Newer CLutch Slipping


Hi everyone, I just replaced my clutch at the tail end of 2011, maybe 10,000 kms (6,200 miles) ago and it started slipping again tonight. It's making me wonder if something made the original clutch start to slip, I missed it, and now it is affecting the new one. Here's a quick list of what I noticed and what I did two years ago. Sorry for the novel, but I am trying to include everything I have ever done to it.

-Noticed that I was starting to have to bleed the clutch fluid as it was getting dark (about 2-3 times a season)
-Over a one month period, I noticed the clutch slip in 6th, 5th and eventually 4th, but only under WOT / heavy acceleration around 8,000rpm and above.
-Right before I replaced the clutch, I noticed the clutch master cylinder was very low. I opened it and the fluid was at least half gone and the diaphragm was sucked in. After much bleeding and a bit of riding, I also noticed the slave cylinder piston cup had a very slight leak.
-As a result, I replaced all the fiber plates and springs with OEM, added a galfer braided clutch line, rebuilt the clutch slave cylinder (piston cup and spring) and of course added fresh DOT4. The steel plates looked fine, no dis-coloring, except for a bit on the pressure plate. I used semi-synthetic oil when I replaced the clutch as that's what had been in it since it was near new.
-After all this, a few friends said OEM busa clutches don't like semi or full synthetic oil, so I removed everything, cleaned the friction plates with brake clean, made sure they were dry, re-soaked them in Suzuki oil and reinstalled.

I've still had the master cylinder fluid going dark, although not as quick, but I noticed over the winter when I bled it, the fluid in the line was clear and it was only the fluid in the master cylinder going dark. I cleaned out the master cylinder, noticed that the very top where the diaphragm sits was dis-colored (black, brown) so I took some very fine sandpaper and gently removed it so it was shiny metal again.

Having said all that, after I rebuilt everything, all was fine since 2011 until tonight... The clutch slipped in 4th gear at about 7,000 rpm, again under heavy or wide open throttle. I've got a 2003 busa with about 70,000 kms (43,000 miles) on it.

What are your thoughts folks? What could be making it slip again so soon?


Donating Member
I take it that you changed the pressure plate springs too? If not you might want to get new ones .
I've never heard that Busa OEM clutches don't like full synthetic. That's what I run and it works fine. Now I did have a problem with the clutch slipping last year. Ended up being the Master Cylinder. It was rebuilt and has been fine ever since. You might consider that as it seems you've done everything else.


Thanks socal blur, I just ordered a rebuild kit from fleabay for $37. Hopefully that will be it! I appreciate the advice.
Please let us know if the rebuild made a difference as I'm planning to rebuild mine as well , the rubber boot is worn off and needs replacement.
I agree, oil is not the problem here unless you were using an energy conserving oil. Hopefully the Master Cylinder will do the trick


Donating Member
been running amsoil full synth for the past 13 yrs. in 2 busas with no issues. hopefully, it's going to be an easy fix that you might of overlooked. to rebuild the master would be relatively inexpensive but i can't see an 11' worn that much.


Sorry for the delay everyone, the rebuild kit came in the mail about a week and a half ago and I just got around to installing it last night. In the picture below, the old internals are on the bottom and the new ones are on the top. It's quite obvious that the outerboot is destroyed and the piston seal isn't as tapered as it should be.

Just from a quick drive up and down the street this morning, the lever is barely away from the grip and the clutch is engaging and it shifts much better. I'll try to see if it slips again over the next week and give another update.



Hmmmm, tried to post this once already, but it didn't go through.

Long story short to save typing. Replaced the master cylinder internals last night and after a quick test drive, the clutch is engaging almost when the lever leaves the grip. From the photo below, you can see that the outer boot is destroyed and the piston seal isn't as tapered as it should be.

I'll update later this week to advise if it is still slipping, but I think this did it. :) Overall the job took about an hour to remove fairing panel, drain everything, remove master cylinder, replace, rebleed, etc... Fairly simple job.


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