Topic: Bike weaves side to side

[Laminar]

I took my 550 cafe project for its maiden voyage yesterday, doing about 5 or 10 miles. The biggest thing I noticed is that it has an odd gradual side to side pull that makes the bike want to weave a little bit. I can counteract this manually, but it feels a bit unstable around corners.

The fork fluid and seals are new. The rear shocks are CB900f units. The wheel bearings are all new. The tires and tubes are brand new and were installed by the local Honda dealer. The steering bearings are brand new tapered units.



Suggestions?

[mystic_1]

Check your swingarm pivot.  Also, double-check to make sure everything was tightened properly.

mystic_1

[GammaFlat]

I'm guessing that any problem or misalignment that causes your bike to initiate moving off of a linear path (even just a little) could cause oscillation.  In my case, I'll next be aligning the front wheel.  The front wheel on 750's is slightly off as documented by HondaMan on this site and in his book. 

Maybe you can use a string to check alignment of your wheels. 

Also, you might think about your steering head bearings and swing arm condition. 

[kvallelunga]

Nice project, looks good. The first thing I would check is the front/rear wheel alignment. Or swing arm issues.

[andy750]

The CB900F shocks are 14` I think - taller than stock anyway -did you compensate for this by changing your front fork tube length?

[Laminar]

The CB900F shocks are 14` I think - taller than stock anyway -did you compensate for this by changing your front fork tube length?

They're 13.5", and I didn't do any compensating.

What exactly should I check on the swingarm pivot? The bolt is nice and tight and the bushings rotated smoothly and freely after I reinstalled it.

[Duke McDukiedook]

I don't think you should be able to rotate your swingarm bushings easily.

[Laminar]

I don't think you should be able to rotate your swingarm bushings easily.

I meant that after installing the swingarm in the bike, the swingarm itself moved freely up and down.

[Gordon]

Lift the rear wheel off the ground and check for side-to-side movement of the swing arm.  There shouldn't be any. 

[Spanner 1]

Try riding your bike before 6 beers, see if it's different..!! ( Just kidding)... I'm with the swingarm crowd.

[number13]

Bent rim?
Loose spokes?
Tire improperly seated?

[camelman]

Put it on the center stand and spin the tires independently.  I noticed my newly mounted front tire was wobbling by up to 1/4" side to side, and was causing "weave" like you are experiencing.  It is pretty obvious to tell if the tire isn't mounted correctly.  Mine actually had a lump of inner tube between the tire and rim!  Damned installers.

Camelman

[xenoscr]

Bent rim?
Loose spokes?
Tire improperly seated?

An improperly seated tire just about bucked me off my bike. There was a "low" spot, only about a 1/4 inch or less lower than the rest of the tire that made the rear jump around pretty good. That's a mistake I'll make only once.

XeNoS

[ChortlingSandcaster]

Okay this may well NOT be the issue based on your description of the symptom, but I had a similar problem on a modded Suzuki 750 that could not be diagnosed (not easily at least) when I put the bike up on a center stand, and not during driving it either.

I checked EVERYTHING, was the triple tree loose NO, were the front wheel bearings snug YEP, rear wheel bearings FINE.

The durned thing would just wiggle a bit.

I finally realized that I had not checked the operation of the swingarm in its up-and-down motion.  Granted it's not super-easy to do that with the bike up on a stand in the garage. 

And I notice you have custom pipes on it.  Looks like on both sides too.

The problem on my Suzuki was *sometimes* the custom exhaust put on by the prior owner
was running into the moving swingarm.

Probably not your issue, but in my case it was not intuitively obvious and it took a couple of
go's at the problem, just thought I' pass it on.

I had bought the bike with the custom exhaust on it and the prior owner did not add enough spacers
so that the custom exhaust would clear the swingarm over the swingarm's full range of motion.

Once I moved the exhaust clear of the swingarm by adding spacers, man-oh-man the handling shot up and
the bike gave a LOT more confidence during rides.

Good luck to you.

[Old Scrambler]

If you installed the tappered steering bearings, check to see if they are spaced -seated -properly. If the bottom spacer is not correct - large washer - the tree will rub on the frame and take some of the weight that should be on the bearing......thus causing the unstable feeling.

[Steve_K]

I did not see a front fender or the fender brace, that can cause problems with the fork moving about when in a turn.  I think that all the above suggestions should be checked too
Steve

[tmac]

I had the same problem & I found that I had tightened the steering head bearings down too much so the bike couldn't track, just weave back & forth in slow traffic almost by itself it seemed.

[Don R]

I found damaged steering neck bearings, the balls would eventually drop into dents in the races. I could stop and turn back and forth several times, that would temporairly move the little balls around out of their nests. tapered bearings cured it, not too tight also, I bought an F and I think the po over tightened the neck, it handles heavy.

[Laminar]

I did not see a front fender or the fender brace, that can cause problems with the fork moving about when in a turn.  I think that all the above suggestions should be checked too
Steve

Look closer.

I found damaged steering neck bearings, the balls would eventually drop into dents in the races. I could stop and turn back and forth several times, that would temporairly move the little balls around out of their nests. tapered bearings cured it, not too tight also, I bought an F and I think the po over tightened the neck, it handles heavy.

 

I had the same problem & I found that I had tightened the steering head bearings down too much so the bike couldn't track, just weave back & forth in slow traffic almost by itself it seemed.

I used the ultra-scientific method of too tight, then loosen enough that everything moves freely. I'll have to check that.

[Steve_K]

Yeah it is there.  Nice looking ride you have there.
Steve

[Laminar]

Got a chance to look at this yesterday. Here's what I found.

- Both tires were around ~25psi. I suppose that should have been on my pre-first-trip checklist.
- The steering bearings were shockingly loose. i suppose the first trip must have worn them in and more fully seated them, so by this second trip they were quite loose.

The confusing thing was that tightening the steering bearings made the weaving horrible and the bike was a bear to handle. It turns out that the tongue on the frame steering tube that provides turning stops was rubbing on the lower triple tree. Every time I'd make a minute steering adjustment while riding, it took so much effort that I overcorrected, and the bike would weave side to side. Tightening the bearings made this much more apparent. I used stock washers, but I did get a couple spares, so I'll have to pull everything apart and put an extra washer underneath the lower bearing to guarantee clearance. Just when I thought I was almost done with the bike.

[Old Scrambler]

Just what I suspected...........because it happened to me on my first bearing conversion.........by raising the frame away from the bottom triple you will create space at the top.  The solution is to either install washers above the headlight ears for a stock applicaiton......or go back to the little balls..........most of the weight is on the bottom bearing.   Whatever you do be sure to have equal spacing and tightness on the top tree at all three points or the tree could break.