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JoeTChicopee
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« on: August 17, 2010, 04:16:36 PM »

I have had my Piaggio BV 250 for a year and I love it except for one thing.  It seems that the front tire sort of bounces as I am riding.  It doesn't seem as bad when I am accelerating as compared to riding slow or at a steady speed.  I had it checked at my first service and they rebalanced the front tire.  That seemed to help but in reality, I think it just started bouncing at a higher speed.

I took it back to a different dealer for it's 3000 mile service and told them about the bounce.  They didn't find anything to cause it and told me that it must be just a characteristic of the scooter.

Any ideas about what I can check to solve this problem?  I only had a one year warranty so I don't want to spend all kinds of money trying to track down something which might really be a characteristic of the scooter design.

Is it possible that this scooter is very sensitive to tire pressure variation?  I do check the tire pressure fairly frequently but not every time I ride.  If I have the tire pressure exact on a cool day, is it going to get higher on a warmer day?  I assume that when I check the pressure and it is fine that I don't need to check it for a week or so.  Is it possible that warm weather is causing me to ride around over-inflated?

Would it cause a problem if I ride under-inflated a couple of pounds in the front tire to "compensate" for the bounce?  It does seem to be worse at times so I am beginning to expect the temperature variation might have something to do with it.  My front tire takes 29 lbs and my rear 32.

The second scooter place said that the weight of the fork oil could be changed but I don't know anything about that and what it should be changed to.  It also would be fairly expensive because of the time just to get the forks exposed.

I am not mechanically inclined and do not want to go on a witch hunt?  Any suggestions?  Do I have to live with this (short of trading?)  Will appreciate any suggestions.  Thanks.

(Another thought I just had as I was proofreading---I seem to get different pressure readings from different tire pressure guages.  I have the simple pencil type, I have a round guage type, and I have an electronic one from Slime. Maybe my guages are inaccurate and I am overfilling the tires.  Is there a proven better pressure guage that I should buy?  It seems that just adding or letting off a little pressure results in a big pressure reading change.)
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« Reply #1 on: August 17, 2010, 04:52:59 PM »

I was going to suggest fork oil as well but only from what I've read about bikes in general.  I'm not really all that up on wrenching either but I'm getting better.
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« Reply #2 on: August 17, 2010, 05:05:24 PM »

Sorry to read of your difficulties.
Not technically able to answer your question other than say that it shouldn't bounce.
I would think it is more an issue of tire balance or a tire problem.  The tire may be slightly out of round.  Find a good tire place and see what they say.
The stock fork oil should be the correct weight so I don't think it is that.
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TechGuy
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« Reply #3 on: August 18, 2010, 12:04:14 AM »

When does this bounce happen?  I have had shudder when decelerating between 35 and 45. To me --- Shudder is when the handlebar grips shudder back and forth in your hand

Do you have any cupping or scalloping on the tire?
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JoeTChicopee
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« Reply #4 on: August 18, 2010, 05:08:19 AM »

Mine is more an up and down movement.  It happens all the time but does seem to be worse at times.  It seems worse at lower speeds and when I am at constant speed rather than when accelerating.  I am thinking a balancing or tire problem too because the faster you go, theoretically I don't think you would feel it as much.

I don't see any cupping or malformations on the tire but I am afraid I will get them if it keeps it up.  I only have 3400 miles on the scooter ( and the tires).
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JoeTChicopee
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« Reply #5 on: August 18, 2010, 05:12:09 AM »

Sorry to read of your difficulties.
Not technically able to answer your question other than say that it shouldn't bounce.
I would think it is more an issue of tire balance or a tire problem.  The tire may be slightly out of round.  Find a good tire place and see what they say.
The stock fork oil should be the correct weight so I don't think it is that.

I agree, the stock fork oil should be correct.  Maybe I should go to an independent motorcycle tire person, if there is such an animal.  Maybe the places who have been checking it have a vested interest in not getting too deep into it.  Now that it is not under warranty that shouldn't be a problem for them. 
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« Reply #6 on: August 18, 2010, 07:51:18 AM »

This is a wild shot, how tall are you? Are you tall enough you are riding way back on the scoot, maybe leaving the front end light? In any case have you tried moving forward to see if it stops the front end bounce? Have you installed an after market windshield or anything that might be trying to fly the front end?
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TechGuy
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« Reply #7 on: August 18, 2010, 08:42:34 PM »

I added DynaBeads to my tires as a way to calm the hopping I was getting from my SEVERELY cupped tires. I also had the shudder i was mentioning.  I added the beads and the up and down motion was drastically improved. They are heavy ceramic beads that move inside the tire in response to the balance of the tire.  The lead weights you add to the tire when it's new are correct that day but may not be as the tire wears. I found the $20 or I spend on beads was money well spent.  I still have the original ones and 2 extra ounces.

