KymcoForum.com
Scooters - 125 to 300 => Downtown 300 => Topic started by: Going Downtown on February 27, 2015, 12:58:14 AM
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I have a new downtown with only 400 miles on it and experienced a front end wobble that scared the hell out of me. Has anyone ever experienced that or can tell me why? The tire pressure was fine, front end wasnt hit or any damage to it, like I said new scoot. Both times it happened I was going into a turn. Anyone know what it could be? Thanks
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A VERY bad out of balance tire can cause that, or an out-of round/out of shape tire.
Balancing has gone to the wayside with Kymco, I got a low miles GrandVista and it had NO balance on the front tire, and was horribly out of balance.
e.g: A tire that has a a heavier and inconsistent tire weight for example right side compared to the left side (would be a tire manufacturing defect) can be perfectly balanced, but this causes a severe wobble.
Other: A (loose) steering head bearing with too much play or a manufacturing defect will cause the same.
No matter what, I would bring that scooter back (I assume you bought from a dealer) and tell them "TOTALLY UNACCEPTABLE" and THEY need to figure it out ASAP, or you want your money back..! "This is UNSAFE and a danger to yourself and others"; any judge will be on your side. Be firm with them, they need to get that immediately fixed!
PS: See that you can set a "benchmark" for speed and wobble on a road that you can easily get to,and then compare "before and after" rerpairs
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Wouldn't it do it more consistantly if it was a problem with the bike? Could it be I was fighting the counter steering? New rider here.
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You could try firming the rear shocks,ie put on higher number ,i have read that this also firms up the front suspension
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Was it with one or no hands?
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I have a new downtown with only 400 miles on it and experienced a front end wobble that scared the hell out of me. Has anyone ever experienced that or can tell me why? The tire pressure was fine, front end wasnt hit or any damage to it, like I said new scoot. Both times it happened I was going into a turn. Anyone know what it could be? Thanks
To make sure we have no misunderstanding, you are saying you had a "handle bar shake" when you talk about the front end wobble? Right?
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Yes the handle bars shake. Both hands are on the handle bars.
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Yes the handle bars shake. Both hands are on the handle bars.
If your tire pressure is 35-38psi then you should have ZERO shake, no matter what. There is nothing YOU can do wrong. There is something seriously out of whack on the front of your D/T! Go to your dealer and "complain with DEMAND!" They better fix that! Don't wait. It could end up for you known in motorcycle riding as a "tank slapper". Look it up... not pretty!
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Dunno if in the US its also called the same, but here in europe we call this shimmy :) As to the topic. If it happens when u have hands on the handlebar and u really can feel it its really strange and should not be disregarded. For example, when u put your hands off, this tends to happen at certain speeds - it depends on the tires you have. For example, on my oem kenda tires i used to observe shimmy between 40-60 kmh when i let the handle go and it was increasing the longer i had my hands away. After I changed the tires to dunlops, i observe no shimmy anymore.
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That is correct what ktienation said or observed.
Balancing a motorcycle tire is a difficult task when the left of the tire is e.g heavier at one spot than the right. That's "torque values" that cause the wobble.
You can balance a WHEEL (=tire + rim) perfectly as a "static balance", but still have a strong wobble on the handlebar at a hands-off speed due to the "dynamic forces" of an uneven weight left to right of the tire or wheel. ONLY a properly set up electronic balancer at a motorcycle shop can correct this, but 90% the personnel does not understand the whole thing technicality and does not do a proper "dynamic balance".
The replacement of the tire and using a more true brand (as our friend above here did) is then usually the solution they default to...
(PS: it is not the only solution, as I explained... but most shops don't have either the equipment, or the "brains" to balance a motorcycle wheel 100% properly. And sometimes, with too much weight off [left to right], it is practically not possible to correct as this are narrow rims when compared to a car rim.)
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I have a new downtown with only 400 miles on it and experienced a front end wobble that scared the hell out of me. ...
Not good. My 2005 GV250 will wobble IF I take my hands off the handle bars but it has never done what you describe. Check for loose bolts .
Use the "Axle Test". - put scoot on center stand and loosen and remove the front axle - be careful not to loose the spacers. Use a digital camera to record how all the pieces go together. IF the axle is difficult to remove / reinstall then the fork tubes are out of alignment. On many scooters there is not easy to adjust or shim them but at least you know where the problem is. My front tire - Avon viper strike is scalloped "cupped" do to mileage ~ 7,700 miles and my scoot still doesn't do what you described.
