Transmission Bearings

[twistdtyphoon]

I have a 07 drr 70 with what I think is a kasea 70 motor. The transmission gears started to tighten up last race so I figured its time to replace the bearings before it breaks. Got the bearings out and was comparing numbers to what is sold on the mini quads web pages. My output shaft needle bearing has these numbers SYI NK 25/16. the ones on the web say they are 2515 are these the same will they work. Does any one have a good place to get these bearings. Is there a better option?

[Nichols Atvs]

use the 25/16 its a better bearing than the 25/15. Brass bushing is another ottion but u will have to press it in w a press.

[mydirtkids]

How are the brass bushings? The "upgraded...Japan" bearings don't seem to last long either. I hear Dave Carter will take the case and machine it for a wider bearing. Just seems if the brass bushing holds up then that may be a better option. Not to rob the thread here but this may help tyistdtyphoon too:cool:

[twistdtyphoon]

where would I get a brass bushing?

[Nichols Atvs]

scootercraft has them.

[mydirtkids]

Think g-force has them too. If not then it may have been hotquads

[twistdtyphoon]

Does anyone have a good way to remove the bearing that is in the back of the case that the idle gear sits in?

[Coley'sdad#8]

It's called a Blind Hole Bearing Puller , I have an OTC and Snap On but the one that fits best is a #95987 set from Harbor Freight Tools (and about a fifth of the money. try getting the bearing cold (contracting it) or WARMING up the outer edge of the aluminum case before pulling it with a handheld propane torch, JUST WARMING aluminum expands more than steel so it doesn't take much.

[jetmedic]

Trust me put a 25/20 in it. you will have to eliminate circlip but this bearing works best. forget brass too much friction and heat.

[twistdtyphoon]

Well I went with the brass bushing. Had it pressed in yesterday. When I went to put the tranny back together the output shaft wont slide through the bushing. I check it before I had it pressed in and the bushing fit over the shaft just fine. Any one else had this problem?

[mydirtkids]

Ahh SH*T... Not what I was hoping to hear.. I just took our practice bike apart to ispect and measure for the bushing. I really wanted to just try one and see the results... Please let me know what you find out..

[jerkyboy]

Ive seen it before on a apex but they come from the factory with that bushing. Dont know if they ever fixed it.

[BradLoomis]

Take a look at this link that we talked about this same thing a while ago, it may help.

http://www.exriders.com/vbb/showthread.php?s=&threadid=295518&highlight=bearing

As far as the bushing not fitting the output shaft... the press tolerance was to tight and it squished the bushing OD. The way to fix this is to have it line honed to the proper ID.
You will lose some top speed with the bushing, as the fluid will start to hydraulically cavitate at high rpm. The roller needle voids allow the oil a place to vacate as the needle rolls around the shaft. Using a thinner viscosity oil will help this situation, but then will not help cusion the gear mesh problem that is helped by running a higher viscosity oil.

[twistdtyphoon]

I was thinking that that was the problem but I couldn't wrap my head around the thought of the bushings ID getting smaller. I helped him press it in with one of the hand presses not even a hydraulic press.

I have heard of people running tranny fluid instead of gear oil would this help with the bushing and top speed. Have you tried this and if so what are your thoughts and what type would you suggest?

Last is it worth it to have it line honed or should I just remove the bushing and install another needle bearing?

[BradLoomis]

If you didn't bore out the case to accept a larger OD bushing, then it will not be as strong as the INA needle bearing and you will still have case flex which leads to gear shear.

We ran Amsoil 125 Severe Gear Lube and had no problems again with snapped gear teeth. If you are TT racing, then I would think of running a thinner fluid... but if you are MX'ing, then I wouldn't drop below 85 wt.