Dare I say it.................oil

[fintip]

I'm no expert, but... The impression I get from all the reading--and I have no good theory to explain it--is that *switching* to synthetic *after* having had conventional oil does sometimes cause problems. My mediocre theories have to do with the plates being dredged in the old oil, and that doing something... And then, there's the 'cleaning' effect synthetic oil has on the inside of an engine where crud would have accumulated before.

Don't know. But I'd be curious to hear if replacing your plates changes things, simply because fresh plates that have never been in conventional oil might make a difference.

Just a hunch from my hours and hours of reading about oils and peoples' opinions and experiences with them in old jap bikes...

Me personally, I finally 'converted' to synth (Rotella 5w40). But the bike has a complicated history, so I can't be of help--the previous owner mentioned that he had converted to synth, and the bike stopped burning oil. I at the time didn't believe that, so I switched back to conventional rotella. The bike did indeed burn oil, and the clutch had some slip at high torque surges--say, 4 or 5k on 2nd or 3rd and then snapping back the throttle, for example. I actually just credit this to clutch wear, given that the bike now has 73.5k (had 65k when I got it in November I think?), and so probably needs new wear plates and spring. However, given the freezing days and frequent rain we've had recently, and some more reading, I finally decided to give synthetic a go and put the bike back on synthetic.

True to form, the bike doesn't burn oil currently. I do feel like it is gentler on the bike for cold starts, and that it warms up faster. The clutch slip did not go away.

But I wonder if maybe the clutch slip (going with my irrational theory above) might have been introduced when the previous owner switched to synthetic, and never went away after.

Who knows! Reading this thread with interest anyways. Pretty sure DavidR has said he's been using synth for about 200 years and never had anything but good things to say about it, but I guess he probably doesn't run a stock clutch, eh? (correct me if I'm wrong!)

[ribbert]

My reasoning is that if the fibres are the same thickness as new and the spring is fresh it should be as it left the factory, but it's not.

I am not an oil expert and have no interest in becoming one but one theory I have is that something in the synthetic has impregnated the fibre plates reducing friction. This has some weight to it as a number of people here have mentioned that over time, after going back to mineral oil, things improved and mine had been improving very slowly. Perhaps if I was harder on the clutch or drag raced at the weekends this process would be accelerated.

If the new plates do the trick, I might clean the old ones with brake cleaner and reinstall just to see what happens.

Although the plates are spec thickness I will replace them with new ones, I had already bought them. I will road test in the next few days. It's not easy finding somewhere close by to ring it out in the higher gears without the risk of having the bike AND myself impounded.

I'm sure when Yamaha were doing the R&D on the clutches they did not factor in super slippery oil.

It has been said here that the clutches are marginal. If it worked perfectly for 20 years and still looks and measures spec, that's all it has to do.  Designing a big margin into it is unnecessary and would just make the clutch heavier. I don't believe slipping clutches were ever an issues in the bikes early life.

I will report my findings.

Noel

[moonrunnah]

just a thought (im not trying to sound degrading) but are you using motorcycle oil or some sorts with the clutch additvie in it or is it just straigh syn motor oil
i am not an oil expert either but if i remember correctly ATF or tannsmision oil is much more of a cleaning agent then syn oil but is made to work with the clutches in the tranny

also how about adding a friction moddifier like in a lsd rear end

[RichBaker]

The factory does a lot of things for marketing purposes... One is installing a clutch spring that "feels good" to a buyer on the showroom floor. It may work great for the 1st few thousand miles, and then starts getting too "light" and allows slippage, usually about the same time the bike gets parked.... We all know that most people that buy motorcycles only put a few thou' miles on them anyways, how many bikes have we seen that were parked with 4000 or 5000 miles and sat 'til someone like us ressurected them?

[ribbert]

just a thought (im not trying to sound degrading) but are you using motorcycle oil or some sorts with the clutch additvie in it or is it just straigh syn motor oil
i am not an oil expert either but if i remember correctly ATF or tannsmision oil is much more of a cleaning agent then syn oil but is made to work with the clutches in the tranny

also how about adding a friction moddifier like in a lsd rear end

I was using motorbike specific synthetic oil.  Shell / Motul.

[RichBaker]

I've been running MC-specific semi-synth for years and no problems. Had some early on, running energy-saving car oil... replaced a couple burnt steels and a glazed fiber, put in a 2nd spring and none since then. I still need to get rid of the smaller plate and remove the wire/spring...

[ribbert]

I've been running MC-specific semi-synth for years and no problems. Had some early on, running energy-saving car oil... replaced a couple burnt steels and a glazed fiber, put in a 2nd spring and none since then. I still need to get rid of the smaller plate and remove the wire/spring...

I'm being a bit pedantic here I know, but to me the second spring fix is masking the problem not fixing it and detracts from the ease of use of the controls.  Also, I am a two finger clutch user.
This only happens under extreme load and is not evident in normal riding, unless your riding style sees you frequently at redline in high gears.

Noel

[ribbert]

The factory does a lot of things for marketing purposes... One is installing a clutch spring that "feels good" to a buyer on the showroom floor. It may work great for the 1st few thousand miles, and then starts getting too "light" and allows slippage, usually about the same time the bike gets parked.... We all know that most people that buy motorcycles only put a few thou' miles on them anyways, how many bikes have we seen that were parked with 4000 or 5000 miles and sat 'til someone like us ressurected them?

