Topic: Hittin' the skids! CB500

[hummbug]

So I was travelling into work in peak hour this morning along the Westgate Freeway in Melbourne - going the speed limit(ish) of 80kph. Suddenly, the kickstart lever brushed my leg as it spun around to the footpeg and rear brake lever,jamming the rear brake on and creating this pretty line along about 50m of road. See pic...
I didn't have time to think about anything except balancing the bike and keeping the rear wheel as straight as I could. Came to a stop and had some luck with the driver behind me being alert. She stopped and held up traffic until I could drag my bike off the road.
Another biker stopped as well but there was very little he could do to help. So there I was on the side of the road with no emergency lane, a bike that wouldn't go anywhere and a line of irate morning drivers heading toward me!

I called Citylink and they arranged a response vehicle to attend. In the meantime I tried to assess the damage and free up the kickstart lever so I could get the bike moving again. My trusty Honda tools were only good enough to get the lever loose but not the foot peg nut.

The response vehicle arrived and together we got the bent foot peg off the bike and removed the kickstart lever. With the brake now off, the bike would only roll so far, not coming out of gear until I put the bike on the centre stand.
After a free tow (thanks Citylink) to my office I have found that the bike will go into neutral, but only when it's on the centre stand and then I can wheel it around. No time today to have a proper look but I will try soon.

So...I now wonder what potential damage I have done and what caused the kickstart lever to engage so violently. I'm guessing the gearbox is a bit mangled right now. I didn't pull the clutch in at all during the skid and was probably in 4th or 5th at the time.

Anyone have any thoughts?

[CBJoe]

   Holy Crap......  talk about a heart stopping experience.

Glad you're alright,  Joe

[hummbug]

Thanks Joe...my heart was going at full revs there for a while!

[hummbug]

Anyone know why the kick start would start spinning like that? It's got me $^W%ed!!!!

[turboguzzi]

what model is it?

if it's a 500/55/650, (dont know others that well but must be similar) the pedal spins a gear wheel that is supposed to float on the shaft but is always meshed with the turning clutch basket.

maybe you've been running VERY low on bad oil and the gear wheel seized VERY suddenly on the shaft.  

first time i ever hear about this happening.

Not sure at all you mangled yoour gearbox though, nothing should happens if youo just jam the rear brake in a panic stop.

I guess that the difficulty you still have in shifting is due to that gear wheel still being seized on the shaft.

Take the clutch cover off to see.

TG

[Kirby]

Hummbug, have you got a manual.  The picture of the cutaway engine at the start of the Engine section will help...also the exploded view of the kick-starter in the appropriate section.  I just took apart two CB500 engines to get one good one for my project.   I am new to motorcycle transmissions, so you experts can correct me at will. 
    The kick starter pinion is always engaged to a cog on the trans output shaft(does not turn the chain sprocket because you are in neutral).  When you step on the kick start lever, you pull the k/s rachet to the right (towards your foot) and its teeth engage the teeth on the pinion, turning the engine over through the gears of the trans.  These are theoretically one-way teeth...they will only engage in the correct direction...if you keep the lever down after starting, you hear the teeth bumping over each other like most rachets.  When you raise your foot the spring on the k/s shaft pushes the rachet away from the pinion.   EVEN if the rachet stayed engaged for some reason, you would just hear the annoying rachet noise, it shouldn't overcome the lever return spring and rotate the shaft.   Apparently, in your case, something came loose all of a sudden and jammed the rachet into the pinion teeth, and it would immediately grab the shaft  and flip the lever aft like yours did.  With the lever off, and if you still have the kick start rachet engaged(jammed), the shaft should rotate with engine turning over(clutch engaged)...that pinion is always turning if the motor is turing and the clutch is engaged.  Maybe a gear tooth, or piece of something broke free and jammed something.  Of course you can't get to the k/s internals without breaking the engine case.  I guess you can do it without upsetting the head and cylinders.  (upside-down)  Not sure if most mechanics recommend that.  Again, I am new at this...would like to hear other opinions.   Glad you stayed upright, and good luck.  Kirby

[turboguzzi]

oops, my mistake, kick start gear is indeed engaged in the internal cavity so removing the clutch cover will not give access....

still, hard to imagine something flying into the tiny space between the ratchet teeth and jamming, sounds more like gear seizing on shaft to me at least.

