RD/TZ Gearbox and Clutch lubrication

[5port]

As we had a bit of discussion about gbox and clutch lube, I thought I might put up a few words of explaination. 
First:  The gearbox.
The gears in the gbox suffer very high loadings of shear, impact and pure point pressure. These loads require higher viscosity oils with great lubricity to reduce the wear effects.  However, the thicker oils have higher pumping losses and absorb more power in use. So, transmission designers try to use the lightest oil that can give a good wear compromise.  That is often relatively thick oil.  Racing gearboxes will want to have minimum power losses but, they also will not want any chance of gbox failure.     So, Yamaha have specified 10W-30 multigrade as generally the lowest viscosity that achieves the requirements in a good quality oil.  That is the spec for most TZ Racing gearboxes with dry clutches, where the only need is reliable operation of the primary transmission and the gears. Same for the last TZ250's, with the occasional TZ spec'd for 10W-40 and/or even R30. 
The gbox bearings are fine on lower viscosity but, even though these dry clutch Racing bikes are for max power, the recommendation is not for lighter oils.
Now: The Wet clutch.
The wet clutch needs oil to control it's friction characteristics and, to cool it.
Older types of oil were used without much in the way of friction modifiers and, the general spec of 10W-30 motor oil was no problem for the RD clutch.
More modern oils with some friction modifiers can cause clutch slip on the old RD wet clutch.  To stop this problem, high performance oils that still work with the wet clutch properly were developed under the MA2 specification.  These great oils offer improved lubrication qualities with the correct operation of wet clutch.
So, that is about it.  The old RD/TZ tranny, needs 10W-30 (or as specified) to achieve the level of lubrication reliability designed for it and, it needs MA2 spec oil for good wet clutch operation if you use a modern high performance oil.     
The points about saving power with a lighter oil in Racing bikes are generally covering very small differences at working temperature.  However, the basic wear protection of the gears will be reduced.

Cheers

5port       

[ajh]

Chris, interesting discussion, if I could ask something thats been perplexing me -

On the 350LC there is a pretty well known problem of difficulty selecting neutral and all sorts of discussions and remedies. Even with perfect mechanics and everything within tolerances it is still a problem for some including me! Now the interesting thing is its not a problem when cold but gradually gets worse as the gearbox warms up. Some people report this can be solved by using gear oil but I dont think its conclusively proved because sometimes people who do have mechanical and wear related issues try to solve it with oil and obviously dont! (Im running castrol 10W30 MA2 etc. )

I know mine is purely down to temperature and gets worse as oil gets hotter/thinner which seems counter intuitive. Some say it may be clutch drag related but I'd expect the clutch to drag more when oil is cold. So assuming its temperature/oil related, whats going on? And why do we have the problem on the LC and not the AC when gearbox/clutch are very similar?

Any thoughts ?

[5port]

Hi Adrian,
I do not know exactly about this but,..  The 250/350LC have a double jointed gear linkage that increases slop.  The LC shifter has a smaller, sharper positive stop detent with a larger dia follower than the aircooled box has.  There is also a combined gear on the pinion shaft that reduces the selectors to 3.  I presume that the gear linkage and the smaller star shaped positive stop will make some differences.

5port 

[pidjones]

I have the same problem as Adrian on two GL1000 GoldWings. It can get so bad that I have to turn the engine off, then key back ON (so the Neutral light functions) then find neutral by shifting the lever with my hand. Yet, when cold both bikes are easy to find neutral normally. I run Rotella 15W40 dino oil (often used in diesels and heavy equipment) in both, and they shift smoothly otherwise.

I am considering Rotella blue jug synthetic 5W40 for the RD400c. This is what I have run for over 120K miles in the GL1800.

[ajh]

Hi Adrian,
I do not know exactly about this but,..  The 250/350LC have a double jointed gear linkage that increases slop.  The LC shifter has a smaller, sharper positive stop detent with a larger dia follower than the aircooled box has.  There is also a combined gear on the pinion shaft that reduces the selectors to 3.  I presume that the gear linkage and the smaller star shaped positive stop will make some differences.

