Check Adjust and replace head bearings - K4/5 750

These clever dicks knows how to do it

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Master Pie Muncher

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Post Tue Feb 21, 2012 11:26 am

Check Adjust and replace head bearings - K4/5 750

How To: Check Adjust and replace head bearings

Firstly to check them your going to need to get the front wheel of the ground, when you know what your looking for you can just get a mate to hold it up on the side stand but its better to put it up on an abbba or paddock stand at the rear and jack the bike up under the header pipes.

You dont actually need to take the fairing of to replace them its just way easier to do so.

I find the best thing to do is stick a small toolbox or chair in front of the wheel to sit on so your nice and steady.

when your sitting comfy cup one hand either side of the wheel right and the bottom of the fork leg...

Start making small movements toward and away from you, you dont need a lot of pressure and the movements should be small like a gentle rocking motion.

Your looking for any radial movement in the forks and steering stem, they should be solid and not move at all.
Make shure you dont interpret movement of the bike on the stand as movement on the steering head.

Now disconnect the steering damper to check for notches in the bearing its fairly easy just one nut and a spanner to counter hold the bolt..

When you have done that put the steering in the middle so the handle bars are strait.

Most of the wear on the bearing is at the center point after all the bike spends most of its time with the bars strait. when you hit that pot hole at errr 60 mph.. or land a wheelie the bars are hopefully strait, if there not you will more than likely be replacing more that just the head bearings

with the steering damper disconnected the bars should fall to one side or the other.

if they dont try turning the bars one way and then the other very gently, there should be little or NO resistance felt. when turning the bars if you feel any point where it takes more effort and then becomes free again the bearings are shot..

If theres just a bit of radial play then you may be able to just re torque them, some people just use a punch on the pegged nut to tighten them but if your going to torque them up to the right setting 45nm on mine then you will need to make your self a pegged socket like this one. i made this out of a 34mm impact socket with a marker pen, angle grinder and a file.

Remove the top yoke free the lock nut and re torque the bearing adjuster nut to the right setting.

Remember to torque the lock nut to the right setting too (mines 80nm) you dont want it coming loose again!!

re-check the play in the forks as before.

ok so if the bearing is shot its not to hard to replace with a few of the right tools.

you will need a nice big drift, dont use a screwdriver its not a good idea brass tip is best.

a bearing driver or as i have use a large socket 41mm fits perfectly.

you will also need a fine chisel and a 2 screwdivers or small pry bars to get the bottom race of the sterring stem.

first off remove the front wheel and stick the calipers on a tall tool box of bench/table you dont really what them dangling!!


before you remove the forks its worth checking and measuring the fork drop threw the yokes with a ruler or vernier calipers....

so remove the forks, loosen the top bearing lock nut take of the lock washer, dust seal and remove the main bearing adjuster nut support the yokes from the bottom so the dont just drop to the floor, easy them out gently.

Now remove the top bearing inner race and ball bearing cage, clean all traces of grease from the top bearing outer race, do the same with the bottom bearing.

If you look down the hole you will see some handy cut aways place you drift in these cut aways and gently and evenly tap the outer races out of the top and bottom of the head stock..

The trickiest bit is getting the lover inner bearing race of the steering stem, when you buy the bearing set make shure you buy the lower dust seal too because there is no way of getting that lower race off without killing the thin metal dust seal...

slip a thin chisel between the dust seal and the bottom yoke and gently tap around it to ease the race up and of the stem.

when you get to a certain point two small pry bars and two blocks of wood help..

or you can just take it to a garage and theywill wip it off and slide the other one on in no time for beer money.

Slip the new dust seal and inner race onto the steering head and tap in down with a drift of a bit of pipe the fit perfectly. make shure you only hit the very inner part of the race and not the curved face that the ball bearings sit on

Now fit the outer races into the headstock,there an in Interference fit into the frame so there tight!! i put mine in the freezer over night although some people say its pointless!!! i say every micron you can conract that race helps!!

use a large socket to drive them in GENTLY and evenly again make shure the socket only bears on the outer edge of the race and not the curved part the balls roll on.

a 41mm is perfect for the outer races on my K4/5 750.


ok now the outer races are in (makes shure the full butted up against the shoulder) grease them up and drop the top ball bearing cage and the inner race in and apply more grease!!

do the same to the lower bearing and them slip the yoke back in to the headstock and refit the dust seal and pegged adjuster nut. torque it up to the right setting 45nm on mine and then do the same with the lock nut.

have a feel of how it moves by turning the yokes should be smooth as silk!!!

errr now just refit the top yoke, the forks and the rest of the front end..

Post Tue Feb 21, 2012 11:41 am

Re: Check Adjust and replace head bearings - K4/5 750

Nice one Carlos son, good on you.

Kev :kev:

Post Tue Feb 21, 2012 11:54 am

Re: Check Adjust and replace head bearings - K4/5 750

Good write up mate
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Master Pie Muncher

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Post Tue Feb 21, 2012 1:09 pm

Re: Check Adjust and replace head bearings - K4/5 750

Great guide!

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