Lurch forward

Hi there,

I had an interesting experience this morning with the Commando (1972 Roadster 750). I rode to work, which I've been doing every decent day for the past few years, and when I arrived at my work parking lot I ended up in a slow moving line and was just a few feet behind the car in front of me. Stopping and starting. At one point the car ahead rolled back a couple of feet, almost touching me, sending my heart into my throat for a second, so I increased my lineup following distance to a good 10 feet or so. Good thing I did, as during the next sit and wait session while holding the clutch lever in, and still in 1st gear, there was a sort of quick whine noise, and the bike momentarily lurched forward hard. It was like I had dropped the clutch lever, but it was still solidly in. I was able to just hold the bike with the brake and my feet, but it gave me a good fright. After that everything seemed totally fine, and I got across the lot, parked and all seemed normal.

Anyone have any idea why this happened? And also, does anyone know how worried I should be about the ride home after work today (in about 4 hours)? I am thinking I will just go into neutral whenever I stop, and will take the scenic, quiet, no traffic route home.

I am also thinking I should pull the primary cover off when I get home and see if there anything stands out?

Thanks a lot,

Jamie

sleeve gear bushings went dry and locked up on mainsaft? Just a guess on my part.

Deets55 said:

sleeve gear bushings went dry and locked up on mainsaft? Just a guess on my part.

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The bike was in 1st gear and not moving when it happened so the mainshaft would not have been turning inside the sleeve gear until the lurch forward occurred.

Seems more like a clutch problem to me, either the clutch bearing locked up momentarily or something(?) locked the clutch.

Thanks folks. Yeah, clutch problem is what I was thinking as well.

Could debris of some kind in the primary cause the clutch bearing or clutch to lock for a moment? Do you think it is likely to happen again over the course of a 10-15 mile run home?

Supercat said:

Could debris of some kind in the primary cause the clutch bearing or clutch to lock for a moment?

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Apparently, something did although it's difficult to say exactly what as it doesn't seem to be one of the 'usual' Commando problems.

If it wasn't the clutch bearing then the only thing I can think of is if perhaps a section of friction material broke away from the plate and momentarily jammed the plates but then I wouldn't expect the clutch action to have returned to normal so quickly.

Supercat said:

Do you think it is likely to happen again over the course of a 10-15 mile run home?

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That, I really couldn't say, not knowing what the problem is.

Supercat said:

Thanks folks. Yeah, clutch problem is what I was thinking as well.

Could debris of some kind in the primary cause the clutch bearing or clutch to lock for a moment? Do you think it is likely to happen again over the course of a 10-15 mile run home?

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You should be OK going home if you leave plenty of room - you can shut it off or bang it into neutral or the false neutral between 3rd and 4th if need be. I would take the clutch apart and unless you see something obvious, go for the clutch bearing.

More guessing, but as for things going arye in primary, I've had the inner cover bolts come loose, one falling out and rattling around. It must have got trapped tween chain and sprockets as the chain rollers were broken in a few links. Did not have strange lurching as described but might be possible.

Ok, I'll leave lots of room and will proceed as discussed. Hopefully things become clear when the primary cover is off. I'll report back when I get the cover off. Thanks again!!

Sounds like the clutch cable is failing. Take a look at the cable barrel at the lever end of the cable.

Supercat said:

Ok, I'll leave lots of room and will proceed as discussed. Hopefully things become clear when the primary cover is off. I'll report back when I get the cover off. Thanks again!!

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Should have mentioned, if you have a kill button...

Hey there, some new information has presented itself. I rode home with absolutely no issues whatsoever. I took the long scenic route, kept a good following distance, and kept her in neutral at stops until ready to go. That said I did purposefully put her in 1st with the clutch lever held in a few times while sitting when I was in a safe place (empty parking lots) and everything seemed fine.

I stopped to pick up a couple of things from a grocery store, just before home, and when I walked back to the bike I approached from behind, unlike after work. I immediately noticed that my rear light fixture is wrecked. The red cover is completely gone, and the fixture is crushed down/forward. The two bolts that held the red cover in place are still where they should be, just bent down along with everything else. The fixture was definitely intact 24 hours ago as I have photos of the bike from last evening. I will have to re-learn how to upload photos here, but when I do I can post a shot of the minor carnage. The bike was parked in a very public spot all day, and I can't imagine anyone would randomly smash someone's taillight in broad daylight. I've been parking there for four years and have never had any hint of an issue, and so have lots of other people with bikes near mine. And if someone was going to vandalize my bike, why would they just focus on taillight fixture and not on very smashable things like the clocks? Amazingly the light still works .

In light of this, I'm now thinking that the lurch forward, and the smashed light fixture could be explained by someone rear-ending me. The conditions for that were perfect in a tightly spaced lineup of cars on a very active large parking lot in the morning rush. I guess pieces of the red light cover would help confirm, and/or security footage if they record and keep recordings for more than a day.

What do you think? Should I be tearing into the primary, or examining the scene of the incident for forensic evidence?

Looking for CCTV footage is best option.

Supercat said:

In light of this, I'm now thinking that the lurch forward, and the smashed light fixture could be explained by someone rear-ending me.

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I did wonder about that but I thought you would have felt the impact if the bike had been hit by another vehicle!

Supercat said:

What do you think? Should I be tearing into the primary,...

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I somehow think that will be unnecessary now.

Yeah, it didn't cross my mind that I might have been struck until I saw the fixture. I would have thought that being rear ended would be an immediate knock down, but if they just sort of nudged me a couple of feet forward from stopped... Would explain the sound too I think.

Perhaps someone bumped into the bike while parked at the grocery store.
The least they could have done was to leave you a note that said,
"Some people have seen me bump and damage your bike, so I am writing this note to make them think I am posting you my DL, and phone number, but I am not."

Slick

texasSlick said:

Perhaps someone bumped into the bike while parked at the grocery store.

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Then not only would the broken lens parts be at the scene but it would probably have knocked the bike over.

Assume the tailght/brake bulb gone? So you were riding along without brake light since it departed.

How is license plate and mudguard, any deformation?

A new lamp bracket and lamp unit at a minimum. Not enough to clear your deductible at around $250 for those bits.

Tornado said:

Assume the tailght/brake bulb gone? So you were riding along without brake light since it departed.

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Supercat said:

Amazingly the light still works .

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Wait til you see how much a Lucas L679 lens costs….just buy the knock off.

*IF* you were sitting there with the clutch in and no brake on, a soft direct hit to the back could easily do the damage you see, not knocked you over, and make it seem like the bike did it, itself. However, I would guess that you had the front brake on which I would think would feel quite different if hit.

So, if you remember where it happened, going and looking for lens parts should answer the issue.