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Old 08-31-2014, 10:26 PM   #1
mrfortynine OP
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Is it OK to run engine without gear box and clutch attached

Planning to replace rear main seal. I figured that I probably should make sure there's no leak after installation before putting everything back. Of course I need to short the neutral switch wires to start the engine.
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Old 08-31-2014, 10:32 PM   #2
ME 109
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What year bike? 81 on with clutch carrier can be done.
Wait till you see how quick they rev up without the clutch and tranny!

Edit, obviously the clutch carrier will need to be bolted on to start the motor.
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Old 09-01-2014, 06:18 AM   #3
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No problem, just make sure the motor is tied down tight. There have been a few folks that used an airhead engine in small airplanes without the transmission,....... worked quite well.
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Old 09-01-2014, 06:50 AM   #4
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On pre '81 engines the flywheel has to be attached and on post '81 engines I guess the clutch carrier has to be attached. Otherwise the crank will fall off the back thrust washer, maybe.
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Old 09-01-2014, 07:06 AM   #5
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... it'd be real hard to start the engine without flywheel/ring gear attached.
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Old 09-01-2014, 07:11 AM   #6
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Quote:
Originally Posted by mrfortynine View Post
Planning to replace rear main seal. I figured that I probably should make sure there's no leak after installation before putting everything back. Of course I need to short the neutral switch wires to start the engine.
No problem, just attach the ground-wire somewhere, fit the clutch-carrier and start. Let it run for a few minutes.

If you have a working clutch-switch you don't have to fiddle with the neutral-switch.
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Old 09-01-2014, 04:21 PM   #7
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Quote:
Originally Posted by mrfortynine View Post
Planning to replace rear main seal. I figured that I probably should make sure there's no leak after installation before putting everything back. Of course I need to short the neutral switch wires to start the engine.
post #78 here http://www.advrider.com/forums/showt...=848159&page=6
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Old 09-02-2014, 08:10 AM   #8
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[QUOTE][/on post '81 engines I guess the clutch carrier has to be attached. Otherwise the crank will fall off the back thrust washer, maybe. QUOTE].....Huh??? As long as the flywheel is attached, which is needed to start the engine, the crank is ok. Its when you pull the flywheel off that the thrust washer can be displaced. The clutch carrier has no affect on crank axial movement.
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Old 09-02-2014, 08:57 AM   #9
disston
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[QUOTE=RayB;24983531]
Quote:
[/on post '81 engines I guess the clutch carrier has to be attached. Otherwise the crank will fall off the back thrust washer, maybe. QUOTE].....Huh??? As long as the flywheel is attached, which is needed to start the engine, the crank is ok. Its when you pull the flywheel off that the thrust washer can be displaced. The clutch carrier has no affect on crank axial movement.
Ray, the post 1980 Airheads do not have a flywheel. The clutch carrier has the starter gear teeth and takes the place of the flywheel.

It has already been pointed out to me that the flywheel or the clutch carrier will be attached so the starter can do it's job. Preventing the crankshaft from falling off the thrust washer may be taken as a secondary function I guess.

The end result is the engine may be started without the clutch parts or the transmission attached.
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Old 09-02-2014, 11:25 AM   #10
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You are right, it not called a flywheel, its called "Clutch Housing" per the Max Parts Fiche.

But it does have some flywheel characteristics ( wR^2) since has a weight and does have a large radius. Clutch plate and presure plates add more flywheel effect since they have weight too.

We can clarify this for the PO..Leave the thingy on that has the gear teeth for the starter to turn and you can run it.
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Old 09-02-2014, 01:00 PM   #11
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Originally Posted by RayB View Post
But it does have some flywheel characteristics ( wR^2) since has a weight and does have a large radius. Clutch plate and presure plates add more flywheel effect since they have weight too.
Indeed.

Judging by the speed of increasing revs with just the carrier installed. In my experience, the engine responded like a two stroke.
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Old 09-02-2014, 02:45 PM   #12
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That's probably the state that the engine was in when BMW dyno tested it at 70bhp!
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