Rear bearings and cassettes

[Mark K Ouimet]

I was doing end of year clean up on our karts and took off the rear axle,cassettes and bearings. Getting the bearings out of the cassettes was extremely difficult, so much so I had to use a hammer and screwdriver to get the bearings out of the cassettes. Thankfully, I didn't damage anything. When reassembling the rear axle should I use some type of lubricant that will prevent this in the future? Is it normally a very tight fit? When reassembling should I heat the cassettes? The kart is a 2000 CRG Heron with stock cassettes and stock bearings. Now a follow up question, how important is the 3rd bearing when racing jr sportsmen? My son weighs all of 80#s wet. Thanks Mark

[Roger Miller]

Mark, several things about your question:

1. The bearings should not be *tight* in the cassette. Snug, with no play, but not tight. They should "float".
2. Use a moly lube, anti-sieze on the bearing shells and in the cassettes. Due to the materials, moisture causes a corrosion that "siezes" the bearings in the cassettes.
3. It is the movement of these bearings in their cassettes that lets the frame flex. If these don't flex, your frame is bound up.
4. Generally, for Junior Sportsman, on hard tires, you don't need the third bearing, but, what most people do is leave it in and use ty-raps to hold it in the cassette instead of bolts. Then, if you need to tighten up the rear, one thing that can be tried is to bolt in the bearing.

If the bearings and cassettes are still a tight fit after cleaning up the surfaces, you could try a light bit of steel wool work to see if that makes theings fit better. I hesitate to say go at it with anything heavier. Others may have a better suggestion. You should not have to heat anything to get it back together.

[Mark K Ouimet]

Rick, no insult taken, I had to use the hammer and screwdriver just to get the bearing to pivot. That sucker didn't want to move.

[Rick Blood]

I don't want to insult anyone but if I had not seen this happen myself then I would not even mention it. I walked into a friends shop one day and saw him with a bearind cassett in his hydraulic press. I grabbed the cassett, rotated it 90 degrees and it fell out in my hand. He had been racing for 2 years and had no idea that they were designed to pivot.

[Kevin Van Caster]

You can also put a shim between the two halfs
to free up the fit.

[Chuck Bunnell]

All you should have to do is put a thin film of grease on both surfaces to mate the bearing with the cassette. It should be a fair amount of work to rotate the bearing in the cassette too, but still mostly by hand. One thing to avoid is bearings with a grease groove on the spherical surface. These are meant for a steel carrier and will destroy an aluminum cassette. I second the use of steel wool, and nothing more than that, to free up the installation of the bearing. Was there corrosion on the spherical part of the old bearing? That would indicate they were installed dry and not properly greased for installation. And I'm not talking about greasing the interior with the balls and races and shields and stuff now either. That's a different topic which has been repeatedly hashed before. In a nutshell there, clean the assembly goo off and grease with a quality synthetic. Clean and regrease as necessary and do not over grease.

[Jon Betts]

My son drives a trackmagic demon 125 shifter, this is our first season, needless to say I have not taken the rear axle assembly apart until now...the end of the season! All 3 of the bearing cassettes are bady seazed and scored. OK do I need to buy new ones? Or is there some proceedure to rcover these ones? I notice that they are in the $50 region so that means $150? What are the best ones to get, anyone have experience with a product called wet kaset?

Thanks Jon

[John Scott]

Jon
Look for cracks around the mounting holes and if the part is solid, clean it up and reuse it following advice above (steel wool).

However if the kart is *high mileage*, the $150 to replace them is a good investment as the cassettes can break, which is not a lot of fun in a 125.

Don't know about the wet stuff, we just use a light coating of antisieze for assembly after a good steel wool job.

[ October 29, 2001: Message edited by: John Scott ]

[Chuck Bunnell]

Jon, Did the bearings have grease grooves in their exteriors? If so, then you need to replace the bearings with ones that have a smooth exterior, (no grease grooves). If not, then you need to grease up the mating surfaces of the bearings and the cassettes prior to assembly. And you may have to make this part of your maintenance schedule to avoid chewing up your cassettes. This may also have contributed to chassis bind, though with a 125 you probably couldn't feel it. The previous advice about cleaning up the cassettes is valid. You want a smooth bearing surface for everything to work well. And that surface needs to be greased.

Wet Kassettes are an assembly that puts the rear axle bearings in an oil bath instead of the standard grease and shields. The Wet Kassettes will spin freely for a long time without a load on them. I've never seen a demonstration under load though supposedly they are great. I remain a firm believer in using a high quality synthetic grease on the rear axle bearings. Remove both shields and flush with solvent to remove all the old grease and any debris. Allow to dry and inspect the races and balls for wear. All should be shiny and free from damage. If so replace with new which will need to be cleaned and greased. They do not ship with real grease in them. Often it's just a anti-rust goo. Don't overgrease the bearings either since it will just push out the excess and fling it all over the place.