wiggles

[GARTHXS]

So the 79f is runnin pretty good but it is not as stable as it should be it seems needs constant input to get a little wiggly I dropped the air in front to about 28psi and the rear is @about 40. The front end seems to be tight , I just don't really know . Any ideas??

[jjwaller]

So the 79f is runnin pretty good but it is not as stable as it should be it seems needs constant input to get a little wiggly I dropped the air in front to about 28psi and the rear is @about 40. The front end seems to be tight , I just don't really know . Any ideas??

I assume you mean "To not get a little wiggly"
Anyway.... 28 seems a little low. 40 is absurdly high.
What tires are you using?? Makes a huge difference!!!
Anecdote: My V65 Sabre back in 85? Was extremely unstable in any kind of crosswind. Due to the stock tires and it's top heaviness. Have no idea what they were. Switched to Michilens and all of a sudden it was stable!
Am running Metzler 880 Marathons on my XS11 and it is not squirlly at all.
Had it over 100 many times and it is fine. Low speed also.
HTH
BTW I assume you've eliminated the font fork bearings and the swing arm bearings?!

[GARTHXS]

bt45

I have the same set on my 78 and it rides fine but I will check the swing arm what psi should I be runnin I am 220lbs , and the front end does not have any play it seems to be mostly low speed

[greatnw]

I'm with JJ on this one. I was riding my son-in-law's 84 V65 Sabre before I picked up and revived my Special. The V65 was really squirrelly over any imperftections. I kept checking the front end. I really thought that the front tire needed replacing although it was a good brand in great shape. Nothing was wrong. Finally replaced the well worn back tire with a Metzler radial...it was like riding a different bike! I would never have guessed the rear tire could be the culprit. After the new tire I tried every crack in the road that used to give me a thrill rolling down the freeway to work. Nothing. Rock solid. Like on a rail.
Don't know about anything unique that would cause the problem in the XS other than making sure all the rolling gear is up to spec. If you don't see anything obvious I'd check that rear tire. Mine had plenty of air, it was just worn out.
28 is what the book says and 40 is max in back. Specs for the rear are 26 to 36 depending on load, ie how big you and your load are.
Good luck.

[Geezer]

New tires have less angle to the plies than the older bias ply tires these bikes came with and should be filled to the max pressure cold listed on the sidewall of the tire.

If your bike is squirrelly then you need to examine the entire front end for problems. I would start at the top and work down. Put the bike on the center stand and place a jack under the engine and raise it until the front wheel is off the ground. Slowly turn the forks left to right and check for tight spots or anything that feels like a detent. If they seem a bit stiff, disassemble the front end, clean and inspect the bearings. If all looks good, repack the bearings and put it back together. Make sure the bearings are properly adjusted and all the bolts in the fork trees are tight.

Next change the fork oil If the fork oil is low or filthy, you many want to flush them out with some solvent and then blow them out with a little compressed air. Not to much pressure or you will damaged the seals (assuming they're good.)

Next inspect the front axle. Make sure the little arrow on the cap on the left side is pointing forward and the nuts are tightened to spec leaving and equal gap front and back. Also torque the axle nut to spec before tightening the cap nuts on the other side.

Turn the front wheel and run you hand slowly over the tire and feel for cupping. Some times you can feel this before you can see it. It may be time for a new tire or to have it balanced.

Geezer

[trbig]

I'm with Geezer. Use the max cold tire inflation pressure on the rear which is 40psi for most new tires. I also use the max pressure in the front. For my aggressive riding style, I don't like my tires rolling around sideways. But yeah, the swingarm could be a culprit. Put the bike on the center stand with the back wheel in the air and see if there's any movement side to side. If it's ok, get a jack and lift the front wheel a touch also and spin it. Watch the tread to see if it rolls true. You could look at that on the back also. That would tell you if you had a broken belt in the tire.


Tod

[GARTHXS]

rear end

The rear en has no play, I rode today it might just be the bars they are a little more forward than my 78 not as comfy , the drop in psi in the front to 28 seemed to help some

[petejw]

Just be careful with regards to checking
s/a bearings, no play doesnt necessarily mean
there ok, unlike wheel bearings they dont rotate fully.

[Crazcnuk]

"New tires have less angle to the plies than the older bias ply tires these bikes came with and should be filled to the max pressure cold listed on the sidewall of the tire."

You should almost never be using the max tire pressure unless your running the max load too.

If you really want to know what pressure to run, load your bike up, they way your going to be using it, then go to your local weigh scale and weigh the front and rear axles seperately.

Than take your weight readings, and divide into the max load rating on the tire (front or rear) and you will get a % number. Multiply the max tire pressure by that % factor and you will get the pressure you should be using.

If you have a vehicle that is heavy enough to require max tire presure, you should be looking into heavier tires.

[TopCatGr58]

Next inspect the front axle. Make sure the little arrow on the cap on the left side is pointing forward and the nuts are tightened to spec leaving and equal gap front and back. Also torque the axle nut to spec before tightening the cap nuts on the other side.

Geezer

Hey Tony,

I know you're an old experienced Yamaha mech, but the book says to make the front end of the axle clamp touch, and that the gap is towards the rear?
T.C.

[GARTHXS]

tc

Hey Tony,

I know you're an old experienced Yamaha mech, but the book says to make the front end of the axle clamp touch, and that the gap is towards the rear?
T.C.

I thought that was the way also

[Geezer]

Hey Tony,

I know you're an old experienced Yamaha mech, but the book says to make the front end of the axle clamp touch, and that the gap is towards the rear?
T.C.

I'll look into that. I know Honda used to do it that way but I don't remember any other bikes doing that.

Geezer

[trbig]

You should almost never be using the max tire pressure unless your running the max load too.

The tire pressure recommendations in the manual are for the tires that were manufactured at that time. Modern bike tires, along with car tires, are recommended to be run at the max cold tire pressure... so I've been told. I know mine handles best at the 40 psi. and I get the best wear out of the tires.


Tod

[Crazcnuk]

"Modern bike tires, along with car tires, are recommended to be run at the max cold tire pressure"

Not true at all. How the tires are rated hasn't changed. The numbers have changed, but how the pressures are calculated hasn't. You won't find anyone who knows anything about tires that just says to routinely put all tires at the max sidewall number.

That's why I didn't say anything about the pressures in the manual.

However, modern tires pressures, on the side of the tire are still the max allowable pressure at max load.

You do not need to run max pressure at anything other than max load. You should find your wearing out the center of your tire prematurely. (Hard to tell on a bike, I know.

Either that, or you ARE at max load for your tires.... ( I blame MSG)

Anyone reading this, that has lower profile tires on thier car, even from the factory, should go out and check their tires to see what the rated pressure is.

For example my 2005 Neon normally comes with 14" tires on steel rims. The sticker on the door is for those tires (35psi max radials) and it recommends 30psi. However, mine came with 15" aluminum mag wheels with a max rating of 44psi. If I run the door pressures it's like riding on half flat tires, which they are.

After consulting the gurus, and doing the calculations I am running 38-39psi, and they work great.

[GARTHXS]

ouch

I am not that fat just big boned