81 carbs initial settings?

[Tbell]

Finished rebuilding the carbs and bench testing the fuel level. Are there any specific things I need to do before I re-install back on the bike? Is there an initial setting for the pilot screws? They were set at 3, 3, 3 1/2 and 4 1/2. Should I stay at that setting or set them all to a specific setting and start from there? Any info will be appreciated. Thanks!

Tom

[WMarshy]

The shot answer is yes, there are other things you can/might want/should do to or check on the carbs prior to putting them back on. Some of those things depends on the condition they were in before they came off the bike. So, was the bike running fairly well prior to takin them off? It might be worth your time to do a bread-tie sync aka "bench sync". Did you check you float heights? If not, there is a way to do it on the bike with fuel in them...some claim the later to be a better method. Anything else guys? You should take some time to look through the tech tips on cleaning/tuning the carbs, it has everything you could imagine.

[Tbell]

The bike sat for about 12 years before I got it. I know the PO and it ran well before he parked it. I have thoroughly cleaned the carbs and all parts and replaced the float valves and all seals. Checked the float levels and then did the clear tubing test. Just need advise on any tips before re-install.

[DGXSER]

Before remounting I recommend a few test.

First, you did check the float heights, right?

Secondly, check the floats valves hold. Per our good friend and guru Prom, with the carbs upside down and bowls removed, hook fuel up to the lines. See that no fuel runs out any valves. Now "blip" the floats to let the air out of the lines and see fuel at the valves. Dry up the fuel with compressed air or towels. And now wait....make a sandwhich and have lunch...and then go back and see if any fuel has leaked out the valves. If not, then move on.

Third test, with bowls on and upside right, hook fuel up to the carbs with carbs level. On the 81 models, there is a test to check fuel level by hooking a piece of fuel line to the drain and opening it as you hold the line up beside the bowl flange. The fuel should come up to about .25" or so below the flange, I forget the specification. More importantly, see that no fuel comes pouring out your carbs and the float valves hold.

Now some folks will tell you that the only way to really set up the carbs correctly is to check that level with the tube and all. I can tell you I tried it a few times and got VERY eroneous results. I have always set my floats with a ruler at 23mm (factory spec) and my bikes have always run pretty nice.

The above test of the float valves could save you a few trips back into the carbs over leaking floats.

[Tbell]

I have read all of the tech tips. Sometimes there are things that others know that aren't documented.
I have measured the floats and they are all set exactly at 23mm.
I will now do the float valve tests suggested by DGXER. Thanks! any other advice? What about the initial pilot settings?

Tom

[DGXSER]

Tom,

I have found that the pilot mixture screws get turned out instead of cleaning up dirty idle jet circuits. I would suggest starting them all at two turns out to begin with. I should start and run at those settings. Might end up closer to 3 turns after you tune the carbs, but I found similar settings on mine before I cleaned them and after 2 to 2-1/2 was good.

[Tbell]

That makes sense. Thank you!

Tom

[WMarshy]

Did you check to make sure none of the pilot screw tips are broken off? Might want to take them our if you havent already done so and check. Just be careful not to bottom them out too hard and break a tip when tuning...

[CatatonicBug]

Mine are all turned out over 4 turns, and I know Bigfoot has his the same way on his MNS. I just re-colortuned last night after installing a Dynojet kit, and had to turn them all out just a bit more.

[Tbell]

I have had the carbs apart and cleaned them up. Everything is in good shape. Nothing broken. They were just gummed up from sitting for so many years with fuel left in them.

Tom

[81xsproject]

Mine are all turned out over 4 turns, and I know Bigfoot has his the same way on his MNS. I just re-colortuned last night after installing a Dynojet kit, and had to turn them all out just a bit more.

EXACTLY what happened to me. Unless the dynojet kit has smaller pilots (and I would be it does not), your colortune is misleading you. I know that many people love them. I followed the lead of my colortune and took my screws out past 4 to get the "golden/yellow" tinge on blue color. Shortly after, I installed the Wideband O2. The mixture was down in the 10's (AFR). I used the wideband and adjusted it back to high 12's and they were around 3 turns out. Just an FYI.

As far as a starting point, after a clean and rebuild, I always start them out at 3 turns out. Fires right up everytime.

[DGXSER]

Colortune

Realistically, from all that I ahve seen and even from folks who swear by the tool, it is a good tool to get you close. You still want to read the plugs and make any adjustments they indicate to be needed. Unless you just hog wild and put an O2 sensor in.

[cywelchjr]

Realistically, from all that I ahve seen and even from folks who swear by the tool, it is a good tool to get you close. You still want to read the plugs and make any adjustments they indicate to be needed. Unless you just hog wild and put an O2 sensor in.

Hey! If you do that it's one step closer to fuel injection (my long term goal).

[CatatonicBug]

Realistically, from all that I ahve seen and even from folks who swear by the tool, it is a good tool to get you close. You still want to read the plugs and make any adjustments they indicate to be needed. Unless you just hog wild and put an O2 sensor in.

Close is close enough for me. The kit doesn't have new pilot jets, but it DOES have larger air jets, which would inherently make the mixture leaner if not adjusted. I'm happy with the plug color, and REALLY happy with the 12mpg increase!

[TopCatGr58]

Hey Tbell,

No aspersions on your skills, etc., but just want to mention that the pilot screws for the 81 has small metal and rubber washers down inside the pilot screw tunnels, and just want to make sure that you found them, and cleaned or replaced them properly. They sometimes get stuck down there, and if you haven't seen the exploded views, you might not know that it wasn't just the metal pilot screw that goes down in there!?

The bench synch with bread tie is okay, but using the view of the 3 small ports on inside upper part of the engine side of the carbs and how far the butterfly covers one of the holes just before it closes, and set them all to the same amount...about covering 1/2 the hole before the butterfly completely closes.

The stock settings for the screws are about 1 1/2 turns out, but they were usually set/tuned lean for EPA, that's why Don suggested going to 2 or more. That's about it, the slide needles aren't really adjustable much. And the pilot jet tower in the bowl side should NOT have any plugs over them, they should both be open to the bowl.

Did you ensure that the small jet down in the BOWL itself was also open and flowing...that's your starter /choke jet!

T.C.