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Not good. My 2005 GV250 will wobble IF I take my hands off the handle bars but it has never done what you describe. Check for loose bolts .
Use the "Axle Test". - put scoot on center stand and loosen and remove the front axle - be careful not to loose the spacers. Use a digital camera to record how all the pieces go together. IF the axle is difficult to remove / reinstall then the fork tubes are out of alignment. On many scooters there is not easy to adjust or shim them but at least you know where the problem is. My front tire - Avon viper strike is scalloped "cupped" do to mileage ~ 7,700 miles and my scoot still doesn't do what you described.
(I have a scalloped 8000 mile rear Michelin City Grip - was told it is due to underinflation (nope, always check them ) and/or too much weight (HEY!!)
Still plenty of good deep tread grooves - works fine in the dry & the wet.
Stig)
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(I have a scalloped 8000 mile rear Michelin City Grip - was told it is due to underinflation (nope, always check them ) and/or too much weight (HEY!!)
Still plenty of good deep tread grooves - works fine in the dry & the wet.
Stig)
Good Stuff Stig,
Totally agree about the under inflation. I check my tires regularly. Regarding weight - I don't believe that either because I only weigh 170 lbs and on my factory tires I had a girl that I was seeing on the back many times - and she wasn't exactly small.
The original factory tires Brand? Scalloped only very slightly in the rear. The Avon Viper Stryke much more so especially in the front and at lower mileage. Glad you recommend Michelin because that is what I ordered from the motorcycle SuperStore. Because my scooter lacks the power and handling of a performance motorcycle I feel like the tires have only a limited effect. I'm mainly interested in miles and general durability / low maintenance. I think the Avon is fine for most people because many people relegate their scoot to a novelty or toy and will never put many miles on it. For me I use it like a car as much as possible.
Michelin Pilot Power Pure SC Rear Tire
Color- Black, Size- 140/70-12
SKU#401636 Shipped $49.99 1
50
$49.99
Michelin City Grip Front Tire
Color- Black, Size- 120/70-12
SKU#256814 Shipped $48.99 1
49
$48.99
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Good Stuff Stig,
Totally agree about the under inflation. I check my tires regularly. Regarding weight - I don't believe that either because I only weigh 170 lbs and on my factory tires I had a girl that I was seeing on the back many times - and she wasn't exactly small.
The original factory tires Brand? Scalloped only very slightly in the rear. The Avon Viper Stryke much more so especially in the front and at lower mileage. Glad you recommend Michelin because that is what I ordered from the motorcycle SuperStore. Because my scooter lacks the power and handling of a performance motorcycle I feel like the tires have only a limited effect. I'm mainly interested in miles and general durability / low maintenance. I think the Avon is fine for most people because many people relegate their scoot to a novelty or toy and will never put many miles on it. For me I use it like a car as much as possible.
Michelin Pilot Power Pure SC Rear Tire
Color- Black, Size- 140/70-12
SKU#401636 Shipped $49.99 1
50
$49.99
Michelin City Grip Front Tire
Color- Black, Size- 120/70-12
SKU#256814 Shipped $48.99 1
49
$48.99
Yep, any time I can get a pair of Michelins for around $100 I'm on it like white on rice.
I've read a couple of articles by motorcycle guys who say that that scalloping is not unusual.....to just keep riding as long as there is good groove depth.
I had the stock Kendas taken off at 400 miles -- 8000 on the City Grips so far on my daily commuter.
Stig
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Yep, any time I can get a pair of Michelins for around $100 I'm on it like white on rice.....
Stig
Motorcycle SuperStore has good prices and super fast free shipping.
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It amazes me how tire threads and "oil threads" are similar: Never ending personal "opinions".
I agree that the Michelin tires are "quite good" (but, NOT perfect at all either), and I disagree that the Kenda tires are that bad to have to be taken off after 400 miles. That's "personal preference", not more.
I went with all my motorcycles and scooters through about 200 tires so far, 65% of that are rear tires, 35% front.
I had only two tires that I absolutely hated, or, did a very lousey performance (wear), and I am not naming the brands, because it was apparently a "screwed up model", or production run of a tire they produced. Actually one manufacturer gave me a FREE new "other tire", (different model) and it was fine.
