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Old 04-26-2009, 11:40 AM   #1
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Default flywheel is sticking

i have an RB .21 nitro engine and upon installation, i noticed that when i try to turn the flywheel over by hand (at this point it is not mounted on the chassis) it does not turn, seems to be stuck. it will turn a little in each direction but once it gets to a certain point it just stops. ive tried loosening the clutch nut, but that just allows the flywheel to turn freely and not turn the engine over. what could cause this and what could fix this. please help thanks in advance.
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Old 04-26-2009, 11:50 AM   #2
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i have an RB .21 nitro engine and upon installation, i noticed that when i try to turn the flywheel over by hand (at this point it is not mounted on the chassis) it does not turn, seems to be stuck. it will turn a little in each direction but once it gets to a certain point it just stops. ive tried loosening the clutch nut, but that just allows the flywheel to turn freely and not turn the engine over. what could cause this and what could fix this. please help thanks in advance.
is it new? if so heat it up to 200 degrees and fire it up
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Old 04-26-2009, 12:00 PM   #3
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Yes if its new you dont want to be doing that you will actually hurt the mill. That just telling you that you have mechanical pinch yes heat gun it and run it.
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Old 04-26-2009, 12:20 PM   #4
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Default New engine pinch?

Assuming this engine is brand new, what you are seeing is called cylinder pinch. The cylinder is actually narrower at the top than the bottom / \ which gives the piston more compression at top dead center since the piston does not have piston rings like on a full size car.

When the engine is brand new, the tolerances are VERY tight to the point of actually preventing the piston from going all the way to the top when rotating by hand, even with a weaker starter box.

To ensure proper break-in and to reduce stress on the connecting rod and cylinder during the first few startups, heat the engine block with a heat gun (like others have recommended) up to 200 degrees F. This will allow the engine parts to expand and create clearance for the piston to move. DO NOT HEAT THE PLASTIC PARTS LIKE THE AIR CLEANER, keep the heat directly on the engine cylinder and block! Once the engine is heated up, it should start normally at that point. Proceed with proper break-in procedure (that is a subject for another thread).

After the engine has been broken in completely (may take several tanks), you will note that the hanging will stop and you will just feel the compression at top dead center while being able to rotate the flywheel by hand. AFTER STOPPING THE ENGINE, MAKE SURE THE PISTON IS AT BOTTOM DEAD CENTER. That way the parts won't contract and cause the piston to be stuck at the top of the cylinder, possibly damaging the cylinder and piston.....
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Old 04-26-2009, 12:41 PM   #5
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Default tried it just now

ok i put everything back on, tightened the clutch nut up, and heated the engine up to 190 couldnt get it to 200. i threw it on the bump box and the flywheel is now spinning freely and not turning the engine over. what else cou be the issue? the engine is used and was running the other day. ive had it for about 2 months. used to run fine but yesterday it started giving me this problem. i cant, for the life of me, figure this out alone lol.
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Old 04-26-2009, 01:24 PM   #6
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if the flywheel is just spinning then you have one of two problems. either the flywheel nut isnt tight enough or your flywheel collet is messed up. if the nut is tight then just buy a new collet and it will be fixed
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Old 04-26-2009, 01:59 PM   #7
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Get a new collet and new flywheel..they're cheap anyway
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Old 05-01-2009, 01:54 PM   #8
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Originally Posted by jedro1 View Post
ok i put everything back on, tightened the clutch nut up, and heated the engine up to 190 couldnt get it to 200. i threw it on the bump box and the flywheel is now spinning freely and not turning the engine over. what else cou be the issue? the engine is used and was running the other day. ive had it for about 2 months. used to run fine but yesterday it started giving me this problem. i cant, for the life of me, figure this out alone lol.
If the engine is used, you need to tear that sucker apart and make sure it doesn't have something in there binding it up. Have you seen it run? Depending on how many gallons that motor has on it, you might not have any pinch left in it and it could be something in the cylinder or in the crankcase.
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Old 05-01-2009, 03:13 PM   #9
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Some engines need to be shimmed between the flywheel and main bearing. Remove the piston and liner so you can check the flywheel properly without the illusion caused by the engines compression. Leave the crank shaft in the engine and mount the collett, flywheel and clutch nut. Make sure that the clutch nut is VERY tight, now check that the flywheel and crank shaft spin freely. The flywheel should not stick AT ALL and spin freely with the crankshaft. If it is binding, even in the slightest, you will need to check:

A: Collet inside the flywheel
B: A small shim between the main bearing and the flywheel

Hope this helps!

If the clutch nut is not tight enough it will spin freely on the starter box. You need to hold the flywheel/lock the crank and really tighten it up!!
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