Wobble at high speed, and carb question...

[sickopsycho]

Hey guys! Got a couple quick tech questions. First, I have a slight wobble at high speeds. It's in the front bars, and it's only when I let go of the bars (I know, I know, I shouldnt be letting go of the bars, but how am i supposed to stand up on my bike at 70mph if I can't let go???). Anyway, if I am going 50mph+ and let go of the bars, the front shakes back and forth. Recently I had an absent minded motorist bump the back of my parked bike- she was pulling into a parking space and didnt see it there. It hit the curb in front of it and fell over. I was literally standing right there and saw the whole thing go down, I almost cried after I almost punched her. Not really- but I was a little upset. I noticed the wobble after that, but it could have been there before. What do you guys think I should check? I can't feel it if I'm holding the bars, it's only when I release them...
Next... what is the difference in the STOCK carbing of the 2007 and earlier (pregen) and this bike (2012)? Is it the same carb? Same jets? The reason why I ask is because I have a 2007 that's just sitting and it has a needle kit in it. I'm wondering if I can swap out the carbs (or the guts) instead of buying a whole new kit/jets/etc. Any info?
Thanks guys!

[Triple Jim]

The first think I'd do is get the wheels off the ground and spin them to see if they're true. A wheel could have gotten bent in the hit.

[subxero]

the wobble you feel could be lots of things. flat spot on the tire, bent wheel, unbalanced, loose bearings somewhere. Do you still have the bar end weights on the bike?

As far as the carb.

I am pretty sure the carb itself is the same for the most part but jetting and needles are probably different. No guarantee the jets from one carb/bike would work well in another even if they are very similar. You could certainly check the jetting recommendations and or what other people are running and if those jets ect... fall into the range then give them a go but if you don't really know anything about carb tuning probably best not to mess around with it. What is wrong with your carb/jets now?

[sickopsycho]

Originally Posted by Triple Jim

The first think I'd do is get the wheels off the ground and spin them to see if they're true. A wheel could have gotten bent in the hit.

Good idea, I have spools on the rear but no stands

Originally Posted by subxero

the wobble you feel could be lots of things. flat spot on the tire, bent wheel, unbalanced, loose bearings somewhere. Do you still have the bar end weights on the bike?

As far as the carb.

I am pretty sure the carb itself is the same for the most part but jetting and needles are probably different. No guarantee the jets from one carb/bike would work well in another even if they are very similar. You could certainly check the jetting recommendations and or what other people are running and if those jets ect... fall into the range then give them a go but if you don't really know anything about carb tuning probably best not to mess around with it. What is wrong with your carb/jets now?

What are the "bar end weights"? It's bone stock, so if Kawasaki put them on, they are probably still there. There is nothing wrong with my jetting now, but I plan on replacing my air filter with a K&N and getting an Area P full exhaust. Then I'll have to rejet. I was mostly just wondering if they are the same carbs so I can use the jet/needle kit thats on my other bike which ran like a top with the same mods I plan on putting on this bike. Didn't want to have to go blow another $100 or so if I didnt have to...

[jkv45]

As TJ noted - check the rims.

Are the bars pointing straight when you are going straight? Sometimes a tip-over can tweak the front end.

How old are the tires? Properly inflated?

Have you checked the steering head bearings? Hold the front brake and push/pull forward/backward on the bars. Listen and feel for any clicking or clunking from the bearings.

Check the rear wheel alignment carefully. Measure from the center of the axle to the center of the swingarm pivot on both sides and compare. The hash marks on the swingarm aren't always very accurate, sometimes not accurate at all.

[sickopsycho]

Originally Posted by jkv45

As TJ noted - check the rims.

Are the bars pointing straight when you are going straight? Sometimes a tip-over can tweak the front end.

How old are the tires? Properly inflated?

Have you checked the steering head bearings? Hold the front brake and push/pull forward/backward on the bars. Listen and feel for any clicking or clunking from the bearings.

Check the rear wheel alignment carefully. Measure from the center of the axle to the center of the swingarm pivot on both sides and compare. The hash marks on the swingarm aren't always very accurate, sometimes not accurate at all.

I am going to bring it in to a shop that said for $35 they would balance both wheels and check a lot of other stuff. Figure if a wheel is bent this will show it. Tires are the ones that came on it in 2012 as far as I know, but they only have 2k miles on them (they don't show any visible signs of wear). I know, they should be changed simply because they are old, but I dont drag a knee around turns nor do I plan on taking it to the track anytime soon- and the tires seem pretty sticky to me... so I'm just gonna let them ride a while longer if I can... Also they ARE properly inflated, I check at least once a week. =)
I will check the other two things you mentioned as well, thanks for the input.

