Highway speed terror!! - Page 5 - Kawasaki KLR 650 Forum
KLR & Other Motorcycle Related Discussion Grab a seat and discuss whatever you like about the KLR or other related topics. Within reason.

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post #41 of 63 Old 05-27-2018, 12:34 PM
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I've never been able to tell or appreciate the differences in aftermarket fenders. This is the Cycra Supermoto fender that I use.


I've been running a low-mount UFO superbike fender for the past year, though, as it has worked better in the wet and I haven't been on much more than gravel roads for a while.
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post #42 of 63 Old 05-27-2018, 12:58 PM
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I worded that poorly; the polisport has a much smaller cross section than the stock fender.....my dislike of the supermoto and low mounted options is mostly just looks though the supermoto isn't great in the mud from most reports. The supermoto doesn't look as bad on a Gen2 vs. the Gen1 IMO.

Dave
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post #43 of 63 Old 05-27-2018, 05:23 PM
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I am not sure why you guys have such a hard time believing the problem is the fender or what else you could really think it was. The symptom follows air speed and not ground speed and cannot be replicated with the front fender removed. With the front fender on and in no wind, the steering wobble starts right around 75mph. With a 10mph tail wind, the problem doesn't happen between 75mph and 85mph. With a 10mph head wind, the problem happens around 65mph. The symptom is sporadic and sometimes much more serious in less predictable wind situations with choppy and/or cross winds.

Those behaviors have been consistent since I bought the bike despite any other changes over time. I've run two very different sets of tires (Kenda K671's & Continental TKC 80's), each balanced when installed, with absolutely no change in symptom. I've been aired up and aired down with absolutely no change in symptom. I've run solo and with 50lbs of gear all without a change in symptom. I've stayed upright and have tucked myself down below the air stream with no change in symptom. The bike is rock solid, stable, and surprisingly smooth right up until the bike hits something around that 75mph air speed mark.

At a minimum, that all seems to indicate to me that the problem is with aerodynamics and not something mechanical. The stock fender is a large and somewhat flexible motocross style fender mounted up high where it would absolutely take a lot of wind. So, it certainly seems plausible that it's the cause of the wobble and that seems pretty obviously confirmed by the fact that I cannot recreate the symptom without the fender installed. I like the look of the stock front fender and generally keep my motorcycles pretty close to factory stock anyway, but not if it is something that impacts handling/safety.

If you guys have something concrete to suggest or offer that I haven't already checked or tested, I'm certainly interested. I've been browsing this and other forums though and it seems like a large percentage of otherwise happy KLR owners have experienced this and narrowed the culprit down to the front fender as well. So, for those of us trying to address the problem, this seems like a safe and relatively affordable/manageable fix.
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post #44 of 63 Old 05-27-2018, 05:25 PM
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Thanks for posting that picture of the Cycra Supermoto on your modern KLR! That helped me make the decision to pick one up myself. I think it looks great, pretty close to stock, and is worth a try.

What brush guards are those?
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post #45 of 63 Old 05-27-2018, 05:50 PM
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Back To The Drawing Board

Well... I finally found this gem from another member and am now rethinking the whole thing.

@DPelletier... I found an older comment of yours where you provided more insights with detail and found that to be informative.

I have to wait a while for the smaller front fender to arrive. So, I guess I'll put the factory one back on and start playing with things again. I really have no idea what's causing this though. I've been riding for over twenty years now and have never had a persistent recurring symptom like this that I couldn't pin down.

Back to the drawing board!

Last edited by Tom Schmitz; 05-27-2018 at 08:16 PM.
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post #46 of 63 Old 05-27-2018, 08:09 PM
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Quote:
Originally Posted by consipio View Post
I am not sure why you guys have such a hard time believing the problem is the fender...
I'm not trying to be a smartass. I've been riding since "Wobble and Weave" was a newish film. The KLR has been my bike of choice for the past 10 or 11 years. I have ridden it, in completely stock form and in a completely 'transformed' form with the stock fender at 90ish mph for hours on end. I know the before and after* characteristics of the suspension, and I know the effects of where I put the weight, what tires I run, and what pressures I run in those tires. Truth be told, I swapped out the OEM front fender because it was unattractive, not because of instability. With good suspension, weight distribution, tires, and pressures, my bike practically steers itself in heavy winds, especially crosswinds. It's like a good horse where you just give it its nose and let it run. It's just a case of 'been there, done that, got the T-shirt'.

