Side to side when braking

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Regarding tyres, I assume Antonio means ‘Avon Roadrider’ universal on the rear... correct Antonio ?

I thought it interesting that you say the problem is worse when you have the shocks on a softer setting. One thing that happens when you soften the shocks is that the rear ride height reduces, this in turn changes the geometry of the bike.

Are you certain that both the forks and the shocks are the correct length?

Are you certain the fork internals are working correctly and have the correct amount of the correct oil?

Please explain, and ideally show some pictures of your spindle / fork slider issue.
 
Beach said:
"The weel axel had play on the fork slider and was modified for proper fitment, i will recheck if that is well enough."

What is this about? Wrong axle, too large hole in slider? This could cause your problem
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If the axle has been made bigger at the slider, can it still slide through ENOUGH to clamp all the other components?
Can the wheel be moved axially at all, when everything is tightened up( it should NOT), and does it spin easily with no run-out at rim?? ( it should!)
 
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Esmerela said:
Have you torqued up the front spindle 60 ftlbs and the the pinch bolt in the rh leg to 15ftlbs. If they are not tight you can see the front mudguard twist when you pump the forks with the brake on.
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This is so true.... I tried to reuse the left fork leg on my rebuild... and I judged that the slight movement of the spindle would be taken up when tightening the pinch bolt
To that degree when I bench tested this before installing the leg I was confident I had sufficient clamping....... WRONG
Just pushing the bike up the drive and applying the front brake had the mudguard twisting and the wheel visibly turning to the right
Despite tightening the pinch bolt all I could it just wouldn't sufficiently clamp the spindle
 
Antonio
You will have to work through everything. Start with steering head bearings, especially if it's been converted to taper rollers.
Yoke pinch bolts, I've had one snap & leave the nut in place. Under braking the clipon moved as did the whole front end.
Wheel bearing spacer. Bearings, wheel spacers. As has been mentioned if anything is worn in this area it all seems to work except under braking or being pushed through bends.
Spindle fit. Some of my fork legs have looked oval! A good fit is important. Loosening off & bouncing the fork to line everything up, holding the brake on. All good but be careful with the pinch bolt. I was told to use a nylon washer in the gap to stop you over tightening.
I would change the front tyre to a new matched tyre just to see. Worst scenario you have a spare.

Once you have done all this & I hope you resolve it before the end of the list. Take an old racers advice!
Problems at the front are often caused by the rear. I don't like your comment about the rear shocks.
Raise the bike at the rear, Jack under the engine & check for play in the rear wheel. Take the shocks of & check for play in the swinging arm area. Peace of mind if nothing else. Rear wheel spindle? Somethings not right.
Good luck hope you sort it but it's a process.
Chris
 
It may just be me, but I'd start first with what I know is suspect. Might prevent a lot of tail chasing.
 
Are you certain the fork stanchions are fully tightened in the top yoke?
The taper must be fully engaged and tight before you tighten the bottom yoke pinch bolts etc
As others have said change the tyre it's easy to do/check
But you are going to have to work your way through the bike on this one
 
Thinking out loud here in reference to very good previous suggestions...
Wheels are balanced?
Rotors are true, no warping?

a combination of faults may be in play...
 
Another thing that could be the issue is the wrong length of fork tubes or the smaller diameter of front tire. If your fork tubes were shorter than normal or your front tire is a smaller diameter, you would end up with less trail on your front end. As your front end compresses under braking, the trail distance reduces, and may be reduced to a point where the front end is unstable and could wobble horribly because of the "caster effect" of not having sufficient trail. Of course, if your parts are all stock parts (wheel size, fork length, and yoke rake angle) then there's no reason your bike should do things bikes with the same parts do not do....

The other thing I might look at is to make sure that both pucks on each side of the caliper move freely. If one puck freezes in place, then the other pushes on the entire wheel when you use the brakes... just another thing to check....
 
Fast Eddie said:
Regarding tyres, I assume Antonio means ‘Avon Roadrider’ universal on the rear... correct Antonio ?

