What the heck is causing that noise?!

[Mike 86 in San Dimas]

When I hit bumps or dips, even small ones, I hear kind of knock. I tried to replicate by holding front brake and pump the front end, but does not happen. It seems to be front end somewhere. Thought it might be fuel tank float bumping tank, but doubt it. I know potentially it could be many possibilities. Any suggestions I can look in to?

Thanks,
Mike 86 in San Dimas

[racerman_27410]

feel any notchiness in the steering head bearings?

if you have a way of getting the front end off the ground you may want to do a push pull test and see if you have any slop.

[SlowOldGuy]

My '85 has done that for years and it drove me crazy.  I finally realized that nothing is trying to fall off and it doesn't bother me anymore.  I think it may be the speedo drive down on the wheel.  There is some slop in the slot.  When the front end compresses, I think the cable may force the drive unit against one side of the alignment boss and cause a clunk.  That's the only thing I've been able to come up with, but I can't confirm it.

DavidR.

[andyoutandabout]

My 86 did similar - turned out to be the front mudguard flapping. The plastic had busted up all around the bolt holes. Cured it with big plastic washers that distribute the bolt pressure over a wider area - held for over a year and aren't really too ugly if you don't stare at them.
Andy F

[doright1]

Mine was a busted front fender/mudguard too.

[SlowOldGuy]

My front fender is just fine.

What I get is a sharp metallic clunk when the front end compresses hard.  Now that I have the correct straight rate springs, I don't hear it near as often as I did with the weaker springs.

DavidR.

[the fan]

Not sure if its possible on the FJ, but on my old CB900F the tank rubbers were worn out and the tank made a loud clunking noise whenever I hit a bump.

[SlowOldGuy]

Not "bump" related (at least mine is not).  Definitely required significant compression of the front forks before it happens.

DavidR.

[Mark Olson]

Mike,

my 86 does make a  clunk when I take it off the centerstand and sometimes when riding over bumps. I traced it to the spacers in the forks moving around. do you have aftermarket springs in your fj?

[Marsh White]

I think it is the centerstand bouncing up and hitting the frame etc.  The centerstand springs weaken over time and the centerstand sags down a bit.  Over bumps it knocks back up.  The vibration/sound can easily sound like it is coming from the front of the bike when it actually is not.  Go and take your FJ off of the centerstand and try and "Kick" or pull it up to test.

I have remedied this in the past by taking off the spring and twisting the end of the spring "U" tighter (essentially making a new "U" a bit farther back) thereby tightening up the spring - but it is a severe bitch to do this - as the spring metal is thick!  But it can be done with some swear words - some heat would probably help quite a bit too.

[56 CHEVY]

I've had the same noise in my 86 for years. Spent too many hours trying to locate the source & have never found it. Finally gave up.

I did the same with my center stand spring as Marsh. It solved the nasty banging sound at the rear, but didn't solve the noise at the front.

Dan

[Klavdy]

Your frame may be cracked.

[teeeeeceeeee]

Not wishing to puy a damper on things but my '84 FJ1100 used to do the same thing. It turned out to be about 1-2mm play in the fork lowers that would "clunk" when going over bumps, I had to fit new forks to fix the problem   .

Try lifting the front wheel off the ground with a jack under the motor and check the forks for any lateral movement.

Hopefully for your sake i'm wrong 

TeeCee

[elbows]

go for better ear plugs you wont hear anything !!!!!

[kenny b]

When I hit bumps or dips, even small ones, I hear kind of knock. I tried to replicate by holding front brake and pump the front end, but does not happen. It seems to be front end somewhere. Thought it might be fuel tank float bumping tank, but doubt it. I know potentially it could be many possibilities. Any suggestions I can look in to?

Thanks,
Mike 86 in San Dimas