[Triple Jim]

If you do have a bent wheel, Woody's Wheel Works is known to do a good job straightening. I can't vouch for cost effectiveness of straightening vs. used wheel, but I'm sure you can figure that out.

[Panda]

The front end wobble is not atypical. Mine will wobble as a decelerate from 60 to 30. IIRC it starts wobbling right around 45MPH.

[sickopsycho]

Originally Posted by Triple Jim

If you do have a bent wheel, Woody's Wheel Works is known to do a good job straightening. I can't vouch for cost effectiveness of straightening vs. used wheel, but I'm sure you can figure that out.

Awesome, thanks Jim!

Originally Posted by Panda

The front end wobble is not atypical. Mine will wobble as a decelerate from 60 to 30. IIRC it starts wobbling right around 45MPH.

That's what it's doing. As I said, problem could have been there all along and I only now noticed it. It's only on deceleration, but it's also not so bad that I can feel it even when I lightly hold the bars. When I let it go, though, it's a little scary. Feels like I'm about to get a tank slapper..

[Triple Jim]

That problem usually shows up when the front tire starts to get worn with a triangular cross section, pointy in the middle.

[sickopsycho]

Originally Posted by Triple Jim

That problem usually shows up when the front tire starts to get worn with a triangular cross section, pointy in the middle.

Explain please. I'm assuming you mean that it loses its "round" and has a high spot in the center? How would that even happen? I understand the logic of it- the tire doesnt want to sit on that high spot so it rocks back and forth causing the bars to wiggle and wobble... but I'm just wondering what would cause that wear other than costantly taking lefts and rights and never going straight lol.

[sickopsycho]

Originally Posted by subxero

the wobble you feel could be lots of things. flat spot on the tire, bent wheel, unbalanced, loose bearings somewhere. Do you still have the bar end weights on the bike?

As far as the carb.

I am pretty sure the carb itself is the same for the most part but jetting and needles are probably different. No guarantee the jets from one carb/bike would work well in another even if they are very similar. You could certainly check the jetting recommendations and or what other people are running and if those jets ect... fall into the range then give them a go but if you don't really know anything about carb tuning probably best not to mess around with it. What is wrong with your carb/jets now?

I just looked up the "bar end weights" and I'm not sure if what I have on my bar ends are stock or not. There is a plastic slider looking piece on the outside of both my grips, about 2" long. It's hollow and has a bolt in the center. I assume they came with the frame slider kit or something because this would be the other part to take damage if the bike fell. When my bike hit the ground, one was scuffed, but it was not really moving and more of a fall over from stop kind of scenerio. There are a few VERY small scratches on one end, but not as if substantial material was worn away.

[jkv45]

Originally Posted by sickopsycho

I am going to bring it in to a shop that said for $35 they would balance both wheels and check a lot of other stuff. Figure if a wheel is bent this will show it. Tires are the ones that came on it in 2012 as far as I know, but they only have 2k miles on them (they don't show any visible signs of wear). I know, they should be changed simply because they are old, but I dont drag a knee around turns nor do I plan on taking it to the track anytime soon- and the tires seem pretty sticky to me... so I'm just gonna let them ride a while longer if I can... Also they ARE properly inflated, I check at least once a week. =)
I will check the other two things you mentioned as well, thanks for the input.

The tires may have been produced in 2011, so are going on 6 years old. That's about the max you can expect from a cycle tire.

Look them over closely. I have seen photos of stock tires that age that are cracking inside the tread - a sure sign the rubber is drying out.

Even though you aren't planning to "drag a knee", you still want the superior traction of new tires for normal riding. In the event that you ever need to make a full-on emergency stop you are going to want that extra grip instead of a lock-up - which is what an old, dry, tire is going to give you.

[sickopsycho]

Originally Posted by jkv45

The tires may have been produced in 2011, so are going on 6 years old. That's about the max you can expect from a cycle tire.

Look them over closely. I have seen photos of stock tires that age that are cracking inside the tread - a sure sign the rubber is drying out.

Even though you aren't planning to "drag a knee", you still want the superior traction of new tires for normal riding. In the event that you ever need to make a full-on emergency stop you are going to want that extra grip instead of a lock-up - which is what an old, dry, tire is going to give you.

Dammit. Okay, Dad. I'll get new tires. **pouts as I walk away**

You're right- I'm just cheap. I guess I didn't think of an emergency stop scenerio. Glad to be here.

[jkv45]

Originally Posted by sickopsycho

Dammit. Okay, Dad. I'll get new tires. **pouts as I walk away**

You're right- I'm just cheap. I guess I didn't think of an emergency stop scenerio. Glad to be here.

Ha! My boys have heard that lecture many times...and it's probably saved them just as many times...

[Triple Jim]

Originally Posted by sickopsycho

Explain please. I'm assuming you mean that it loses its "round" and has a high spot in the center? How would that even happen?

