change things too. If it's running and not breaking nearby windows, I guess it's tuned just fine, eh?

Title: Re: On reading pipes and plugs
Post by photojoe on 06/07/08 at 11:18:23

Sandy: You just described the color of my header, and this just happened during the last couple of weeks. I have an '87 as well.

I pulled up pictures that I took last month while documenting the oil leak. I did get the exhaust header in the pix, and it was just a bit blue going into yellow. Got back from a ride earlier today and noticed a big change in color. Huge increase in blue and yellow from the cyl head, through the bend and down about a foot. The only thing I've done different in the last few weeks is go to lower octane fuel. I was running 93 octane, until reading that it was overkill, so I changed to 89. Didn't change to save money (it's only a few cents more anyway), more to heed suggestions I've read regarding octane in an '87.

Bike seems to backfire when it wants. I haven't noticed backfire at all in the last few weeks, but today riding 2-up, I was getting it a decel, and also got the fart at shutdown after a 20 mile ride through the back roads at 40-70 mph. I'll pull the plug in the next couple of days, it's about time for a change anyway.

Title: Re: On reading pipes and plugs
Post by bill67 on 06/07/08 at 11:30:46

I think running 93 octane gas which burns slower is like retarding the spark which would made it run cooler

Title: Re: On reading pipes and plugs
Post by photojoe on 06/07/08 at 11:41:17

I'm going to have to agree with you Bill. I did read lengthy discussions/debates about octane for older bikes, and decided to make the change to lower octane. I'm going to burn through this tank, and fill it back up with premium. Being that the temp is in the high 90's now, the last thing we need is a hotter engine. I guess it warrants a ride along the cool shore roads tonight to get rid of the 89.