Help Diagnose: rowdy front end

[Meter Man]

I have a 1993 Nighthawk 250. It has a rowdy front end. Bouncy and wants to go into a tank slapper at almost any speed. I have been riding it a bit, and it has gotten a bit worse over time. Has about 35,000 miles on it.

It began to do this after it spent a winter outside in Montana. I have been unsuccessful diagnosing it.

I have replaced:

Fork Seals
Went back to the OEM front tire
Played with tire pressure.


Possible suspects?
Wheel bearings
Steering Stem bearings
Bent wheel

I am afraid to start replacing parts willy nilly, and perhaps my diagnosis skills are poor.

Any thoughts?

[anotherguy]

Steering head bearing wear or adjustment. I'd start by disassembling,cleaning and inspecting them. If they're OK adjustment can be taken care of on reassembly. With a bike that age it's at least a good idea to give 'em a look unless you are sure they've been serviced properly.

[Tosh Togo]

Originally Posted by Meter Man

I have a 1993 Nighthawk 250. It has a rowdy front end. Bouncy and wants to go into a tank slapper at almost any speed. I have been riding it a bit, and it has gotten a bit worse over time. Has about 35,000 miles on it.

It began to do this after it spent a winter outside in Montana. I have been unsuccessful diagnosing it.

I have replaced:

Fork Seals
Went back to the OEM front tire
Played with tire pressure.


Possible suspects?
Wheel bearings
Steering Stem bearings
Bent wheel

I am afraid to start replacing parts willy nilly, and perhaps my diagnosis skills are poor.

Any thoughts?

Was the fork oil changed when the seals were replaced, and if so, with what, and how much?.

[Meter Man]

Originally Posted by Tosh Togo

Was the fork oil changed when the seals were replaced, and if so, with what, and how much?.

Don't know, but the problem occurred before and after the change. It did not affect it at all.

[OldPete]

Originally Posted by anotherguy

Steering head bearing wear or adjustment. I'd start by disassembling,cleaning and inspecting them. If they're OK adjustment can be taken care of on reassembly. With a bike that age it's at least a good idea to give 'em a look unless you are sure they've been serviced properly.

Yep!
If the stock stem bearings are ball... Replace with tapered roller.
Done that on several older bikes with very improved front-end feel and no shimmy.

[GreaseMonkey]

What speed does it start at? When you start moving, 5mph, 10 mph, 35 mph, etc?

Put the bike up on the center stand and give the front wheel a spin, do you see any wobbles anywhere? Shake the forks, does anything move?

Answer that stuff for starts and we can go from there.

[ADV8]

Originally Posted by Meter Man

I have a 1993 Nighthawk 250. It has a rowdy front end. Bouncy and wants to go into a tank slapper at almost any speed.

If it is bouncy it has little or no damping in the forks (oil related).
That in itself will lead to bad road manors.
As suggested up the page,check the oil - level and viscosity.

Things like steering head bearings are only a matter of getting the wheel up off the ground to check for play and rough running lock to lock.
Same for checking wheel rim out and the wheel bearings.

[Meter Man]

Broke down and took it to the local dealership.

They checked everything and the diagnosis was bad rear shocks.

They stated that the bad shocks makes the rear end go to far down and the front to high up, creating altering the way the bike handles.

Does this sound like a reasonable explanation? The rear shocks have been used and abused over 35,000 miles with a 240 to 270lb rider and luggage.

They did note that the front wheel had a small bend, but did not think that was the cause.....

[LuciferMutt]

Originally Posted by Meter Man

Broke down and took it to the local dealership.

They checked everything and the diagnosis was bad rear shocks.

They stated that the bad shocks makes the rear end go to far down and the front to high up, creating altering the way the bike handles.

Does this sound like a reasonable explanation? The rear shocks have been used and abused over 35,000 miles with a 240 to 270lb rider and luggage.

They did note that the front wheel had a small bend, but did not think that was the cause.....

Yes a front end riding high will handle like ass. Usually, though, bad shocks have nothing to do with ride height? The spring controls that...

[MrBob]

Bad shocks could easily be a part of the picture. When replacing the shocks make sure you get springs matched to the weight they'll be supporting.
When you get your shocks installed check front and rear sag. You may also need heavier springs in the forks to provide more damping. Your sag numbers will tell you that.
A quick and cheap way to plant the front wheel more firmly is to move the forks up in the triple trees a few millimeters at a time and check for stability. I did this on my Wee Strom and it planted the front wheel much more firmly. While you're looking at the forks, make certain the triple trees are lined up by loosening the lower triple tree and bouncing the bike up and down on the forks a few times before re-tightening the lower TT.

[kpt4321]

Originally Posted by MrBob

You may also need heavier springs in the forks to provide more damping.

Springs don't provide damping.

A quick and cheap way to plant the front wheel more firmly is to move the forks up in the triple trees a few millimeters at a time and check for stability.

Careful. Moving the forks UP reduces rake and trail, which can make a bike quicker to turn in (and less stable).

[MrBob]

Originally Posted by kpt4321

Springs don't provide damping.



Careful. Moving the forks UP reduces rake and trail, which can make a bike quicker to turn in (and less stable).

I was incorrect on the first point - oil provides for fork damping, but moving the forks up can make a noticeable difference in stability but should be done in small increments. This is from experience.

[LuciferMutt]

I think there is confusion here regarding moving the "forks" "up."

If you actually loosen the triple clamps and slide the fork TUBES UP through the triple clamps, you are LOWERING the front of the bike. This makes the bike turn more quickly and if you go too far, will make the front end twitchy and dangerous.

Moving the fork TUBES DOWN through the triple camps RAISES the front of the bike which will increase straight line stability at the expense of quick turn in. If you go too far this way the front and will again become unstable but in a different, weavy, understeery sort of way.

[HapHazard]

Originally Posted by Meter Man

Broke down and took it to the local dealership.

They checked everything and the diagnosis was bad rear shocks.

They stated that the bad shocks makes the rear end go to far down and the front to high up, creating altering the way the bike handles.

Does this sound like a reasonable explanation? The rear shocks have been used and abused over 35,000 miles with a 240 to 270lb rider and luggage.

They did note that the front wheel had a small bend, but did not think that was the cause.....

I've had bikes with bad/worthless/shot rear shocks and none of them behaved as you describe.

The "small bend" may indicate an "impact", causing damage to the steering stem bearings, or misalignment of the forks.

Did you check the steering head and wheel as GreaseMonkey suggested? What were the results? If not, why not?

[Meter Man]

Got the motorcycle back.

They replaced the steering stem bearings.

They also attempted to true the front wheel. It was very square as I had failed to keep the spokes tight enough (big blame to me)

The problem is almost all gone, however they said a new wheel is needed to fully repair the motorcycle. I am going to source one from Ebay and get the tire put on it.