So, do not be totally discouraged by lower price in regards to grip, however "usually" the more expensive tires do have less issues with "wobble" as they are more precisely manufactured (not only top to bottom = "static balance", but also side-to-side evenness = dynamic balance = related to handlebar shake, exactly what we are discussing here. Right?!
So, leaving all personal "Opinions" behind, IF your local scooter/motorcycle shop has an electronic balancer where they see the "dynamic values" and also can correct them, then you should work with them all the way through rather than buying "cheap" some grey market second/third quality tire on-line.... You (can quite often) get what you payed for, good or bad... either way.
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It amazes me how tire threads and "oil threads" are similar: Never ending personal "opinions".
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I had no problem with the original OEM Kenda tires except the common cracking in the side wall after 6 years and 2600 miles. I rode with the cracks and ran the tires up to 8000 miles then replaced them. Even though I bought my last and new set of tires online they are quality brands - Avon & Michelin. Regarding the shaking handle bars - it's not the balance or tires as both the Kenda and Avons did / do the exact same thing at the same speeds regardless of miles. The Avons were installed and balance by my local dealer at a cost of $98 just to mount / dismount and spin balance. I removed and reinstalled the tires from the scooter myself. Most local shops in SD don't give any discount for buying the tires from them and don't stock my rear tire size. Over the years I've seen increasing shoddy work by dealers and bizarre polices - for my BMW we can't install the tires you just bought from us because we don't sell bmw. Why didn't anyone tell me that before I bought the tires? AND you sold and installed the tires that I'm currently replacing! They recanted and agreed to install them. When I install these Michelin's I might just get the front balanced.
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I for my BMW we can't install the tires you just bought from us because we don't sell bmw. Why didn't anyone tell me that before I bought the tires? AND you sold and installed the tires that I'm currently replacing! They recanted and agreed to install them. When I install these Michelin's I might just get the front balanced.
Mrbios, this seems to be quite a lousy dealer how he treated you, but we have good and bad ones in the country, so, it is fortunately not the standard. Most good dealers would not do that to a customer what you experienced.
I understand wheels and tires very well due to my business background. There are unfortunately only very few shops (motorcycle) that do understand how to counter "steering wobble" on the electronic balancer. A static balancer can not do this, it can ONLY give a regular balance, which does not address the wobble problem. The wobble has often to do with the tire construction itself and then the final dynamic balance, if you want to do the best to remove a handle bar wobble. Some can not be resolved, and for example Kawasaki installed steering dampers to resolve this problem already on their 70's motorcycles, and steering dampers are common on many brand name sport bikes today.
Some motorcycles/scooters have much less issues than others, depends on rake and general front-end geometry; and then there is the possibility of "wear" of the steering head bearing that is another factor with aging bikes.
Summary: A good quality front tire "helps to minimize" the problem in the first place, but it is not the only solution to a wobble problem; it's many factors, as described above.
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It amazes me how tire threads and "oil threads" are similar: Never ending personal "opinions".
H e l l o !
Please include: "valve lash checks - hot or cold engine - mandatory or waste of time & $$!. Breaking in the new engine - trash it or baby it. Gasoline octanes. Service intervals. Kevlar vs stock belts. Sliders vs rollers." etc., etc.
When you're new to scootering - and wanting to take good care of your new scooter - forums can be crazy making.
The certified Honda tech who made a house call to my scooter had some amusing thoughts on forum experts.
I smile when I read the remarks from 2-wheel mag columnists regarding bike & scoot 'forums' .
"D o n o h a r m."
trying to live that - Stig
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H e l l o !
Please include: "valve lash checks - hot or cold engine - mandatory or waste of time & $$!. Breaking in the new engine - trash it or baby it. Gasoline octanes. Service intervals. Kevlar vs stock belts. Sliders vs rollers." etc., etc.
When you're new to scootering - and wanting to take good care of your new scooter - forums can be crazy making.
The certified Honda tech who made a house call to my scooter had some amusing thoughts on forum experts.
I smile when I read the remarks from 2-wheel mag columnists regarding bike & scoot 'forums' .
"D o n o h a r m."
trying to live that - Stig
Hey, this is America and we're still entitled to our opinions!!!!!
