1981 xs1100 running rough at low rpm

[TopCatGr58]

Hey Dave,

Glad it's behaving better. As to pulling the plugs after a short run, you need to perform the throttle chop method to properly evaluate the MAIN JETS.
Find a decent slight incline grade, hold the throttle steady at around 4-5k rpm for 30 seconds to a minute, then hit the kill switch while pulling in the clutch at the same time, coast to the roadside, and then pull the plugs and take a look.

If you just ride it around a bit and then pull the plugs, you'll be checking the pilot jets mostly.

And remember, the Pilot jet screws are FUEL/AIR mixture screws, not air screws. More turns out richens, turns in leans.

T.C.

[leggman1]

Have you ever used a colortune plug?

[skids]

Have you ever used a colortune plug?

I have a colortune kit. That device is more for setting idle circuit richness. It won't tell you what is happening under load.

[leggman1]

it is running somewhat better but still not right. I went for a short ride a little while ago and I think its only running on three cylinders. sometimes the forth one kicks in and it smoothes out and has way more power. I am suspecting a stuck needle in number four carb. When I first put it back together the needle in 4 was stuck open and gas was coming from everywhere
I tapped on the bowl and the gas stopped. so now I think it is starved for fuel because #4 is sweating and the other three are dry.

[leggman1]

OK this time I really got it. The only thing I didn't do when I went into the carbs the other day was pull the floats and clean the needles/seats/screens. Today I did and I found a bunch of crapola under the #3 screen which was blocking fuel from getting into the bowl.
After a good cleaning and some reassembly it starts great runs strong on ALL cylinders and idles smoothly at 1000 rpm. NO and I mean NO hesitation when you give it a twist. It will be tomorrow when I can go for a good ride but I really believe it is fixed Woo Hoo.
Thanks to all who helped. Dave

[bikerphil]

Dave, are you running fuel filters? If not, it might be a good idea.

[leggman1]

Yes, I have two small filters (one for each side) coming off the tank. I eliminated the octy and plugged the front tubes on the petcocks.
When I pulled the needles and seats I noticed the seats has small screens on the top.
Tomorrow I will go for another test ride. Can't wait.
I am not sure what year carbs I have. I would post a pic but that's something I haven't figured out yet.

[leggman1]

I went for a 20 mile ride earlier and it runs soo much better when it's hitting on all four cylinders.
This bike is really a LOT different than my BMW. The Beemer is gobs of low end torque and lower rpms where the Yamaha is living at a much higher rpm range.
Some changes will have to be made to this bike if I am going to keep it. I am six 1 and 250 on a good day and the stepped seat and roto tiller handlebars are just too uncomfortable. If I could stretch the frame about six inches then maybe but I won't do that.
The bike runs great now and it is street legal after sitting for about fifteen years. I guess the PO didn't want to deal with the carb issues it had.
I would like to know what other xs owners have done to make these bikes ridable.

[skids]

I would like to know what other xs owners have done to make these bikes ridable.

Highway pegs on crash bars.
Goldwing bars. Actually, the 81 standard bars are the best. (used both)

[leggman1]

I am just not a fan of the seat. The bars are different but comfortable. I think maybe a seat from a 79 where it doesn't have such a big step might be better. It really makes you wonder what they were thinking back then. It's like one manufacturer comes up with a bad idea and everyone else has to copy that same bad idea.
I like the looks of the cafe racers but I could see where a 20 minute ride would kill your butt.
My 78 bmw had a rather flat seat from the factory and after a year or two I got a corbin seat. Much better.

[bikerphil]

Here is the seat interchange guide...

http://www.xs11.com/forum/showthread.php?t=36552

[leggman1]

Phil, You are a wealth of information. I like the 79 seat much better than the factory king/queen seat.

[leggman1]

I think I got the photos thing working
Carbs
https://i.imgur.com/E8mZSv6.jpg
https://i.imgur.com/nU7kk1J.jpg