Motorbike Front End Shake

[PyroboyUK]

This weekend I finished putting on a new set of tyres onto the CBR. This job also included the addition of a second hand rim due to a meeting with a pot hole making a nice big dent in my front wheel.

The job on the whole included a set of new bearing for the acquired front wheel and taking the pads out of the callipers and giving em a good scrub!

Today I have noticed a small abnormality in the bikes behaviour when riding to work. When slowing down the bike under the bikes own engine braking I can feel the front end shaking. This can be seen if I release pressure from the front end and you can watch the front end start to shake left to right. I would not call this shake violent by any means its more of a vibration, i will add that is it more noticeable between 50 and 40 mph when decelerating. This does not involve any use of the front brakes.

Is there anything obvious I need to look for to resolve this? I have never encountered this before and before I take the wheel of and try to re-fit again I thought I would try and get some feedback is this is a common problem after re-fitting a wheel etc..

 

[PyroboyUK]

The wheels where balanced, after speaking to a friend he said I should also check to see if any of the weights on the wheel have been flung off.

I hope its not the head bearing, doesnt sound like an easy job.

I will just check the weights now.

EDIT: All weights appear to be stuck to the wheel and intact.

Is there a technique to check for head bearing wear?

 

[PyroboyUK]

Yea head bearings is great fun... on a side not the old head racers make a nice paperweight

I shall dive into the service manual and have my self some bed time reading tonight.

Cheers for the input guys! Always much appreciated.

 

[PyroboyUK]

Well still carrying out various tests to try and determine the cause of the wobble between 40 and 50mph...

Got the old wheel away for inspection to see if the dent can be repaired, i never got any vibrations or wobbles from that wheel. It just had a blooming big dent in it! So if that wheel is repairable I will change a tyre on to it and give it a shot...

The head bearing seems to be ok, no abnormal play or noises present.

What I will make comment on is that between 60 and 30mph under quite heavy braking there is some helish vibrations coming through the front end, enough to shake the mirrors....

Could this be disc issues?

 

[PyroboyUK]

Could be, check the pads and discs, are they your old dics or ones that came with the new wheel? if they are your old ones, try swapping them either side and see if that make a difference.

They are off my old wheel. This vibration was present on my old wheel, but I just assumed it was down to my very un-even tyre wear. However I can now feel it under heavy braking on the new wheel. Thing is though the old wheel did not wobble like the new one.
I should have also mentioned earlier that due to me not thinking on this job I put the wrong disc on the wrong side when fitted, I did not take into account any directional rotation arrows. The wobble is present whatever side the disc is on.

I wonder if this could be a balancing issue?

 

[PyroboyUK]

There's a lot of things that can cause head shake

buckled wheel - Motoliner can sort out buckled/bent wheels
Incorrect wheel balancing - rebalance to make sure
Wheel bearings - Change them
head bearings - adjust/change them
warped/worn discs - beg/borrow/steal a dti gauge and check the discs
worn/badly adjusted suspension - service the front suspension and reset to manufacturers setup. Rear replace or send to be serviced.
Worn tyres (front and rear) - bin them and stick new rubber on.

Work through the list until it behaves itself, cheapest/easiest first

You said it was vibrating before you changed the wheel, is their anything you changed on the bike recently? (other than the wheel).

Fog

Well I had my old Dented wheel repaired and fitted it back on Saturday. The wobble seems to have disappeared now. I am 90% sure its fixed now, it sounds silly saying this but my mind seems to play tricks and the slightest wobble or vibration and I feel like its back again. So I am just riding it back and forth to work to get the feeling back.
I would like to get into contact with Motoliner to see what they can do with my old wheel which I now believe is buckled.

The front end has a slight vibration under very heavy braking down to 30mph, but this is very small. The vibrations with the old wheel where quite scary under heavy braking from 60mph. I am not sure if the vibrations are just from the road being picked up from the tyre. I just dont like the prices of front discs....