head bearing problems

tattoo · Post by **tattoo** » Tue May 15, 2012 4:46 pm

has anyone else had this problem with koyo taper roller head bearings....i've had 3 sets and when fitted everyone of them has had what i can only discribe as a "flat spot" when the bars are in the straight position...i thought the stem was bent alittle so replaced that and i'm still getting the same thing...it feels like there's a groove in the race and the bearings are dropping into it as i swing the wheel from lock to lock,i've inspected them,my mates inspected them and the local bike shop has inspected them but none of us can find anything wrong,i've tried turning them 1/4 turn and still this flat spot is in the same place..i've tried 3 different methods to insert the races and each time they've sat square and seated perfect...

any advise PLEEEEEASE as this is now doing my head in.

tony.mon · Post by **tony.mon** » Tue May 15, 2012 5:27 pm

Check very carefully around the steering stem.
Things like the horn catching on the fairing, brake pipes catching on the fairing stay, etc, can give this sort of problem.

BTW, with taper rollers, you aren't doing them up as tight as the Haynes manual says, are you?

That's the tightness for normal ball roller style bearings, taper rollers need to just barely be nipped up so that the play is removed, no more.

tattoo · Post by **tattoo** » Tue May 15, 2012 7:30 pm

tbh tony the first thing i did was check for anything fouling but found nothing and only did them up finger tight to start with then nipped them to take the play out...i'm starting to think it would be easier to pay the 150quid for another set fitting at local bike shop..

lloydie · Post by **lloydie** » Tue May 15, 2012 10:03 pm

I have that brand fitted to mine and they feel good . Are they seated correctly ?

tony.mon · Post by **tony.mon** » Tue May 15, 2012 10:10 pm

Have you tried riding the bike anyway?

Reason being that the bearings often seem properly seated, but after a few miles (10 will do) they seat a bit more firmly, and need re-tightening.
If they aren't quite home or true then this will sort itself out over a few miles, then nip up and job done.

Any flat spots or depressions on the races that would be able to be felt should easily be visible.

It's not the dust seals, is it? Wiring harness catching behind the instrument cluster? Try undoing the cluster and lifting it clear, no need to disconnect wiring; just moving it upwards should show if that's the issue.

chi kung · Post by **chi kung** » Wed May 16, 2012 10:38 am

As said before they are probably no seated fully in. If you look where the bearing housing sits you will see a sort of ridge, you need go past this so its fully up against the headstock. Or it could be you have the tapers the wrong way around ask me how i know...........

Failing that i have no idea.

AMCQ46 · Post by **AMCQ46** » Wed May 16, 2012 1:30 pm

only other factors could be:
1) the headstock is not round where the bearing fits in, either the bike had a crash, or brutal removal of bearings.
2) the botton seal is catching on something.....but as this is changed with every set, that would mean it is the headstock not the seal.

tattoo · Post by **tattoo** » Thu May 17, 2012 10:22 am

update;

at 5am yesterday morning i finally found the cause of my problem,well a combination of causes really..

firstly. the bearing wasn't seating square,my bearing shell installer was a cats cracker bigger than the head stock and wasn't pushing it down square so it's off to be turned down so it fits

secondly.the grease i used to pack the bearings was black grease not multi purpose grease which made them so stiff they felt like i'd packed them with cold treacle so i repacked with vasaline

thirdly.after i nipped them up to take out the play i tightened the lock collar and noticed both were turning,over tightening them somewhat.then on reassembly i noticed the brake lines hung odd,one of the banjo's had moved causing the line to snag

thanks for all the advise from a very red

faced member that should of spotted all of the above problems as they happened

tony.mon · Post by **tony.mon** » Thu May 17, 2012 10:29 am

Well done for admitting what had happened, glad you found it and got it sorted.
I've had the brake line snagging before, also the horn fouls if the bracket is knocked putting the fairing on.

I re-use the old bearing outers, grind off a small amount of the outside faces and then use them to re-insert the new bearings.
That way you always get a good fit, and they will go in square. And you can't damage the new bearing faces.

The note of the hammer blow changes as they seat properly, so listening carefully will tell you that they've gone as far as they can.
I also use a dentist's pick to feel behind the seat to make sure that they're seated squarely and tight against the seat.

tattoo · Post by **tattoo** » Thu May 17, 2012 10:59 am

i always admit it when i'm wrong tony as it'll always come out in the end if i hadn't

the bearing installer i have i got for doing car wheel bearings,it has ally cups that screw onto a steel shaft and then sit inside the bearing shell so it can be knocked it square,trouble was the cup was slightly bigger than the bearing shell so when i knocked it into the head stock the cup hit the frame giving the sound you said,making me think it was fully home....

still feel such a rock for not spotting it 2 sets of bearing earlier tho

AMCQ46 · Post by **AMCQ46** » Thu May 17, 2012 11:34 am

Glad you found the problem.

the tightening for taper bearings is a problem, you dont want them in preload, you want them just at the point where there is no slack, but not so much that there is extra friction to turn them. the way to evaluate is to see when the steering wont fall to full lock under the weight of the bars [with wheel in the air]. test it with the bearings slack and then keep tightening till you see it start to change and sit in one position till you push the bars.

BUT

I find you have to have it too slack on the castle nuts to compensate for the effect of tightening the steering stem nut, and do the final test with the top yoke and stem fitted and torqued down.......... takes me at least 4 goes to get it right, but you will learn that you dont need to take the bars and yokes off each time if you bolt the bars higher up the forks, undo the stem nut and the top pinch bolts so the yoke can move up 5mm, then you can turn the castle nuts by hand [wheel on the ground helps to unload them]. also worth putting a mark on the castle and yoke so you can see by eye how much you have moved since the previous test.

its a bit of a faf, but worth it in the end, you dont want them too slack or you get a clunck on braking, and too tight gives you a strange weaving effect on the steering.

jonacol · Post by **jonacol** » Fri May 18, 2012 5:31 pm

Seconded on the tricky to get set right, a slightly too tight feeling can usually be cured with a few cac handed wheelies

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