Exciting moments in drive train failure!

so I'm blasting from Austin to San Antonio, and I'm taking the 410 around San Antonio, fighting traffic, doing lots of shifting. and I notice my clutch cable seems to be getting longer, and longer. And I'm not really in a position to do much about it, because I'm trying not to get smeared by rush hour traffic on the 410. Entirely too soon for my liking, I suddenly have failure on my clutch lever. I cannot disengage the clutch at all. I'm not happy, but I can bangshift the last 20 miles. Yes, I winced with -every- shift, doing it as tenderly as I could, feeling like a horrible person. However, I was kinda stuck with the situation. And if I stopped, I'd -be- stopped, with no-one to come pick me (or my bike) up and take us home.

So I'm coming onto my final turn, and I need to slow down even more. I make one final bang-shift, and there's this jar, and a horrible grinding and banging noise, sounding like I've completely smashed my trans.

I'm also, blessedly, free-rolling, instead of my rear wheel locking up.

The end result was a bit odd..

Apparently the adjuster screw on the clutch arm had managed to un-screw itself rather neatly... And the horrible noise? yeah, that was the end of my drive shaft uncoupling itself. Apparently someone, a long time ago, didn't put it back together right, and cross threaded the nut holding the final-drive end of the nut on, and stripped the threads out, hard. The end result eventually un-threaded itself, and broke free when a hard enough bang-shift was applied.

Ouch. So glad you are ok, the bike can be fixed, but our bodies, not so much.

Wayne

Yeah, I had a brief moment of pants-crapping fear when the horrible noises started, I was dead certain the trans was locked, and I was about to get tossed.

Glad it didn't break worse, or break you. That kind of traffic is bad enough with a bike that works, let alone one in semi-survival mode.

You need to accumulate more friends with trailers. Or enroll in a decent roadside assistance program. The annual fee will be less than the probable cost of that driveshaft.

PGlaves said:

... enroll in a decent roadside assistance program. The annual fee will be less than the probable cost of that driveshaft.

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The roadside assistance offered by the MOA seems to me to be a very good one, since you are already a member. I am thinking this year to give it a try myself.

Monster torque required on this nut during assembly... 150-180 ft/lbs; coupled with the taper, it's the only thing that transmit the power through the coupler.

You've got to ask yourself how the guy that assembled this failed to realize he had cross threaded that nut. It's either that, or he used a mondo 3/4" impact wrench on it an stripped them in place. Judging from the galling it looks like it's been slipping for a while.

mmmmm .. ... tell me a "bang shift" isn't what it sounds like.

lmo1131 said:

mmmmm .. ... tell me a "bang shift" isn't what it sounds like.

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With that early shaft there's probably also a full weight early flywheel. Probably not so much a "bang shift" as a "BANG SHIFT."

Very glad for you that it didn't lock up, Rogue!

A 'bang shift' is where you blip the throttle, ease off quickly, and in that brief moment when the entire drive train is 'floating free' jab the shifter up or down, and 'bang' into a different gear. Done right, it's as smooth or smoother than a clutch shift. Done wrong, and the whole bike jerks as you 'bang' into the the next gear. Relatively harmless if done perfectly, but potentially very very bad if you 'miss'.

Actually the bike has a rather professionally lightened flywheel.

It might have started life as a 1977 R75/7, but it's a rolling mish-mash now.

/6 heads.

/5 trans.

/5 forks

unknown jugs, but bigger than 750cc, and -not- /7

lightened flywheel.


It's name is 'Mutant'.