Front tires get a lot of their wear when cornering, when you're leaned over. Therefore, looking at the profile, you get two flat areas, one on each side of center, and the center gets a sharper radius than it had when it was new (a little pointy looking).

I don't know the physics of why, but when my front tires get that way, they get noticeably squirly. One symptom is the no-hands wobble around 35 mph that you're seeing. Another I'm getting now on my Moto Guzzi is the tendency to "fall into" turns. When my front tire was new, steering was very neutral, and it felt like I could take my hands off the bar in a turn and it would just keep going around. Now on a sharp turn, the bike feels like it wants to fall over to the inside, and I have to consciously turn sharper to straighten it up.

A new pair of tires for that bike is waiting for me to put them on.

By the way, tire aging is quite variable. If your bike is stored indoors without any direct sunlight on the tires, and if you live away from big cities that have ozone problems, your tires may be fine. On the other hand, if you do park outside in daylight in a big city, they may be getting oxidized and hard by now. I'm in the garage parking, country air category, and six years of aging doesn't change my tire rubber much, on bikes that don't get a lot of miles on them.

[Zaph42]

People need to recognize all the interacting factors that cause head shake. It's not just one thing. Bearing wear and slop, head nut torque (and that's the nut under the top triple clamp), uneven side to side tire wear (cupping), size of the contact patch, frame flex and fork flex. If a few conditions line up just right, the head shake appears. Change one thing in this equation and the end result might not = head shake.

Putting new tires on has small chance at changing the equation enough to make the head shake go away. But for most people, replacing the head bearings has a much higher chance of doing something. I've heard a few people say new tires didn't solve the problem, but I've never heard anyone say that new head bearings didn't work.

That said, people should first check the front tire visually by spinning it and looking for cupping, and checking the torque of the stem nut. These are the cheap and easy checks.

BTW, I believe a front tire that is worn with a flat spot, or a sport touring style tire that has a larger upright contact patch is more likely to contribute to head shake. Pointier tires, such as true supersport, or tires that are seriously worn from track use are likely to feel "skittish" and fall into turns but actually be less likely to cause head shake. Two completely different issues not to be confused.

[Motofool]

Originally Posted by sickopsycho

.........I noticed the wobble after that, but it could have been there before. What do you guys think I should check?.......

http://faq.ninja250.org/wiki/I_need_...nd_front_wheel

http://faq.ninja250.org/wiki/How_doe...ometry_help%3F

http://faq.ninja250.org/wiki/Servicing_the_swingarm

http://faq.ninja250.org/wiki/Uni_Tra...ge_Lubrication

http://faq.ninja250.org/wiki/Steerin...ng_replacement

[sickopsycho]

Originally Posted by Triple Jim

Front tires get a lot of their wear when cornering, when you're leaned over. Therefore, looking at the profile, you get two flat areas, one on each side of center, and the center gets a sharper radius than it had when it was new (a little pointy looking).

I don't know the physics of why, but when my front tires get that way, they get noticeably squirly. One symptom is the no-hands wobble around 35 mph that you're seeing. Another I'm getting now on my Moto Guzzi is the tendency to "fall into" turns. When my front tire was new, steering was very neutral, and it felt like I could take my hands off the bar in a turn and it would just keep going around. Now on a sharp turn, the bike feels like it wants to fall over to the inside, and I have to consciously turn sharper to straighten it up.

A new pair of tires for that bike is waiting for me to put them on.

By the way, tire aging is quite variable. If your bike is stored indoors without any direct sunlight on the tires, and if you live away from big cities that have ozone problems, your tires may be fine. On the other hand, if you do park outside in daylight in a big city, they may be getting oxidized and hard by now. I'm in the garage parking, country air category, and six years of aging doesn't change my tire rubber much, on bikes that don't get a lot of miles on them.

Thanks for the confirmation, Jim! This bike was garage kept by the previous owner, and I also keep it in the garage. I checked the tires over closely, no cracks at all (inside or outside tread marks). I can easily dig a fingernail into the rubber, it seems soft to me. I only have VERY minimal (almost unmeasureable- certainly can't see any with my eyes) wear on these tires and I hate to toss all this rubber if I dont have to... but even still since I dont know for certain how the bike spent it's first 5 years I guess I should go the safe route and replace.

Originally Posted by Zaph42

People need to recognize all the interacting factors that cause head shake. It's not just one thing. Bearing wear and slop, head nut torque (and that's the nut under the top triple clamp), uneven side to side tire wear (cupping), size of the contact patch, frame flex and fork flex. If a few conditions line up just right, the head shake appears. Change one thing in this equation and the end result might not = head shake.

Putting new tires on has small chance at changing the equation enough to make the head shake go away. But for most people, replacing the head bearings has a much higher chance of doing something. I've heard a few people say new tires didn't solve the problem, but I've never heard anyone say that new head bearings didn't work.

