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Old 03-09-2013, 12:45 AM   #1
TheFunk625 OP
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Joined: Feb 2012
Oddometer: 6
2004 625 SMC Abnormal Vibration

I'm wondering if any of you knowledgeable folks may have some insight on what may have happened to my bike today. I pulled up to a red light , waited and when it turned green I took off. after letting out the clutch I immediately noticed the bike vibrating more than normal. The vibration was no present when I pulled in the clutch and coasted and was dependent on engine RPM. I checked all of the motor mounts and attempted to check the valve clearances, however it seems that the exhaust valves tightened way up(this has happened before after I put a new rocker in and didn't know I had to peen the little pin that holds it to the valve cover). I pulled the valve cover and the pins hadn't moved but I noticed some metal flakes around the cam bearing. So I pulled it off and I'm going to replace it just in case. The bike has roughly 19,000 miles on it. Also there is no noticeable loss in power or popping or anything weird like that...just way more vibes than normal. Is this a sign of a crank bearing or something like that? I don't really want to have to pull the whole motor apart...

Thanks again for your expert help as always!

Also I tried to search but everything with three letters gets filtered out :-(
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Old 03-09-2013, 09:12 AM   #2
gunnerbuck
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Location: N.V.I, B.C.
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Quote:
Originally Posted by TheFunk625 View Post
I'm wondering if any of you knowledgeable folks may have some insight on what may have happened to my bike today. I pulled up to a red light , waited and when it turned green I took off. after letting out the clutch I immediately noticed the bike vibrating more than normal. The vibration was no present when I pulled in the clutch and coasted and was dependent on engine RPM. I checked all of the motor mounts and attempted to check the valve clearances, however it seems that the exhaust valves tightened way up(this has happened before after I put a new rocker in and didn't know I had to peen the little pin that holds it to the valve cover). I pulled the valve cover and the pins hadn't moved but I noticed some metal flakes around the cam bearing. So I pulled it off and I'm going to replace it just in case. The bike has roughly 19,000 miles on it. Also there is no noticeable loss in power or popping or anything weird like that...just way more vibes than normal. Is this a sign of a crank bearing or something like that? I don't really want to have to pull the whole motor apart...

Thanks again for your expert help as always!

Also I tried to search but everything with three letters gets filtered out :-(
If the new bearing is not the fix, I would pull the clutch cover off, plus the clutch and inspect the left side shaft end bearings for slop...Try wiggling the ends of the shafts to see if they have slop, the crank shaft as well and you will be able to see if there is any bearing debris in the bottom of the cases... Also inspect the balancer gear and bearings to make sure they are working right... If all is well on the clutch side you could pull the flywheel cover, check for end shaft wiggle and make sure there is no debris floating around in there..
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Old 03-09-2013, 12:39 PM   #3
TheFunk625 OP
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Originally Posted by gunnerbuck View Post
If the new bearing is not the fix, I would pull the clutch cover off, plus the clutch and inspect the left side shaft end bearings for slop...Try wiggling the ends of the shafts to see if they have slop, the crank shaft as well and you will be able to see if there is any bearing debris in the bottom of the cases... Also inspect the balancer gear and bearings to make sure they are working right... If all is well on the clutch side you could pull the flywheel cover, check for end shaft wiggle and make sure there is no debris floating around in there..
Awesome, thanks for the advice. I'm going to pull it apart today and see what shakes down.
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Old 03-09-2013, 02:53 PM   #4
TheFunk625 OP
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Originally Posted by gunnerbuck View Post
If the new bearing is not the fix, I would pull the clutch cover off, plus the clutch and inspect the left side shaft end bearings for slop...Try wiggling the ends of the shafts to see if they have slop, the crank shaft as well and you will be able to see if there is any bearing debris in the bottom of the cases... Also inspect the balancer gear and bearings to make sure they are working right... If all is well on the clutch side you could pull the flywheel cover, check for end shaft wiggle and make sure there is no debris floating around in there..
There doesn't seem to be any slop in anything but the counter balancer. Is it supposed to wiggle around in there?
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Old 03-09-2013, 07:09 PM   #5
gunnerbuck
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Originally Posted by TheFunk625 View Post
There doesn't seem to be any slop in anything but the counter balancer. Is it supposed to wiggle around in there?
Yes, the counter balancer will have some wiggle when the side cover bearing is not there to support it... Check the bearing in the side cover and make sure it spins freely but is still tight... Is there any scarring on the cases that may indicate the balance weight has been flailing around on worn bearings?

