2002 Magna Fork Resonances

[WC]

Hi. My Magna fork (s) resonate at 65mph over bumps, but not smooth roads. .......Worse after warmup. The resonance can last for 3 seconds. I have checked the bike thoroughly, bolts & looseness, tapping with fists & mallets- nothing. The resonance is always in sync with the bumps. The dealer tells me that the bike was lowered. I tried changing to 15 wt. oil- no go. Any ideas? Thanks.

[lragan]

When I replaced my front fork springs with Progressive springs, it stopped the nose dive when I brake hard, and generally gave the bike a more solid "feel", and better turning performance, even as it made it ride a bit rougher over bumps and cattle guards.  Another thing it did was cause the steering to be slightly underdamped.  When I pass a car, for example, on the Texas roads, the center stripe is raised a bit, so the path of the bike is disturbed slightly crossing this stripe.  The bike corrects, as all do, depending on rake, balance, etc, but it over-corrects slightly, and I can feel it "wobble" for about three cycles.

To my knowledge, no others on the forum who have switched to Progressive springs have reported this effect.  Maybe I need a bit heavier oil, less preload, less weight in my ample posterior, whatever, I don't know.  When I first noticed it, I was somewhat perturbed, but now I just ignore it.  It seems worse at higher speeds, but I seldom ride at speeds in excess of 65 mph, so am not sure if it is more pronounced at higher speeds, or less...

In any case, I recently purchased another '96 for out of town friends to ride with me.  It is not as stiff on the front springs as my "main" (Old Blue) bike, yet seems to me to have acceptable "dive response" on hard braking, so I suspect the springs have been changed on it as well.  I have not noticed the underdamping effect on this second bike, but I may be so used to it that I routinely ignore it.  I will try to get a chance to ride it in the next few days, will test to see how it performs, and report back here.

[hootmon]

WC - welcome from Safety Harbor, Floriduh...

I don't have any suggestions for you.. Sorry.. Someone will come up with something, which may be just some more questions to better understand your issue..

where are you from??

[WC]

Thanks for the feedback. I'm located here in Daytona Beach, Florida.

[hootmon]

Cool.. We will have to hook up sometime..

[Charles S Otwell]

When you changed oil did you check the old oil for metallic particles, and did you pull the springs and spacers out and check them? I wanted a little stiffer suspension so I replaced the stock spacer with the PVC and added about an inch (couldn't afford progressive springs) very pleased with the results. PVC is cheap you might try changing yours just to see if it makes a difference, before investing in progressives.

[Sledge Hammer]

Hi. My Magna fork (s) resonate at 65mph over bumps, but not smooth roads. .......Worse after warmup. The resonance can last for 3 seconds. I have checked the bike thoroughly, bolts & looseness, tapping with fists & mallets- nothing. The resonance is always in sync with the bumps. The dealer tells me that the bike was lowered. I tried changing to 15 wt. oil- no go. Any ideas? Thanks.

By "resonate" I take it you mean the bar ends waggle form side to side. Everything I can find on the subject points out that lowering the front suspension reduces the trail measurement, effectively quickening the steering, but reducing stability in the process. Great up to a point, horrible when it leads to a violent tankslapper such this one http://www.youtube.com/watch?v=XiKmPFo6xNA&feature=player_profilepage. I'm no mechanical expert, but if the bars are bouncing back and forth for several seconds, my advice would be to STOP RIDING IT UNTIL IT IS FIXED. There is no guarantee that you won't encounter conditions serious enough to make it oscillate long enough, fast enough, and violently enough to cause you to crash. First and foremost, I would bring the ride height back into specification. I had to do that with mine when I bought it, and while it still isn't perfect, it isn't as scary to ride as it was when I test rode it.

[Sledge Hammer]

Well, I did wind up putting my money where my mouth is. I just picke dup my bike after letting MSP Cycles in Decatur work on it. Rod was able to rule out tweaked fork tubes but noted that with the wheels properly aligned that adjuster marks were off by about 3/4 of a mark and that there is about 1 mm difference in length of exposed thread on the adjuster screws. I also wound up getting a new front tire since the previous one was dry rotting, doubtless some new old-stock item the dealership's distributor had lying around. Anyway, slick new tire notwithstanding, the bike feels more neutral now. I still have some visual cues of being leaned a little to port when I'm going straight, but my wife -- who was following behind me on the freeway -- said she could not detect any leaning, so I think I am picking visual reference points. Also have fresh fork oil.

By the way, last weekend when I dropped it off, what should I see but...