That said, people should first check the front tire visually by spinning it and looking for cupping, and checking the torque of the stem nut. These are the cheap and easy checks.

BTW, I believe a front tire that is worn with a flat spot, or a sport touring style tire that has a larger upright contact patch is more likely to contribute to head shake. Pointier tires, such as true supersport, or tires that are seriously worn from track use are likely to feel "skittish" and fall into turns but actually be less likely to cause head shake. Two completely different issues not to be confused.

I forgot to mention that this bike, while a 2012, only has 2000 miles on it... and I put 1000 of those (very light riding). So- bearing wear is unlikely. The tires I have on the bike *I think* are the ones that came from the factory. It is a Road Winner RX-01F. Below is a picture of the wear...

[sickopsycho]

Originally Posted by Motofool

http://faq.ninja250.org/wiki/I_need_...nd_front_wheel

http://faq.ninja250.org/wiki/How_doe...ometry_help%3F

http://faq.ninja250.org/wiki/Servicing_the_swingarm

http://faq.ninja250.org/wiki/Uni_Tra...ge_Lubrication

http://faq.ninja250.org/wiki/Steerin...ng_replacement

Curiously enough, I think you have helped me with ANOTHER bike by sending me this info. According to the first post, forks that are bent *but not creased* can be straightened. I have a 2007 pregen 250 that was in a head on collision with a car (see my post in the pregen section for pics). The front forks are bent so bad that the center stand doesnt even hold the bike off the ground anymore. However, there are no creases- so apparently these forks can be straightened. Good info!

[Triple Jim]

Originally Posted by Zaph42

People need to recognize all the interacting factors that cause head shake. It's not just one thing. Bearing wear and slop, head nut torque (and that's the nut under the top triple clamp), uneven side to side tire wear (cupping), size of the contact patch, frame flex and fork flex. If a few conditions line up just right, the head shake appears. Change one thing in this equation and the end result might not = head shake.

No argument here. Swing arm bearing/bushing play and wheel bearing play are two more to add.

In my case, all bearings are properly adjusted and in good condition and my wheels are true. The head shake I'm referring to is most likely initiated by the tire being slightly out of true, combined with the peaky wear. The shake, which happens when going through about 35 mph, usually when coasting to a stop, is at wheel speed. It's not severe, and stops if the bar is gripped normally. It was not present when the tire was new.

I've had it happen over the decades with some tires when they get worn, but not with other tires. The Pirelli Sport Demon I'm getting ready to replace was not made perfectly, and from the start I could see a slight side to side out of true.

Your point is a good one, John. If there's any head shake, the bike should be checked for looseness in any place related to steering and wheels. But in my experience, even if everything is good, it can still be noticeable with a front tire that's approaching its end of life.

[Zaph42]

Originally Posted by sickopsycho

I forgot to mention that this bike, while a 2012, only has 2000 miles on it... and I put 1000 of those (very light riding). So- bearing wear is unlikely. The tires I have on the bike *I think* are the ones that came from the factory. It is a Road Winner RX-01F. Below is a picture of the wear...

Interesting story about my bike, it had 500 miles on it when I got it. I took it to the track and started the day with good bearings and ended the day with bad bearings. Only 100 miles of track time did it. I had brand new dunlop race tires on at the time.

A new set of All Balls tapered bearings solved my problem with no other work. Not only that, I could feel a difference in the bike, it felt more planted and stable in corners.

In general I get the feeling that people chasing after tire or wheel issues are likely barking up the wrong tree. But nobody wants it to be the bearings because they are a huge pain in the ass to change out. Hard to DIY in your garage and expensive to bring in. But it's something I recommend every ninjette owner do, even those who don't have a head shake problem yet.

[Triple Jim]

Nearly 40 years ago I put a grease fitting in the head tube of my H2. The original ball bearings are still like new, not notchy, and stay adjusted. It's amazing what good lubrication and the sealing out of moisture can do. But one of my motorcycles needs new head bearings and I have the tapered rollers ready to go in. Unfortunately the previous owners didn't maintain the originals.

[twincam8888]

First things first. Check your tire pressure then adjust your neck bearings. That took care of my deceleration wobble.

[Z1R rider]

As already stated, many things can start weaves or wobbles, many times multiple things acting together. Most bikes will exhibit bar shake when slowing without hanging onto the bars at around 45 MPH, some brands or types of tires in the same brand, will damp this and others can make it worse, no way that I know of to know which type or brand works best with each bike as they all have different chassis harmonics. I've also had bikes head shake because of dented steering head bearings and also from the bearing being adjusted too tight. Here's some interesting reading on the subject.

https://books.google.com/books?id=mt...monics&f=false