Regretfully, any deeper investigation will mean splitting the cases.

[Hannibal Smith]

Your "free spinning" gear is rotating rearward (direction of kick) as the bike is underway.

Your uni-directional engagement cog is physically held away from engaging by helical ramp until the start lever is pushed rearward allowing the starting gear (fixed to the shaft) to come forward and engage the "free spinning" gear.

It sounds as if the lever snapping back did the deed, and applied the rear binder, not a tranny lockup.

I would pull the clutch cover first and see if your main kickstart return spring is not broken. If that main spring broke, then the "free spinning" gear will take the kickstart lever for a brief ride, not with much force, but with parasitic drag- that is a strong possibility.

Internally, the helical ramp is is held rearward (while the kick lever is up) by a stamped steel captive system, and failure there would be highly unlikely IMO.
In my mind's eye, I would say that the main lever return spring accessible from the clutch cover is more than likely the suspect. Could be wrong, but it is an easy check.

[Hannibal Smith]

Here are some images.

The orange gear is the freespinner that rotates with the tranny when underway. Note the uni-directional teeth on the engagement gear.
Note the main lever spring in the last image, that is the one I am talking about.

[turboguzzi]

Your "free spinning" gear is rotating rearward (direction of kick) as the bike is underway.

Your uni-directional engagement cog is physically held away from engaging by helical ramp until the start lever is pushed rearward allowing the starting gear (fixed to the shaft) to come forward and engage the "free spinning" gear.

It sounds as if the lever snapping back did the deed, and applied the rear binder, not a tranny lockup.

I would pull the clutch cover first and see if your main kickstart return spring is not broken. If that main spring broke, then the "free spinning" gear will take the kickstart lever for a brief ride, not with much force, but with parasitic drag- that is a strong possibility.

Internally, the helical ramp is is held rearward (while the kick lever is up) by a stamped steel captive system, and failure there would be highly unlikely IMO.
In my mind's eye, I would say that the main lever return spring accessible from the clutch cover is more than likely the suspect. Could be wrong, but it is an easy check.

Hanibal, even if the return spring failed, or the dissengagment plate failed, still, the cog should have free wheeled on the shaft, not rotated it so hard it jams the brake, that would take some real force, that's  why I believe its a (lack of)  lubrication seizure of the gear on the shaft.

[Hannibal Smith]

Your "free spinning" gear is rotating rearward (direction of kick) as the bike is underway.

Your uni-directional engagement cog is physically held away from engaging by helical ramp until the start lever is pushed rearward allowing the starting gear (fixed to the shaft) to come forward and engage the "free spinning" gear.

It sounds as if the lever snapping back did the deed, and applied the rear binder, not a tranny lockup.

I would pull the clutch cover first and see if your main kickstart return spring is not broken. If that main spring broke, then the "free spinning" gear will take the kickstart lever for a brief ride, not with much force, but with parasitic drag- that is a strong possibility.

Internally, the helical ramp is is held rearward (while the kick lever is up) by a stamped steel captive system, and failure there would be highly unlikely IMO.
In my mind's eye, I would say that the main lever return spring accessible from the clutch cover is more than likely the suspect. Could be wrong, but it is an easy check.

Hanibal, even if the return spring failed, or the dissengagment plate failed, still, the cog should have free wheeled on the shaft, not rotated it so hard it jams the brake, that would take some real force, that's  why I believe its a (lack of)  lubrication seizure of the gear on the shaft.

That does sound true, it would definitely have grabbed it! That would overcome the big lever main spring for sure.

