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Early C10 fork oil spec

Mercer

Mercer

Guest
Guest
On comparison of fork oil levels compared between stock values early/late model and Race tech value as well. Am still in my mind trying to reconcile the disparity between compressed and not compressed fork values. That on the early model.

With my 1987 fork set to stock values I have found this observation. If on early model 14 (13.9) inches is in spec extended then it is reading 8 inches when compressed.

Then so what accounts for difference in newer models at 6.5 or so compressed?

Race tech has values for tuning oil by height of fill with emulators. But they recommend 6 inches (150mm) as start with fork compressed. All with purpose of tuning brake dive at last third of suspension travel. They specify no consideration for early/late model factory specs.

In looking at parts fiche can find no real reason for different spec between early/late models save addition of air on early model. Most parts are interchangeable. Which one would think would have little to nothing in effect on oil capacities.

Anyone have some insight as to what I am missing. This is not affecting tuning as yet as I am still at 14 inches extended. I do plan to add oil incrementally to affect last third of travel. I am extremely curious as to my starting point on a 1987 fork. Why the different values from Kawasaki. Why does Race Tech ignore them.
 
I made commentary a while back about the differences in the forks...
the 'lowers' had physically different internal volumes, between pre and post '94...

the fiche does not show efficiently the difference, so what you see is what I noted....
as your bike had the air crossover tube for equalization of air, it made a difference, thus the outlined differences in the manuals for procedure, and the outcome when they are not followed...

http://forum.cog-online.org/tiressuspension-c10/fork-oil-volume/msg647752/#msg647752

my comments in that thread can be used, or refuted if desired, I just explained facts, and why it's my belief to use the methods outlined in the FSM for each model... and when aftermarket parts are used, caveat emptor is all you have to fall back on.

now, literature printed by Race tech, and outside 'parts' vendors, do not take this blatant difference in fork volume in heart, and totally neglect it actually exists....
 
Thanks for link. I have read and even commented on that one too. Read it again just now.

Two things become apparent. To me anyway. Obviously Kawasaki provided different specs per early/late model C10. Less obvious perhaps is why. If the internal dimensions are that different between the early/late model forks with internals removed for measure procedure, would appear a lot of difference by specs and a little difference by summary of parts. This just my less than absolute opinion as I have no late model fork to compare.

Thinking on a practical level I would need to start my oil level experiments for tuning and controlling last third of fork travel at the 14 inch fully extended measure point for the 87 fork. Thinking also might attempt a Race Tech support contact if they have such service.

I realize there is some debate here on oil level protocols that is ongoing. I have no additional thoughts to add but do have concerns as to a real starting point for experimenting with my year model. Due to poor road conditions here in Louisiana. I also realize my requirement may be softer than most here who ride on better more stable road beds than a swamp state.

I thank everyone who has posted to COG on subject. As this tuning process is ongoing, will continue to post my findings for any with interest.

P.S. If someone ever wants to donate a late model one tube assembly I would do a side by side off bike evaluation as I have an extra early model tube assembly to compare to. Just a thought to objectify differences.
 
Lee said:
Thanks for link. I have read and even commented on that one too. Read it again just now.

Two things become apparent. To me anyway. Obviously Kawasaki provided different specs per early/late model C10. Less obvious perhaps is why. If the internal dimensions are that different between the early/late model forks with internals removed for measure procedure, would appear a lot of difference by specs and a little difference by summary of parts. This just my less than absolute opinion as I have no late model fork to compare.

Thinking on a practical level I would need to start my oil level experiments for tuning and controlling last third of fork travel at the 14 inch fully extended measure point for the 87 fork. Thinking also might attempt a Race Tech support contact if they have such service.

I realize there is some debate here on oil level protocols that is ongoing. I have no additional thoughts to add but do have concerns as to a real starting point for experimenting with my year model. Due to poor road conditions here in Louisiana. I also realize my requirement may be softer than most here who ride on better more stable road beds than a swamp state.

I thank everyone who has posted to COG on subject. As this tuning process is ongoing, will continue to post my findings for any with interest.

P.S. If someone ever wants to donate a late model one tube assembly I would do a side by side off bike evaluation as I have an extra early model tube assembly to compare to. Just a thought to objectify differences.
Click to expand...

http://forum.cog-online.org/tiressuspension-c10/fork-oil-volume/msg647859/#msg647859

Ted said:

http://forum.cog-online.org/tiressuspension-c10/fork-oil-volume/msg647995/#msg647995

we know what the compressed level should be for a post '94, you don't need one of those, because it's been prior verified, and everyone filling post 94 forks compressed felt good..... what you need to do is verify what Ted said about the '86 level, when it's 14" deep at extended, and what you find at fully compressed...
then, we can put it all to bed... you have the forks to do the comparo already, but you mentioned up top in your first post some 8" dimension.. I don't know if you mentioned it was a real measurement, or just an assumption.

