Clunking on decel - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 23 (permalink) Old 08-21-2012, 08:53 AM Thread Starter
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Clunking on decel

Hi everyone,
I'm new to this forum. I've been riding my 2000 VStar 650 Classic for almost five yrs back and forth to work logging 20,000 miles on a bike that had 12,000 when purchased.Last week coming home I noticed a single clunking sound when I would back off the throttle when slowing for a traffic light. It started off just noticeable and ended up being a LOUD clunk before entering my driveway.
Next day I put the bike on a stand with the rear wheel off the ground and rotated the rear wheel back and forth to see if I could replicate the clunking sound. I could not feel any type of play in the universal joint or make any sounds. I started the bike and shifted into fifth gear and let it run. It made clunking sounds (while idiling in gear) coming from the lower end (similar to something being rather loose in the crankcase. I shut it down, drained the oil and removed the crankcase cover fully expecting to find something very loose inside. I also removed the cover for the middle drive pinion gears for a looksee. Upon inspection I could not locate anything loose so I removed the entire clutch assembly. With the clutch housing removed I rotated the transmission mainshaft back and forth and could definitely replicate a clunking sound when the tranny is in gear. Should I be able to rotate the mainshaft back and forth approximately 30 degrees+ before the shaft engages solid? Seems like an awful lot of play. Just trying to figure this all out.
Thanks for any and all help.
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post #2 of 23 (permalink) Old 08-21-2012, 09:55 AM
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The tranny gears slide on a spline and there defenitely should not be 30 degrees between "clunks" in the spline, nor is there 30 degrees of backlash between meshed gears. However there is a loose fit of the dogs on the side of the sliding gears that engage into the side of the fixed gears....but 30 degrees still seems excessive, but then again there just might be more distance between "clunks" in 1st as compared to 5th.



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post #3 of 23 (permalink) Old 08-21-2012, 10:52 AM Thread Starter
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Originally Posted by stratowart View Post
The tranny gears slide on a spline and there defenitely should not be 30 degrees between "clunks" in the spline, nor is there 30 degrees of backlash between meshed gears. However there is a loose fit of the dogs on the side of the sliding gears that engage into the side of the fixed gears....but 30 degrees still seems excessive, but then again there just might be more distance between "clunks" in 1st as compared to 5th.
stratowart,
I can feel a difference in the amount of slop by going thru the gears. It still seems excessive in all the gears though. This problem seems to have reared it's ugly head all at once versus something that I noticed and got gradually worse. The bike has run perfect. The only thing that comes to mind is that over the past couple of months (this only happened maybe three times) when I was getting ready to up shift the bike would jump into the next gear before I hardly depressed the clutch lever. Kind of like speed shifting without trying. I wrote it off as sloppy shifting on my part.

Last edited by GaryS; 08-21-2012 at 05:26 PM.
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post #4 of 23 (permalink) Old 08-21-2012, 11:25 AM
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Its hard to say you can't jack the back half up and test these bikes aren't built to very tight tolerances and besides your not going to replicate the same force you would under a load. if you shift early you can get some clunking coming from the crankcase area. I know you checked for play but have you serviced the differential?

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post #5 of 23 (permalink) Old 08-21-2012, 11:28 AM
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I wish I knew where to go look to find out what is an acceptable amount of slop between the two tranny shafts but I don't. I can tell you, even tho I don't have a shaft drive scoot, that I will get a very audible "clunk" when dropping it into 1st at a dead stop. I've always attributed that to the loose fit of the dogs on the sides of the gears. Elevate my rear tire, put it in any gear and I can rotate the back wheel several degrees CW and CCW and get a "clunk" as well. I'm not sure if you are going to pull out the tranny shafts and inspect the gears but I wouldn't blame you if you didn't because I can't imagine the dogs to wear out "overnight" like you just experienced. And being a drive shaft bike you already did the most logical check which is the universal joints (it was my first guess until I read your entire post at the top of your thread).



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post #6 of 23 (permalink) Old 08-21-2012, 02:26 PM Thread Starter
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I know you checked for play but have you serviced the differential?
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SSC,
If by differential you mean the middle drive and middle driven pinion gears I have removed the access cover and inspected them for any wear or play. They seem fine to me.

stratowart,
I'm trying to avoid splitting the crankcase in two if I'm not 100% sure that's where the problem lies. I'm going to spend some more time going over it to see what else I can come up with.

Thanks,
Gary
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post #7 of 23 (permalink) Old 08-21-2012, 02:53 PM
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I agree, unless you see good size bits of steel in your drained crankcase oil I would NOT crack the engine cases open either. But I would at least check your drained oil for stuff that shouldn't be there. I hope it ain't too late to check it..



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post #8 of 23 (permalink) Old 08-21-2012, 03:26 PM Thread Starter
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I agree, unless you see good size bits of steel in your drained crankcase oil I would NOT crack the engine cases open either. But I would at least check your drained oil for stuff that shouldn't be there. I hope it ain't too late to check it..
That was my next thought was to filter the drained oil and see what shows up.
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post #9 of 23 (permalink) Old 08-21-2012, 05:24 PM Thread Starter
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Well gentlemen I may have located the culprit. While the crankcase oil was straining I decided to take a better look at the universal joint. While manually turning the drive shaft back and forth by hand to see if I could detect play in the UJ I felt the drive shaft freewheel in the final about 5-10 degrees. This action when done forcefully generated a loud clunk from the final. I remember the first couple times I heard it the noise sounded like it came from behind me and I wasn't even sure it came from the bike. The last time it occured as I was approaching my driveway and a LOUD clunk came from under and slightly behind to my left which would be in that area. So, I drained the final and what came out looked like metalflaked gear oil. Not large chunks but enough to make the oil look kind of milky when it was draining.
The strained crankcase oil showed just a tiny bit of metalflaking. My Clymer repair manual says take the final to a qualified repair center as it takes special tools and knowledge to repair.
Thoughts?
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post #10 of 23 (permalink) Old 08-21-2012, 05:45 PM
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Only because I've heard shaft drive repairs get pricey, my thoughts are filled with sympathy. Thinking the final is mainly a small spiral bevel pinion on the end of the driveshaft that churns against a large spiral bevel gear in the wheel hub tells me one or both have gaulled faces on the gear teeth. I can't imagine what special tools would be needed. Wish I could be more help but I'm completely ignorant of shaft drive scoots.



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