[hummbug]

Thanks Gents, I haven't had a chacne to get out my manual or have a look at the bike. Some facts which may help though - I recently replaced o-rings on my oil pump to try and stop a leak of oil from the clutch cover and gear change lever. It didn't stop the leak. A couple of times I have removed the clutch cover to a pool of oil inside the cover.
I keep the oil topped up as I go and in fact did so yesterday morning...
Last oil change I found some shavings in the oil, one was a bit bigger than the others.
So, could the oil pump be malfunctioning or have an air bubble which stopped oil reaching the gearbox?

I can get the bike into gear and into neutral and I have started it. The clutch still works but the bike stops and stalls once the clutch goes all the way out....I'm not going to try too hard.

Either way, it may be time for me to split cases and have a bit of a look around, maybe a little rebuild...bugger.

At least I didn't fall off and get run over by a truck!

[Hannibal Smith]

While running, your freespinner doesn't have jack for a load on it.

Whatever the issue turns out to be, you are going to have to crack the cases to do the job right and for peace of mind.

Does the kickstart lever work again?

[hummbug]

The bracket that the lever sits in is cracked at it's weakest point and I had to pull it off to get the rear brake off...more to come...stay tuned...

[Old75_ratafe]

Man glad your alright that sounds like one of my worst nightmares that could have been a really bad accident.

[dave500]

umm??the small circlip that holds the kick assembly together may have popped off,drop the pan and with a good torch have a look,have the clutch cover off aswell so you can rock the transmission back and forth,if the engine is running you can actually try to kick the bike and there will be no consequence,an un planned rear wheel lock up!!you did well.,i wouldnt say its a common thing as far as a dry shaft grab, plenty of dry barn finds have only been fired up tuned and then ridden,,i used to live in melbourne,we threw a non working hr holden radio off the top of the westgate bridge in the mid eighties.,but no bodies.

[hummbug]

Just an update on this - did some work over the weekend and found the problem. It's posted in this link:

http://forums.sohc4.net/index.php?topic=74892.0

[saltandconcrete]

Hey, sorry to bump this super old thread - but I am living in fear of this happening now. I pretty much am just finishing up overhauling everything on my 71 cb500 (full electrical, electric ignition, threaded brake lines, new carbs, new airbox, new wheels, cogs, chain etc) but am not touching the engine as it has great compression and runs/starts fine. Also, no issues with the tranny (knock on wood) that I can tell, yet....

Can anyone tell me what the warning signs of this happening are? Is it specific to the 500 tranny? Should I do a preemptive strike (haven't even thought of looking at the tranny until I read up about this issue).

22,000 on the bike.

Thanks!

[hummbug]

Hello mate,

Well it seems like you've done a lot of work on your bike so I wouldn't worry too much. It was more likely that my incident was a result of low oil to the critical area of the gearbox which could have been an existing issue or something that I did to make it worse.

It could also have been from some over-enthusiastic kickstarting by my mate when I first got the bike, leading to a some weakness in the mechanism, compounded by low-oil supply.

If I could suggest anything it would be to ensure you have proper oil levels, use a good quality oil without additives (I use mineral oil now) and use the electric starter when possible OR teach your mates to kick it properly (find TDC before kicking down).

Aside from that, just get on and ride your bike! Mine's been fixed for years now and still going like a champ!

[trigger]

Don't be surprised to find the needle bearing on the main gear shaft has let go and jammed the gear box. This is a common problem if low or old oil. This needle bearing will overheat and lock up.
 

[dave500]

only common if some dick has run out of oil,you wont seize one normally,even #$%*ty old oil is way better than none.

[trigger]

only common if some dick has run out of oil,you wont seize one normally,even #$%*ty old oil is way better than none.

Seen two like this in the last year. Both on the left side needle roller and the right one was fine. But, i have only been building Honda engines for 26 years

[dave500]

ive seen them rusty,thatll fail if its used.