5th gear doomsday-prophets were right!
 

All this banter about 5th gear damage finally got to me and i checked it out...
Thanks you to all those who warned me, my 5th was well into retirement- to think i NEARLY set off into Africa with that gives me nightmares!

Jim

When you have new one: never ride at low tours/speeds at 4th and 5th just to hear the nice pom pom pom sound! that is the main source of the problem. {for all monos not just ténéré's)
Don't drive full either for example against front wind or just a highway, always stay 500 under max torque= 5000 tr/min
Not more than 110 Km/h in a continous way, and theoretically the gears should stay as new !
Oh, and a good and thick oil also like those specially developped for V-twins.
Don't forgett to change the gearbox bearings at the same time, they can also be responsable for some deterioration of the teeth, only put original ones not C3.
Then, never have your secondary chain to hardly tend...
Start the engin with the kick as often as possible.
Sorry for my english,

Mattias

Hi Matt,
Thanks for the tips...
Im interested why you recommend that i do not use c3 bearings?? The originals are SO expensive!

Jim

At any local bearing shop you can buy any bearing you like. Also the ones that Yammie use. C3 is a code for the internal play. Btw, the clearing ranges for C3 and standard ones have an overlap, so nothing is as exact as it seems. If you have problems getting the correct ones let me know.

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Fred, XTZ660, Holland.

Because in the gearbox, a bigger play in the bearings will theoretically make the 5th gear problem appear even faster, its hard to explain as my english is kind of rusty.
Due to the contact surface of the two wheels of the 5th gear, if what holds these wheels is lying in 4 bearings C3, they will with time not be as rigid as they should be and all the gearbox will have unwanted mouvments L/R wich will result in the most solicitated wheels to be eaten like a cheese by rats, this + the high torque is not good for any gearwheel of any bike.
Better take original play in gearbox though the 6307's of the engine can be C3.

Cheers

Matt

Thanks for the tips Matt and Klaus.
Only trouble is Ive already fitted NSK C3 bearings... Im told by Kim in Cape Town that this will be fine, but now Im not so sure. Ive not fitted the engine yet, so should I consider other bearings? I'm really hoping your answer will be No...

Thanks Again!
Jim

Hi again,

It won't be catastrophic but it might not do 50 000 Kms without noise.
Its not the most expensive so I would buy original play.
As you have the engin open I would like to recomend you another thing, the 5th wheels, buy those from the 3AJ they have been improved to eliminate the sickness of Ténérés(gearbox problem) and are smaller with less teeth and better demuliplication, normally they should fit with the shaft and other gears, I did it on a 1VJ and worked fine
though the 55W and 34L has almost the same gearbox as 1VJ except the 3rd 4th that are others (in demultiplication), then you should fit the oil thing from a 3AJ onto the carter to have better lubrifcation in gearbox, not hard to do (I think).
The reason why the 5th brake on early 600's is the demultiplication that is to exagerated and the wheels are "bombarded" by the engin torque at low rpm's, one wheel accelerates a lot, I read that when you change your gears from 4-5 when you use the clutch one of the wheels slows down then when you engage it takes a nasty acceleration and this detail could be responsable for much of the problem, better not use clutch and put in 5th maybe... but youll deteriorate other parts as selection mecanism(maybe) etc.
Up to 3500 rpm the wheels accelerate the most thats why you should try to always stay above(not always easy).
The best speed on highway is in reality 125/135 Km/h for gearbox; but not for piston! need to make a choice wich part you wanna destroy..
Use "castrol bike!" 10/20W60 or above as oil (I read on a german site) and it makes sense, as car gearbox uses minimum 80 why use less in a motorbike that uses same oil for box and engin! full synthes of course: it stands more heavy charges and stays cleaner.
For the 3AJ gear wheels Im only sure at 95% it will fit so its only an advice but personally I wouldlike to try when mine will need it, though she has only 7000 miles on the counter so I ll do it later.

Matt

thanks for the info guys!

Im pretty limited by the price and availiability of spares where I live so for now i have to take my chances with only the new 5th gear and C3 bearings. Lets hope they get me to Cairo... and possibly back again!