With your vibration coming on all of a sudden it is almost like something let go rather than a gradual increase that comes from a worn bearing... How are your water pump bearings? Are they 19,000 miles old or have they been replaced?

If your vibration is only present when the clutch is putting power to the transmission then it is possible that the issue is coming from the clutch or tranny and not the crank or top end...
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Old 03-09-2013, 07:43 PM   #6
TheFunk625 OP
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The counter balancer side cover bearing spins freely with no slop and is snug in the case. There is no scarring or other signs of a struggle under the clutch cover(except like an ass I broke the inner clutch hub trying to torque the nut down without the proper tool).

I agree with the theory that something all of a sudden let go. I pulled off the clutch and everything seems tight with no slop except the shaft the clutch is on has some left-right play in it. The crank didn't seem to have any slop in it. The water pump bearings I think are original. I can spin the shaft in the water pump with my fingers and there is no slop or "chunky" feeling if you know what I mean. It also doesn't leak or anything. I also pulled off the stator cover and the flywheel was on tight with no slop. There was however those same little metal flakes around the pulser coil , so maybe that is where those came from. Its also weird that the exhaust valves seemed to tighten up without the intake valves moving any. Also it seems to vibrate the same weird way when its in neutral and I rev the engine with no real change when I pull in the clutch except a very small audible difference which was noticeable before the vibration happened.

Anyway , thank you for your input and sorry for the wall of text. I'm still kind of new to the LC4 motor , and while I do have the workshop manual your info is still very helpful and much appreciated.
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Old 03-10-2013, 12:19 AM   #7
gunnerbuck
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Originally Posted by TheFunk625 View Post
The counter balancer side cover bearing spins freely with no slop and is snug in the case. There is no scarring or other signs of a struggle under the clutch cover(except like an ass I broke the inner clutch hub trying to torque the nut down without the proper tool).

I agree with the theory that something all of a sudden let go. I pulled off the clutch and everything seems tight with no slop except the shaft the clutch is on has some left-right play in it. The crank didn't seem to have any slop in it. The water pump bearings I think are original. I can spin the shaft in the water pump with my fingers and there is no slop or "chunky" feeling if you know what I mean. It also doesn't leak or anything. I also pulled off the stator cover and the flywheel was on tight with no slop. There was however those same little metal flakes around the pulser coil , so maybe that is where those came from. Its also weird that the exhaust valves seemed to tighten up without the intake valves moving any. Also it seems to vibrate the same weird way when its in neutral and I rev the engine with no real change when I pull in the clutch except a very small audible difference which was noticeable before the vibration happened.

Anyway , thank you for your input and sorry for the wall of text. I'm still kind of new to the LC4 motor , and while I do have the workshop manual your info is still very helpful and much appreciated.
Having the exhaust valves wear quicker than the intakes is not the norm for the LC 4 but shouldn't be too much of an issue... The normal I have found is that the intakes usually wear faster and will need replacement sooner...

You mentioned you checked your motor mount bolts for proper torque, did you check the one that crosses under the front of the engine hidden behind the plastic plugs? I have seen this one break from fatigue before... Also inspect the frame and the welds as any small breaks can really add to the vibration level...

One thing that can also cause cavitation in the motor is if a chunk of debris lodges between the rollers on the crank end bearings... The bearing may suffer a momentary seizure which will gall up the bearing race surface enough to cause higher vibration from then on... If you put a dial guage on the balancer end of the crankshaft you can spin the engine and check for excessive run out of the con rod, crank and bearing assembly..

gunnerbuck screwed with this post 03-10-2013 at 11:12 AM
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