Knock when shifting

[GaryIF]

I have a 2001 GS500 with 4200 miles.  It has developed a pronounced knock when shifting under rapid acceleration.  It is coming from the left side of the bike.  It almost sounds like something physically knocking against something else -- one knock with each shift.  No such sound during moderate acceleration; it's only occuring with more aggressive accleration.  My shifting is fairly smooth, relative to the pace of acceleration.  Otherwise, everything's operating perfectly.

Please factor in the following things I've done between the pre/post noise situation:
1.  A few weeks ago, I accidentally hit the engine kill switch while riding the bike then switched it back on within a few seconds, all with the bike remaining in motion.  The engine restarted itself immediately, with a loud backfire (because of the accumulation of unburned fuel during the few seconds the kill switch was activated).  Everything seemed fine thereafter.  I continued riding for about 15 or so minutes -- No problems; no strange noises.  And, because of the weather, no riding since.
2.  I changed the air filter (factory filter) during a brief weather break.  That, as all of you know, requires lifting the fuel tank slightly to access the filter.  I believe I remounted the fuel tank properly.  Perhaps not.; and
3.  Last night, my first ride since the kill-switch goof, the bike fell -- gently and safely, thankfully.  It fell on its side onto a snow covered patch in my yard (which never melts until spring) while I was walking it, engine idling, out to the driveway.  FYI -- the bike's winter home is a storage area behind my house which means a brief journey across the yard to the driveway.
It was a soft landing, cushioned by the snow and my right leg (ouch; I'm okay).  As soon as it fell the engine stopped running -- no gravity; no fuel to flow to the carbs.  No damage to the bike, only to my pride.  I left it laying on its side for a minute or so while I strategized how I would lift it without slipping and breaking my neck on the slippery patch of icy snow.  I know, I know -- dumb thing to be walking a motorcycle across a slippery surface but I needed my riding fix and the road conditions were perfect.

Any ideas?  Thanks, everyone.

[JamesG]

None of those things should have caused a problem.

Check your chain tension and that the sprockets aren't worn out. Adelita's GS would clank and make pinball machine sounds when shifting because the chain and sprockets were worn out.

[scratch]

I don't have any answers, just questions:

Does the bike shift allright? If it shifts allright, check your oil level. Did the engine make a loud 'Kuh-chunk' when it stopped?

[GaryIF]

I don't have any answers, just questions:

Does the bike shift allright? If it shifts allright, check your oil level. Did the engine make a loud 'Kuh-chunk' when it stopped?

Questions welcomed -- It shifts fine (actually, quite easily).  I will check the oil level.   As I retraced my steps last night, I figured out why the engine died when the bike fell.  I had the transmission in 1st gear and was feathering the clutch while walking the bike across the patch of snow.  When it fell, my hand let go of the clutch and the engine stalled out.  No loud "kuh-chunk", just a stalled engine.

Also, the knock can be generated by a hard acceleration/deceleration in 1st gear, without shifting.

When I get a break in the weather, I'm going to pull the fuel tank off and check to see if something's actually loose underneath it.  Also, I'll check the chain tension.

All other ideas appreciated.

[yamahonkawazuki]

what youve described, without shifting&acceleration/deceleration, im leaning toward something in the driveline, after checking chain and sprockets, check the primary sprocket, the 16t in the front, see if any side play? check retaining clip?, dunno, just my guess :dunno:

[GaryIF]

what youve described, without shifting&acceleration/deceleration, im leaning toward something in the driveline, after checking chain and sprockets, check the primary sprocket, the 16t in the front, see if any side play? check retaining clip?, dunno, just my guess :dunno:

Good suggestions -- thanks.  The chain or something related to the chain makes sense.  That's the location of the sound.  Perhaps something came loose and the chain is slapping against the chain guard when I'm shifting or accelerating/decelarating abruptly.  Hopefully, there'll be a 40+ degree day this weekend so that I can sort it out.

This board is great.  Many thanks to everyone.  Makes owning the GS that much more enjoyable.

[scratch]

Oh, yeah, welcome to the board!

[Kerry]

[...] check the primary sprocket, the 16t in the front, see if any side play?

This reminded me of something.  Do you know if your front sprocket has ever been replaced?

I replaced the original 16-tooth front sprocket on my '99 with a 16-tooth unit from Sprocket Specialists.  I started to hear some pretty startling sounds from the countershaft area, and I eventually suspected that it had to do with the lack of a "spacer" on the Sprocket Specialists sprocket.

To see what I mean, check out this picture:



The sprockets are all 16-tooth units.  From left to right they are:

1) OEM
2) Sprocket Specialists
3) JT Sprockets[/list:u]Notice that the Sprocket Specialists unit has no "shoulder" built into it.  The OEM sprockets were like this for the model years 1989-1993 (or 1994?) but then something was changed in the countershaft area and the stock sprockets came with the built-in shoulder.

