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Discussion Starter · #1 ·
I have two 2005-06 Kawasaki Ninja ZX6R 636s.

One is fully race-built, but came with normal weight springs. The levers are CRG adjustable foldable levers..

The other is street legal, but I rebuilt it from the ground up after 2 years of owning it. With the rebuild came the EBC racing clutch kit that included the stiffer clutch springs. The levers are just adjustable foldable shorty levers from ebay.


The street legal one has always had a heavy clutch pull weight. After I got the racebuilt one earlier this year, I noticed there was a good difference in clutch pull weight.

With everything greased (cable, clutch parts, levers, perch, basically anything that moved or could cause resistance) I measured the pull weights (lb-force) required to full pull in the clutch using a digital hang scale. The street bike measured at 20-22lb-force, the racebuilt bike measuered at 14-16lb-force.

I swapped the racing clutch and springs into the racebike after noticing this, because anytime I ride for more than 30 minutes my hand gets tired on the street. On track its fine.

This only changed the pull weight slightly on both bike. Realistically the stiffer springs are only noticeable while riding, mainly off the line.

Because of this, I again cleaned & lubed the clutch cable, greased all the clutch parts, ground down the ebay levers, cleaned and greased all lever parts, and even the lever perch parts on the street legal bike. The racebuilt bike I did the same minus the grinding of any lever.

After all that, I measured both bikes again. The racebuilt bike measured (with stiffer springs and above mentioned cleaning and greasing) at 16-18lb-force now, and the street bike still read higher at 18-20lb force required to fully pull in. I even tried swapping levers on both bikes, with no change at all in readings

Trying to figure out if this is normal for the 05-06 636, or if there's something internally that is causing this on the street bike. My only options short of going internal to the engine now is to either increase mechanical advantage and modify the lever itself, or buy and ez pull to also increase mechanical advantage.
 

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You don't mention changing the cable itself between bikes..... Could be the routing is different, or the one on the street bike is far more clogged up, or damaged.....
 

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Discussion Starter · #3 ·
They're both new, but I may have routed the street bike one differently, but only slightly. They still come out from under the tank plastic at the same point and are routed to the clutch lever the same though, not enough difference in routing to cause this.
 

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Discussion Starter · #4 ·
The only difference in routing is one goes over the throttle body and the other goes under if I remember correctly.
 

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Try 'copy exact' and see if that's the difference..... Every cable run has a minimum bend radius before it starts to bind. A couple of pounds is something I would expect from the cable dragging on the sheath.
 

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Discussion Starter · #6 ·
I took off the cable, inspected and lubed it again. Didn't find any excessive bends or binds, no pinching, to tearing, still looked new except for the boot on the case end (little rubber dust boot, which isn't causing any problems. Off bike and lubed felt great going back and forth going through the sleeve. Routed it exactly the same way, actually worked better than the racebike somehow for fitment. Got it all mounted and adjusted, felt exactly the same as the racebike, then I measured it again. Still at least 2-3 pounds more required at the same point than the racebike. My only other option now is to modify the lever to create more mechanical advantage.
 

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If you can measure the difference, but not feel it...... Is it worth pursuing? Any idea of what the design tolerance may be?
 

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A couple pounds difference isn't really anything. If the levers are different lengths, that will make a difference in the pull force required as well.
 

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Discussion Starter · #9 ·
The difference is enough that I can't ride on the street with it. Track days are fine, but on the street in LA traffic I only last about 30 minutes before my hand starts to give out. Can't find a tolerance in the service manual either.

I was going to modify the lever itself, but there wasn't enough room to drill another hole. I ended up ordering an EZ pull to add mechanical advantage, it now reads about 14-16lb-force to pull it in, matching the racebike at the same point on it's CRG lever (longer lever on the racebike).

It is worth pursuing for me because I haven't ridden this 636 on the street except maybe 2 or 3 times since moving to SoCal because of how tired my hand gets. Instead I've ridden my 250 for commuting, but I'm tight financially so I'm having to sell the 250 and the Racebike to make ends meet right now, but have poured years and lots of time into perfecting my street 636, and will need it for commuting.

I posted this trying to see if anyone had experienced a problem with the clutch internally that might have caused this on the 05-06 636.
 

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