Backfire / Rich condition after sealing airbox. Airscrews?

[bwringer]

I've got the mixture screw on #1 cylinder screwed all the way in, and I am still running lean on that cylinder.

Um... yer backwards there -- OUT is rich, IN is lean.


Also, were the carbs rejetted before you got the bike? The only way to know is to look at the mains, pilots, and needles and compare these to what they should be stock. This info is normally on the microfiche in the descriptions of the parts -- it'll say something like "JET MAIN 110" or whatever.

[bwringer]

Is there some kind of zero point for the idle synch?

Yes -- look up "bench sync". It's what you do when reassembling carbs to get the sync in the ballpark so you can start the bike.

However, synchronization will not cause or fix the symptoms you are having. It has nothing to do with mixture -- it simply means fine-tuning the linkages between the carbs so that the throttles all open at exactly the same time. A bike will actually run and ride fine even if it's badly out of sync, but it will sound and feel a lot smoother, especially at idle, when you take care of this last step.

You need to back up and verify whether or not you have stock jetting, since you returned to stock intake and (I think) stock exhaust.

It would also be an EXCELLENT idea to completely disassemble and clean the carbs and replace all the o-rings per the Carb Cleanup Series. In fact, farting around further without doing this is pretty pointless. Since you hadn't removed the plugs over the mixture screws before now, I bet you tried to get away without this.

There's therefore no way to know how elderly the o-rings in the carbs are. The tiny o-ring around the idle mixture screw in particular will create all sorts of problems when it deteriorates.

Finally, if the carbs have been rebuilt with kits, this may be causing some of the problems. Carb kits are well-known to include shoddy out-of-spec imitation parts, and if the jets have been replaced with shonky kit parts, there's no way to tell what's really in there, and they definitely won't work right (Guess how I know this? Go on, guess.).

Carb kits are a complete waste of money -- all you need to rebuild is a $15 o-ring kit from our pal Robert Barr ( http://cycleorings.com ) and possibly float bowl gaskets, which are about $3 - $4 each.

[Steve]

Alright, I've got the valve clearances all at .05mm or more.
"or more"? Hopefully not much more than .09mm, specs call for a max of .08mm.

I've got the mixture screw on #1 cylinder screwed all the way in, and I am still running lean on that cylinder.
That would be NO surprise. Turning IN leans it out, turning OUT richens. Try 1.5 turns, since your original post said you were at 2 turns.

Fire is strong, and I didn't have this problem before sealing the air box.

The float levels were checked 2 years ago when I first got this thing to run.
Levels checked 2 years ago? Why not more recently?

Dyna S, Green Dyna Coils, Clean and slightly oiled air filter....

Remember... everything was A-OK before I sealed the air box.
Apparently things were adjusted to compensate for the air leaks. Sealing the leaks is now making it a bit rich.

Soo..... what gives? Any ideas?
Another common cause of backfiring is leaking exhaust gaskets. The clamps might be a bit loose or the gasket itself might be faulty. Be careful, those clamp bolts are VERY prone to breaking off. :shock:

I'm reading the plug to come to this conclusion. It's not reading like I'm getting oil in my cylinder and burning that up, and it's not smoking, but it is still freaking backfiring like the original post.

I'll try to synchronize the carbs tonight, as I've still got a slow-to-warm #2 cylinder.
One cylinder that is slow to warm could be out-of-sync or might have dirty pilot jets. Check again after the sync to see if it warms quicker.

Will carbs out of synch give me backfire after sealing the airbox?
Carbs out of sync should not cause backfiring. What they will do is cause rough idling and ragged response just off-idle. You will also notice a buzziness in the handlebars due to uneven firing pulses. I know you don't have one, but the 1000s and 1100s seem to be more sensitive to carb balance to run smoothly at speed.

[uudfourty]

I mistyped: The mixture screw is all the way in and it's still too rich. My bad.

Got the synchronization squared away and leveled out. It does run much better since I adjusted the valves and whatnot...

But it still idles weird, so apparently not all is well in the state of Denmark.

I'll have to go back and re-set to the highest speed method I suppose, but If number 1 carb is still way to rich (sorry again) with the screw all the way in, what's that indicative of?

And... somehow.... the backfiring is gone.

It wasn't gone after I adjusted the valves, went away last night after I leveled off the vacuum on the carbs...

Hang on a second while I go get another job.