"Thunk" from the front end of my SS

[sid_for_speed]

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I believe they could be steering head bearings...Shocks look ok...but I get this "thunk" noise every time I go over a slight bump...on deeper crater like potholes of our city, no audible noise is heard...

Any ideas of mechanics who could check steering head bearing condition? I wanna take it to a dealer but wanna weigh my options 1st... I 've read CBR 600 forums and some say this noise is due to shocks and that is a non issue but I do not want to just assume this condition

 

[TK4]

Jack the front of the bike up enough that you can rotate the handlebars.
If there is any notchiness the steering head bearings are toast.
Grab the lower fork legs and see if there's any sloppiness. If there is, try to isolate it.
Steering head bearings might need adjustment OR the front wheel bearings and/or front fork bushings or springs made need replacement.
Any competent shop/mechanic can perform the necessary repairs, but it won't be cheap.
Not a home repair job unless you're confident and prepared to have parts all over the place.

 

[Trials]

Takes all of 2 seconds to check your steering head bearing for play; sit on the bike and push your thumb up against the part where the bearing turns, pull on the front brake and rock the bike forward and then backwards hard against the force of the brake, if you feel any movement in the bearing other then axially then your bearing is too lose.

When did you last change or inspect the level of your fork oil?
I rebuilt a set of forks for a rider last week and they had no oil left in them, the things were clunking everywhere. So were his brakes and wheel bearings.

... was cheap for him, I did it for free so it only cost him the parts.

 

[250R-ICE]

I'm hearing a similar noise on a new bike. Only 1,000 km S. Like Trials noted, I first checked to see if it was suspension or steering related by sitting on the bike pressing in front brake. Then rocking bike back and forth also compressing front down. For me no noises or clunk felt. I believe my situation is happening when braking. If I brake hard and fast, i feel a slight clunk and noise. Very minor. But it's there. I'm thinking it's brake related , either it's the play in the semi floating rotors or brakes pads settling in position just before they start grabbing. I'm bringing bike in for its first service in a couple of weeks. I will confirm then if it's normal or not.

 

[jc100]

I had a fork cartridge replaced on my KTM with the same symptoms. That solved things. I get a thunk if the bump is too big and my suspension is set stiff but I think that’s expected. Set to off-road (max travel) all is fine.

How stiff is your suspension set up?

 

[GreyGhost]

Takes all of 2 seconds to check your steering head bearing for play; sit on the bike and push your thumb up against the part where the bearing turns, pull on the front brake and rock the bike forward and then backwards hard against the force of the brake, if you feel any movement in the bearing other then axially then your bearing is too lose.

When did you last change or inspect the level of your fork oil?
I rebuilt a set of forks for a rider last week and they had no oil left in them, the things were clunking everywhere. So were his brakes and wheel bearings.

... was cheap for him, I did it for free so it only cost him the parts.

Well that's extra dodgy. Where did the oil go? I've seen forks with sludge in them, but never empty forks.

 

[Trials]

Well that's extra dodgy. Where did the oil go? I've seen forks with sludge in them, but never empty forks.

all over the front brake and the sand pits he and previous owners were riding in,
is a 2001 KX125 ... he needs a whole new rear brake if anybody has one.

 

[sid_for_speed]

When did you last change or inspect the level of your fork oil?

Never...and I don't think the previous owner did either...it's a 5 year old bike...but there are tell tale signs of what could have happened. When the bike was safetied, it needed a front tire.The owner also gave me straps as a "free gift" that he used to strap the front end down while the bike was being trailered to wherever....those straps are legit but I've heard moto suspension being affected by those when not setup right.

...I guess coming from a 300 to an SS, suspension checkups/setups is new to me...

 

[mbroyda]

take it to a shop and have them check the bike, its probably also time to change the fork oil

125, 300, 1000, or whatever CC doesnt matter, if it has fluids it it they need to be changed every so often

 

[xrljoel]

take it to a shop and have them check the bike, its probably also time to change the fork oil

125, 300, 1000, or whatever CC doesnt matter, if it has fluids it it they need to be changed every so often

I agree completely with taking it to a shop, in particular for a newbie, but I would spend some time (like you're doing) trying to figure out where it's originating. Follow the advice given already and check it out. When you take it to a mechanic ask him what he's going to do to diagnose the issue and perhaps ask him/her walk you through it.


The more you know about the machine and issues that arise the better informed and prepared you are in the future.

 

[Trials]

Fork service will be detailed in your shop service manual right along with the tolerance limits for the fork spring or springs. You measure the length of the spring to determine if it has sagged and requires replacement, that's the only thing that can be harmed by strapping them down for a prolonged period.

The forks you strip down, clean inside and out just like you would clean a gun and then reassemble them. Riders who take them to a shop for service and don't stick around to watch, learn nothing.

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