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Old 04-08-2010, 09:30 AM   #1
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Default clutch bell questions

Hello there everyone. I am an electric guy who has been pulled over to the dark side and own a nitro car now. My car is an OFNA Ravager that I bought used. It has the force .28 engine in it and I recently smoked the clutch bell bearings and replaced them. My question is how do I know when the clutch bell is tight enough? I installed it and then ran the car and after a tumble the clutch bell seems to have shifted and it is making contact with the center diff gear. I had some bad fuel in the car and foolishly loosened the clutch bell slightly because it was stalling when I hit the brakes. I checked the carb set up at idle and all is well, but it never dawned on me that the fuel was old and probably needed to be drained before I ran it. Once good fuel was put in the tank and run the car pulled hard and the braking was good with no stalls.

Any insight to a newbi nitro guy?

Thanks!

Ben
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Old 04-08-2010, 09:38 AM   #2
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if you are talking about the nut that holds the cb over the crank, you NEVER untighten that. Your bell should be able to move freely w/o loosening that nut. To align the cb mesh with the spur, you place a piece of cardboard, just for reference I'd say use a cardboard same thickness as a cue-card. But rememer if your cb is not moving freely before you mount the engine in the car then you need to make sure you have it shimmed properly and all the bearings, shoes and springs are not holding it.

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Old 04-08-2010, 09:40 AM   #3
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I allow for a half a millimeter of movement in and out. the clutch should spin freely. As for your your clutch bell making contact with the center diff gear, the motor needs to be moved back. there should be at least an eighth inch minimum between the bell and the gear.
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Old 04-08-2010, 11:57 AM   #4
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Originally Posted by xjqkz View Post
if you are talking about the nut that holds the cb over the crank, you NEVER untighten that. Your bell should be able to move freely w/o loosening that nut. To align the cb mesh with the spur, you place a piece of cardboard, just for reference I'd say use a cardboard same thickness as a cue-card. But rememer if your cb is not moving freely before you mount the engine in the car then you need to make sure you have it shimmed properly and all the bearings, shoes and springs are not holding it.

ps. welcome to the "darkside"
Okay so i needed to replace the clutch bell bearings and there were some rings that came out, but i am not sure if they are the shields for the bearings or if they were the shims. I have no clue how to shim a clutch bell. can you please give me some tips on that? The last thing I want to do is to kill this car. What should I be doing to shim the clutch bell for proper operation
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Old 04-08-2010, 12:25 PM   #5
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Quote:
Originally Posted by bschanz View Post
Okay so i needed to replace the clutch bell bearings and there were some rings that came out, but i am not sure if they are the shields for the bearings or if they were the shims. I have no clue how to shim a clutch bell. can you please give me some tips on that? The last thing I want to do is to kill this car. What should I be doing to shim the clutch bell for proper operation
ben
Probably both shields AND shims came out. They look very similar... but a shim will JUST fit over the crankshaft... a bearing shield will be loose.

You want to set it for just a TINY bit of endplay using shims. In other words the clutchbell should be able to move forward and back maybe .5 mm... just a tiny bit. Too much play is bad... too little (i.e. NONE) will kill bearings very rapidly. The bolt in the end of the crank MUST BE TIGHT!!! Use the shims to set play.

Note that in most cases you have shims behind the inner bearing AND outside of the outer one. The point of the inner shims is to make sure the clutchbell is not contacting the end of the pins on the flywheel, the face of the clutch shoes, or the face of the flywheel. They are not always needed, but I usually have at least one. In any case the clutch bell should spin absolutely freely like the wheel on a roller skate or something.

The tooth mesh most people set by putting a strip of paper between the clutch bell teeth and the spur gear teeth, then move the engine over so it is tight... tighten down the mount bolts and remove the paper. That gives just enough play to allow it to "work" as the car goes over bumps, etc.
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Old 04-08-2010, 01:31 PM   #6
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Originally Posted by bschanz View Post
Okay so i needed to replace the clutch bell bearings and there were some rings that came out, but i am not sure if they are the shields for the bearings or if they were the shims. I have no clue how to shim a clutch bell. can you please give me some tips on that? The last thing I want to do is to kill this car. What should I be doing to shim the clutch bell for proper operation
ben
domit pretty much summed it up
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Old 04-08-2010, 01:43 PM   #7
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gear mesh is not a concern. I know how to do that. That is equally important on electrics, where I am pretty experienced. I will get that bell off and put the shims in as suggested and make sure the screw that holds the clutch bell is as tight as I can get it. My intent is to learn the ropes with this car and eventually get a racing machine that I won't screw up due to lack of knowledge. I don't want to drop the coin on say and Rc8 and tear it up because I don't know what I am doing. Thanks for all the insight. You nitro guys ain't half bad...

I would say this nitro car is much like my harley.. it stinks, is always dirty, it makes so much noise you know it is coming and there are few things on this earth that are more fun
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Old 04-08-2010, 02:06 PM   #8
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think of shims as spacers you want to put enough space between the top of the clutch and the cb so that it clears w/o touching it and at the same time you don't want to run out of space on your crank. The end product should have less than 1mm movement (along the same axis as the crank shaft) and the cb should be able to spin freely.
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