I don't think manufacturers stoop to these practices, it's not necessary.  If the above scenario were to happen the weakness would become common knowledge very quickly and have a far more detrimental effect on sales. Cars or bikes that develop flaws early in their life are the result of an unforeseen design or manufacturing problem, not a marketing exercise. Nobody builds a vehicle with a designed in weakness just to get them off the showroom floor.

Bikes don't have heavy clutches anymore. Hyabusa's, R1's, BMW's can get nearly 200hp to the wheel with a light clutch feel.

And, my clutch was perfect for 80,000k's.

Noel

[SlowOldGuy]

FWIW,
The first gen R1 clutch is identical to the FJ clutch.

DavidR.

[Pat Conlon]

IMHO, it's all about the clamping force of the clutch spring (or lack there of)....and not the oil.

I have a light 2 finger clutch with no slipping on 20-50 synthetic and handling the torque of a 1350 engine.
A Barnett coil spring clutch and FJR m/c will do that for you...

Leon said it best, "You will never find your kookaloo with a shitty clutch"...(spring)

[ribbert]

IMHO, it's all about the clamping force of the clutch spring (or lack there of)....and not the oil.

I have a light 2 finger clutch with no slipping on 20-50 synthetic and handling the torque of a 1350 engine.
A Barnett coil spring clutch and FJR m/c will do that for you...

Leon said it best, "You will never find your kookaloo with a shitty clutch"...(spring)

Can't agree with you on that Pat. It's about both. When the clutch is released not all the oil between the plates is expelled and the plates hold oil, the slipperiness of the film that remains will contribute to how well it holds. Ever driven (or tried to drive) a car where the rear main has let go and got oil on the clutch.

I have no doubt that increasing the clamping force on the clutch then overcoming that by increasing the advantage at the lever works.

I don't appear to have made myself clear. I'm not looking for A solution, I'm looking for MY solution. I know all the popular mods to overcome a slipping clutch but that was not my quest.

If a standard clutch can work flawlessly for 80,000k and I have not increased the power of the motor, why can't I just replace the worn bits, being the spring and the fibres, and return it to that condition.   

Unless a part on a vehicle is known to fail prematurely or is inadequate from the onset it is common practice to replace it with the same part when it wears out and expect it to restore as new performance.
In this case I don't seen why that replacement part has to be beefed up on the original just to perform the original task.

There appears to be a lot of people out there running double springs etc on standard motors. I don't understand why.

I am not trying to win anyone over here nor promote a particular fix. I am just explaining why I asked the question and what I'm trying to achieve.

Noel

[Pat Conlon]

Noel, sure, no problem, you can replace your weak diaphragm spring with a new oem spring and things will be better for the next 80,000k...until you have to do it again....and again.
I guess it depends on how long you want to keep your FJ....and how many times you want to buy a new spring.
I've had my '84 FJ for 28 years now and in '96 went to the Barnett and have never looked back. I did change the fibers in '99 but never the coil springs.

Therefore...I'll bet you a jelly donut that my 6 coil springs will last longer than your oem diaphragm spring.
Besides, the Barnett spring is not that expensive, and is upgradable with heavier coils if need be.

I'm just saying, if you are gonna fix it, and you want to do it once, do it right.
If you don't like the heavy pull of a double diaphragm spring, (and I don't) consider a coil spring conversion.
Do it once and be done with it.
Kookaloo amigo!

[The General]

IMHO, it's all about the clamping force of the clutch spring (or lack there of)....and not the oil.

I have a light 2 finger clutch with no slipping on 20-50 synthetic and handling the torque of a 1350 engine.
A Barnett coil spring clutch and FJR m/c will do that for you...

Leon said it best, "You will never find your kookaloo with a shitty clutch"...(spring)

If a standard clutch can work flawlessly for 80,000k and I have not increased the power of the motor, why can't I just replace the worn bits, being the spring and the fibres, and return it to that condition.   

Noel

If all is returned to standard condition, the only possible variable is the oil makeup since manufacture. Today`s Motul 10/50 will slip on all 3 of my FJ`s. 10/40 won`t. (Just). So i agree with you Noel. But aren`t the newer oils better for other bits? - ummm ...sounds like a barnett for my beefed up motor for sure. (When I build it) - meanwhile I`ll stick with standard Clutch & 10/40 Motul. (A bit expensive, but I buy in bulk). Dare ya go. 

[ribbert]

Noel, sure, no problem, you can replace your weak diaphragm spring with a new oem spring and things will be better for the next 80,000k...until you have to do it again....and again.
I guess it depends on how long you want to keep your FJ....and how many times you want to buy a new spring.
I've had my '84 FJ for 28 years now and in '96 went to the Barnett and have never looked back. I did change the fibers in '99 but never the coil springs.

Therefore...I'll bet you a jelly donut that my 6 coil springs will last longer than your oem diaphragm spring.
Besides, the Barnett spring is not that expensive, and is upgradable with heavier coils if need be.

I'm just saying, if you are gonna fix it, and you want to do it once, do it right.
If you don't like the heavy pull of a double diaphragm spring, (and I don't) consider a coil spring conversion.
Do it once and be done with it.
Kookaloo amigo!

I have no doubt the coil spring pressure plate will outlast the standard one. It is a superior design and what they used to use. The FJ spring is a poor mans version of a car pressure plate.

Not sure I'll be in any condition to worry about the clutch in another 28 years though. I'll be happy if I'm wiping my own chin!

Noel

[Pat Conlon]

Not sure I'll be in any condition to worry about the clutch in another 28 years though. I'll be happy if I'm wiping my own chin!

Ha! Yea, I hear you...
It's not the next 28 years you have to worry about,  but the next 80,000k (54k miles)