Really bizarre handling issue??? 83 xj900's

Hi gents,

Ive got too 1983 XJ 900's, and both exhibit this weird handling problem.
When taking a high speed corner, say 120km/h + the bike "moves around" in this uncanny manner. Its not steering head shake (speed wobbles) although they both do it at 170km/h but i believe that is due to the handle bar mounted fairing, and you can power on through it.

Its more like there is something wrong with the front tire. Like instead of taking a particular line around the corner its like it cant find one and moves left to right "off line". At high speeds this is quite worrying although i just grit my teeth and hope for the best, and power through it. One day my luck will run out and i would like to fix it before then.

Thanks if you can help guys!

 

My 1984 XJ900 is fairly fussy about pressure in the front tyre. If the pressure drops, my front wheel has a tendency to "wander" as you describe. It's not dramatic. I just take it as a reminder to check my pressures!

I don't know if this happens on all XJ900s, and I'm sure it will vary with the type of tyre fitted.

When I first bought my bike, the front tyre was very worn, and the steering was really bad at all speeds.
Anyway, have a look at the front tyre. Won't cost anything and might just effect a "miracle" cure!

 

The reviews of the day when the XJ 900 was new described steering problems due to the bikini faring mounted to the forks. The solution was to mount the faring to the frame.

 

If this is a new development, it might be worth checking your front wheel bearings along with the tire pressure that Ross suggested.

 

Over the last almost 2 years I've been discussing the ill handling manors of bikes that have bar or fork mounted windscreens and fairings. I know there are many that have had no issues and have owned bikes that had no issues but the few times that I have had issues have scared teh bajebas out of me. The main problem that I've seen is with cross winds but there may be other issues with oscilation caused by disturbances in airflow while changing direction.

A fairing mounted to the frame makes for a much more stabile platform than one attached to the bars/forks that can easily affect the handling of you bike.

The others here have very good advice as well. There are many other things that can cause these issues; wheels, bearings, tires, warped rotor, bent or misaligned forks, etc, etc.

Good luck with problem.

The Buff

 

Thanks guys, im very careful with my pressure and always have them on spec. Front wheel bearings are new, steering head bearings "feel" ok, im starting to lean towards it being as suggested miss aligned forks or possibly needing a better/wider front tire. At the moment its running a Bridgestone battle axe.

Is checking the fork alignment just done by eye?

Yesterday when riding one of them it was wandering left to right while i was riding in a straight line? it was quite hard to keep it just going in s straight line. The wander wasn't bad just this little roll to the left than to the right. What could that be? It only lasted for about 10 kms than went away. And it definitely wasn't the road surface as i go that way allot and it has never happened before/

 

Rear swingarm bearings or issues?

 

Yeah could be. i didn't notice anything unusual when i was painting my black one as i had the whole back end apart, but swing arm still on frame. I gave it a wobble / shake and it felt ok, moved up and down clean. I may strip it again and just check it. The condition of the swing arm bearings on my stock 900 though i have no clue

 

I was just thinking the same as Chacal. Rear wheel / shaft bearings could cause the bike to wander. If it where that, You may feel as though the rear of the bike was stepping out, kind of like your butt was moving sideways. I've experianced that just once on an 72 or 73 waterbuffalo.

How old are these tires and have they been sitting?

I'm not real sure how you would check fork alienment.

As for the Head bearings. How did you check them? I'm not trying to insult your intelegence cause God knows I'm lacking in that department bad.

Put the bike up on the center stand and have one of you heavy weight buddies sit far back in the seat to lift the front tire off the ground. Grab ahold of the forks near the axel and lift up an forward then let it return. Do this acouple of times to see if there is any play. If there is I would sugest replacing that.

I keep going back to that as your problem. If it was the fairing/windscreen I think you would experiance a wooble not drifting.

Good luck on this one. Make sure you sort out the problem before you push it so hard you can't bring it back.

The Buff

 

Thanks Buff,

Your right with the testing of the steering head bearings. If you don't have a heavy set mate you can always put a jack under the front of the frame . Just have a feel for play and notchy ness in turning.

