Running rich at highway speeds

[Crazcnuk]

My 80 std is running very rich at highway speeds, I think. Just wondering which part would cause this, as, if anything, I should be running lean.

I have S&S 4 into 2 exhaust, K&N air filter, all else is stock. It's an 81 special engine using 80G carbs.

The bike runs fine at low to mid speeds. It will pull right to redline in 1st and 2nd, but 3rd 4th and 5th each have less pull after 7000rpm.

The bike is getting about 26mpg, right now, and it 'smells' very much like it's rich and burning oil when cruising down the highway.

I set the floats at 23mm before I put them on the bike. I don't have any leaks or overflow problems.

Is it possible that one or two cylinders are just so far out of synch it would cause this?

[egsols]

I'm still learning more about the carbs everyday. I can't quite remember the specs for your carbs but isn't the float setting closer to 25MM? Also are your mains bigger than stock?

Ernie

[79XS11F]

If jetting changes were made for the pipe and K@N filter you may be too large on the main jets. Syncing the carbs is in deed a good place to start before you get into messing around with the jetting.
Rob

[TADracer]

Highway speeds (4000 RPM) is usually running on the mid and main jet circuits. Your mains may be too big but before changing any of that, try resetting your floats and syncronizing your carbs. That is easy to do and cost nothing.

I believe stock is 25.7mm (+/- 1mm) from the gasket surface without the gasket in place. If that is the right setting for your bike, then 23mm will definately give you a rich feeling. 1mm on the float setting will make a difference and 2.7mm, as you are set, will put your carbs on the rich side.

[mro]

80 carbs, 23mm float height

Would sync and see how it runs.
Should make a noticeable improvement
110 mains if stock on the 80 carbs.
might have 115 in center pair


mro

[trapper_492001]

Crazcnuk

When I resurrected my 81 SH I didn't know about this forum and went thru a lot of trial and error with the carbs. I had it dialed in pretty good but had the same problem with it running rich at higher rpms. Then I found this forum and all of the vast knowledge. In the teck tips is a thread on adjusting the float hight using a clear plastic hose from the float bowl drain. I set my carbs in a vice and leveled them then used the clear plastic tube to see EXaltly where the fuel level was. To My suprise even tho all floats where the same hight the fuel levels where not the same. With the fuel levels in all the carbs the same hight my plugs are all a uniform color and no mure rich smell. Then I learned the true meaning to a death grip. It was a while before the grin went away.

Trapper

[trapper_492001]

By the way I did resinc the carbs again after I adjusted the floats

[Crazcnuk]

The jets are all stock, for an 80. It has the 110s all across, IIRC.

I thought the float height was 21mm for these, but 23mm was recommended here in the forums.

I will have to recheck. Just thought I would ask before I rip them out.

The idle mixture screw on #1 is all chewed up, so that I can't turn it with a screwdriver, so I have to fix that anyway.

[mro]

screw on #1 is all chewed up

Sometimes can use an "awl" (sharp metal pointy thing, like a heavy needle)
If it can get a purchase on outside edge of screw can sorta spin the screw out. Would spray screw with some super lube first.


mro
really works...sorta...sometimes
well it works for me

[Crazcnuk]

Took the carbs off tongiht, and cleaned them. Checked my specs, 80G should be 23mm +/-.5.

I set them to 24mm. I set the idle mixtures on the 3 that I can turn the screws.

Will see how it runs tomorrow, going on another toy run.

[Crazcnuk]

Took it for about 180kms. Haven't had a chance to really check the fuel mileage, as th etrip involved a 1.5hr, under 20kph, 28C day, parade.

The bike, and a few hundered others were getting pretty hot. I can never understand why parade planners can't understand AIR COOLING!


Anyway, the first half of the trip seemed better, about 120kms on the same amount of fuel I was getting 90kms with before. However, won't know until I can get a clean run.

Otherwise it seemed to run pretty much as before. I am burning a fair amount of oil, which isn't good.