clutch slip on new TT50

[virtual120]

Just finished building new raptor 50 se. Ran for a while then found when throttling up the blades wern't engaging and the engine was just revving real high. Any idea what would cause this ?

Thanks
TIm

[LAMAR COOLEY]

virtual120,
I'll try to help you get the ball rolling.
First, did you use the engine washer under the fan.
I'm not familier with the TT50's length from back plate to thrust washer, but the lack of this washer may have the clutch protruding to far below the clutch bell ?
Note: With the OS 50 this washer is not needed which allows the clutch to" fully "
insert into the bell.
Second, the engine may have started and been running backwards.
However in most cases( backwards) this would cause the clutch to instantly grab the clutch and spin the blades.
Three, Could you have possibly installed the "main" one-way bearing backwards ?
( Not likely, I know )
Four, Could you penion have come loose ? ( not likely because the counterclockwise rotation (looking down on it) of the clutch bell would spin it onto the penion.
O.K I'm out of other ideas right now.
Anyone else care to help a brother.
Regards

[stevehonn]

Check to see if the bolts holding the clutch are still in one piece. There were a few fans that weren't tapped deep enough, you tighten the cap head screws and it seems tight but isn't, the clutch chatters against the screws and shears them off.

[virtual120]

virtual120,

Note: With the OS 50 this washer is not needed which allows the clutch to" fully "
insert into the bell.
Regards


Hi LAMAR

Is this the washer you mean that i dont need: will this not cause 'play' in the starter shaft if removed ?. Thanks for your help. ps. i have the TT50 motor.

http://www.cablebaybedandbreakfast.co.nz/washer.jpg

[LAMAR COOLEY]

virtual120,
NO sir this is NOT the washer I am refering to. It will be a washer that came with the engine. The washer I refered to is not indicated in the Raptor manual at all. But is shown on page 10 of the OS 50 engine book
This washer "COULD" be placed on the engine shaft between the fan and the engine drive hub. But it is not required or needed if useing an OS50 with the Raptor 50 or 90.
But as I said it may be needed with the TT50 if the clutch is not going into the bell so that at least the bottom of the clutch is flush with the bottom of the bell. Ideally the clutch should be centered on the clutch pad( liner ). ( not sticking out the bottom nor contacting the top inside of the bell.
Sometimes when this washer is used it causes the clutch to contact the inside top of the bell = ( bad ).
I really think that the engine was - is probably running backwards. Which is very easy to happen especially with a rich low end ( idle ) " needle "and breaking in a new engine.
As the low screw and high needle come from the factory with a rich setting
The engine "backfires" and starts running backwards
What are you using for an engine starter ?
The starter must turn counterclockwise when viewing the top of the heli.
Because you've stated that this is a new build then I would have to rule out a bad clutch liner and or a bad clutch. But anything is possible.
If your throttle linkage is setup properly ( 50% throttle-collective will equal 50% carb. barrel open) in which case the blades should start to turn with about 25% and upwards of throttle.
Might I suggest checking out http://raptortechnique.com
Mr. Mike Prewitt has an excellent site on Raptors and all sorts of other nifty how-to's.
I hope this is of some small help.
Regards

[virtual120]

Thanks for your advice. Yes the engine is running the right way. Its definately the clutch slipping but cant see why. New line, new clutch etc. Ill have to do another strip down and take another look.

Cheers
Tim

[Canadian Man]

did you ever get this figured out? My heli is doing the same thing and you originally described.

Thanks

[virtual120]

did you ever get this figured out? My heli is doing the same thing and you originally described.

Thanks

I just replaced the clutch in the end aith an after market vented style clutch and never had the problem since.