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H e l l o !
Please include: "valve lash checks - hot or cold engine - mandatory or waste of time & $$!. Breaking in the new engine - trash it or baby it. Gasoline octanes. Service intervals. Kevlar vs stock belts. Sliders vs rollers." etc., etc.
When you're new to scootering - and wanting to take good care of your new scooter - forums can be crazy making.
"D o n o h a r m."
trying to live that - Stig
Stig, you raise very good points and I think there is a distinct difference between solutions or products that work and make a real difference and opinions. To me style, colors etc are matters of opinion while the trade off between a soft grippy tires at the expensive of high miles falls into the fact vs opinion category. Fact: tire pressure. Run low - get a softer ride probably at the expense of gas mileage and tread life. Is that and acceptable trade off? That's a matter of opinion and personal goals.
Regarding your list:
Weights flat vs roller: I couldn't tell much of a difference and I'm hoping flat will last longer. I made the switch around 10K miles to heavier weights to cut rpm's at the expense of acceleration off the line. At 10K miles my rollers still seemed to work ok and I don't know how many scooter riders in the US will ever ride more than 10K but I do so I lean toward almost any solution that keeps maintenance low. If I want more power I'll buy a sport bike motorcycle.
Valves:
I've always read cold. Waste of money? Yes if the mechanic isn't acutally doing anything. No if he is really checking and putting them back in spec.
Mandatory? Usually not. In college my 1981 yamaha 650 special was supposed to be checked ever 2500? miles. I bought it used in 1988? with 14K miles on it no knowing if it ever had been checked. at around 25K miles the exhaust valve stuck open and the motor had almost no power. I brought it to a near by ducati dealer and they adjusted it for ~ $30 ($65 inflation adjusted). It was the screw type like on our scoots and had simple caps for direct access. That fixed the problem. I sold the bike a few years later for parts after a crash with a car at around 40K miles. Most scooters in the use will never see more that 7K miles? I adjusted my Kymco at 10K and it is running great with 16K on the clock. Will probably check valves next around 18K. Same with my 1992 bmw k75 (sold in 2009 with 64K miles still running good). I had the dealer adjust and was maybe 20K over the check them interval. Dealer said no problem and said usually intake is fine and exhaust tends to tighten which makes them quieter not louder so ticking is not always a good indicator.
My 1997 Saturn SW2 (original owner). Hydraulic valve lash adjusters (no adjustment needed). Last year I got the head planed to replace the head gasket. Machine shop said valves worn less than 10% from original spec and did not recommend a valve job. Timing chain adjuster show 30% wear with 160K miles. I have always used generic walmart type oil and change it ever 3K miles and monitor / top off between oil changes. No doubt synthetic would have reduced the wear but at almost 19 years and the Saturn brand discontinued how much longer does it need to last? Motor still starts and runs the same as when it was new.
Kevlar vs stock belts:
I've been happy with the first and second stock belt. I changed it eary at 10K out of "fear" of it breaking even though it appeared to be very good condition and tested well with in speck for width. I'm mad about paying $85 at the dealer when I could have got an aftermarket Kevlar or otherwise for $50. Next belt will be aftermarket. Again, how many people are ever going to exceed 12K? miles when the belt may be worn enough to replace.
Gasoline Octane:
Here I'm gonna sound like hypocrite. You know I don't hesitate to flaunt the maintenance schedule by going 2, 3 or even 4x beyond the recommended interval but with gas I believe super reduces denotation and might matter over the long haul. The scooter takes so little gas I see the cost difference as minor. I would not shame anyone for running regular especially because most scooter / motorcycle owners in the US prefer their ride parked in the garage (with un-stabilized gas slowly jelling the fuel system) so in most cases what difference does it make.
Oil: 15w40 @ 1200 miles - I believe it matters (IF you plan to put over 20K miles on your scoot). AND check the level. Our scoots only take about 1 qt and it can get low by a few oz after about 400? miles. Never waste money on synthetic - unless you simply enjoy using top quality oil.
Final note: I ride fast but I don't abuse the clutch /belt etc by revving the engine on a hill at a red light. I take off smooth get full clutch engagement then apply the gas, sometimes to full throttle. Highway - 80 to 100% to maintain 72 mph to keep with traffic.
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My opinion is that this thread is gonna get NASTY!!!!