I thought it interesting that you say the problem is worse when you have the shocks on a softer setting. One thing that happens when you soften the shocks is that the rear ride height reduces, this in turn changes the geometry of the bike.

Are you certain that both the forks and the shocks are the correct length?

Are you certain the fork internals are working correctly and have the correct amount of the correct oil?

Please explain, and ideally show some pictures of your spindle / fork slider issue.
Click to expand...

If the rear of the bike is down, that increases the rake and thus the trail. I would expect the bike to weave when accelerating out of corners, rather than when braking. However if the geometry of the bike is designed for a 19 inch wheel, and an 18 inch wheel has been fitted, that decreases the trail and you would be more likely to have weaving as you braked.
 
acotrel said:
If the rear of the bike is down, that increases the rake and thus the trail. I would expect the bike to weave when accelerating out of corners, rather than when braking. However if the geometry of the bike is designed for a 19 inch wheel, and an 18 inch wheel has been fitted, that decreases the trail and you would be more likely to have weaving as you brake. I think you have to be very careful if your bike is sending you messages like weaving. It can easily turn onto a lock to lock tank slapper and deck you.
Click to expand...
 
acotrel said:
If the rear of the bike is down, that increases the rake and thus the trail. I would expect the bike to weave when accelerating out of corners, rather than when braking. However if the geometry of the bike is designed for a 19 inch wheel, and an 18 inch wheel has been fitted, that decreases the trail and you would be more likely to have weaving as you braked.
Click to expand...

In general terms Al, I agree. Regarding the geometry topic, my interest was in the fact that Antonio says the symptoms are worse with the shocks on a softer setting, this will lower the rear ride height. However, like you, I can’t explain why the symptoms only occur under braking, that seems kinda counter intuitive to me! Of course, it could be something entirely different.

Antonio is using 19” front and rear. Avon say that when fitted to their recommended rim sizes, there is 3/10 of an inch difference in the rolling radius, so a 1.5/10 effect on ride height. Antonio is using rim sizes slightly different to the recommended size, even so, I would suggest the difference is insignificant. Therefore it is not his tyre choice that is the cause here. I also know that cos I run the same tyre combo on two bikes!
 
Beach said:
"The weel axel had play on the fork slider and was modified for proper fitment, i will recheck if that is well enough. "

What is this about? Wrong axle, too large hole in slider? This could cause your problem
Click to expand...
Too large hole in the slider was found, an aluminum insert was fited, as there is not much material the shaft was reduced in order to place the insert properly.
 
The rim sizes used where to mach Roadriders technical bulletin for weel size.

I have been informed that a smaller 325 improves the Norton handling this is the reason it was fitted with matching 1,85rim.

The wider rear 2,50 rim is to mach Avon's recommendation for 100/90 19.

Both wheels where built to mach Avon Roadrider recommendation for what is available for 19 tires.
 
I forgot to say that the movement comes if I take a hand off, to adjust the helmet...
 
There is something so loose , shouldn't be hard to find. Start with obvious. You know what they say about not seeing the forest for the trees. Set on center stand and have someone set there and hold bars while you hold wheel tween legs. Try moving bars to see if there is play. Grab lower legs and pull and push forward and back checking for stem bearing play.
 
NorCat said:
The rim sizes used where to mach Roadriders technical bulletin for weel size.

I have been informed that a smaller 325 improves the Norton handling this is the reason it was fitted with matching 1,85rim.

The wider rear 2,50 rim is to mach Avon's recommendation for 100/90 19.

Both wheels where built to mach Avon Roadrider recommendation for what is available for 19 tires.
Click to expand...

I’m just going off of Avon‘s web site:https://www.avontyres.com/en-gb/tyres/roadrider-mkii?cartype=motorcycle

They say that the recommended rim for a 3.25/19 is 2.15, whereas you have 1.85, which is fine as it’s still within the acceptable range. All I’m saying is that the stated overall diameter of the tyre, is for when using the recommended rim. Yours therefore may be slightly different.

But, as I said, any difference is minuscule, and (I believe) insignificant.
 
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