1974 r90 /6 bmw. Bridgestone spitfires, front tire with 12k miles, fork oil who knows. Seems like lately the front end is a little bouncy. Almost feels like at times its got a bounce to it, but will run smooth others when the road is smooth. Its NOT a high speed vibration. Tire does show a small amount of cupping that can be seen in when the shadows are right (like at certain angels with the sun). As I am new to this, (only 20k miles under my belt) and this only my second front tire. Never changed fork oil, and its on my list (probably need to do a full rebuild too). Lets hear your thoughts
Could be an out of round tire. Happened to me and it was the rear tire. Made the front pogo a bit just as you describe. Put it on the center stand and have someone spinnit as you hold a straight edge to it
Hit any curbs lately? I had the same situation. Right around 40mph it would start bouncing like a pogo stick. Turned out the front wheel had a "hop" in it. Trued wheel, problem solved. Or as hardwaregrrl suggested, it could be an out-of-round tire. If you watch it closely as you spin it, you should be able to tell.
Know I need to get the fork oil changed. Its been on my list....as well as many other things Hit nothing. Will the "out of round" issue be present all the time? Would think it would be. The is seems like a rebounding issue. But as this is the only street bike I have ever ridden, I have no frame of reference for whats normal.
On two airheads and a Honda Hawk GT 650 i followed Race Tech's instruction when installing springs, oil and their emulators. Some of the best money i spent on all three bikes. A few mc web sites have it posted. Google mcallister suspension 101 for mind boggling detail on suspension set-up.
I dont need complicated and crazy detail, I need simple for stupid! The link posted early in this thread didnt work. Is it just as simple as support the forks, draining fluid, out the bottom, take off caps and replace measured amount in the top?
That's how I'd do it, but I would remove the caps to make sure that a vacuum did not occur to hinder draining. That will get you back to a baseline so that you can then begin picking off the pogo issue.
Sorry, i should have known better than post in an airhead thread. Most want a quick, cheap, dirty fix or a 15 second sound byte that tells or fixes all. Read over at Race Tech's site about suspension with simple words. Remove and fully service the forks as new oil will just stir-up old crud inside'em. Seriously consider new spring and emulator along with new seals. Sheesh! Again sorry and i'll never post in an airhead thread again even though i owned two of'em. I found them to be boring bikes BTW.
I have had a few older cars that when I first got them did a "double oil change" for that reason. Not ready and have time for the full project of rebuilding the forks. It is on my list. Baby steps!
It sometimes helps to pump the forks after the initial drain, to make sure you get all the old fluid out. Then maybe fill 'em, ride a while, and repeat? If the first fill fixes the problem, though, you have my blessing to stop there! And maybe point it away from anything you care about when pumping them. My mountainbike fork filled my eye with old fluid. Bastard.
:eek1 thats a lot of miles on a front tire. Time for a new one I reckon. Get the wheel balanced when new tire is fitted. And you need a basic Haynes workshop manual, so will see changing fork oil is very simple, eg put on centrestand, drain oil out the bottom, fill in the top. Be sure you can get the fork top nuts undone before draining the oil, they can be a bitch. While you have it on the centrestand, spin the front wheel and make sure it runs true with about 1mm, maybe 2mm max. Tighten spokes if necessary to true rim. If you have snowflake mags, they always run out out so tighten steering head bearings to take up the shimmy if needed. And whiel on centrestand check steering head bearings and tighten if needed. All real simple stuff and no need to dig into any high tech solutions until you have eliminated the simple basics.
How does the fork feel when you dive it standing still with front brake on? Does it return as fast as it compresses? The Racetech stuff is great and a worthy investment, but may be overkill for your riding style. If it were my bike I would do this: Drain and replace fork oil to see if there is any change. No real change for the better? Then... Check your static sag. If it sags too much under its own weight then new springs are in order, but probably not the cause of the pogo. disassemble forks. There are rubber bits in there that break down and can cause a pogo effect. Don't mess with the wiper rings unless they aren't there. The new ones are too big and require filing. Carefully reassemble, re-align and refill.
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.
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.
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!
As says Redrockmania sometimes the front end problem are a resultant of rear problem, worn shoccks, ball bearings etc