As to the hopping; I have found that different speeds are worse for hopping than others.  I think it's called "harmonics".  My bike hopped worst at 35 MPH and again at 70 MPH.
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JoeTChicopee
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« Reply #8 on: August 20, 2010, 06:15:11 AM »

This is a wild shot, how tall are you? Are you tall enough you are riding way back on the scoot, maybe leaving the front end light? In any case have you tried moving forward to see if it stops the front end bounce? Have you installed an after market windshield or anything that might be trying to fly the front end?

I'm 6'1".  I do ride as far back as the seat hump will let me.  I haven't moved forward but I can try that.  My scooter does have a windshield that came with it.  It is the windshield that you see on my avatar.  There is a top case that was added by the dealer when I bought it.

It doesn't seem so bad when I first start off but it seems to get worse the longer I ride it.  It causes me to wonder if the tires get heated up and the pressure gets higher as I ride.  I do not notice it as much when I am accelerating.  I even feel it when I am coasting down a hill.

Think I should try riding without the top case?
I do have four settings for the rear suspension and I have it set in the 3rd position which is next to the last for a stiffer suspension I think.  If I were trying to carry a rider, I would have in in the fourth postion.
Maybe I should try it in the first and second positions?

I guess I should start a list of all the suggestions and systematically try the process of elimination for them.
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JoeTChicopee
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« Reply #9 on: August 20, 2010, 06:18:15 AM »

I added DynaBeads to my tires as a way to calm the hopping I was getting from my SEVERELY cupped tires. I also had the shudder i was mentioning.  I added the beads and the up and down motion was drastically improved. They are heavy ceramic beads that move inside the tire in response to the balance of the tire.  The lead weights you add to the tire when it's new are correct that day but may not be as the tire wears. I found the $20 or I spend on beads was money well spent.  I still have the original ones and 2 extra ounces.

As to the hopping; I have found that different speeds are worse for hopping than others.  I think it's called "harmonics".  My bike hopped worst at 35 MPH and again at 70 MPH.

Don't know anything about the beads. How do you get them in the tire?  How do you know how many to use?  Is it trial and error.  Put some in try it, add more?
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« Reply #10 on: August 20, 2010, 06:36:33 AM »

I used DynaBeads in my SportCity which is known to have a bit of head shake. Also changed out the front tire to a Pirelli Diablo.
The Beads smoothed things out enough to recommend them. Most scoots will use between 1 -2 ozs.  here is a chart: http://www.innovativebalancing.com/chart.htm#MotorcycleChart    Very easy to install.
http://www.innovativebalancing.com/index.html

If it's really hopping, it sounds like the tire is out of round, as mentioned above. My only other suggestion would be (heavier) bar end weights. And have the fork/steering stem checked.
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JoeTChicopee
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« Reply #11 on: August 20, 2010, 03:02:44 PM »

I checked out the links to the dyna-beads.  Thanks very much.  If I have the fork/steering stem checked, what would they be looking for?  Leaking fluid, loose nuts.  I'm not that mechanical and I don't know what it looks like under that plastic so I am just curious.
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TechGuy
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« Reply #12 on: August 20, 2010, 08:28:27 PM »

As for the head shake that is mentioned in my post about my P250 and the SportCity,  and possibly your bike too in the future.  The common design element for these three bikes (and several other motorcycles) is that the front forks are closer being upright.  This is known as a rake angle.  These bikes all have a steep rake angle and a smallish trail (see image).  When you get a bike with a shallow rake and a longer trail you get a bike that is very stable at highway speeds but much harder to turn at low speeds. Your bike as well as mine have the steep angle/small rake that makes a bike more nimble in traffic but less stable.  This geometry is what I personally feel is the reason my bike and other similar bikes are prone to head shake.



The hopping, I think may also be made easier by the shallow rake. Tire pressure, tire selection (brand model) and wheel balance are the largest factors. 

