So here I am checking my engine after damage that suddenly occured when riding at the top of mountains in Andorra !
A hammering noise: I told myself "it must be fuel detonating in exhaust because of altitude..!" at least I hoped it was.
A few minutes later a hammer sound came out from engine again..this time it stopped engine and when trying to bump start, engine was blocking back wheel !
I understood that it was serious but couldn't understand how the f*** #Z%*/§$ it could happend as I have been servicing and checking more than necessary!

Could cam chain have been braking off letting piston hit valves?!
Could it be starter fly wheel blocking crank?!
Could piston have melted together with cylinder?!
Could it be conrod bending as a result of driving with a heavy loaded bike up the mountains?!

No No and No, it was nothing of this!!

What really happened:
The big(secured!) bolt holding primary wheel on crank shaft and syncro wheel for balance shaft has loosened and gone off !
Separating the balance syncro wheels, the hammer sound was balance shaft hitting crank
shaft, bending conrod in pieces!
It should theoretically never have happend, Yamaha have mounted the bolt with correct torque, and even secured it.
I have never seen this before, neither has my mechanic.
Though it seem to be possible and I'm glad I wasn't in the middle of Sahara when it happened!

The guilty is probably engine break and heavy luggage and/or something else !!

If anyone has experienced the same or has an idea, let me know.

I will definately fasten the bolt of my next ténéré either permanently or gluing it with some lochtight.

The good point is that everything else in engine seems ok, even after my long rude travellings, so I don't really worry about ténéré quality.


Matt

I have seen and heard of something comparable happening to the gearwheel / key of the balancing shaft.
What happened was that the balancing shaft wieght exited the engine block behind the cylinder. Everything gone.
What I did was on all my XT's to put in new keys on crank and balancing shaft, and didn't have problems till now.
You are lucky in a sense that your engine casing is still OK; crankshaft might be possible to repair, balancing shaft there's so many lying around.

good luck!
Auke

__________________
Auke
http://aukemarieke.blogspot.com

Every 660 sooner or later gets the nut loose on the crankshaft holding the small gear wheel. Everyone should remove this nut, clean it and the thread on the crankshaft and glue it with Locktite red, before it happens.

------------------
Fred, XTZ660, Holland.

__________________
Fred, XTZ660, Holland.

I probably will replace engine with a 3TB one, is that a good option and will everything fit like CDI, stator conections etc?

Cheers,

Matt

hi matt,

yes, 3TB is good but i can't say wether cdi etc will fit because i don't know your previous engine / model.

and yes, many xt engines died because of loosend primary wheel. as fred already recommended, glue the nut with loctite red (supertight) and apply correct torque. to dismount, heat up the nut to 300°C.

best regards
klaus
xt600.de / tech. dep.

hi matt,

yes on the 660 this is very usual problem, but I thought you ride a 1VJ ?

enjoy working in spain, I try to find a job in switzerland

greetings mika

------------------

Hi,
Good you're back Klaus.
Yes, now I ride a 600cc 3AJ, have also been riding 1VJ and 34L.
But have never had this problem before.
Is it complicated to fit the complete 3TB engine; will I need to replace cables, cdi and ignition coil?

Good luck in Switzerland Mika !
See you over there, when bike will function again.

Matt

mechanically, the engine will fit 1:1
early 3AJ ('88) have different primary / secondary ratio than 3TB.
ignition system is different (exception: 3TB kick-start), so best would be to take wirings, tci-unit, ignition coil etc. from 3TB as well.
or take alternator stator / engine side cover from old engine and keep old ignition system / wiring.

best regards
klaus
xt600.de / tech. dep.

Interesting postings.
I'm starting to develop a bit of a bottom end knocking in my 3AJ and don't fancy going too much further before sorting it. But all this sounds a little beyond my mechanical ability. I haven't split a case before. But it sounds like it could be the start of a journey into the unknown. If only I had the time.

Cheers for the warnings
George

Hello again,

I'm decided for the 3TB option, last questions;
I'm going to buy only the complete low engine and fit my 3AJ cylinder, carbs, etc no problem there?

The 3TB engine (not kickstart), comes without starter engine, will my 3AJ starter engine fit onto, attachements etc? braker says no..!?

For better price I buy only engine part and will fit my right/left covers aswell.
Concerning the ignition, do I only need to change stator and not rotor? are rotors the same?

Is gearbox of 3TB bulletproof as rumour says?

Thanks very much for advice,

Matt

[This message has been edited by Matt595 (edited 23 September 2005).]

matt:
cylinder etc. will fit on 3TB bottom without probs.
starter engine will fit as well. maybe you have to do something on the right hand mount, 3TB starter engine is fixed to right hand crankcase, 3AJ is fixed on right hand engine cover. shouldn't be a problem.
rotor: it depends. stay with old rotor to be sure. if you use appropriate tool, changing is easy.
gearbox: fear of fith gear?
3TB gearbox is definitly not bulletproof, although better than before because of extra lubrication, different ratio, different gears.
but it depends mainly on the way you ride.
avoid low revs, especially don't accelerate hard from low revs. try to stay as much as possible between 4500 ... 5500 revs.

best regards
klaus
xt600.de / tech. dep.

Hi. Lucky me. I ve been riding for a while ( let say 9000 Kms ) with a "clok clock,clock clock clock,clock ,clock clock, ...only at low revs.
At frst people said it was normal for an old ténéré.Then the noise got worse.
some guys said there was something wrong with the pushrod...and a clever mechanic from yamaha, suggested a loose nut somewhere (possibly on the balancing shaft)...I decided to have a look. Horror, i discovered that the main nut at the end of the crankshaft was completely loose. The noise came from the pinions banging together , at low revs. Apparently,at higher revs ,the centrifugal force kept them nice and tight.
I had a bit of wear with the pinions but with a new cotter (pin?) and washer
the mechanics said it would be OK; Which it is...
All this , drove me to the XT trap (and dry sump engine, all very new to me): New oil filling.
I think i put to much :3 liters ( instead of 2 or 2,4 ? ). maybe i did not run the engine for long enough. Should i go for a test ride? and recheck the level?
Should i drain the extra 0,6 ( or 1 ) liter, and if yes can i do it only from the oil tank ?
The reason i did not go for a test trive is that i am scared that something
is wrong with the "return circuit" ?
Any answer is welcome ! I know i could try to find a previous post, but the
search engine seems to be pretty ineffective.

sorry for the long post;

Steph

Good for you that you found & corrected the prob in time!

As to overfilling: no immediate danger of killing the engine, so test drive possible.
Not really necessary, but for peace of mind: with the engine idling, unscrew filler cap of oil tank and look inside with flashlight. You'll see oil being returned from the engine.

If, after half an hour riding and checking oil level as per the Rules :-) you find you overfilled, just remove the excess.

Auke

__________________
Auke
http://aukemarieke.blogspot.com

Hi auke, thanks for the tip.
I went for a test ride, and everything seems to be alright.
Apparently the 3 liters seems about right, as it brings the oil level to 3 /4 of the reading stick ( unsrewed...) ,and after three differents readings (after Half an hour ride).
So at last i am back on the road.
Now i have to decide wether i keep the ténéré and start preparing it or swap it for a 650 africatwin...But that's another story.
Thanks.

Steph