"Squirrely" over 70mph

WOW! so many replies so fast! Thanks Guys!

I am going to give the bike another "going over" on Sunday afternoon, I will take 3 or 4 hours and inspect it minuteley from front to rear.

Have checked the tire pressures, they are bob on at 36psi.

Will recheck swingarm, steering, and wheel bearings......... although this time I will drop the rear shocks off the mounts to see if there is any play on the bushes/bearings on the swingarm.

May also do the "string check' to see if wheels are properly aligned, and also if chain has been maladjusted anf the rear wheel is 'tweaked' to one side.

Thanks for the Input fellow KZ riders.

Martyn

I had a similar problem at 90 mph, here's how I fixed it:

On my '77 KZ650C1, I recently replaced my Michelin Macadam tires with Pirelli Sport Demons. The Macadams had about 6,700 miles on them and they were the source of a high speed (90+ mph) wobble despite being properly mounted and balanced and having much tread left. Below 90 mph the wobble was not noticeable, but even though I only hit 90+ occasionally the thought of the wobble waiting there for me was unnerving. I replaced my bike's wheel bearings, steering stem bearings, and swingarm bushings in trying to eliminate the wobble; I already had new top quality shocks. I'm glad I replaced these items, and doing so reduced the severity of the wobble somewhat, but these items obviously were not the source of the problem as it persisted. After replacing the Michelins with the Pirellis the wobble is eliminated. I have taken the bike up to an indicated 120 mph and it is completely stable. As a bonus, the Pirellis have better traction, particularly in braking, than the Macadams. I used a 100/90 V 19 on the front and 120/90 V 18 on the rear using new Metzeler tubes as recommended by Pirelli. These are the same tire sizes as the Macadams I replaced. I have put a little over 1,000 miles on the new tires, so I cannot give a long term opinion, but so far I really like them. These tires have a modern asymmetrical tread pattern similar in appearance to some radial tires (see link). I bought mine at Ron Ayers. Ed

Sport Demons

My bike used to follow grooves in the road badly enough to make you need a diaper. The tires were about 10 years old and had about 4,000 miles on them. The spoke wheels ran very true and the tires were well balanced, but there was a wobble at 30 to 50 MPH, and the bike danced around on grooves like a junk yard dog in a meat plant.

Then I bought new tires and alloy wheels. Now the motorcycle ignores grooves, and the wobble is gone. The bike is totally smooth and stable from 0 - 115 MPH. I believe that the old tires were very poorly contoured, partly from wear, plus poorly designed when new.

For what it is worth, the original front 19" spoke wheel width was only 1.85", with a 100/90-19 tire. The alloy front wheel is 2.15" wide, and I changed to a 90/90-19" tire. The rear wheel stayed the same at 3" wide.

The motorcycle handles soooooo much better. It used to have a "rubbery" feeling as you change directions. In my opinion, the front wheel was too narrow for the tire width. Now the handling is very crisp.

TIRES make a huge difference.

Rear wheel miss-alignment will cause weaving....in spades. I have put center punch marks on both ends of the swingarm pivot axle and the wheel axle. Do this by spinning them in a lathe and marking the spot with a tiny marker, then hit it with the punch once the lathe stops.

I made a telescopic wand out of an old magnet wand. It has a small pin welded to each end, that fit into the center punch holes. Now I can get both sides of the axle perfectly aligned by comparing one side to the other. This cured most of the weaving.

This combined with a gusseted frame, stiffer aluminum swingarm, and a steering damper made the bike rock steady at 100per.

WABBMW wrote:

My bike used to follow grooves in the road badly enough to make you need a diaper.

\\\\


A man who understands! .......... :laugh:

so your saying the diaper i wear for kicks..is abnormal......hmmmm...interesting...i'll check into this......would explain some looks i get at the market....



Martynbiker wrote:

WABBMW wrote:

My bike used to follow grooves in the road badly enough to make you need a diaper.

\\\\


A man who understands! .......... :laugh:

I've been there, for me it was too wide a tire for the narrow rim.
They look cool but can realy screw up the stability in the corners or a straight line.
I ditched the Dunlops and went with the standard size Metzeler Lazertechs, best move I ever made. Rock stable now and high speed corners are what they should be.
You might check this out if you haven't already.
Hope this helps out,
Netcats

Assuming the frame is straight, I would check that top box of yours. IIRC (I don't have one on my police bike) the original top box was not rigidly fastened but used a system with springs because a rigidly mounted top box made the bike unstable. Remember that basically the same model was made from 1982 until 2000-something. If it behaved like this, they would have done something about it during its 20-year production run.
The stuff already mentioned (especially decent tires and decent rear shocks) make a lot of difference. Steering head bearings were conical type as standard, so should be ok. But even with the crappy run-flats it should handle better than you describe.

Zthou1977 wrote:

Assuming the frame is straight, I would check that top box of yours. IIRC (I don't have one on my police bike) the original top box was not rigidly fastened but used a system with springs because a rigidly mounted top box made the bike unstable.

You are correct Sir! the topbox is mounted on the p;olice mounts and is moveable by 2 inches either side.... it was weird to me, I thought the topbox was the cause of problems so removed it... bike still same... so refitted it.

i think the problem is Tires... but i am pretty broke so will put up with thew weird handling for another 2 or 3,000 miles.

we put a new rear on my 900 cause it picked up a slice.....and even though my old rear was the same (avon roadrider) and was only a few months old,and even though i ran 36 psi in both,and even though my shock settings,chain adjust marks and all else is set exactly as it was on the old tire.....


my bike is completely different feeling than it ws yesterday in the rear.....it feels like i clicked my koni's up to passenger settings and is way smooth on tracking setting into freeway sweepers and 90 degree in town turns.....


go figure...see what it feels like in 50 miles....

Craig,

I am assuming you changed the tire yourself. I've never changed my own motorcycle tires although I could if I had tire irons. My question is, if you balanced them yourself, do you need a supply of different weights? And do you do it on the bike?

Ross

i will draw fire for this but.....nah i don't balance em ...there is a circle that looks like a @ and some times the tire has a dot thats got yellow marker dye on it.....i put that @ mark where the valve stem is...so far so good...rock solid up to 125, as fast as i wanna go,for now on this tired old girl...i was taking a shot by shot to post for folks who wanna buy a ten dollar set of irons and mount there own....i got the needed tips here on KZR to start doing my own...lost my valve stem remover and ended up finishing in the dark with a drop light...after a trip to auto zone......talcum powder in the tire for tube free slide to re-aline the stem after the last bead gets ironed over the lip...15 minutes if all tools are there....turkey pan for every single nut,clip ect that comes off....keeps ya from getting any roll aways ......if not for kzr...i would still be begging shops to mount a tire i got online and getting dirty looks...screw em...i don't trust em any way with my life...imo