In my shade-tree mechanic, scooter-riding experience, I would try the beads and see if they solve the problem for you.  They are cheap and non-permanent.
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JoeTChicopee
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« Reply #13 on: August 20, 2010, 09:57:27 PM »


In my shade-tree mechanic, scooter-riding experience, I would try the beads and see if they solve the problem for you.  They are cheap and non-permanent.

Sounds like a good idea.  Thanks for your input.  I am in favor of starting cheap before working up to more expensive solutions.  One more question.  Should I keep on the balancing weights that I have now and just add the beads or should I remove the balancing weights before adding the beads?
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JoeTChicopee
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« Reply #14 on: August 20, 2010, 10:03:27 PM »

Your diagram did not show in the post so I am including it here for anyone else who might be following this thread.

http://www.carbibles.com/images/bikegeometry.jpg

Thanks again.  I do have Pirelli's on my scooter so I am going to check which model I have.
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TechGuy
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« Reply #15 on: August 25, 2010, 12:13:15 AM »

I would try with them on first. Honestly though, the beads should adjust either way.
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JoeTChicopee
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« Reply #16 on: August 25, 2010, 01:51:55 AM »

Thanks for all your help.  I will try the dyna-beads.
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JoeTChicopee
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« Reply #17 on: September 30, 2010, 04:24:50 AM »

Fixed the front end bounce on the BV250 today.  Traded it in for a new 2009 Yamaha TMAX 500! :D

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« Reply #18 on: September 30, 2010, 10:26:09 PM »

Now there is an interesting fix Joe!  Congrats on the new TMax.
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« Reply #19 on: October 01, 2010, 01:52:58 AM »

You look like a happy guy in that picture!
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« Reply #20 on: October 01, 2010, 01:57:51 AM »

There is remove and replace parts and then there is REMOVE and REPLACE all parts.
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JoeTChicopee
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« Reply #21 on: October 01, 2010, 04:12:47 AM »

Now there is an interesting fix Joe!  Congrats on the new TMax.
THanks.  Unfortunately I can't afford to use that "repair" method too often!
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« Reply #22 on: October 01, 2010, 01:56:46 PM »

Now there is an interesting fix Joe!  Congrats on the new TMax.
THanks.  Unfortunately I can't afford to use that "repair" method too often!

This was an inspired solution! While I appreciate not affording such a solution too often, you selected a ride that should give very few, if any, problems for years to come. Congratulations!
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« Reply #23 on: October 05, 2010, 07:16:49 PM »

now the only thing bouncing up and down is diversions avatar
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JoeTChicopee
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« Reply #24 on: October 05, 2010, 10:52:30 PM »

As for the head shake that is mentioned in my post about my P250 and the SportCity,  and possibly your bike too in the future.  The common design element for these three bikes (and several other motorcycles) is that the front forks are closer being upright.  This is known as a rake angle.  These bikes all have a steep rake angle and a smallish trail (see image).  When you get a bike with a shallow rake and a longer trail you get a bike that is very stable at highway speeds but much harder to turn at low speeds. Your bike as well as mine have the steep angle/small rake that makes a bike more nimble in traffic but less stable.  This geometry is what I personally feel is the reason my bike and other similar bikes are prone to head shake.



The hopping, I think may also be made easier by the shallow rake. Tire pressure, tire selection (brand model) and wheel balance are the largest factors. 

In my shade-tree mechanic, scooter-riding experience, I would try the beads and see if they solve the problem for you.  They are cheap and non-permanent.


I think you may have been right about the cause of the problem.  The BV250 was very nimble in traffic.  I think it might be a design problem.  Also one that I did not want to live with. So far I am happy with the Yamaha TMAX.  It is certainly heavier which gives a better ride yet it also extends my range.  I wanted the ability to get on some major roads from time to time and now I think I can "safely" do that.
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JoeTChicopee
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« Reply #25 on: October 05, 2010, 10:53:52 PM »

now the only thing bouncing up and down is diversions avatar

I'm not sure I've seen diversion's avatar but I may have seen one like it.  Is it a Honda?
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JoeTChicopee
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« Reply #26 on: October 05, 2010, 10:56:26 PM »

Yep, it/they are Hondas! 
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TechGuy
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« Reply #27 on: October 06, 2010, 09:43:22 PM »

Funny, I am going to guess your solution cost a tad more than the $20 DynaBeads I suggested... 


Enjoy the new ride!
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