XJ750 pulls hard to left

Can you guys give me some tips of what to look for to find what's causing my 1982 XJ750 Maxim to pull (fairly hard) to the left when riding at speed? It's not subtle -- not a strong force, but it will quickly pull to full lock if I don't apply constant pressure to the right bar. It's trying to yank me into oncoming traffic!

I can't blatantly see anything out of alignment, so I need to know what to check and how to measure it.

I checked the steering head bearing by propping up the front end and making sure it glides nicely without binding. It does, seems smooth enough, no notches. Not too light, not to tight. Same in both directions. I don't think it's the steering head bearing or cable binding.

The front wheel spins freely with the calipers on, so it doesn't seem to be brake binding or warped rotors.

Both tires are new, professionally installed, less than 2k miles on them, and I don't see any bubbles, cracking, or warping. Could be unbalanced, I haven't checked.

I believe my fork springs are completely worn out. Front end dives hard while braking, and bottoms out easily. Could it be uneven spring wear? How would I test that? I've been putting off a fork rebuild until everything else is perfect.

Any guesses as to likely culprits?

 

My guess on testing forks would be to remove front wheel and brake caliper and set the bike on the forks itself (on a padded surface, gently), and see if the bike stands upright or tries to lean and fall over to one side. (Be ready to catch it, of course!)

You can also check the air pressure in both forks easily enough with a standard schrader measuring tool--they're valves at the top of both underneath that little black cover, assuming they're the same setup as the 650, which I am not sure of but I would assume to be true.

I'm just tossing an idea out there, amateur speaking here. I'll be watching to see what others say.

 

My bike did that when my steering bearings were bad. It sounds like you might have several things contributing to the problem. Do a search on here for fork alignment. I have seen the procedure for checking and adjusting it on here several times. You should also raise the front end and spin the front wheel and check to see if the rim is bent. Check to make sure your front axle is properly tightened. Since you know that the springs are shot, I would look into replacing them. Are your fork seals leaking? It might be time to rebuild your front end. Replace the steering bearings with new roller bearings from a company like All Balls. Replace the springs and fork seals. Wheel bearings could also be bad. Was the bike left sitting for a period of time after you replaced the tires? Even with the low mileage, letting the bike sit could have created a flat spot.

 

I believe the air-assist is linked between the forks on my bike, so there's only one valve. Presumably, they can't be different from each other.

Fork seals don't appear to be leaking... or, if they are, they're 100% leaked

I didn't check to see if the steering bearings have front/back play. I guess I need to do that.

I don't know the history of this bike. Bought it from a guy who admitted he hadn't done anything to it, not even an oil change, in the year he owned it. I've been fixing it up, and I've only put a couple thousand miles on it while I prepare for the big stuff: carbs and forks. It rides nicely despite everything being due for maintenance., and gets wonderful gas mileage.

 

From your description, it sounds like the fork seals are gone and the forks have no fluid left in them.

Remember that you need to check the valve clearances every 5000 miles, and if you KNOW that all necessary maintenance was neglected, best move that to the top of your list.

It's a prerequisite for carb sync anyway.

 

Hmmm - if it hasn't been maintained well, I used to see a lot of bikes where the person adjusting the chain had only adjusted one side, which made the wheel alignment somewhat odd. Also the adjuster marks were not always 100% accurate (or maybe our old bikes were twisted elsewhere...)

Put the bike on the centrestand and centre the front wheel/handlebars as much as possible. Then from the rear, sight along the sides of the tyre onto the front along each side. You should be able to see if the rear wheel is out of line or the front wheel is out of plane. {If the front wheel is out of plane, you can't do much without a frame straightener, so assume it is the back wheel out of line, so use the wheel adjusters to set it straight.

When the back wheel is in line and so is the front, double check that the handlebars are too (otherwise the bars and wheel are pointing different ways, indicating bent bars, twisted forks in the yokes (loosen and straighten) or bent forks.

Admittedly there are tools which would do this more accurately than sighting along the tyres, not least because sometimes tyres don't sit exactly right, but this check costs nothing and you can have a cup of coffee at the same time.

If your forks are diving too easily, change the fork oil. People leave it in too long anyway. If the seals are shot, they're not expensive to change and you'll be able to test the fork stanchions for straightness once the bottom sliders are off. I nearly always do this with the legs still on the bike, so the easy way is then to put a straight edge against the leg, but if you take them off, you can roll them on a flat surface to check they're true.

 

Ummm... wheel adjusters? On a shaft-driven bike?

If the bike is seriously out of line, then something's tweaked in front or one of the swingarm bearings is gone.

 

Put a string on it, make sure the frame is straight or take measurements from another bike of the same model....if available.

Also check to see that the rear wheel is plumb to the frame and not cocked to one side.

Does the pulling occur only under accelleration or is it constant?

 

Doh !

Yes he did say it was a 750 and I read that too.

Well it's one way to check that the swingarm is not twisted and the frame not bent, but you wouldn't be able to do anything about it.

 

I think others have already said it, but I will, too.

1. check to make sure your forks are PARALLEL.

2. make sure that the swing arm bearings are good.

3.. make sure that the back rim is straight, true, and parallel to the front rim.

It sure sounds like either a swingarrm is not lined up right, or the front rim is not lined up right.

4. Check to make sure that you don't have a crack in the frame. I JUST got a text from a friend of mine who found a crack in HIS frame, so check it over thoroughly.

Dave F