5port

Yeah some people say modifying the star improves things and a mate recently renewed his linkage and says that made things better but I would guess those things effect whole temperature range. Im trying to understand the theory as to why it gets worse as the temperature increases. Maybe I'll experiment with some gear oil first, if it actually works then it'll really bug me to understand why

[ajh]

I have the same problem as Adrian on two GL1000 GoldWings. It can get so bad that I have to turn the engine off, then key back ON (so the Neutral light functions) then find neutral by shifting the lever with my hand. Yet, when cold both bikes are easy to find neutral normally. I run Rotella 15W40 dino oil (often used in diesels and heavy equipment) in both, and they shift smoothly otherwise.

I am considering Rotella blue jug synthetic 5W40 for the RD400c. This is what I have run for over 120K miles in the GL1800.

Interesting you have the problem on other bikes. This has been a widespread problem on LCs but some dont have the problem at all, its weird. Many people just learn to live with it - go from second to neutral blipping throttle as you roll up to a stop. But even that is tricky sometimes

[betty foRD]

I can shed light on the Neutral topic on LC (and RD to an extent ) .
But not this evening...remind me if I forget !

[5port]

I can shed light on the Neutral topic on LC (and RD to an extent ) .
But not this evening...remind me if I forget !

Go on..

5port

[ajh]

I can shed light on the Neutral topic on LC (and RD to an extent ) .
But not this evening...remind me if I forget !

Go on..

5port

Tensions killing me....

[5port]

I can hear Betty typing..   

5port

[betty foRD]

Ok, in a fit state now....
so it runs like this.
The ease of finding neutral hot or cold is a function of how slick the box is. The more force required to change gear the more likely the inertia of the selector (when it does eventually move) will just result in it carrying on and skipping neutral completely.

To get the dogs to disengage easily requires the load to be taken off them, but clutch drag of some degree or another always exists. There’s a whole pile of things that effect that, starting with the most obvious which is the clutch adjustment.

So two questions to answer .
Why are some boxes better than others.....simply some are much slicker between gears ..so temp effects don’t have big impact on critical clutch drag. ( drag that is high enough to trigger ‘jump mode’).
Why does temperature seem to effect some...simply for those boxes that aren’t so slick between gears the situation gets worse when the clutch or (oil more precisely) gets hot as the drag increases as temp rise and viscosity drops.

The same root cause also has another noticeable effect. Sat with the bike in gear and clutch in, some bikes will try to pull forward more when hot than cold. All related to clutch drag being greater when hot. Obviously they shouldn’t pull forward at all...but that’s how many are until some sorts them out.....

Situation is not helped as many also suffer from clutch slip...again not voodo and can generally easily be sorted when oil, frictions, springs are correct. But the bikes that are fighting clutch slip inevitably (but wrongly) get setup so they only just disengage with the clutch in...some type of false logic that ignores how the bite point should relate to the whole of the clutch actuation envelope.


So bikes will only struggle to find neutral if they have more drag than they should and those bikes will get worse as they get hot as the clutch drag gets worse when hot , principally due to effects of temperature on viscosity and clutch pack friction.

[5port]

Thanks Peter. 

5port

[ajh]

Thanks Peter, great explanation, makes sense with my LC as I know it has a bit of clutch drag. Help me understand though why does drag increase with viscosity drop? It seems wrong way round to me - I would think thicker oil causes more drag

Cheers
Adrian

[betty foRD]

The clutch drag is principally by plate to plate contact...albeit at low contact pressure. It’s not acting as a viscous torque converter, so the thinner the oil the less the plates can ‘surf’ on a separating layer.  In addition the design of the friction plate is to eject the oil from the slots between the contact surfaces and the thinner it is the easier to eject.

In summary, it’s lining to plate friction drag not viscous drag.

[ajh]

The clutch drag is principally by plate to plate contact...albeit at low contact pressure. It’s not acting as a viscous torque converter, so the thinner the oil the less the plates can ‘surf’ on a separating layer.  In addition the design of the friction plate is to eject the oil from the slots between the contact surfaces and the thinner it is the easier to eject.

In summary, it’s lining to plate friction drag not viscous drag.

thanks incredibly useful! Now to work out how to improve