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Old 05-24-2012, 12:57 AM   #16
Redrockmania
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Front End Pogo Dancing

Although my experience of this problem was with a 250 single road registered trail bike, there are some common lessons. I solved the problem after these interventions. The up and down pogo movement occurred within a specific speed range. I incorrectly assumed it was either front suspension and / or front wheel / tyre.
Replaced the front tyre and inner tube - no joy. Balanced the front rim and checked rim runout (runout within spec) - still no joy. Checked and tightened spokes - still no joy. Fitted new front wheel bearings - still no joy. checked front end alignment and torque values - Still no joy. Checked steering stem bearings for play - still no joy. Checked front brake disc for runout - still no joy.
Then I reviewed work I had done just before the problem emerged. I recall fitting a new rear tyre shortly before and had not balanced it. I took off the rear wheel, cleaned the rim, checked the rim for runout and for spoke tightness - still no joy. I then removed the rear tyre and inner tube,and balanced the rim. The rim was badly out of balance. I fitted necessary balance weights to the inside of the rim under the spoke / tube protector rubber band, then refitted the tube and tyre and rebalanced the wheel again. This solved the pogo problem.
Lesson Learned was: Although all indications were that something in the front was causing the pogo effect, in fact it was an out of balance rear wheel. As part of your pogo effect diagnosis check your rear wheel for balance.
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Old 05-24-2012, 07:00 PM   #17
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in conjunction with what the n00b said, i've had a couple of bikes (current r65 included) where the rear suspension could be set too soft (not enough preload) and the front would get hoppy on certain stretches of road.

the po had a works performance shock that was set up for more weight, which caused the rear to bounce. i went back to stock, which cured the rear but the front would get weird. turned up the preload a notch or two and the problem was gone.
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Old 05-24-2012, 07:53 PM   #18
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Man, the responses are all over the map.

You need a new front tire.

You need to change fork oil. Do not follow Duane's fork draining short cut. At least not this time. My advise is to ignore a lot of that article. Changing the fork oil the right way is a bit of a job but it needs to be done in order to make sure your bottom rubber bumpers have not turned to mush in the oil. Use new bottom cap crush washers and new damper rod washers. Torque the caps per the manual. DO NOT over torque the damper rod nuts. It breaks off the end of the damper rods! First make sure your axle slides in and out of the sliders very easily. Is one slider just the tiniest bit higher than the other? It could be alignment or it could be the top rubber bumpers have come apart and are letting the sliders rest at different levels on the damper rods. Either way the forks need to come apart to find out.

You don't need emulators unless you are needing more rebound or less compression damping. You very well might need to adjust the preload on the fork springs. Read up on fork sag and let us know how much you are running. Knowing your sag is THE first place to start understanding how to set up your suspension. For that matter, what is your sag in back? What kind of shocks and so on? Good luck!

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Old 05-27-2012, 12:57 PM   #19
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As says Redrockmania sometimes the front end problem are a resultant of rear problem, worn shoccks, ball bearings etc
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Old 06-09-2012, 01:46 AM   #20
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Ok, school me on fork oil. Is it one size fits all? What do i need to look for? Different "ratings"?
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Old 06-09-2012, 02:01 AM   #21
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Unfortunately, fork oil doesn't really have a standard. Bell ray's 6.5 maybe Gloden Spector's 8.0

You want quick and simple? Go down to the BMW shop and get what's recommended for your bike. Or, you take my word, a guy you never met, and use Mobile 1 synthetic ATF. That's what I use. I like it. And I'm known as an upstanding pillar of society.
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Old 06-09-2012, 08:47 AM   #22
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Quote:
Originally Posted by supershaft View Post
Man, the responses are all over the map.

Changing the fork oil the right way is a bit of a job but it needs to be done in order to make sure your bottom rubber bumpers have not turned to mush in the oil.


My money is on this for being a culprit.
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Old 06-24-2012, 03:03 PM   #23
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Ok, still been doing my reading and researching. Currently looking for an easy to find local source for fluid (not prepared to use ATF at this time due to some of what I have read.