Neither Dave nor I are trying to be argumentative, honest. And I, for one, have no issue with someone swapping out a fender to solve an instability problem. If it gets the job done, all well and good.

Over the years I have found that the root cause of instability usually lies in not enough weight forward, crap front wheel damping such that the front wheel undulates in its pressure on the road, in the case of the tall, skinny, 90/90-21, not enough pressure causing too much deformation, and tires that just don't track for beans sometimes.

My brush guards are HDB - Highway Dirt Bike. https://www.highwaydirtbikes.com/ind...ow&ref=HDB-100



*My suspension consists of a Cogent shock built to accommodate my size and riding style, including a 1" lift, Gen 1 linkage for a bit more lift and travel, uprated springs in the front, preload adjusters for fine tuning the front springs, and RaceTech emulators. Weight distribution has included a Molle tank cover to move a fair amount of weight forward, carrying heavy things low and forward in hard cases. Tires are almost always Kenda K761 with the front mounted backward with inflation at 36psi F/34 psi R.
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The kid poured him another straight rye and I think he doctored it with water down behind the bar because when he came up with it he looked as guilty as if he'd kicked his grandmother. -Philip Marlowe

'Why' and 'How' are words so important they cannot be too often used. -Napoleon Bonaparte

Sting like a butterfly.
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Last edited by Tom Schmitz; 05-27-2018 at 08:13 PM.
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post #47 of 63 Old 05-27-2018, 09:20 PM
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I guess it only felt argumentative because I've been at a loss trying to solve this so my frustration is sort of high going in, but I appreciate the clarification and would dig the advice if I felt like I could do anything useful with it. I went over the bike again earlier today and just set my tire pressures to 26 in the front and 32 in the rear after finding a document from Continental showing that recommendation for TKC80's on the KLR, but the wobble symptom remains unchanged with the front fender installed.

It's definitely possible my suspension is not tuned exactly right, but my sag in the rear should be right around 3.25", it doesn't seem stiff in the rear but it doesn't bottom out either, and the bike doesn't feel like it's trying to buck me when off road. I haven't checked the sag in the front, but understand all of that to be more of a chore on the KLR because they don't have adjustments. I can try to check the sag up front, but am not sure how to adjust anything up there without looking in to the spacers I've read about and maybe different shock oil.

I have the feeling my frustration at this point is due mostly to my lack of knowledge and experience with the KLR or even bikes like it more than anything else, but solving that over the Internet isn't exactly easy.

Cheers!
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post #48 of 63 Old 05-27-2018, 09:46 PM
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Hey, if installing a different fender makes the problem go away for your usage, do it, be happy, and move on!

There's no reason to fix everything to perfection. Might come the day when you want to improve the KLR's capabilities off-road. That's the time to dig into the suspension because there is no band-aid for suspension that sucks off-road. What got me to modifying the KLR's suspension was really that I couldn't ride on washboard roads at much over 15mph without the suspension packing up*. I also couldn't ride smoothly over really rough terrain at any speed. Its on-road behavior was acceptable.

Pretty much got that sorted and a side benefit is that the on-road manners are that much better.


*Packing up - the suspension can not rebound from repeated hits that compress the suspension, so the bike just sits down on its springs and stays there.

Tom [email protected]

The kid poured him another straight rye and I think he doctored it with water down behind the bar because when he came up with it he looked as guilty as if he'd kicked his grandmother. -Philip Marlowe

'Why' and 'How' are words so important they cannot be too often used. -Napoleon Bonaparte

Sting like a butterfly.
Noli Timere Messorem
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post #49 of 63 Old 05-28-2018, 11:08 AM
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Quote:
Originally Posted by consipio View Post
I guess it only felt argumentative because I've been at a loss trying to solve this so my frustration is sort of high going in, but I appreciate the clarification and would dig the advice if I felt like I could do anything useful with it. I went over the bike again earlier today and just set my tire pressures to 26 in the front and 32 in the rear after finding a document from Continental showing that recommendation for TKC80's on the KLR, but the wobble symptom remains unchanged with the front fender installed.

