Which way do I turn air screws to run less rich?

**almarconi** · 02-22-2010, 01:25 PM

You turn them in to lean the mixture, out to richen the mixture.

**Larry D** · 02-22-2010, 01:53 PM

Those screws only control the mixture at idle. The jets inside the carbs provide the proper mixture for other throttle positions. If you have no mods, they should be about 2-2 1/2 turns out from lightly seated. YMMV, I think the ones on my 750 are 2 3/4 turns out. Also, they all may not end up the same. Search for the highest rpm method for tuning.

When you had your carbs apart, did you verify that the correct jets (pilot,main) were in there ?

**Steve** · 02-22-2010, 02:42 PM

Any of the adjustment screws on any of the carbs on our bikes work the same way:
Turn them clockwise to reduce what they are controlling.
Turn them counter-clockwise to increase what they are controlling.

The trick is to know what they are controlling.

On the VM carbs, there are separate screws for air and fuel. Turning the fuel screw out will richen the mixture, turning the air screw out will lean it. See? Same motion, different results because you are controlling different things.

On the BS carbs (like your '82), the screws actually control a pre-set mixture of air and fuel, but you can still control how much of that there is, essentially richening and leaning the total mixture that gets to the cylinder.

If your carbs are running rich with the screws turned all the way IN, the first thing to check is your float level. If the level is high, the carb will run rich in all of its circuits. If the level is right, check your pilot fuel jet to make sure it's the right size. If it's larger than stock, you will need to turn the screws in to compensate.

When you "ran the bike for 30 minutes", were you just running the engine in the garage or were you out riding? It makes a difference for troubleshooting. Running in the garage will basically not use anything but the pilot (idle) circuit. Riding the bike stands a better chance of using them all.

.

**1_v8_merc** · 02-22-2010, 05:26 PM

Alright guys, thanks alot.

I got it running better now.

I was wrong, I actually had them turned out over 2 1/2 turns!
(i don't know if I was drunk when I originally set it, or didn't count the turns accurately or what!

)

I tightened them down all the way, and the bike wouldn't even start right.
I loosened them about 2 turns each, and it fired right up and ran ALOT better.

I still have a slight Idle issue with the bike, but once the bike warms up, it usually Idles correctly.

I also didn't have an erratic RPM jumping issues like I did a few weeks ago, which was when I first fired up the bike!(wooohooo!)

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BTW: I DO have correct Pilot Jets installed....brand new, matched the numbers up, they are correct.

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I also still have one Carb that WONT let me mess with the Air/Fuel screw....it's completely stuck and the surrounding threading is stripped.
However that carb doesn't appear to be running wild or out of whack so far......

I also have some Valve Clacking noises from the top of the engine, so that's my main priority next!!!
(i just wanted to get the bike running somewhat normally first.)

**Steve** · 02-22-2010, 06:05 PM

Originally posted by 1_v8_merc

I also have some Valve Clacking noises from the top of the engine, so that's my main priority next!!!
(i just wanted to get the bike running somewhat normally first.)

Nice to hear about the success with the carbs, but I have always felt that valves have a higher priority than the carbs.

If the valves are not set right, the piston will not be drawing the right amount of air through the carbs, so the mix will be off a bit. Get the proper amount of air flowing, then play with how much gas you feed it.

Valves "clacking"? If so, you have some serious problems as the maximum limit on the specs for valve adjustment is only the thickness of a piece of paper. Hardly enough room for them to "clack", so if they are "clacking", there's WAY too much clearance.

May I also suggest that you send a request for my spreadsheet? Could help a bit with your valve adjustment. Look in my sig for details.

.

**1_v8_merc** · 02-22-2010, 09:57 PM

Originally posted by Steve

Nice to hear about the success with the carbs, but I have always felt that valves have a higher priority than the carbs.

If the valves are not set right, the piston will not be drawing the right amount of air through the carbs, so the mix will be off a bit. Get the proper amount of air flowing, then play with how much gas you feed it.

Valves "clacking"? If so, you have some serious problems as the maximum limit on the specs for valve adjustment is only the thickness of a piece of paper. Hardly enough room for them to "clack", so if they are "clacking", there's WAY too much clearance.

May I also suggest that you send a request for my spreadsheet? Could help a bit with your valve adjustment. Look in my sig for details.

.

Okay, e-mail sent.

Oh yeah, forgot to mention, my valves aren't always clacking, it's like On and Off at random....but It's kind of like I hear a smaller noise in them too, maybe it's just normal....
But ONLY the right side of the top engine is making the Loud noise, whenever the noise does come.

I don't expect any diagnose or anything, lol, im just putting that out there anyways!

**Steve** · 02-22-2010, 10:09 PM

Does your "clacking" go away if you rev it up to about 1500 rpm?

Could be the infamous "cam walk". Fixable, but not cheap, just get used to it, it won't hurt anything.

.

Which way do I turn air screws to run less rich?

Which way do I turn air screws to run less rich?

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