xj1100 slow surge in high gear 6500 RPM

I have a strange slow surging at 6500 in fifth gear. The bike stops pulling hard and then it pulls for a sec and then not so much and then pulls again. Not like my GS when it had a bad 2nd gear and it would jump in and out of gear. MAYBE the fuel flow is low or clutch? Let me know if you have experienced this or have a good idea what it could be? Clean carbs and sync new lines and new NOS vacuum thingy. rebuilt petcocks. ?

 

Oh where to start, could be a number of things
Float levels
sticking carb slides or leaking diaphrams
Carb jetting
dirty fuel screens in petcocks or float valve screen
Are you running stock exhaust and air box or are they modified?

 

everything is stock , so you think its fuel flow. I would thinks so too. But everything was cleaned recently except petcock screens but I have cleaned them in the past. tank looks new inside no rust at all.

 

When you cleaned the carbs did you check the fuel level in the float bowls (wet set)? Did you synch the carbs? When was the last time valve clearances were checked (thinking about a possible vacuum issue causing a slide to "bounce")?

 

Carbs cleaned and checked 1 week ago. synchronized 1 week ago valves done 2 weeks ago. newer intake boots and caps.
Set floats with tubes a few years ago did not change setting. cheeked with metric ruler last week looked okay. Slides cheeked with drop test and compresses air into air port. Seemed to be okay.

Vacuum hoses are good. what about the boost controller? does that control high rpm spark or only when its accelerating? I am thinking that the vacuum might be sucking the line shut to the Boost controller. The line is a bit soft but no leakage.

 

Boost controller? On an XJ1100?
Are you talking about having bypassed the "octopus"?

 

YES there is a Boost controller on the XJ1100 its a back box with a vacuum line on one side and wires on the other. What it actually does is a mystery to me. Must work like a vacuum advance I think.

 

YAY! I got to learn about a new thing. That always makes me happy.

 

Yes the vacuum boost does control timing.
Have you checked the plug color to see if it is running rich or lean?
I am thinking there is something in the ignition that is acting up at 6500 rpm.

 

not yet I will take a look in s few days when I get back to it.

 

Double check your float levels using a bit of clear tubing to see exactly where it is. You only have a 2mm range to work with, so fuel levels are critial.

Wet set, in case you have not seen it.

I don't know a thing about how the vac-advance on an 1100 works, but a photo of it might give me a clue. Can the casing be opened like it can on the XS1100? The internals may just be gunked up.

 

Not sure if it can be opened or not. I don't think so but I will check.
I have not checked the float level but never changed them since I did it last time. It was done wet with the tubes.
I would think that a advance would only be needed when the rpm is increasing rapidly. Like in cars.
Maybe the one of the coils is not working at high rpm could that be?

I will check the float level again as soon as I can. Having some health issues so taking one day at a time. thanks for your input I do appreciate it.

 

Advance has to occur at a set RPM range. The rate of acceleration does not matter. I have a story about a cross-state trip that took three times as long, because the vacuum advance on my truck gave out and I couldn't get a replacement at the time. 120 miles at 35 MPH...wooo fun.

How about you do this. Check the fuel levels and report back. One thing at a time. Jumping around won't solve this any faster, and may make it take longer. The first rule of troubleshooting is to find all of the things that do work.

 

I pulled the plugs today and found that #1 was running hot or lean, the plug was white the other three looked okay.
I cleaned them and reinstalled. I lean pop on that side and found that the exhaust was not tight on all of the pipes.
Number 1 was loose. I noted the pop after this and had already played with the number one mix and could not get rid if the pop so I knew I had to get to the #2 adjustment. Had to pull the tank and octopus thingy to get to it. Backed it out and the popping is now gone! I broke one of the little plastic T that sits between the carbs so I just removed the octopus and went from the on port to the carbs and the prime to each other. I will have to ride it for a bit to see if 1 is still lean.