Topic: Anti-lock clutch?

[Raul CB750K1]

My Sanglas (Yamaha XS400 engine) got me puzzled. It runs well, the engine starts well, the gears shift smooth, but there is something strange with it.

I noticed it the first time I run out of battery. Tired of kickstarting it, I decided to let it run down the sloppy road. Third gear, clutch in, let speed build, ignition on, release clutch.... and the bike continued rolling with the engine frozen!  WTF? I loosened the clutch cable sleeve in case it was too tight, but the same happened. Finally I "landed" on the bike momentum near a car shop and politely asked them to jumpstart my bike. Went back home but didn't forget about it.


I asked other owners in my Sanglas club and none of them recognize such a strange behaviour. Most all of them remember having his bike pushstarted.

Last saturday, with a fully-loaded battery, I decided to try it again. Nada. The bike would roll and the engine won't move, regardless of the tension of the clutch cable.


Prognosis? I would say worn clutch, but the bike runs like a champ! There is no slippage whatsoever under hard acceleration or hills, it seems that the clutch grips perfectly. I can't understand what's going on. First I thought there could be some kind of -one way- clutch in the final drive train, but the parts manual doesn't show anything strange. Then I thought in my brainstorming: "what if the clutch discs have some kind of matching surface that they only grasp in one direction, nor the other? -like the starter clutch-. But I have had a couple of scary moments when downshifting, when the rear wheel locked. That's exactly the same thing than pushstarting the bike: the wheel wants to go faster than the engine, but the engine wouldn't allow it. So the wheel must either lock or make the engine spin faster.



I can't think of any other reason for this to happen, so I hope some of you in your previous experience has gone through this before and can shed some light. It is not just curiosity: the bike is light and I can push it up a hill -i.e. the garage ramp- to start it downhill in case I run out of battery, but if this doesn't work, I will have to carry my jumpercables everywhere.

[bryanj]

Raul, there is nothing i can remember on the Yams that would do this, only mechanical things possible is:-
false neutral
clutch not biting for some reason.

try putting on stand and spining the wheel in gear with lever in and out

[Raul CB750K1]

Raul, there is nothing i can remember on the Yams that would do this, only mechanical things possible is:-
false neutral
clutch not biting for some reason.

try putting on stand and spining the wheel in gear with lever in and out

As I said, something odd. I know the clutch doesn't bit as it should. When I needed to remove the alternator rotor -posted some pictures here back then-, I tried the easy things first: shift to high gear, lock the rear wheel with straps, and turn the rotor extractor bolt. Nope, the engine would turn while in gear. I just thought I was exerting too much force so the clutch slippped, but hey!, more force exerts the engine when running and the clutch doesn't slip.


As I said, I have had some rear wheel lockups while downshifting, so the clutch usually bites. Only thing that comes to my mind is that the clutch could be in its service limit, so the springs doesn't press the plates together as they should. Maybe I could have loose springs too. I don't know the whole background of the bike. They say that car oil can ruin clutch plates because of the additives. Don't know if somebody used car oil before in the bike.


I guess I will just have to wait until the clutch slips in normal use or it's time for engine rebuild, whatever comes first. The engine uses a little oil so I guess rings and/or valve guides are almost due...

[malcolmgb]

Isn't that the action of a slipper clutch?

[Bob Wessner]

Isn't that the action of a slipper clutch?

Hadn't heard of them before. In case others haven't....

http://en.wikipedia.org/wiki/Slipper_clutch

[Raul CB750K1]

Isn't that the action of a slipper clutch?

Slipper clutch, that's what I meant. I didn't knew the right english term. Yeah, that's exactly what I thought when it happened: Yamaha was offering slipper clutch 25 years before they went into the racetrack!!!! 

[bryanj]

Otherwise known as centifugal clutch----not fitted by yamaha to any large bike in uk to best of my memory

[merc2dogs]

 Slipper clutch isn't the same as as cetrifugal clutch, the slipper clutch generally has one way ramps and bearings that only allow it to drive but not brake the bike, but behaves as a regular clutch as long as the engine is running

 centrifugal engages at a set engine speed and above that speed works as well as a regular clutch for engine braking etc untill speed falls low enough to disengage.

 Had a slipper on an old BSA years ago, was a real pain in the butt because I regularly use engine braking, and that one had no ability to engine brake, you could drop right down to near idle speeds without hitting the clutch, traded it to a guy for a regular clutch and $50 the following summer.

quick rundown on op here:
 http://www.yoyodyneti.com/motorcycle_slipper_clutch_operat.htm

 Some people LOVE slippers, I like them but not on my daily rider, but can see on some long hauls tthey may be nice to have, taking your hand off the throttle and coast a bit without having to hold the clutch or find nuetral would be nice in some cases.

Ken

edit to include centrigugal clutch link

 centrifugal clutches shown here:
http://www.heeters.com/kartclutches.shtml

Ken

[DarkRider]

it may not have been factory equipment but then again whats to say that someone didnt retrofit a slipper clutch on the bike during its life?

[Raul CB750K1]

it may not have been factory equipment but then again whats to say that someone didnt retrofit a slipper clutch on the bike during its life?

PO, when the starter motor broke, found the estimate so steep that told the mechanic to close everything back, and he would start the bike with the kickstarter from then on...


I don't think he was an "upgrader".....