Front wheel bearing removal

[HondoMan]

Sharing some learning - The front wheel bearings on my ST90 project were completely frozen and in need of replacement. These bearings are very difficult to remove. There is an axle sleeve in the hub - in between the two bearings. The presence of the the sleeve makes it impossible to tap either bearing out from the opposite side. I thought a bearing removal tool was the answer, but found that the removal tool arbor did not achieve enough "grip" on the inner bearing surface to pull the bearing out. I finally found a solution after chatting with a long-time motorcycle mechanic. Take a dremel with a cutting wheel and carefully cut two grooves in one of the inner bearing races. The grooves should be as deep as possible and perhaps 30 degrees apart. Once cut, take an old screw driver and drive it into one of the grooves. It should fracture the inner race and with a bit more work allow you to remove it. Once removed, the axle sleeve can be removed. Then you can tap the opposite bearing out. Finally, carefully cut two grooves in the inner side of the remaining outer bearing race. This should relax the race enough that it can be tapped out. Job done.

 

[69ST]

To be clear, from the start, I've not worked on an ST90 hub, only CT70s & Z50s. That said, press-fit ball bearings are pretty much the same setup, only a matter of how tight the interference fit might be...and that has limits, beyond which the bearings would fail, or the hub would fracture.

There are a number of ways to drive-out the first bearing, after which the opposite side is dead easy. I've always found that one end of the "distance collar" will have a little wiggle room, literally...just enough to expose part of the inner race. From there, a small (~.250" diameter) punch can be used. When there's minimal exposed edge, a tapered punch can be driven into place, from the opposite side, locking the straight punch solidly in place; then you just hammer the bearing free.

That said, regardless of your chosen extraction method, your best friend & helper is heat. Heating the outside of the bearing seat, quickly, using a propane torch, will expand the hub metal enough to seriously loosen its grip on the bearing. Sometimes, the bearing will fall out with nothing more than a gravity assist.

Not criticizing the method you used, it is sound. IMHO, it seems a bit more time & labor intensive than might be absolutely necessary.

 

[HondoMan]

Thanks! I had read about heat application, but I was reluctant to try it for fear of damaging the material.

 

[69ST]

Just take care not to overheat the hub. Most paints, including cloud silver, will survive ~300F...that temp is not needed. 150-200F should be plenty hot to loosen the bearing and it can be achieved quickly enough to heat the hub more than the bearing, just what you want.

 

[fogmoto]

Two thumbs up to racerx! Was having a hard time trying to drive out front wheel bearings on my 79 ct70. Heated up hub with a mapp gas torch and popped it out with a long screwdriver from other side. Thank you. This site is great!