Local napa has this:



whatdayathink?

about the ATF, have seen mention that ATF has friction modifiers in it.

http://www.advrider.com/forums/showthread.php?t=452366

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auto tranny fluid will probably work fine.
but it isn't the same as fork oil (hydraulic fluid).

put a drop of auto tranny fluid between your finger and thumb. rub lightlly. you will feel an abrasive quality to the fluid.

now clean your fingers (or use the other hand) and put a drop of hydraulic fluid between finger and thumb. rub lightly. slick as snotty teflon.

Have also seen mention of aviation 5606

http://www.bmwmotorcycletech.info/miscl.htm

Quote:
You will probably find that a 4 or 5 weight or 7-1/2 wt oil is about correct, with a 10 wt usually too stiff. BMW's original red oil was really a MIL-spec oil, MIL5606, and was close to a SAE4, but BMW's literature here and there may indicate a 7-1/2 wt. oil.
I have access to all the free 5606 that I want from the aviation work I do. My understanding is 5606 is basically mineral oil and paraffin wax.
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Old 06-24-2012, 03:43 PM   #24
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IMO experimenting with oil in the middle of problems is not the solution. Get some Spectro 5wt fork oil if your bike is a 70's model I believe?
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Old 06-24-2012, 04:14 PM   #25
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IMO experimenting with oil in the middle of problems is not the solution. Get some Spectro 5wt fork oil if your bike is a 70's model I believe?
I had thought in my reading that the fork oil was supposed to be a 7.5 weight according to the BMW spec, but now dont remember where I read that. I dont have a supplier for any of the oils listed in the hayens manual yet. Still searching (all bmw dealers are over an hour away from me)
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Old 06-24-2012, 04:22 PM   #26
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So you've found a hydraulic oil at NAPA that is "suitable for cold climates" and you are in... Florida.

Spectro 5wt is the ticket.


^^^oops, was thinking BelRay amd wrote Spectro. Same diff, tho.
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Old 06-24-2012, 04:24 PM   #27
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They started out recommending 2.5 weight and went up to 7.5. IMO they work best with 5wt unless you ride real hard. Spectro that is. Call up your local bike shops or mail order it from any number of places.
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Old 06-24-2012, 04:34 PM   #28
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First thing I'd do is make sure that everything suspension related front and rear is working
Make sure the forks are straight and true, that the wheel is in fact round and the bearings are in good shape.
Then check swingarm pivots and shock bushings. and rear wheel.
Tweaked fork tubes or bent axles can jack up the way a fork works.

Then go about draining and refiling the fork oil. I lean more toward's what Shafti was saying rather then duane.

Also use fork oil rather then ATF, when these bikes were new ATF was used a lot as there just wasn't really that much for oil around. Now there is, and now it's good stuff.
Trouble is what's 5 weight from one brand is 2 weight from another and still 8 from someone else.
So when trying to find the right weight use the same brand. I've used and have been happy with both Spectro and Honda Pro Oils.

I start out with a thinner oil and work my way to a thicker oil if needed.
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Old 06-25-2012, 09:29 PM   #29
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Ok good news, the cycle gear across town has the belray in 5,10, and 15 weight. So thats under control. Need to find a measuring device and make a tool to loosen then fork caps next. (recovered my seat this weekend, so not wasting time!)
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loner, lonegunman, get it. Thatís the whole point. I like the lifestyle, the image. Look a the way I dress.
Quote:
Originally Posted by bgoodsoil View Post
Cavemen must've designed them shortly after inventing the wheel.
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Old 06-26-2012, 01:33 AM   #30
batoutoflahonda
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The only time I've ever rubbed ATF between my fingers is when I was trying to get it out of my hair. Usually after lying under some four wheeled contraption. Not a fair experiment tho, as I'm sure ATF doesn't contain sticks and rocks. Well, maybe some of the GM stuff does.

Nice that you have a store that has the same brand with varying weights. Now you can do some real trials. Good luck.
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