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Just back in from runs on the mountain. Went to center clip on the needle and back to 280 mains.....not much power and WHITE plugs at WOT chop. Back home, clip still in middle but put in 320 mains and advanced the timing a bit. Much better WOT plugs and nice bump in power all throughout. It's still stuttering at just off idle but less. Idle is good with brown plugs with light dusting of black/gray. Still no pinging so I will advance a bit more and see what happens. Buster runs really well now...and with all the tire/rim/shock changes...swallows corners like a crackho'
Cheers! :p

Redman,

What do the plugs look like at the base of the insulator? All those plug diagrams in the Chilton's manuals are pretty useless. Plug should be totally clean after a chop. Do yourself a favor and cut the plug open. Cut right around the base of the threads. There should be about a band of carbon deposits about 1 mm wide at the base of the insulator. 320 mains sound insanely rich.

Good luck.

No man...they come out very clean but not white anymore. I mean, the insulator is white but the light cream/tan is 3/4 of the ground electrode and the depths have the slightest dusting od black/gray, as does the end of the threaded part..but just a dusting. No pinging at all and runs strong.
These are Monoblocs...remember. I run Dunstall Decibels too, which are very nonrestrictive...and velo stax, so, lots of air gettin thru there.

I realize that Monoblocs run a couple sizes richer than Concentrics, but even on my lightning racer, with open stacks and straight-through absorption mufflers, anything over 200 is too rich. Stock were 190's. OTOH, plugs don't lie. Here's a really good article on plug reading . It took me a long time to figure out how to do this right and cutting the plugs open was like an epiphany. Nothing but the insulator really tells the story.

stuttering at just off idle

These are amals? What needle jet? What cut away on the slide? Anything worn? Dirty? How is the gas? Darn thing. The blend changes as they guess the weather. This time of year even in your next of the woods, might be spotty, and inconsistent.

Thanks for the article: will read.

Thanks guys.....but.....
Stock for Monos 689/389 is 270 to 290 so 320 is not much more than a 10% change.
Needle jet 106, cutaway 3.5, everything NEW and sleeved, clean as it gets, gas is always 91octane Union 76 Super mixed 3/1 with 110octane race gas.

I bring my Xray specs with me and look deep into the plug. I look for cream on the ground at least halfway back to plug body and color ring way down in where insulator cone meets body. Since I am advancing timing now, I am careful to look for shiny dots or balls of alloy and blistering on insulator too.

Hmmmm,

New and sleeved? Smaller tolerance? Some have pointed out makes it run richer. More signal on jets. But sounds like yours is opposite.

I missed a part. You moved the needle before which way?

Gas sounds good.

You went with richer main, how about richer needle jet? Less cut away?

How high was that mountain? Did it run better on the mountain?

Don't mind me if I seem a pest. I am just learning, and hope to benefit from your hard work.

"smaller tolerance?" could be...tight slide fit, that's for sure.
Clip was up a notch..leaner...now it's in the middle.
Gas is good
midrange is great with punch and smooth running so I'm sticking with what I've got in there.
Mt. Tam is less than 2000ft high at peak so no changes in air density 1/2 way up
I'd sure like to get rid of the stuttering...someday.

Redman,

Strange coincidence. Have you seen this thread yet?

http://www.britbike.com/ubb/noncgi/ultimatebb.php?/ubb/get_topic/f/13/t/006773/p/1.html#000003

Thanks BT...went, saw, posted, hopefully will conquer.

I`m not an expert on this but I assume the mixture just off idle would be depending on the throttle cutaway and therefore that your slides (3,5) might be to lean. What does the book say about cutaway? One other thing, if the main jet had to be enrichened how come the cutaway wouldn`t be needing the same cure?

Just my personal opinion.. Good luck

Well, according to all the written material and the gurus here on the forum, "JUST off idle" is the pilot circuit. 1/4 throttle to 1/3 or so is the cutaway, but if I can't sort it out trying that route, I may drop the bux and get #3 slides. Mine are sleeved so it's a few dollars and UPS to Lund's and back plus their charges sleeving new slides to match the OD of my existing slides so they retain the nice fit to the bores... Better yet, if I have to go that route I'll get 2.5s so I can open them up a bit if need be.

Redman,
I put new Concentrics on my 66 A65 that as you know originally came with Monoblocs. The first year for Concentrics was 68 and specs called for 2 1/2 slides but everyone told me that would be too rich so I started at 3 1/2 and had that stutter on acceleration. I moved down to 3's and eventually 2 1/2. The plug is a little darker for my kind of riding, the stutter is gone and I have yet to foul a plug. The needle jet if I recall is in the top slot (richest). I live in NC where summers are pretty hot so I would rather be a tad rich than too lean.

Mr Mike

Thanks MM! Nice to hear real world info....if I have to go that way, I'll get 2.5s...I can always open them up a bit. I thought of cutting a bit off the bottom of my current slided but that would lower the needle etc. May as well start looking for some 2.5s and send'em to Lunds.