It's definitely possible my suspension is not tuned exactly right, but my sag in the rear should be right around 3.25", it doesn't seem stiff in the rear but it doesn't bottom out either, and the bike doesn't feel like it's trying to buck me when off road. I haven't checked the sag in the front, but understand all of that to be more of a chore on the KLR because they don't have adjustments. I can try to check the sag up front, but am not sure how to adjust anything up there without looking in to the spacers I've read about and maybe different shock oil.

I have the feeling my frustration at this point is due mostly to my lack of knowledge and experience with the KLR or even bikes like it more than anything else, but solving that over the Internet isn't exactly easy.

Cheers!
I too have no problem with the fender swap if it works for you; I simply remain convinced (I've been riding and racing since 1975) that the fender isn't the root/cause of any instability, though I will concede that it can be the "last straw" that allows instability to manifest and therefore removing/replacing it can help.

A couple other thoughts;

- tire pressures; anything under 30psi may not be enough for sustained high speed use IMO. and, in addition, there is zero reason to run less tire pressure in the front unless you are loaded 2 up or have panniers loaded equally heavy. Even with the same pressure, the rear tire has more load carrying ability simply due to the increased size/air volume. I know what the manuals and manufacturer's say but that is usually to allow for varying loads. All that said, my highway use is limited and I'm lazy so I leave mine at 22-24 front and 20-22 rear and mine are very stable.

- suspension; I believe that Tom's observation that the front fork dampening is a big contributer to instability is very likely true. The entire KLR suspension system leaves a lot to be desired but there are relatively cheap "fixes" that will help. Also like Tom, I run Cogent shocks as well as Cogent DDC's and springs in both my KLR's......they were both rock solid after the suspension upgrades with the stock fenders, large handguards, etc. I believe you have a Gen2? ....not sure what year but 3.25" of sag is way too much IMO; Gen2 rear suspension has 7.3" of travel and the very generic rule of thumb of 33% sag would be 2.4" though with the short Gen2 travel, I like to keep it around 2 - 2.25" (28% - 31%). I have a ton of suspension information so if you are interested in discussing suspension in more detail, just let me know.

Cheers,
Dave
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post #50 of 63 Old 05-29-2018, 10:21 AM
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Quote:
Originally Posted by consipio View Post
I am not sure why you guys have such a hard time believing the problem is the fender or what else you could really think it was. The symptom follows air speed and not ground speed and cannot be replicated with the front fender removed. With the front fender on and in no wind, the steering wobble starts right around 75mph. With a 10mph tail wind, the problem doesn't happen between 75mph and 85mph. With a 10mph head wind, the problem happens around 65mph. The symptom is sporadic and sometimes much more serious in less predictable wind situations with choppy and/or cross winds.

Those behaviors have been consistent since I bought the bike despite any other changes over time. I've run two very different sets of tires (Kenda K671's & Continental TKC 80's), each balanced when installed, with absolutely no change in symptom. I've been aired up and aired down with absolutely no change in symptom. I've run solo and with 50lbs of gear all without a change in symptom. I've stayed upright and have tucked myself down below the air stream with no change in symptom. The bike is rock solid, stable, and surprisingly smooth right up until the bike hits something around that 75mph air speed mark.

At a minimum, that all seems to indicate to me that the problem is with aerodynamics and not something mechanical. The stock fender is a large and somewhat flexible motocross style fender mounted up high where it would absolutely take a lot of wind. So, it certainly seems plausible that it's the cause of the wobble and that seems pretty obviously confirmed by the fact that I cannot recreate the symptom without the fender installed. I like the look of the stock front fender and generally keep my motorcycles pretty close to factory stock anyway, but not if it is something that impacts handling/safety.

If you guys have something concrete to suggest or offer that I haven't already checked or tested, I'm certainly interested. I've been browsing this and other forums though and it seems like a large percentage of otherwise happy KLR owners have experienced this and narrowed the culprit down to the front fender as well. So, for those of us trying to address the problem, this seems like a safe and relatively affordable/manageable fix.
Did you put a windshield on yet?
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