Front tire cupping

[MPittma100]

Magazine

Curious....Anybody reading this post that has timed their 11 at the track?

I have some old motorcycle publications with articles on these bikes. Seems that at least one concerned straight line tests. Will see if I can find them. I do not doubt that a properly tuned XS1100 can make under 12 second 1/4 mile squirts. Sub 12 second passes is not that fast in today's world.

[imflynn]

11 sec XS11

Drove my new XS1100 to North Star Dragstrip in the Twin Cities end of April 1978,unhooked the electrical plug,removed the Windjammer and pulled up to the line. Third run 11.92/115.00 ... fifth 11.89/114.79 and sixth 11.89/114.50. Later that night I put the fairing back on and drove 90 miles back home. Bike was bone stock and I still have the timeslips.
Mike Flynn

[jetmechmarty]

Mike,

That tells me you are highly skilled at green light departures.

[Radioguylogs]

Drove my new XS1100 to North Star Dragstrip in the Twin Cities end of April 1978,unhooked the electrical plug,removed the Windjammer and pulled up to the line. Third run 11.92/115.00 ... fifth 11.89/114.79 and sixth 11.89/114.50. Later that night I put the fairing back on and drove 90 miles back home. Bike was bone stock and I still have the timeslips.
Mike Flynn

That's why I asked.

So many posts suggest <12 sec times were only obtainable with a tiny Japanese expert rider and a team of engineers. It is interesting hear the bike really can make those numbers- and noting you must have some skill.

[sail4free]

Mike,

That tells me you are highly skilled at green light departures.

==========
Or at least *WAS* . . . 37 years ago. I still get the green light jump on kids with their dropped little sports cars -- mag wheels maybe 1" off the ground -- but I can't be sure they know we're racing.
JIM P.
==========

[Bartman]

Thanks for the drag strip input!

Update, replaced both tires and when I was looking at the front end I found several things that may have an effect of my cupping.

First: I noticed the front tire also seemed to be wearing more to one side than the other, when I got to taking apart the front end I found that the forks were not equal height-wise. The right side was about ¼” above the head and the left side was 1/8” above. I set both back to level with the top of the triple tree head when I put it back together.

Second: The red grease that I had used on the head bearings was still red on the bottom bearings but black on the top ones. Repacked and put back together. 10k miles ago it would “flop” left or right with little help. I don’t have a torque wrench for the spanner nuts so I hand tighten, this time it might be a little tighter, it will move with slight help but not “flop”……wondering if I need to loosen up?

Third: Bleed front brakes with a Mighty Vac. Left side sucked out oil with no problem. Right side would not. Collapsed the plastic vacuum line trying. So I held the brake with my hand and loosened the bleed nut and it squirted out fluid. Did that a few times and then Might Vac worked…..so might have been a little off balanced braking………

Fourth: I hand mounted the tires 10K ago and used Dyna Beads (I know everyone has an opinion) but really had no problem till lately after I dropped the bike and replaced the clutch cable that I noticed the cupping and out of balance feeling. THIS TIME I paid a local shop to mount and balance both new tires. (Real weights on wheels)

So yesterday I finally got it all back together and took it for a 100 mile spin to get the tires roughed up. The wind was blowing good but that has never been an issue. BUT, the front seems to be twitchy. Running up the interstate at 75 MPH it felt a little unnerving. I slowed it back down. This bike has always been solid up to a quick 100. So now I am wondering about all of the changes that were made and what might be the problem.

I did buy the same brand X of tire but a little higher dollar one for possibly better life and such with a matching rear. (Don’t want to get into a tire debate).

SO, do I ride a while and see if settles in, or loosen up the triple tree so that it will flop, or take off the weights and put in Dyna beads……

I am afraid that this will get a lot of sideways comments.

[jetmechmarty]

No. You're on the right track. Put the bike on the centerstand. Put something under the bike so the front wheel is off the deck. Turn the front wheel side to side. It should be perfectly smooth. Grab the wheel and shake it. There should be no looseness it the steering head. (Your symptom makes it sound like it's too loose.) You may tighten it, but it will bind when too tight. Loosen until it's not binding.