Don't know who the owner is but maybe she visits this board and will recognize her bike. For me, it's the first time I have encountered another 3rd Generation Magna while out and about on my own.

[Greg Cothern]

Remember that the handlebars are mounted in rubber bushings through the triple tree.  Straddle the bike, have someone hold the front wheel between their legs, such as you did as a kid, and counter twist the bars and to make sure its not slightly tweaked to one side.  THIS is very common and can be adjusted either way easily.

Tires in my experience has been the culprit majority of the time folks have said the bike has a shimmy, wander, etc.

[Sledge Hammer]

Remember that the handlebars are mounted in rubber bushings through the triple tree.  Straddle the bike, have someone hold the front wheel between their legs, such as you did as a kid, and counter twist the bars and to make sure its not slightly tweaked to one side.  THIS is very common and can be adjusted either way easily.

Tires in my experience has been the culprit majority of the time folks have said the bike has a shimmy, wander, etc.

Only resurrecting this thread to serve as reference material for anybody else who experiences similar issues.

It turns out my bike really did have some alignment problems. Last month, I took it down to essentially a rolling frame with motor.



I sent it off to GMD Computrack in Jasper, GA, for an assessment of its alignment. Here is the report:



Note the offset of the front wheel with respect to the back. Built-in countersteering to the right, and doubtless why I got the bike so cheap. Other prospective buyers must have picked up on it and took a pass.

The assessment cost me $100 (on sale). The question then was whether to spend $500 to $1000 to address the issue or to put that money toward another bike, even a new one. After spending a weekend with the wife's blessing looking at all sorts of new and used bikes, I cam very close to pulling the trigger on a DL650 or a Versys and even was ready to make an offer on a Blackbird. But none of them lit my jets enough to make me willing to just give up on my Magna. Oh, and did any of you notice that we haven't had a recession, after all? At least, not one you could tell from what dealers and individuals were asking and getting for their bikes. In the end, I could not see that the potentially $1300 saved by not doing the work, when added to the sale of my Magna, would buy anything that would make me want to replace it. I have also come to appreciate a little pearl of wisdom that goes something like "It's cooler to have an okay bike that's paid off than a really cool bike on which you still owe somebody lots of money."

Anyway, I told Kent at Computrack to go ahead with the correction. Counting the transportation cost ($100 round-trip for transportation, not too bad since his tech was using his personal truck to provide the transportation and it ain't a short drive), Kent estimated originally $150 for assessment and $700-800 for the corrective actions, and I factored in $150-250 for replace-with-new hardware.

In taking it apart further than I had, Kent's technician found that the driveway tumble(s) by the previous owner along with my own might have tweaked the lower triple clamps, but they were still within specification. There was no evidence that the bike had ever been in a real wreck. In fact, every individual component was still within factory specification, but the deviations from nominal all added up to reinforce one another. The swing arm contributed, as did the triple clamp, and the frame. Ironically, the fork tubes did not need any straightening. The price tag for the adjustments came to $500.

Last weekend, I finished putting it all back together, which -- believe it or not -- was a lot easier than taking it apart. I replaced some rusted fasteners on the exhaust system, replaced the crushable gaskets for the exhaust headers, replaced the air filter, cleaned out the tank and replaced the fuel strainer, all of which set me back another $170 with shipping, ordering on-line from Babbitt's.

The verdict? Best $870 I have yet spent on the bike. It is now totally neutral in handling and is perfectly vertical on the level straightaways. It feels like a different machine, being much more composed in corners than it was before. With less than 8000 miles on the odometer, I now have a bike with which I can probably keep myself entertained for another 5 years.

[lragan]

WOW!

Great report, Mike.

When in this unaligned state, did you notice unusual tire wear?  Patterns, asymmetry, whatever?

I have two '96 models, and except for the occasional handle bar realignment that Greg references, have not noticed anything untoward in the riding.  I hope I would know if they were messed up, but am not really sure.

[TLRam1]

Great report Mike, thanks for being persistence, taking the time to do this and sharing with us.

How did you come to find someone who could do this? Where did he get his specs from or is this general knowledge working with frames?

[Sledge Hammer]

WOW!

Great report, Mike.

When in this unaligned state, did you notice unusual tire wear?  Patterns, asymmetry, whatever?

I have two '96 models, and except for the occasional handle bar realignment that Greg references, have not noticed anything untoward in the riding.  I hope I would know if they were messed up, but am not really sure.

Great report Mike, thanks for being persistence, taking the time to do this and sharing with us.

How did you come to find someone who could do this? Where did he get his specs from or is this general knowledge working with frames?

Good questions. Taking them in order...

