Harmonic Balancer damper - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 8 (permalink) Old 09-18-2016, 01:01 PM Thread Starter
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Harmonic Balancer damper

just curios if anyone knows what type of "rotational play" is acceptable for the balancer gear?

I pulled the left side stator cover off and pulled the pickup coils out of the way to investigate. You can clearly see the damper gear. While turning the engine by hand, how much rotational play is normal before the outer gear (hub) starts to move?
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post #2 of 8 (permalink) Old 09-18-2016, 09:11 PM
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When I did the installation the dampers were quite snug and didn't allow movement.

I do not know how much they 'break in' after use, so can't comment on normal play.

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post #3 of 8 (permalink) Old 09-19-2016, 04:55 PM Thread Starter
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Quote:
Originally Posted by thtanner View Post
When I did the installation the dampers were quite snug and didn't allow movement.

I do not know how much they 'break in' after use, so can't comment on normal play.
I appreciate that Tanner...thanks! yeah, a brandy new set of dampers would not give us a realistic view....a broken in set would be ideal.
It really is easy to check, and would only take about 15 minutes.

I am not willing to tell people to wait until they have a problem before they do replace them. and doing so as a preventative measure...well, if it looks good, why bother?
The problem is that historically, damper failures are catastrophic and can be very costly.

I am hoping someone either has their stator cover off for other reasons, or might be willing to pop off the cover and let me know how much movement they see on a bike with no issues so we have a decent reference point to work with.
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post #4 of 8 (permalink) Old 09-21-2016, 04:57 PM Thread Starter
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post #5 of 8 (permalink) Old 09-21-2016, 08:26 PM
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well the last time I started Melissa Fahye she felt kinda like Goofyfoot's Sporty(minus the Millennium Falcon's acceleration, of course),the motor on the floor in my shop hasn't been run in over 8 years,and my parts bike has a hole in the case down on the bottom by the balancers, so I'm out

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post #6 of 8 (permalink) Old 09-24-2016, 05:32 AM
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I'm psyching myself up to replace a broken shift linkage, so I'll be opening up all covers, and I'd be happy to check.
How exactly does one manually turn the engine by hand to check the balancer play?
Don't want to spin the wrong thing and give you bad info!

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post #7 of 8 (permalink) Old 09-25-2016, 07:08 AM Thread Starter
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The center bolt on the flywheel (under the stator cover) is where I put a socket and turned the motor by hand. I also left the spark plugs in when I did this, so compression will give resistance.
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post #8 of 8 (permalink) Old 10-05-2016, 06:50 PM Thread Starter
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Well, I can tell you this....if you turn the flywheel counter clockwise and you can see the gap on the balancer damper almost make contact(rubber dampers are being compressed) between the inner hub and outer gear......the dampers are worn...lol

I was hoping someone would provide a good reference to validate my suspicions, but I could not wait.

My bike runs and performs great, but an intermittent knock at idle was developing. There were no vibration issues, and I suspected the dampers were going soft and allowing the hub and outer gear to make contact when at low idle(little momentum from cam rotation). At higher RPM and highway speeds, there were no knocks or performance issues.

I decided that I wanted to fix it before it wobbled and chewed up the left lower front portion of the engine case.
I pulled my motor and replaced the dampers (and the stator while I was there) and compared the rotational play between the old dampers and new.

Remove the left stator cover and the top pickup coil and you will be able to watch the balancer gear turn as you rotate the engine (by turning the flywheel counter clockwise).
Looking at the left balancer gear, you will see 2 large holes in the gear. Inside each opening, you should see a rubber damper and a metal post sticking through it (from the hub on the other side of the gear). As the cam turns the hub, the rubber bushings will give a tiny bit prior to the outer gear starts moving. Here is what I observed:

Old dampers - outer gear did not turn until the hub almost touched the gear opening (the rubber dampers were nearly completely compressed).

New dampers - The outer gear started moving immediately with only a TINY bit of give from the bushings (less than 10% compression of the damper bushing)

When I removed the old ones, they looked and felt pretty much like the new ones (no visible signs of cracks or missing rubber, but the inner metal ring was a bit worn), but obviously they had softened after 14K miles and 10 years. You could not tell that they were softer by using your hands to feel them.

Hopefully this will be some type of a guide for others to gauge if your dampers are worn.....prior to having a failure that is catastrophic.
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