While the front is still up, loosen the forks in the trees and the axle too. Loosen the fork brace if you have one. Start from the top and work your way down (I think that's right) resetting the torque on all the fasteners. Make sure the proper alignment is maintained. It should fix you up.

Are you sure the forks aren't bent?

You're about 50 miles from me. Perhaps we can schedule a get together.

[Bartman]

I took it back down to the spanner bolts. Left the front tire/wheel on but did loosen the axle and all pinch bolts. I did slightly tighten the spanner nut. I followed the book the other day "tighten/torque pinch bolt then tighten/torque head bolt". Tonight I left handed snugged up all of the pinch bolts to help hold all parts then torqued the head bolt. I wondered the other day if only one pinch bolt at 14.5 lbs to hold every thing while torquing down the head bolt was a good idea.

I had to stop for the night but should get it together tomorrow night.

[Bartman]

And yes Marty, one of these days I need to swing by and swap stories.

[3Phase]

Bartman,

You've got the tightening sequence backwards or sideways, sort of.

If you have a '79 Standard you're supposed to remove the left front brake caliper to pull the wheel. When you put the wheel back on everything gets tightened:
Axle nut -> brake caliper -> pinch bolt after you've aligned the left front brake caliper with the brake disk.

The pinch bolts are tightened front nut first, then the rear to snug it up like closing a clamp. The book doesn't mention the fender.


If it's a '79 Special you're supposed to remove the front fender too, then it's:
Axle bolt -> fender -> pinch bolt after you've aligned the brake caliper with the brake brake disk.

Again, the pinch bolts are tightened front nut first, then the rear to snug it up like closing a clamp. The book does't mention removing any front brake calipers.

Happy torquing!

.

[motoman]

No. You're on the right track. Put the bike on the centerstand. Put something under the bike so the front wheel is off the deck. Turn the front wheel side to side. It should be perfectly smooth. Grab the wheel and shake it. There should be no looseness it the steering head. (Your symptom makes it sound like it's too loose.) You may tighten it, but it will bind when too tight. Loosen until it's not binding.

While the front is still up, loosen the forks in the trees and the axle too. Loosen the fork brace if you have one. Start from the top and work your way down (I think that's right) resetting the torque on all the fasteners. Make sure the proper alignment is maintained. It should fix you up.

Are you sure the forks aren't bent?

You're about 50 miles from me. Perhaps we can schedule a get together.

I might add that setting preload on steering head bearings, front wheel off ground, bars rotated off center either direction should have JUST enough resistance that rotaion off center, wheel/bars slowly fall to either direction on its own......flop either direction easily and quickly, not enough bearing preload.

[Bartman]

I believe that the smooth action of the handlebars is fine. Everything torqued in the right sequence. Steering seems quick/twitchy on the road. Straight up to 80 but coasting back down seemed to feel like it was isolating left-right. Of course on an old country road. I will ride to work for a few days and watch it.

[jetmechmarty]

Oscillating could be loose steering head bearings. Are the shocks standard length and functioning? Do you have a luggage rack with a load on it?

[TopCatGr58]

I believe that the smooth action of the handlebars is fine. Everything torqued in the right sequence. Steering seems quick/twitchy on the road. Straight up to 80 but coasting back down seemed to feel like it was isolating left-right. Of course on an old country road. I will ride to work for a few days and watch it.

Oscillating could be loose steering head bearings. Are the shocks standard length and functioning? Do you have a luggage rack with a load on it?

Hey Marty,Bartman,

I don't know if he meant Oscillating vs. what he wrote "Isolating" which makes me think it was sort of sticking slightly in that direction, like it would NOT follow the road on it's own, but that he had to provide steering input, a little left, then right, to keep it going straight. If that was the case, then the steering head bearings were actually BINDING which kept it in one position, and not allowing it to slightly swivel left/right to autobalance/caster affect!? I remember my old Yamaha 305 with the hand crankable/tightenable knob on the steering joint that I could hand tighten while riding...to help stiffen up the steering a bit....but if I got it too tight, it would not track properly and felt unstable despite the steering head was actually too stiff!

T.C.

[Bartman]

Coasting down the bike "felt" like it was not tracking straight but was slowly tilting left and right. Like maybe on a ridge and couldn't stay on the top feeling.
I came home and checked air pressure and they were fine. I have a front fairing and back bags. Same shocks.