Clutch Slipping or worse?

Recently I've noticed that in 4th and 5th gear when I hit about 7500 rpm at full throttle the engine will rev almost to redline without any increase in mph, then drop back to 7500 and accelerate. If the clutch was slipping, it would make sense for it to do it in the bottom gears where there is more torque on the clutch, but it has never done that, only in 4th and 5th. What's going on?

I too am experiencing this pehnomina. What gives?

what oil is in your engine? if it is "car" oil your clutch will slip , you need to use proper motorcycle oil, a car has a dry clutch,your bike has a wet clutch.

I use honda motorcycle oil

cte10 wrote:

Recently I've noticed that in 4th and 5th gear when I hit about 7500 rpm at full throttle the engine will rev almost to redline without any increase in mph, then drop back to 7500 and accelerate. If the clutch was slipping, it would make sense for it to do it in the bottom gears where there is more torque on the clutch, but it has never done that, only in 4th and 5th. What's going on?

My 750 has horsepower curves for the engine and HP increases linearly up to the peak just before redline so the slippage you have is occuring where maximum HP is. It could simply be a slipping clutch.

how much freeplay do you have at the lever i have never in all my years of running these bikes on the street and at the track ever had major clutch slippage if i was you i would redo my clutch adjustment starting at the main adjuster on the countershaft cover then work my way up to the lever you need at least an 1/8" free play at the lever. the cluches in these bikes are pretty much bulletproof.

Clutch pushrod adjustment will likely resolve the issue. This is usually specified as a routine maintenance item.

Would also assure sufficient slack in the cable itself, and that the cable is properly lubed and isn't frayed or sticking.

Good Luck!

As mentioned, start with your simple adjustments and take her out on a test ride.... If no longer an issue, good to go... If still an issue then proceed to next....

As in my case, not severe slippage but enough for me to go Hmmm, that's not right.... Out with the tools and caliper for some measurements...

The image is for my KZ900 specifications, yours may be different but it gives you an idea of what to measure in the plate thicknesses and springs, refer to your service manual for tolerances...

After 30 years of riding, yeah they do wear out....

OMR

rosken wrote:

what oil is in your engine? if it is "car" oil your clutch will slip , you need to use proper motorcycle oil, a car has a dry clutch,your bike has a wet clutch.

lotsa people on here use "car oil"....no problems with slippage.......

I started experiencing the exact same thing once I rebuilt my engine and gained about 50% in HP. My clutch is adjusted EXACTLY to spec. It could be an oil or oil additive problem. Because in recent times oils have changed quite a bit and many of the oil manufacturers have changed their formulas and additives, this is my suspicion. The biggest mistake someone can make is to use ANY oil with Molly, Graphite, or STP/ Motor Honey, type additives. I have been running synthetics for years without any problems. after rebuilding the engine I went to a standard mineral oil and a small amount of STP, for the extra ZDDP in it and I started experiencing this problem, It is now time to change the oil, and I will find out if in fact the STP created this situation. Also the assembly lube used on cam shafts and new bearings has Molly and Lithium, a small amount of these can make a clutch slip. Many modern oils are starting to use in place of ZDDP.

It is true most oil makers have mostly eliminated the zinc and added some kind of moly junk to "replace" it. It doesn't do the same thing, and about 99% of the oils out there now are no longer adequate for use in flat tappet engines. That is bad for old engines, but that's the way it is now.

Adding STP will give you enough zinc compounds to restore to adequate levels. Some bike clutches will slip using car oil which is labeled "energy conserving" because of the friction modifiers they put in them.

Both "Molly" and STP will definitely make your clutch slip. I went to "Redline" oil additive for the ZDDP. The STP will rinse out with time but the Molly will destroy the clutch plates.