Bike feels very unbalanced and sways back and forth... = (

[undercoverbs]

Hi all...just my second post here I think. I live in China and have a gn250... basically the same bike as the gz250, but a little different.

My problem is that suddenly the bike feels very unbalanced. At slow speeds, its difficult to go in an exact straight line. At high speeds, it tilts back and forth, left to right.

I thought I had a flat tire even though it didn't appear flat, so I had air added. Feels exactly the same. There are no screws out of place, so I have no idea what's causing this condition.

Any ideas!?

[alantf]

I have no idea what's causing this condition.

Any ideas!?

Yes, you bought a Chinese made bike! ( :whistle: ) :roll:

No,but seriously - have you checked for play in the bearings, on the shaft that supports the front forks? I can't think of the exact name for it!

[Easy Rider]

My problem is that suddenly the bike feels very unbalanced.

Most certainly a tire, wheel or suspension problem.

First, how about finding a tire gauge and putting the proper amount of air in both. :)

Then, carefully inspect the tires, rims, front and rear axles, chain slack (which might give you a clue that the rear axle is not tight), shocks (forks in front) and rear springs.

The most common causes of that are: very low air pressure, tires worn excessivley or unevenly OR rear wheel not aligned straight.

[Viirin]

Did you ever crash the bike? - having a knock on the bike can bend the forks and put the bike out of alignment

[alanmcorcoran]

This probably isn't it, but, if you are a new rider, certain types of roads will give you a wiggly/squirrelly feeling on the Geezer and no amount of tinkering will fix it. Particularly wiggly are grooved and, what I call "scalloped" surfaces. The tire tread and the generally smaller weight/frame wheel base, etc. provides a jumpier ride than larger bikes.

If that's not it and it's none of the above -do you have spokes on your wheels? Check for loose or bent ones. I'm somewhat ignorant of how spokes work on the MC wheels, but they play a very important role on bicycle wheels. On a bicycle, they are what keeps the wheel round, among other important things - and over time, they can loosen up and your wheel goes out of round. In severe cases, the wheel can "taco", which, if you are not familiar with Mexican food, is not a good thing.

How old is the bike? How many miles on the tires? Did you buy it new?

[undercoverbs]

Hi all, thanks for the quick responses.

Ha, yes, I guess it's a Chinese made Suzuki. These are popular here,but more so in the 125 model. But also it's cheaper too. I paid about 14000rmb, so about $2100usd.

1. There are not spokes. It's a sort of 5-6 section metal rim basically, that looks sort of like a star. But not spokes.
2. No crashes
3. About air pressure - it's a good idea to check first, I'll do it tomorrow. No bike shops use guages. They just feel it and say its ok.
4. About the bearings, fork, etc. It makes sense as a possible area to check, but i've looked at it with an untrained eye and don't notice anything. Is there something with the fork or bearings that would indicate that it is the cause of the problem?

5. The rear wheel not aligned seems most reasonable to me... but how to know it and/or align it? I guess only a shop can do it?

6. Bike is only 1 year and 3 months old, and only has about 4,000km on it. Bought it new.

Thanks again!

[dentheman]

I agree with the others who say check for accurate tire pressure and tire condition first, but if that doesn't fix it:

Jack the bike up in a manner to allow you to freely spin the front wheel, then you can easily check for wheel out of round, and slowly turn the wheel to see if the wheel bearings are binding (you might be able to feel a binding or scraping), then jiggle the wheel side to side to see if there is looseness in the bearings. Then move the handlebar back and forth slowly to see if the steering bearings are catching. Your symptoms sound similar to what I experienced with bad steering head bearings on a bicycle.

Then lift the rear wheel and check it similarly, if needed.

[Easy Rider]

The rear wheel not aligned seems most reasonable to me... but how to know it and/or align it? I guess only a shop can do it?

There should be index marks near the rear axle on both sides, stamped into the frame. The indicator should be pointing at the same mark on each side.

Any shop that would gague tire pressure by feel is not to be trusted. :skull:

Alan's suggestion about grooved pavement has turned out to be the key factor for more than one new rider.

[Water Warrior 2]

Ditto for the rear suspension. Give the rear shocks and springs a good inspection. Push pull bounce the shocks. It might be that a rear spring broke. If that happened then the swing arm would likely twist a bit and make all sorts of things go out of alignment. You might want to give the swing arm a good visual inspection for any loose welds or cracks. Actually, go over the entire bike for welds and frame cracks. Have you made a chain adjustment lately ?? Possibly a misaligned rear wheel or loose axle nut would do it too. Also check out the swing arm pivot bolt to see if it is coming loose.
And as suggested, the roads you are riding on. Does this happen on all surfaces or just grooved or rough surfaces ?? You didn't mentioned this but is it with or without a passenger or load. A lot of possible reasons but we will try to help you along.

[undercoverbs]

My attempts to find out whats wrong have failed! Taking it to the shop tomorrow... will post the outcome later....

[jonathan180iq]

Looking over something with an untrained eye is not the same as physically checking all bolts are snug and tight. A simple set of hand tools and wrenches can go a long way.

http://reason.com/assets/mc/psuderman/2010_05/confused.jpg

PS: And for what it's worth, I've logged many miles on a Chinese bike and the quality of the motors are fine. It's the plastics and subsystems that are the weak points.

[alantf]

the quality of the motors are fine. It's the plastics and subsystems that are the weak points.

That's because they buy in Japanese motors. The motor on my Lanvertti (a Honda motor) was fine, but the rest of the bike was so bad, & was in the workshop so many times, that the bike shop owner got my money back for me, & stopped selling Lanvertti on the spot. :cry: