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Old June 15th, 2019, 01:05 PM   #1
Sflynn
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Bucking while leaned over?

Hey guys I’ve got an 09 ninja 250r with 55,000 km on it. I’ve only put about 20,000 km on it. While leaning it over I’ve noticed it starts bucking me off. It doesn’t start until pretty steep lean angles but it is quite disconcerting if I come into a corner a little hotter than I want to. Also it’s much more noticeable during left hand turns. Anyone have any ideas as to what’s causing it. Could it be a preload issue?
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Old June 15th, 2019, 02:29 PM   #2
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Hi and welcome!

Something may be loose. Check and torque every nut & bolt related to suspension.
Check wheel bearings.
Inspect your tyres very carefully for blisters or bulging spots indicative of damaged casing.
Fork service may be in order with new oil.
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Old June 15th, 2019, 03:11 PM   #3
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possible, high lean angles= high g-forces, could you be bottoming out in these high g turns, g out was a problem on my 300
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Old June 16th, 2019, 02:52 PM   #4
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Usually relates to a loose swing arm or bad wheel bearings. Possibly be worth checking the integrity of the fork bridge under the front guard and even tightness of the triple clamp bolts and steering head bearings. These things usually handle beautifully so something must have come loose or gotten bent!
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Old June 16th, 2019, 08:48 PM   #5
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Check the easy stuff first;

1. Check tire pressure
2. ****Check chain slack****
3. Bounce the bike to look/listen/feel for suspension movement
4. Lift the wheels and give them a spin checking bearings, for missing wheel spacers and overall tire condition
5. Check for a dragging front brake, rotors for warping and leaky fork seals while you got the front wheel in the air
6. Check rear rotor for warping and swingarm main bolt while you got the rear in the air
7. Check top and bottom motor mount bolts
8. Check steering stem nut and general triple clamp tightness
9. Put a zip tie on your upper fork leg and check for bottoming out and proper travel

Now the hard stuff or stuff that will cost you more time and/or $$$.

1. Check fork legs for straightness
2. Check for proper fork oil consistency and level
3. Check spring rate (front and rear)
4. Check rear shock
5. If all else fails, get a new set of tires if they are even remotely close to suspect

Hmmmmmmmm, gut feeling here. On left side, while only at lean.... Has the bike been sitting on the side stand for a long time without moving it? Outside? With 0/low tire pressure and in the cold? aka, check for flat spots on the tires.

Welcome and good luck, please don't forget to follow up when you solve the problem. Pay it forward ya know.



EDIT: Has the bike ever been down? And if so, what side?
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Old June 17th, 2019, 07:16 AM   #6
Sflynn
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Quote:
Originally Posted by csmith12 View Post
Check the easy stuff first;

1. Check tire pressure
2. ****Check chain slack****
3. Bounce the bike to look/listen/feel for suspension movement
4. Lift the wheels and give them a spin checking bearings, for missing wheel spacers and overall tire condition
5. Check for a dragging front brake, rotors for warping and leaky fork seals while you got the front wheel in the air
6. Check rear rotor for warping and swingarm main bolt while you got the rear in the air
7. Check top and bottom motor mount bolts
8. Check steering stem nut and general triple clamp tightness
9. Put a zip tie on your upper fork leg and check for bottoming out and proper travel

Now the hard stuff or stuff that will cost you more time and/or $$$.

1. Check fork legs for straightness
2. Check for proper fork oil consistency and level
3. Check spring rate (front and rear)
4. Check rear shock
5. If all else fails, get a new set of tires if they are even remotely close to suspect

Hmmmmmmmm, gut feeling here. On left side, while only at lean.... Has the bike been sitting on the side stand for a long time without moving it? Outside? With 0/low tire pressure and in the cold? aka, check for flat spots on the tires.

Welcome and good luck, please don't forget to follow up when you solve the problem. Pay it forward ya know.



EDIT: Has the bike ever been down? And if so, what side?
Hmmmmm the cold theory does make sense. We had a brutally cold winter up here with a few weeks where the temperatures rarely got above -20°C although the tires always had air in them and whenever it was above -10 if the roads were dry I would take her out to keep things from sitting. Hell one day out of a ram 1500 and Kia Soul the only thing that would start was the ninja. Otherwise the suspension feels okay, front brake could very likely be dragging and the swing arm linkage has probably seen better days even though it feels like it’s still working properly. It has been down twice on the right side, both times at a standstill in the driveway when I was first learning but it’s been shiny side up for well over a year and I haven’t noticed this until much more recently.
I will torque all the major bolts and see if that helps at all.
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Old June 17th, 2019, 10:37 AM   #7
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How old are the tires, what brand are they, and what is their overall condition?

Any scalloping wear on the tread blocks?

Were the pressures set properly?
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Old June 17th, 2019, 12:48 PM   #8
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I have 2 year old Micheal street radials. The front still looks brand new rear is starting to flatten out (I love twistys but I do a lot of touring) and pressures are 28 front 32 rear as speced on the swing arm. I took it through some twistys today pretty hard and it only started to act up on me in the exit of a right hand sweeper at the speed limit of 140km/hr�� let’s just say it was on the track
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Old June 17th, 2019, 01:15 PM   #9
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Can you describe more about how it wants to "buck you off"?

Does it feel like it's sliding and catching, or the front wants to tuck under?

Does the front oscillate or wiggle?
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Old June 17th, 2019, 02:46 PM   #10
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First day on track this year, I felt front-end chattering in middle of steady-state corners. Only did it middle of long corners when I'm not on brakes or throttle. Talked to my coach/mentor about this. He bounced front-end up & down and said it was too "springy".

Turns out, I made mistake of rebuilding my forks over winter with 10w oil in attempt to get more front-end traction. Also zip-tie showed I'm 5mm away from using up all suspension-travel in front. So I replaced oil with 15w, turned up compression-damping a tiny bit, added 5mm more fork-oil than stock. Next time out, no more chattering and front-end feels firmly planted!!!
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Old June 17th, 2019, 04:37 PM   #11
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Quote:
Originally Posted by jkv45 View Post
Can you describe more about how it wants to "buck you off"?

Does it feel like it's sliding and catching, or the front wants to tuck under?

Does the front oscillate or wiggle?
It feel like the rear wheel is bouncing on and off the ground and stepping out everytime it does so
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Old June 17th, 2019, 04:39 PM   #12
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Quote:
Originally Posted by DannoXYZ View Post
First day on track this year, I felt front-end chattering in middle of steady-state corners. Only did it middle of long corners when I'm not on brakes or throttle. Talked to my coach/mentor about this. He bounced front-end up & down and said it was too "springy".

Turns out, I made mistake of rebuilding my forks over winter with 10w oil in attempt to get more front-end traction. Also zip-tie showed I'm 5mm away from using up all suspension-travel in front. So I replaced oil with 15w, turned up compression-damping a tiny bit, added 5mm more fork-oil than stock. Next time out, no more chattering and front-end feels firmly planted!!!
That feels like problem except it on the rear end how would one go about fixing this on the shock not the fork
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Old June 17th, 2019, 06:16 PM   #13
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That feels like problem except it on the rear end how would one go about fixing this on the shock not the fork
are you at a speed now where your experiencing how flexy are frames are?
getting some wiggle?
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Old June 17th, 2019, 06:18 PM   #14
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Quote:
Originally Posted by Sflynn View Post
It feel like the rear wheel is bouncing on and off the ground and stepping out everytime it does so
I think we were focusing more on the front.

In that case, start by looking at the tire, tire balance, and alignment.

Next would be the chain/sprocket condition and adjustment.

Grab the wheel and see if you can twist it. Try to move the swingarm side to side.

59096, csmith, and danno have pretty much covered most of the possibilities.
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Old June 17th, 2019, 06:48 PM   #15
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Quote:
Originally Posted by Sflynn View Post
That feels like problem except it on the rear end how would one go about fixing this on the shock not the fork
Hmm, something loose in rear-end?

Check chain-wear and slack.
Make sure rear-tyre isn't mounted backwards.
Hang rear of bike in air by frame so swingarm is free of any load.
Grab rear-wheel and wiggle it around in all directions.
Grab swingarm and yank sideways, up & down.
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Old June 18th, 2019, 06:34 PM   #16
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Quote:
Originally Posted by DannoXYZ View Post
Hmm, something loose in rear-end?

Check chain-wear and slack.
Make sure rear-tyre isn't mounted backwards.
Hang rear of bike in air by frame so swingarm is free of any load.
Grab rear-wheel and wiggle it around in all directions.
Grab swingarm and yank sideways, up & down.
Chain is brand new maybe 3,000 km on it O ring I forget the brand but a good quality one. The OE one was not doing so hot after 50,000 clicks.
I’ve checked the tire and rear wheel bearing. Haven’t checked the swing arm bearings by jacking the frame up I will definitely give that a try thank you.
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Old June 18th, 2019, 06:38 PM   #17
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Is there any chance it’s a body position or I’m just riding it wrong. Like I have a decent amount of riding experience and am usually the fastest through corners on group rides (cbr 600, ninja 400, fz 07, we even have another ninja 250 so some real competition). But I’m wondering if the bike is fine and I’m doing something wrong
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Old June 18th, 2019, 07:41 PM   #18
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I was going to ask about the rider in my original post but changed my mind. Since you asked about the rider... yea, being tight on the bars can cause little slides in the rear and a general feeling of an unsettled ride. You would be the first rider that I have run accross to describe it as the bike is trying to "buck" you off. Perhaps it's not quite "bucking", can you be a bit more specific as to what you feel?

Another thing is moving your bum around after the bike has some lean. Basically, get off the seat before you turn. Aka, get off early and stay there until the bike nearly straight up and down on corner exit. If you take the skill to near peak ability, you will always be on the throttle when your bum moves. You make up a considerable portion of the mass/weight of the entire operation, the suspension can't compensate for you moving around on the seat while mid-corner.

The bike has a base level of suspension ability, good throttle control keeps the suspension in a compliant range where the bike is stable. Lack of good throttle control can detract from the working range of suspension. You have one job as the rider. "Keep the bike stable." Say it 1000 times so it sinks in real good.

Do you do any of these things? Do you trail brake deep into the corners?
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Old June 18th, 2019, 08:01 PM   #19
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Quote:
Originally Posted by Sflynn View Post
Chain is brand new maybe 3,000 km on it O ring I forget the brand but a good quality one. The OE one was not doing so hot after 50,000 clicks.
I’ve checked the tire and rear wheel bearing. Haven’t checked the swing arm bearings by jacking the frame up I will definitely give that a try thank you.
Did you replace the sprockets too? New chain on worn sprockets can actually slip.
Tension? At middle static ride-height, chain is most loose, then it tightens up as suspension compresses or extends from there.
When you've got bike suspended, and swingarm fully extended, re-check the chain-tension.

How heavy are you? It's very possible you're bottoming shock as JRshooter suggests. Stock shock is very soft and with age, damping levels decrease as well.
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Old June 19th, 2019, 06:37 AM   #20
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Originally Posted by DannoXYZ View Post
Did you replace the sprockets too? New chain on worn sprockets can actually slip.
Tension? At middle static ride-height, chain is most loose, then it tightens up as suspension compresses or extends from there.

When you've got bike suspended, and swingarm fully extended, re-check the chain-tension.

How heavy are you? It's very possible you're bottoming shock as JRshooter suggests. Stock shock is very soft and with age, damping levels decrease as well.
That was my next question...
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Old June 19th, 2019, 12:02 PM   #21
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Around 160 with gear and after a Big Mac. Not a heavy rider by any means. I’m going to check the swing arm bearings right now so I will let you know how that goes
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Old June 19th, 2019, 12:24 PM   #22
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Replaced sprockets with the chain, or no?
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Old June 19th, 2019, 12:28 PM   #23
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Replaced sprockets with the chain, or no?
No I did not sorry trying to upload a picture of the sprockets but I can’t seem to get that to work. Either way they are still in good shape no shark teeth, and still lots of metal left on them.
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Old June 19th, 2019, 12:38 PM   #24
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No I did not sorry trying to upload a picture of the sprockets but I can’t seem to get that to work. Either way they are still in good shape no shark teeth, and still lots of metal left on them.
Sometimes a new chain doesn't work with even moderately worn sprockets.

Spin the rear wheel and look for any jumping of the chain, fluctuations in tension, or odd noises.
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