Surging On The Highway

Hey everyone, a bit of an interesting issue with my bike.

So you know what I'm working with:

82 xj650rj 23k on the clock.

Carbs spotless, synced, floats wet set
Stock jets and stock air box
No vacuum leaks
Valves in spec
Color tuned, plugs look good to me
Petcock rebuilt
New fuel line and filter
Clutch lever properly adjusted
New tires, properly inflated

The issue is that I get a pretty significant bit of surging or pulsing when running in 4th or 5th at 7k+ rpm. When I hit the on ramp and give it WOT in 1st, the tach is smooth through the entire range, right up to red line, shift into 2nd and all is still good to red line, 3rd is the same, but when I hit 4th the problem appears. All is good to 7k rpm then it starts to surge a bit, struggling to move the needle, shift to 5th and surging is very noticeable, but I'm also then well above the 100 mph so back off. I'm a big guy, 230+ and not equipped with any type of aero package so I could be part of the problem.

This shouldn't be a fuel delivery problem or I would notice it in 1st, 2nd and 3rd gear. I am leaning towards a slipping clutch, but everything is properly adjusted and my rpms surge, not the mph. Could this be caused by oil? I'm running 10w - 40 right now but have thought of switching back to Rotella T. We are down to about 2 months left in riding season before the snow blower will get more use, so I would prefer to leave the clutch alone until then unless it is vital to pull the cover.

Thanks

 

it is the clutch but the clutch works in oil and it's easier to change the oil. go back to the Rotella and see what happens.
the clutch and springs have been in there a long time, even if the oil fixes it you should think about a clutch rebuild

 

230 not a problem
maybe slow down too

10 40 oil what it your temps outside

 

^^^^+2 What thy say sounds like clutch slip

 

+4
Clutch, and I doubt that an oil change will make it any better.

 

Thanks for the confirmation that the clutch is the culprit. I'm not regularly running it that hard, but our interstate speed is 80 mph. Knowing that the clutch is going to slip when passing at that speed doesn't install much confidence.

 

Replace not that expensive.

 

Clutch replacement only takes an hour in your driveway.

 

Alright, didn't want to be one of those people who ask a question, get great answers and disappears never to be heard from again.

Swapped friction disks, springs, gasket, clutch cover to fix a scar and oil. Adjusted the cable per the manual's specifications. Getting really close to the flush oil change at 250 miles.

The end results are being able to cruise at 80 to 85 mph, grab a fbit of throttle to make a pass. No stumble, no surge, no hesitation, just a smooth pull to passing speed before settling back down.

Thanks all for the help