I hadn't been riding the bike very long before I picked up that something was amiss, so the tires did not get enough miles on them to show unusual wear patterns before I intentionally set the rear wheel alignment to whatever would mitigate the leaning, along with the definite pull to the right. I rode it that way for several hundred miles, during which time the sprockets showed no severe or unusual wear but the rear tire certainly did. It is now worn asymmetrically and can sometimes give some interesting squiggles when the bar is held just right.

I can tell you that the bike would exhibit head shake when leaned over in sweepers, with more head shake at higher speed. (I use an off-ramp on my way to work that makes a perfect testing ground for such behavior.) Since getting the bike back and still running the same set of tires (Dunlop OEM), I can feel no such instability in the front end. Note that no suspension component was replaced. In fact, I specifically asked Kent if we should just replace the triple clamp with new components and be done with it; his response was, no, unless the metal had been overstressed or had been otherwise materially damaged, a brand new set could be out just as much. He emphasized that triple clamps are all pretty cheesy regardless of manufacturer or model and are typically not precision components as they come from the OEM manufacturer.

I originally started looking for a motorcycle suspension shop when I reasoned that the bike's behavior (i.e. leaning which could not be eliminated but only aggravated or reduced by adjusting rear wheel alignment) required an offset between the front and rear wheel. In other words, they were not tracking in the same plane and could only be made to track parallel with each other when "straight" but could not be lined up. I also guessed that the front had to be offset to the right of the rear. I bounced this theory off the owner of shop in Convington, who said that was actually far more common that most people would realize and especially on cruisers. That guy is a degreed mechanical engineer, and I was convinced I had found the right guy to check things out until one of my friends asked how he could check with the necessary precision without a precision fixture. I couldn't argue with that logic, so I ran a Google search for "motorcycle frame alignment and came across lots of references to Computrack in several sport bike forums. There are several Computrack franchises in the US, but this is North American HQ, and a discussion with Kent over the phone convinced me that he already had several strong, well-reasoned ideas for what was likely wrong. After looking to see if I could dig up any complaints about his work and failing to do so, I committed to having the bike transported to Jasper after I disassembled it at my parents' house. (BTW, my next house will have a full basement. I am done with crawlspaces and miniscule garages on poorly poured slabs of badly prepared concrete.)

To answer your question, Terry, I don't know if Kent could get a specification set for each component (if he can, I'd like to order a notebook full of them), but the nominal specifications for wheel base, rake, and trail are easy enough to find, and Kent seems to be a whiz at plane geometry, so I think he interpolated the component specs from the overall numbers.

You can see that my bike with an unworn and actually somewhat loose chain exceeds nominal wheelbase length by 1" (66" vs 65") and the rake and trail numbers are also greater than nominal (33.6° vs 32° for 5% relative difference and 6.07" vs 5.39" for 12% relative difference). If the bike had been in collision, I would have expected less than nominal rake and trail, so it tends to make me believe that there was considerable slop in the manufacturing process, but whether that is from batch to batch or from year to year I couldn't venture to say. Those of you with two bikes might be better able to answer.

Now, I also have another theory, which tends to support Greg's assertion, and that is that tires can and do make a huge difference in handling and can contribute to steering bias. That made perfect sense when I thought about an old Plymouth Fury I used to have which had bias-ply tires on it and would wander all over the road depending on the surface texture, like a puppy chasing a ball. Cute, I guess, when you can watch from a safe distance, but a little less endearing when you're inside and fighting to stay out of oncoming traffic or to avoid leaving a bridge through the guard rails. Anyway, the OEM Dunlops are bias-ply, so wouldn't it be reasonable to think they could exhibit similar behavior? I would like to know how many Magna owners found their bikes to become more neutral-handling after ditching the OEM Dunlops for other brands or even for other models of Dunlop.

One point which Kent covered with me was NEVER to use a wheel chock to capture the front wheel when transporting a bike. He said doing so puts the lower triple clamp under exceptional strain and is very good for his business.

[Greg Cothern]

Probably dropped..  If it were only $500 might be worth it,  but more than that I would find another Magna and use this one as a parts bike etc.

[hootmon]

One point which Kent covered with me was NEVER to use a wheel chock to capture the front wheel when transporting a bike. He said doing so puts the lower triple clamp under exceptional strain and is very good for his business.

Oh Michael, you have no idea what you have unleashed with this little comment. I'm on another forum and there is a grouchy old bastard that makes everyone think you are an absolute idiot if you don't use a wheel chock when transporting a bike.. I can't wait to stir up the hornets nest with this little quote!! -

What???
Me?????
Instigate???

Whatever do you mean???