Its really hard to tell what it could be, although it does feel like the front end, rather than a drift.

 

Now this is a drift

 

If you still have the 25 year old stock steering head bearings, they need to be replaced!

 

hey flash,
I had a similar problem on my XJ900. And I had a Bridgestone F11 spitfire front tire. Turned out the sidewall had busted on the left side. Not enough to collapse the tire but enough to throw off the handling. I replaced the front tire and all's been well.

 

I had the same problem on my 650 Maxim. Replaced the front tire - no dice. Replaced the steering head bearings - again no dice. Constantly monitored front tire pressure, so that wasn't the issue.
It turns out the Rear tire pressure was low. I was so caught up in trying to solve the problem at the front end, I missed it.

Don't ignore the rear tire!

 

Another thing to look at:

Make sure the back of the ignition (where the steering lock stick out) is not hitting or rubbing on the other half of the steering lock on the top of the goose neck on the frame.

Caused minor dramas for my handling and is easily fixed.

 

Alive,
Very interesting. A strange issue I don't think I'd have ever thought of.
O' the Many things you can learn from other inmates
The Buff

 

CycleWorld a few months back had a review of this new fork alignment tool from MotionPro. If you run out of ideas, it may be worth a shot, although I think it's mainly meant to address stiction and seal wear issues:

http://www.motionpro.com/motorcycle/partno/08-0412

Also, you may want to accurately check your rear wheel alignment. If it's cocked a little to one side, it will try to steer your bike to one side, which you'll correct the other way, etc.etc.

Here's one article detailing how to do it. WARNING: It may dredge up bad memories of high school algebra and trigonometry!

http://www.motorcycle.com/how-to/chassi ... -3444.html

Here's another, simpler explanation with pictures:

http://www.motorcyclistonline.com/howto ... index.html

Hope you get it sorted out!

Herb

 

mhhpartner

Good work! Thats what I love about this forum; People aren't afraid to spend some of their own time helping each other out. Talk about a community.

Very Kewl

The Buff

 

Well i have not been on here for a while as i have had allot of other projects on the go and to be honest had forgotten about this site! i know im really bad! and should be ashamed!

Anyway,

I was emailed the other day from another site member asking if i have sorted out my handling issue's. Well the answer is kind of. So i thought i would post up my reply to him here so other members can leave comments and opinions and maybe even help some other members with the same issues...... here goes,

I am still yet to tune out the wobble in the corners. I have heard many people say that it is just a trait of the bike, it being 26 years old with 26year old chassis technology, but i still have not given up hope. Although i am yet to get rid of it completely i have be able to "raise the bar" as it were.

I have been able to get it so it will easily do about 100 - 120km/h on some pretty good sweeping corners (rated speed 75-85km/h say) and even up around 140 on the more open ones. The wobble is there but it doesn't feel as nervous. And although the "big boys" get away from me on the straights, i still surprise the shit out of them once we get to the twistier stuff that the old XJ can mix it with the best of them. You see them look twice in the mirrors as they still can't believe its my headlight shining in there eyes sorry I'm drifting off topic.



I originally had the bike setup on the solo settings recommended in the book, as this gave a reasonable ride (on the softer cruising side) and still ok in the corners, but that dam wobble was really bad at times. What i have done now is firm it up quite a fair bit, this has made the bike 10x better. Instead of wallowing over bumps it hits them and settles straight away. This has also improved the chuckabillity of the bike in the slower speed stuff as it responds to input allot better.



My bikes are 31a 's so the first of the XJ900's with the fairing mounted to the steering. So the first thing to do it take it easy on the handle bars when cornering. This really affects the bike as the wind is also affecting the steering as well. Remember to slide your body off the bike not just your bum, sliding your bum off the bike still keeps the top half of your body centralised with the centre of the bike, hence, not really shifting your weight. You want to move the top half of your body off the bike kind of putting your helmet in line with the mirror and put most your weight through the foot pegs and resting the outside knee against the tank. By no means am i a super bike rider and I'm still learning this technique, but it has helped the handling heaps. Sorry if you already know all this as you have just wasted 10Min's reading it



Next,



Firm the old girl up!!! My standard 31a still has the old anti dive front forks and the original dampener adjustable rear suspension. What i did was.....