Please do your compression and tell us what transpires.

thanks
 
Lee said:
"With my 1987 fork set to stock values I have found this observation. If on early model 14 (13.9) inches is in spec extended then it is reading 8 inches when compressed." No it was not assumption but the actual finding.

Do not know if this would put subject to bed, but that is what I found when pursuing the question the other day. Hence my thinking on 14 inches extended as my start point for monkeying with oil level tuning from that point on my early model.

What will be the kicker if adding oil I end up "happy" at 12 inches extended and 6 inches compressed! Or some such close and similar conclusion.

In time I will find out. Still going to see if Race Tech will have experience and comment for C10 differences, hopefully they will. Their manual indicates adding 10ml at a time in testing. Uggh!
Click to expand...
 
Apparently I miss-used the quote feature in my last post above. Not my intent to have all in blue highlight. Hopefully that does not muddy the water. Sorry first time I used that COG forum feature!
 
Good day to all reading here.

Spoke to Race Tech support this morning. Wow, they were working like myself on the holiday! Jake, there, was most helpful and well acquainted with the Concours seemly.

He specified 6 inches forks compressed emulator in regardless of early/late model C10 fork. This is verbatim as to their web references. He stated further that in their data and experience base on C10, this is what always worked best regardless of model fork.

Jake was most helpful and pleasant. This when we where talking about a used bike. As I was not original purchaser of their parts. Gave measure to check fatigue on 1.0 springs at 340mm. Said that mileage was not a consideration. The springs last.

Would theorize that this oil level spec is due to no matter what amount of oil capacity volume the lowers have between early/late models, the compressible air in tube at top of fork volume is the same. This is what is actually being tuned in last 1/3 of fork travel and brake dive is this column of air.

Would also suspect as early model forks have air at 7 lbs pressure they are designed to different oil spec. Believe pressured to 1.5 atmospheres this changes the column's compress-ability value and hence less oil is needed at 8 inches compressed or 14 inches extended for early model fork.

I hope I am adding to our understanding of our now ancient C10. Again am no expert on subject. Just a guy who has wanted one of these bikes since 1986 when they were introduced. It is now my used modern replacement for my Norton 750. Yes am in luv with them both!
 
With my 1987 fork set to stock values I have found this observation. If on early model 14 (13.9) inches is in spec extended then it is reading 8 inches when compressed.

Based on Lee's test (above),, I will admit my memory was wrong.
I sed I recalled the dimension was 6 3/4" Compressed,, and he found that the actual dimension is 8" compressed..
Apparently I was incorrect. The level works out to 8" compressed...
But, I still maintain I set my 86' forks at 6 1/2" compressed (no air pressure added) and it works well.

I corrected my original statement, below...
1) I already "did" what your suggesting. I developed the 6 1/2" dimension on my 86.
    **ie; I serviced the 86 fork {extended}, then compressed the fork and remeasured the fluid level.
          As I recall: It was closer to 6 3/4" 8" but I prefer less dive when I brake, so I raised it an extra 1/4" 1 1/2" {became 6 1/2"}
      I AGREEE, the OP can repeat my test.

Lee started this discussion with; On comparison of fork oil levels compared between stock values early/late model and Race tech value as well. Am still in my mind trying to reconcile the disparity between compressed and not compressed fork values.

I think; Lee figured out the reason for the difference when he said; Believe pressured to 1.5 atmospheres this changes the column's compress-ability value and hence less oil is needed at 8 inches compressed or 14 inches extended for early model fork.
         
I feel that; there is "not" a large volumetric difference in the design of the 2 forks.
                They increased the oil amount by 41 ml on later models intentionally to get the same basic ride and decrease dive,,
                  without the use of air pressure..     (*See manual reference below)

NOTE: Race tech recommends 5.9" compressed, so the 6 1/2" compressed setting I suggested, will work fine.

** From my manual; Amount of oil when changing oil is 330 ml on the early bikes and 320 ml on the later bikes.
                                  NOTE: Here the volume of oil is similar 330/320; probably because later models do not have a drain screw.
                                            Because of this, all the oil can not be easily removed when doing a normal (on the bike) service.
** From my manual; Amount of oil after disassembly/completely dry is 338 ml on the early bikes and 379 ml on the later bikes.
        Here there is a 41 ml difference in the amount of oil that you put in the different model forks. {338/379}..
        The 41 ml difference explains the difference in fluid level. NOT a difference in internal volume.

        Ride safe, Ted
 
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