79 XS11 Idle Issues

[dondons1984]

You can never sync these monsters to perfection. I was thinking at first that maybe you were running lean. did you ever do the spark plug check? But as for 90 miles on one tank before the light that is normal. Question I got is are you getting a lot of vibration? sputtering? what do you have everything set to now? I.E. mix screws

[Schrock86]

Finally got some time to work on the bike again. The mix screws are at 2 turns out, and I vacuum sync'd the carbs. Everything was going well until the bike warmed up. I realize I should probably sync the carbs when the engine is warm but I thought I could get them close cold since it only has issues when warm. Anyway once it warmed up the idle started to climb again. And the number 3 carb had quite a bit more vac than the other three. I sprayed carb cleaner all over while it was running and the idle didn't change at all. So what should I look for internally.

[Schrock86]

Question I got is are you getting a lot of vibration? sputtering? what do you have everything set to now? I.E. mix screws

No vibration, or sputtering just idles high when warm

[donebysunday]

Bad gas

No vibration, or sputtering just idles high when warm

After you either clean the tank out or run enough fuel through it to rid the float bowls of this spoiled E10 crap you will continue to have mixed problems. Set the idle where it's supposed to be and then correct the bad gas problem.

[bikerphil]

To get the most accurate sync, take the bike up to highway speeds on the superslab for a nice good warmup, then bring her back home and put the box fan on the engine and sync away. JMHO

[Schrock86]

Hey Schrock-- maybe go to my recent thread--"unwanted revving issue". There might be some ideas you can use. These guys are very knowledgeable, and helped me get my '79 xs running sweetly. One suggestion ( from a lot of guys) was to replace K&L pilot jets with genuine Mikuni jets. That was the 'magic ' fix. My bike runs like a beast.

Mine also has K&L jets currently, I plan to put Mikuni's in tomorrow then take if for a ride and re sync. Hopefully that clears up the problem. On a side note my oil light came on while trying to diagnose all this. Thanks to bikerphil it was an easy fix just a little twist to the LCU harness and the light went right out.

[natemoen]

As it warmed up and the idle started climing did you turn the main idle adjustment down to compensate? That usually what needs to be done.

[Schrock86]

Pulled the carbs tonight and replaced K&L jets with stock Mikuni's. I wish I would have just cleaned the stock jets from the beginning instead of installing the new clean ones when I originally cleaned the carbs. I rode for about ten minutes tonight and everything seemed fine. Previously it would idle up in less than 5 minutes. If I get time this weekend i'll go for an extended ride and resync when I get home.

[Schrock86]

Time for a long overdue update. The bike was not fine and started to idle high the next time I rode it. And that was the last I touched it until this spring. I sprayed around the carbs again with some carb cleaner and determined the throttle shaft seals were leaking. I replaced them and the idle problem has finally gone away. But now it had a misfire around 5k. I performed and ohms test on the ignition system and found 3 resistor caps above 5 ohms, one was over 15 ohms. I replaced those today with new NGK LB05F and XB05F caps. Now the misfire has gone but it feels like it is running out of gas. It feels just like you didnt turn the petcocks on. Right around 7k it just runs out of steam. I can back off the throttle and ease it back on, and it will climb right up to redline. But if i just hammer it, no go. Where do I need to look, will adjusting the Idle air screws help? By the way It has never idled so well or accelerated so smooth. Its amazing how much the resister caps did for the bike.

[MPittma100]

Steam

Check your gas cap vent. Sounds like it may be stopped up. Take the cap apart for inspection. Look for kinked fuel lines. If lines are looped down and back up between the carbs, this will cause a problem more so when tank is half full.

[Schrock86]

My fuel lines were looped down and back up to the carbs. I cut the lines and ran them straight down to the fuel tees. I had already eliminated the octopus mess and have a single line from each petcock directly to the fuel tee. I did the test drive with the fuel cap open just to elimate it entirely from the equation and it still has the same issue. It is less exaggerated now and I can keep it wide open and it will come out of it. Where do I look next?

[mack]

Welcome

I have an SF as well. My idle screws are turned out one full turn, plus 35 minutes as you would look at a clock. Our gas is different up here but I get 110-115 miles before the red light comes on. Sluggish like that is one of the symptoms of being rich.
Do you have brass floats and what height are they set at?

[Schrock86]

They are brass im not sure of the height off the top of my head. I set them at whatever my manual specified. My plugs are black by the way I chalked it up to weak ignition but am wondering if maybe the carbs are set rich as well. Now that the ignition is fixed ill have to read the plugs again.

[Schrock86]

I decided to remove the carbs again and check everything once again. I did find a very small amount of sludge on the emulsion tube. Also 3 of the 4 floats were a little high and one was low. After a tedious cleaning and measuring of float height. I reassembled everything and went for a ride. All is finally well. I am planning on installing an inline filter now just as extra insurance.