Get rid of the 5w fork oil in favour of 10w.

Also make sure your fork seals are in good condition, and if the oil has not been changed in a while, either strip the forks right down and clean them or flush them with lots of oil and keep draining them until it comes out clean. A cheap alternative to fork oil for flushing is a cheap engine oil with the first half of the specs at 10w, so a 10w/50 or 10w/40. As the thin/cold rating of the oil is the same, so if a little bit stays in there after draining it will not affect the fork oil



Cut a piece of think wall pipe the same size as the inside and outside diameter of the fork spring. at 25mm (1 inch) long.

(a good time to do this is when changing the fork oil)

Take off your handle bars, loosen the pinch bolts, unsrcew the caps at the top of the fork

legs (I welded the head of a bolt the same size as the hex hole in the fork leg plug to an old 1/2 inch socket, this makes it 10x easier as they can be quite tight) sit the bit of pipe on top and with great difficulty push the plug back down and screw it in. This firms up tired old spring dramatically. But be careful when pushing the spring back in, that bit of pipe can shot off with some real force if your not careful!!!!!!!



Put about 7-10psi of air in the front forks through the air valve just under the left hand side handle bar. I'm a light weight (about 74kg) so if your heavier i would go for around 10psi.



Crank up the anti dive to the third hardest setting. Your book will tell you how to do this, and if you don't have a book... GET ONE!!!



I also have bought a generic steering head dampener that i am yet to fit (to many projects on the go) which should take out the steering head shake at around 160-170km/h.

I will let you know how that goes.



Next the rear!



I set the rear spring pre load to 4. This may be a little firm for some but as i said before, it really firms the whole bike up and i found it actually handles the bumps better. It will also complement the firmer front end.



I also set the rear dampening to its second hardest setting (same as you would if caring a pillion) This made the bike respond to the bumps and turn in allot better as the rear doesn't stay "pushed" down after turn in.



Also check your rear shock rubbers, if they are soft, perished, or just crap, get some new ones. I'm looking at getting some urethane ones and making them the suitable size to replace the rubber ones.



That's about all i can remember at the moment. Its hasn't "fixed" the bike, but it has made it allot better and a bit faster around the twisty stuff.

 

A new set of shocks would improve it greatly .. when I replaced my old originals th bike really sharpened up iin th corners .. th line you want .. not nearly th line .. an all over smoother to ride.

 

Not much mention of the "what I think" is the steering dampening disc. A round disc that mounts on the bottom of the tapered tube. Does it need lubricating or overhaul?
My 81 XJ750 is not equipped with this unit. Only my 83. It mounts on a spline and has a locking bolt. It's the lower most item on the steering tube (bolt) Page 260 in the Haynes manual. How does it work? Should I take it off, after installing roller bearings ???

 

First thing I did on my current xj900 project is throw away the anti-dive forks and replaced them with a set from a 1985 xj900N. The are just conventional forks with no fancy add ons ,and filled with 10w fork oil., Cheers , and MERRY XMAS , Murray

 

.... and I was going to add that , of the half dozen or so xj900,s that Ive seen around my neck of the woods , none have had their original rear shocks , they,ve all had old Konis fitted. Seems either the originals didnt last, or where quickly changed for a better shock. And you can still get parts to rebuild them from Ikon shocks here in Australia. I,d certainly suggest ditching the originals for a quality after market unit, they,ll make a big difference, cheers, Murray

 

I know this is an extremely old post but did you ever figure out what your wobbling issue was?

 

problem with old threads is the member
FLASH4 was last seen:Mar 16, 2010
if you click on the avatar it will pop up a screen and you can see when they were here last.
I did ebjoy reading the thread.

he did answer this question on his last post to this thread

 

Yes, good read. Outside of the known issues with rear and front tyres and pressures, add knacked rear shock absorbers, knacked or just not maintained forks, loose head bearings, you have the issue Yamaha themselves found and fixed, namely the fork hung fairing.
I seem to recall many instances of tank slappers caused by combinations of fork fairings and rear paniers or top box.