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Old 10-23-2008, 07:15 AM   #1
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Questions?? MR Ninja MR21 B01 BEARING REPLACEMENT HELP!!

Fellow Racers,
I need to replace the front and rear engine bearings in my .21 Ninja. I have tried like hell to find a link or suggestions, but have had no luck. I am new to the sport and my background is in motocross so, I have rebuilt a ton of 2 stroke motors, just never a small nitro.

People have already told me to use a replacement ceramic bearing like the ones offered through Bocca. Before I tear it down and head to Carolinas RC, I would really appreciate some feedback or better yet a link to how it should be done.

Thanks,
Robb
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Old 10-23-2008, 07:35 AM   #2
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Just disassemble the motor completely and place the crank case in the oven @ 300 degrees for 10 mins. Alsp place the new bearings in the freezer for about 2 hours. The old bearings should just pop right out and the new bearing should slide right in. I just did it to my Vspec...
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Old 10-23-2008, 07:38 AM   #3
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I am not good posting links

go to rbproducts.com and there is a section in there that tells you how to replace bearings without having the specialized tools for the job. They tell you to use a hot plate, I use an oven like stated above.
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Old 10-23-2008, 08:23 AM   #4
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Thats a great link:
http://www.rbproducts.com/mainEn.php...ncept%20engine
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Old 10-23-2008, 08:38 AM   #5
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Default MR ninja

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Originally Posted by DaveNJ80 View Post
Thanks guys is the RB bearing replacemnt identical to the Ninja?

Also has anyone gone to a bearing supply shop to buy the bearings?

How long has it taken you to do this I am debating if I want to do now or after I race on Friday

Thanks,
Robb
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Old 10-23-2008, 08:43 AM   #6
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Adding in the time for dis-assembly of the engine and re-assembly plus 'cook time' for the mill it usually takes approx 45 min of labor and watching the oven. Just make sure you keep the new ones in the freezer like stated above for at least two hours before you make the swap. Obviously this should most likely go without saying but make sure strip the engine completely, even the exhaust gasket or it will melt. Good luck, post up your results!

PS the easiest way to get the rear bearing out is to tap the mill on a piece of wood. The bearing will come right out. I use a wood dowell to nail out the front bearing.
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Old 10-23-2008, 08:44 AM   #7
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Also while you're rebuilding, I would look into TKO ceramic bearings. They are cheap. Usually 20 or so for the rear and 15 for the front and you will notice a significant performance increase and a steadier idle.
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Old 10-23-2008, 08:55 AM   #8
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Questions?? what about this

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Originally Posted by clarksib View Post
Also while you're rebuilding, I would look into TKO ceramic bearings. They are cheap. Usually 20 or so for the rear and 15 for the front and you will notice a significant performance increase and a steadier idle.

Guys thanks for the fast replies when I was talking about going to a bearing shop this was what I was talking about. Here is a link to Carolinas RC for the 2 bearings I am looking at around $65.00 I assume that the tko ceramics are more??

Do I need to buy any sort of gasket kit?
What about the head bolts do they need to be replaced?
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Old 10-23-2008, 09:19 AM   #9
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Originally Posted by robbdny View Post
Guys thanks for the fast replies when I was talking about going to a bearing shop this was what I was talking about. Here is a link to Carolinas RC for the 2 bearings I am looking at around $65.00 I assume that the tko ceramics are more??

Do I need to buy any sort of gasket kit?
What about the head bolts do they need to be replaced?
The TKO (for v-specs at least) are roughly 20 for the rear bearing and 15 for the front. 35 bucks. Didnt find any for the MR Ninja but im sure someone can post for you the sizes needed. These will be cheaper than buying the GRP brand steel bearings.

As far as gaskets go. You should inspect the exhaust port gasket and replace if needed. Also inspect your carb gasket. If you are really unsure about this process I would recomend sending the mill to a modder to have the bearings replaced.

You can do a quick search on here and find a modder you want.
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Old 10-23-2008, 09:24 AM   #10
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I've always used TKO bearings and had nothing but excellent results with them. Also just for precaution I always use a little liquid gasket like luck 7 (http://www.amainhobbies.com/product_...ducts_id/25728) on the carb neck and back plate.
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Old 10-23-2008, 09:36 AM   #11
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Okay first off if you felt there was a need to replace the bearings do not wait. If you do, something will go wrong and you will kick yourself in the butt.

TKO ceramic bearings will run about 45 bucks for both. They are the same size as OS Vpec motors so they are very common. Go to Carolinas and pick up a set. Just make sure when you disassemble your motor you roll the piston up to TDC so you don't break the skirt off the piston. Clean everything up before you put it back together on the inside and oil up everything just like real motors. I richen up my needles a little and run a tank on the stand to let the bearings "seat" into the races. Just idle and some easy blipping no death revs. Thats it put it on the track, tune it and let it rip
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Old 10-23-2008, 09:58 AM   #12
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I would say check out www.Bocabearing.com also. They are great people to deal with and have bearings in different price range. I use their new Ceramic MX and they are awesome my engines have never idled and ran better. They have free shipping available too which is nice if you are willing to late a little longer. Check em out and give em a call, ask for Teddy.
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Old 10-23-2008, 03:27 PM   #13
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Default MR ninja

Quote:
Originally Posted by DaveNJ80 View Post
Thanks guys is the RB bearing replacemnt identical to the Ninja?

Also has anyone gone to a bearing supply shop to buy the bearings?

How long has it taken you to do this I am debating if I want to do now or after I race on Friday

Thanks,
Robb
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Old 10-23-2008, 03:32 PM   #14
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Your bearing sizes should be 7mm x 19mm for the front and 14mm x 25.4 for the main. A RB C6 has a 14mm x 25.6mm I believe.

the oven trick works well but I have since bought the GRP bearing removal, installation tool and it works great..

I have never tried a local bearing supply for them, for the rpms we turn in these engines, I;m not sure that I would trust one.
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Old 10-23-2008, 03:38 PM   #15
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Default ? about ceramics

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Originally Posted by katjim00 View Post
Okay first off if you felt there was a need to replace the bearings do not wait. If you do, something will go wrong and you will kick yourself in the butt.

TKO ceramic bearings will run about 45 bucks for both. They are the same size as OS Vpec motors so they are very common. Go to Carolinas and pick up a set. Just make sure when you disassemble your motor you roll the piston up to TDC so you don't break the skirt off the piston. Clean everything up before you put it back together on the inside and oil up everything just like real motors. I richen up my needles a little and run a tank on the stand to let the bearings "seat" into the races. Just idle and some easy blipping no death revs. Thats it put it on the track, tune it and let it rip

Maybe I spoke to a newbee at Carolinas RC but when I called about the front and rear bearings the guy I spoke with on the phone said they didnt have a ceramic frt and rear in stock? Just so I understand everyone the OS V is the same as on my Ninja as well as the GRP? The other thing he told me was the rear was 46.00 and front was like $20? Something just dosent seem right here.
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