Headshake FE390

Tonibe63 · Nov 20, 2011

Hi folks
Husaberg newbie here and yes you've guessed it my first post is about a problem

.
I bought a 2010 husaberg 390 about 5 months ago and love the bike apart from the mega headshake I'm getting.
I'm approx 100kg in gear, late 40's trailrider (not a racer), with 7 years experience on everything from a CCM644 down to my last bike which was a WR250F (very softly sprung).
The first time I rode the bike I got headshake going across an open field in 4th gear, so I moved my ass up the seat which helped a little but didn't prevent me having to slow down to get it to stop shaking.
I then checked all the settings and found the previous owner had got way too much sag on the rear shock and the forks were pushed up through the clamps but that's not totally suprising as he was a lot lighter and smaller than me.
I've reset everything back to standard as per the manual but last time out on fast trails with gravel/fist sized rocks the bike again went into massive headshake (around the 4th gear area) which was boarding on a full on tank slapper. At the time I was standing up on the pegs and just kept it on the throttle trying to keep the front light. It did straighten out but then started to headshake again after deflecting off a rock a couple more times in the next half mile or so. In the end I backed off as I could no longer hold onto the bars.
So what do you guys suggest?
Do these bikes have known headshake problems?
Is there a common area to look at?
I must admit I've always preferred my bikes to be softly sprung even if it means riding slower (I'm too old for racing on trails) so I don't want a razor sharp race bike but an exciting trailbike.

Cheers-Tony

Radbuster · Nov 20, 2011

Hi Tony,
A guess would be the springs being too soft.
Stock, they are for your previos owner, so with a heavier rider including all gear, the stock springs are way off.
Also, pls change the stock oils seals and dust wipers for the SKF ones (greeish colored, plainly visible). The stock one's sabotage the basic function in many ways.
Other than that, see if the oil in the forks is fresh and the oil level is around 110-125mm.
After this, the bike should work pretty well and stop trying to throw you off.
Good luck, Fred

OldNewbie · Nov 20, 2011

I'll share my recent experience regarding spring rates.

The bike has to handle, first and foremost. To do this, you need the correct spring rates for your weight.

Ride should be a distant second priority. If the springs are right, the ride should be close to optimum.

I recently figured out that the horrible problems I've had all year have been due to setup - the bike was severely undersprung. It's not there yet, but I'm riding faster, longer, without physical exhaustion that used to come after mere minutes of fighting the machine.

kwezel · Nov 20, 2011

Fred, could you be so kind as to tell a bit more abour the skf seals?
Do you happen to know the partnumbers?

What's the secret? do they have less friction maybe?

Thanks!

Radbuster · Nov 22, 2011

Hi, sure, stiction is a biggie.
Have a look at this clip:
http://www.youtube.com/watch?v=J2he17P1D1U

There are several clips on youtube if you search for "SKF fork seals" showing the tremendous difference.

They are not available through normal industrial SKF channels, but through a motorcycle specific agent.
Each country seems to have a separate importer and I can't remember the main website, but, try asking your favorite KTM parts supplier and they should know about them. They are also available through Enduro Engineering.

They are available for most forks, even the old 43mm, etc. Probably the best gains are for WP, as Kayaba and Showa are not nearly as bad. For the WP 48's there are two kinds, one "normal" and one "heavy duty". The normal seems to have a normally long service life be comparable to Kayaba or Showa seals. The heavy duty I'd guess is for longer service life, but even that one is also really smooth.

A kit consists of an oil seal and a dust wiper for ONE leg. Prices should be around 30USD per kit.

Remember to heat the upper fork leg well before disassembly and reassembly, or the washer inside will get cupped, take too much space, hinder reassembly (new one's are cheap) and not allow the lock ring to snap into the groove.

Good luck, Fred

E-Ticket · Nov 23, 2011

Since it's a used bike ... I would *definitely* recommend taking apart the headset, clean, inspect, and re-grease it ... and then re-set the proper bearing pre-load. A loose headset can cause a whole bunch of issues.

And if you're running a steering stabilizer - that can hide loose headset/bad bearings as well.
You need to have it removed/disabled before trying to adjust your headset.

Good luck! E-Ticket

Tonibe63 · Feb 19, 2012

I've found the solution to my problems and just to bring this to a conclusion I'll tell you how I did it.
You guys were right all along-my bike was seriously undersprung on the back end :cheers: .
I rang up an Ebay retailer in the UK who straight away said you need to go up 2 sizes on the rear spring (I guess that officially makes me an FB). Fitted new spring and no headshake at all and the deflecting off rocks from the front end seems to be much better too.
Like you've said get the basic springing right and it will be just a case of fine tuning after that.
Thanks again chaps :rock:

dutch gunsmoke · Feb 19, 2012

Nice to read that you solved your problems.be sure of correct basic adjustments in combination with your weight
i find the bike very stabile because of the light feeling front end perhaps in my case with the available 570 power. always ready too pull it straight if you dare to turn the throttle. wen i rode your story i directly thought about problems one of my friends had. it took a while too find out that he turned his low triple clamp much much much to thight and damaged his outer fork tubes .because of that he had several high speed freightning moments and crashes.repaird it and he was happy again ( his wife also) the handle bar mounted in most forward position could give an extra impuls for a headshake
take care and good luck

Noppy · Feb 19, 2012

I'm 93 kg's and my bike 2010 390 is setup for 100kg. I rode it with and without steering damper and no headshake at all. Ultra stable.

Yesterday I bounced into two big 1ft boulders covered by grass at high speed. Didn't throw me off :cheers:

In fact it was the same boulder twice, but I encountered it in two rounds before I learned to stay away from it :mrgreen:

Chesh05 · Aug 28, 2018

No fork springs?

I have the same problem , did you only change the shock spring? If so shouldn’t you have got the matching fork springs ?

Justinberg · Sep 6, 2023

Hey, I've got headshake at high speed on the highway, FE450 07. I want to tighten the steering neck bolt to take the play out of it, but can't get it to budge. there is a crenelated nut under the top triple clamp. I thought I might have to loosen that first, but it won't budge either. I have loosened all the triple clamp bolts so it's not that. Any help much appreciated.

Taffy · Sep 7, 2023

you need to loosen it then and start again!

make sure the front wheel is hanging and wobble the wheel backwards and forwards as you tighten the castleated nut. when you get down to 2-3mm your next problem is that the forks clonk at the bushes so you have to separate movement of one fom the other.

if the thing has been overtightened the bottom cup will have become 'dented' or 'thrupenny bitted' as we english would say. you then need a new bottom cup and bearing.

Taffy

Headshake FE390

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