Engine speed normal rev, road speed lags

Hi guys, I'm new to the kzrider.com forum community. I have a 1981 kz650 H1 CSR. The bike idles well and revs well on my rpms. However, throughout all gears the road speed will lag behind the throttle. Occurs mostly in the 2500-4000 rpm range. I am thinking that this is either an issue of the clutch slipping, or some sort of final drive problem, but I also wonder if I should adjust my clutch free play (as in maybe it is not fully disengaging until high rpms) ?

Any advice/suggestions would be greatly appreciated and duly noted. By the way, I have a physical copy of the Clymer service manual (which has supplemental information for my '81), although I have heard that these are not the best...

Does the Clymer manual give a full description on how to adjust the clutch? There are 3 points of adjustment - one is under the little cover on the left side of engine; one is in about the middle of the clutch cable; and one is at the clutch lever. Adjusting the clutch requires all 3 to be addressed.

What motor oil are you using? If it is car oil rather than oil that has the "JASO-MA" designation on the container it can cause the clutch to slip and should not be used.

Ed

Clutch adjustment. In the clymer manual for the 81 650 use the procedure in the supplement.
counterclockwise first until hard to turn, then clockwise 1/4 turn.

The following site has the 81 KZ650 pdf in the Files section. jarlef z650

Yes, the manual includes that process. I have been using SAE 10w40 as per the manual--didn't realize that there was a JASO-MA designation. Is this something that one can find at O'Reilly's or what? I'm based in Nashville, TN if that helps anyone.

Shell Rotella 15W-40 in the white bottle has the JASO-MA rating.
It may not be suitable during startup in really cold weather, though.

turning the adjustment screw counterclockwise only loosens it in its housing--it doesn't make it "hard to turn," unless that is what is meant?

You need a manual. You adjust it until you feel it bottom, then turn it back 1/4 turn and tighten the lock nut. If it hasn't been cleaned and greased in a long time you need to do that first.
Steve

Alright--that makes sense! I corrected the lagging problem I was having. Now I just need to better adjust the clutch. Then, I plan to change the oil and use the JASO-MA designation

My local O'Reilly's carries Lucas Oil 10w40 high performance motorcycle oil that meets/exceeds JASO MA specs. Anyone used it? Looks good but want to be sure/learn from those with more experience.

Also, thanks a bunch for the help--fixed the clutch lag!

Good company but have not used ........ Valvoline 10/40 bike oil at Farm and Fleet is 4.69 a quart and what I decided on.... Rotella does get alot of good reviews on here...... Jaso approved is the main thing..... everyone has their favorites ..... my dad drinks Bud and no one's gonna get him to change after 65 years of being his fav.