Poor fuel mileage

[ChrisO]

Hey guys, I'm new to the forums, but I've been turning wrenches on my 79 for around 2 years now.

I've got the 79 1000 with carbs from an 83 1100A, and I was getting around 20mpg. I decided to rejet (80/145 to 60/130) and see if I couldn't lean it out that way, and my mileage dropped to 16mpg.
I've been told to set float height, and I'm seeing 15.5mm as the setting, and I just want to verify that. Also, I've been told to check for shims under the needle, but also told that would be far less significant than the float height.

The only other thing I've done to the engine is a set of Accel supercoils and wires. I'm at a loss here, and I plan on tearing back into it this weekend and see about addressing a few of these issues.

Thanks in advance!

[ChrisO]

I'll also add that it feels like cylinders are starting to skip intermittently at cruising speeds.

[Track T 2411]

15.5 mm is the correct setting. Have you tried a plug 'chop' or compared plugs? Even though the 1100 carbs are less than ideal on a 1000, you should be getting better mileage than that. I'd be looking at your idle circuits and pilot screw settings... My 2 cents.

[Whiskerfish]

Got to be either a hanging brake or your carbs are fouled somehow.

[ChrisO]

I'm going to devote Saturday to going through everything I can fit a wrench to. I recently upgraded my plugs to iridium resistor plugs to get a little hotter spark (which was visible with the plug out of the chamber) but I probably need to rewire my electronic ignition.

On top of that, I'll get the float height set as best I can and check every port on the carbs for blockages or leaks.

[avg_joe]

Check the CV slides for scuffing, too. I think it was more of an issue in 82, but worth checking into.

[roachb]

Have you checked your compression?

But with mileage that low I would be looking for a binding brake.

[ChrisO]

Just got done putting it back together enough to get it to run after adjusting the float heights. Couple of things: first, both side would backfire under open throttle and cough out some rich black smoke. Second, it seems like the throttle response improved, but it's likeit's like there's a random misfire occasionally. I'm pretty concerned about the black smoke misfires, I'll try to get a video of it this afternoon.

Back brake isn't hanging, wheel turns freely on the center stand.

[ChrisO]

Also, and I just discovered this, spraying carb or brake cleaner into the plenum will kill the engine. Almost like it's completely flooding it out.

[desertrefugee]

You might want to check and verify that the choke is correctly opening up the plates. If not, it could cause the symptoms you describe.

[ChrisO]

I've disconnected the choke because it only actuated one side. I'm not sure what else I can do with the choke, since the only way to close it is by hand at the carbs...

[Whiskerfish]

I think you need to do a Complete rebuild on those carbs.

[ChrisO]

I thought I did when I put the Randakk's kit in it. If I were to split them again, what are the key points I may have missed?

[robin1731]

Double check that the chokes aren't closed. Even disconnected they can stick closed. Also make sure you don't have any plug wires crossed.

.

[ChrisO]

Just got it back together and rode some this evening. It seemed to be all there with the air filter and housing off, albeit rich, but it seemed like everything was functioning properly. I stuck my phone in the plenum and watched the slides bob up and down when I rolled the throttle, and the choke plates were all open. When the carbs were off, I adjusted the floats out to the best of my ability, but it didn't seem to help.

Once I got the bike back together, I rode to the gas station to fill up, and the bike felt like it was only running on 2 or 3 cylinders under a load. I threw in some seafoam to see if it would clean them out a bit before tearing back into it, but it just wouldn't perform in gear. I got home, removed the filter, no difference. Still ran like it was missing. All of the spark plugs were fouled out, but they were all also dry, so I can't imagine it wasn't firing.

I'm thinking about going to a single carb conversion, but I hear those also have issues, but I'd need someone interested in my 1000's and my 1100's to fund the swap. I'd like these to work as they were intended, which means I'll switch the Jets back out to the stock ones and cut my losses there, but I still don't know where to go from here.

Thanks for all the help this far. It's really appreciated.