Have you trued the wheel ie individually tightened and loosened each spoke of an untired rim until it doesn't wobble? PIA but it is needed before tire is added.

 

[QUOTE=armycopter;444278]... even though I had it balanced twice with the rim lock installed.
QUOTE]

Must have been someone who didn't know how to do a balance. I have the older style Motion Pro rim lock (metal, heavy) in my front and it got balanced just fine. Took a fair bit of weight but turned out great.

The newer MP rim locks are much lighter. Oh well.

 

I was also able to balance the front with an all metal motion pro rim lock. It took several ounces of tape weight.

I rode with the unbalanced frot and rear wheels for awhile and the symptoms are best decribed as a hopping front end that gets worse with speed. When you are riding, sight down the front fork and the front axle will be moving fore and aft as the heavy side of the wheel spins. Pretty amazing. Keep adding weight until the axle is stationary. A good starting point is to weigh the rim-lock before intallation and put that much weight on the opposite side of the rim.

I still believe that rim-locks are worth the balancing effort. Once balanced there is no negative to rim locks. Flat tires suck. Flat tires because of a torn valve suck more and cost 20$ more to fix.

 

I know this is an old thread but I had the same issue after putting a new Kenda Parker DT 110/100-18 on the rear. The front end would become unstable at speed higher than 55 mph. It was like the front end would do a snake dance, going from left to right quite easily.

After reading the previous post, I lowered the rear shock preload by 1mm, set the rear pressure tire to 17 instead of 20 and set the front tire (TMII that I don't like) pressure to 20 instead of 17. I did this to lower the rear end a bit while lifting the front end.

As marginal as these changes can be, believe it or not, it worked! I went for a ride on the highway today and the front end snaking was gone. I had the bike up to 65 mph with a good headwind and everything was fine. I never go faster than that with my 13 tooth sprocket.

Thanks for your help everyone