Greetings my friends,
I have a front wheel that shakes when I go 70-75mph. To be a little more discriptive, the handle bars give me feedback left to right vigorously where I literally have to lock my arms. Even on smooth pavement I still get the shimie and I think this matter can be very dangerous. Any thoughts?

 

You either have a tire/wheel out-of-balance condition or out-of-round condition. . . have a bike shop check and adjust this for you. . . .VERY DANGEROUS!

 

This may sound arrogant but slow down and it'll go away,you need to remember your on knobby tires and they dont usually balance them

 

Slow down. It's not a sports bike. I'm sure when you're doing 75mph it's on the blacktop. Try 75mph down a local trail. You'll slow down.

 

Its more or less a common thing with this dualsport. Gotta remember, its a 250 dirt bike converted for street use. I also did encounter the front wheel wobble while passing a 18-wheeler at 70mph. Handle bars started moving to and throw. I just locked my left arm and gave it all the throttle it had. Straightened right up and cleared past the 18-wheeler. Not a friendly experience, especially if you are a rookie on motorcycles and don't know how to treat the condition when it aburpts.

 

I had the same thing above 65 on mine. I weigh 250lbs and what I did was check the book on air pressure. The book reccomends a bit higher pressure for heavier riders. I put 22 in the front tire, and 25 in the back tire, and it got rid of all my wobble and shake. Now at 65+ its nice and smooth.

 

I don't normaly go 70-75, but even at 65 it can do the same thing mildly. My friend has the same bike too and his runs smooth at 85mph. I understand that this bike isn't a sports bike, but come-on you should still expect to run at 95-100% with no trouble and if I understand 87mph is approx 100% with stock gearing. Do you guys think when I cranked the rear shock spring to accomidate a passenger might play a factor? I never put the shock back, but I will if it helps and also check the TP. Thanks in advance.
Hobbs

 

When I still had the stock fork springs, I could induce the wobble much easier because the weak forks caused the front end to be lower...kind of the same effect as raising the forks in the triple clamps...less stability at high speed. If I leaned back, the wobble was way harder to induce. Now that I have the stiffer fork springs from Moto-Pro the wobble is nearly non-existent. A very weak version of the old wobble can still be induced, but it takes effort to even get that.

If your rear shock spring is sinking down less because of you cranking on the preload, there's a good chance you can reduce the instances of wobble by backing it off some. While you're at it, might as well do some measurements and set the proper rider sag for your weight.

If you still have the stock shock springs, I recommend getting some stiffer ones for your weight. To give you an idea, the correct enduro fork spring rate for my whopping 150lbs would be .40 according to the spring rate calculator at Moto-Pro. The stock fork spring rate is only .37, so it's only suitable for gradeschoolers. I went all the way down to 107lbs on the calculator before the stock spring rate became OK.

 

Tremor brings up a good point, suspension setup is crucial. Correctly setup the suspension is very important,start with front end ,back the clickers all the way out then start from there. Set the rear sag, then from there see how it goes start with ONE CHANGE AT A TIME and then see if there are differences. Check steering head bearings and there proper tension wheel balance also. If after all this see if your buddy will swap front wheels with you to see if this helps.

Good luck

 

Yup its suspension and wind...Yup and tires..

When it starts wobbling lower your head down and youll feel it go away slightly....Move your butt further back or forward and youll feel it calm down....Dialing in the suspension is key..If I can remember too soft allows the forks to pull up with wind drag with our front fender and cowl....I did change my fender out and it has been alot better.

But speed is the enemy when the rider and gear and fluids are almost equal to the bikes weight..

Rocco