Some folks with 1994+ bikes have used

Sprocket Specialists units with no problems, so maybe my rear wheel alignment was off.  Others have added a plain old washer (or 2?) next to the sprocket to act as a spacer.

All I know is that since I replaced the Sprocket Specialists sprocket with the one from JT Sprockets I haven't heard anymore complaints from my countershaft....

EDIT: Changed link from sisna.com to bbburma.net  Also changed Sunstar to JT Sprockets.

[dgyver]

Kerry... does the shoulder extend out on both sides? or just away from the engine when installed?

[Kerry]

Kerry... does the shoulder extend out on both sides? or just away from the engine when installed?

The shoulder is only on one side.

It's been a couple years since I've had that side cover off, but I'm pretty sure the shoulder goes between the sprocket and the engine.  I don't remember the shoulder being up against the circlip (on the end of the countershaft) as I removed & reinstalled the sprocket.

[GaryIF]

[...] check the primary sprocket, the 16t in the front, see if any side play?

This reminded me of something.  Do you know if your front sprocket has ever been replaced?

I replaced the original 16-tooth front sprocket on my '99 with a 16-tooth unit from Sprocket Specialists.  I started to hear some pretty startling sounds from the countershaft area, and I eventually suspected that it had to do with the lack of a "spacer" on the Sprocket Specialists sprocket.

To see what I mean, check out this picture:



The sprockets are all 16-tooth units.  From left to right they are:

1) OEM
2) Sprocket Specialists
3) Sunstar[/list:u]Notice that the Sprocket Specialists unit has no "shoulder" built into it.  The OEM sprockets were like this for the model years 1989-1993 (or 1994?) but then something was changed in the countershaft area and the stock sprockets came with the built-in shoulder.

Some folks with 1994+ bikes have used

Sprocket Specialists units with no problems, so maybe my rear wheel alignment was off.  Others have added a plain old washer (or 2?) next to the sprocket to act as a spacer.

All I know is that since I replaced the Sprocket Specialists sprocket with the one from Sunstar I haven't heard anymore complaints from my countershaft....

Hmm.  Not sure but I'll check.  The bike's an '01 so it has the newer sprocket you noted.  The low mileage and routine chain care make me suspicious about something being worn out.  But, clearly something happened when it fell and stalled out.  Thank goodness for snow and a sturdy right leg.  I would have been really bumbed had anything happened to the bike.

It's clear I need to focus on the chain area.  The bike is safely under wraps on its centerstand and the weather is looking promising for tomorrow.  Hopefully, the fix will be straightforward and I can get in more riding time before the next winter frost/snow.

Thanks again, everyone.

[Kerry]

Gary,

I infer from your last post that you're not the original owner of the '01.  Am I right?  If so, the previous owner may have swapped out the OEM 16-tooth front sprocket for a 15-tooth unit.  It's a common mod which gives better acceleration, more "oomph" in 6th gear, etc.

My point is that you still may have a Sprocket Specialists sprocket on the front.  I know someone out there has one of these, because I resold an (unused) 15-tooth, shoulderless Sprocket Specialists sprocket to someone on this board after I had the problems with the 16-toother.

I think they had a pre-1994 model though.

[yamahonkawazuki]

my '97 has the shoulder on it, like the oem one in kerry's post, my 15t from sunstar has a larger (but still same thickness) one on it, goes to the inside. the front cover (over sprocket,) takes about at the most 5 min to remove. i did in 20 deg. weather. worth a look at least

[GaryIF]

Gary,

I infer from your last post that you're not the original owner of the '01.  Am I right?  If so, the previous owner may have swapped out the OEM 16-tooth front sprocket for a 15-tooth unit.  It's a common mod which gives better acceleration, more "oomph" in 6th gear, etc.

My point is that you still may have a Sprocket Specialists sprocket on the front.  I know someone out there has one of these, because I resold an (unused) 15-tooth, shoulderless Sprocket Specialists sprocket to someone on this board after I had the problems with the 16-toother.

I think they had a pre-1994 model though.

Thanks, everyone.  The noise has been cured -- slightly loose chain; just enough for it to slap when shifting.  Seems so obvious in hindsight.  With it adjusted to specs, everything's back to normal.

[yamahonkawazuki]

if you ever put a 15t on, you will have to re-adjust chain, im talkin MAJOR chain play , but hey at least you got her goin, w/o expense, other than your time

if you ever put a 15t on, oyu will

,
boy, hooked on phonics worked for me!!! :mrgreen: