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Centrifugal clutch ?

T

TWalker

Guest
I think I know in general how a centrifugal clutch works: it engages itself as it starts spinning faster, negating the need for a clutch lever to engagage disengage.

I'm not sure about one thing though> at low RPM is it completely disengaged? I'm considering using a pocket bike motor for a project and I want to know will it roll freely if the engine is off or idling?

Any experience on durability of 2 stroke pocket bike motors compared to happy times?


Thanks ahead of time for your help
 


L

Large Filipino

Guest
You would think if the engine was off it would never engage. That's because the clutch pads would not be spinning. Clutch pads not spinning means the spring would never let the clutch pads expand. It would stay disengaged and your drive wheel will roll freely even if you're going down a hill at 100 miles an hour.
Now depending on how stiff your clutch springs are will dictate at what idle speed is safe for your drive wheel to roll freely. Now the stiffer the spring of course,the higher RPM you can have your engine before engaging.
 

Simon_A

Member
Joined
May 2, 2008
Messages
224
Yup, they are completely disengaged at low RPM. The shoe's are held to the hub with springs, different strength springs are fitted to the shoe arms dependant on what RPM you want them to lockup. Most air cooled stock clutches only contact around 2000+ rpm. Allows the motor to get some speed up and approaching the powerband so it doesnt bog down before takeoff.

Depending on the powerband of the motor (primarily dictated my the expansion chamber of the exhaust) depends on when the clutch should engage. My race clutch only provides total lockup at 8000rpm just at the start of the powerband.
 

justin

New Member
Joined
Mar 26, 2008
Messages
26
Any idea if you could put one on an HT engine? I would love to play around with that. Any links would be good too. Tried the search, but maybe I'm doing it wrong. Didn't come up with anything good.
 

Simon_A

Member
Joined
May 2, 2008
Messages
224
I dont know if one would fit a HT engine, as mine is in the mail system as I type this.

What sort of links etc.? are you looking for? Do you want photo's of a centrifical clutch? I dont know what you are asking for.
 

adamtheha

Member
Joined
Apr 28, 2008
Messages
72
I just found a centrifugal clutch for a HT engine on Ebay, here's the link

http://cgi.ebay.ca/Automatic-Centrifugal-Clutch-Kit-Motor-Bicycle-Engine_W0QQitemZ220239220848QQihZ012QQcategoryZ11332QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

You'll need a pull start for it as well, boygofast sells them also on Ebay. Altogether, this cost me about $140 over and above everything else I've spent on this build!
Altogether I've spent
$200 - Bike
$165 - Engine
$15 - Paint
$120 - Lights
$40 - Accessories
$140 - Clutch parts
=$680 Total
Hopefully I could sell it for over $1000.
 

adamtheha

Member
Joined
Apr 28, 2008
Messages
72
Yeah, it looks as though it was welded together after market, but hopefully they've mastered the technique and tested them before selling!
 

fatboy67

Member
Joined
Mar 29, 2008
Messages
107
You can buy a 70cc HT motor that is already a pull start with a centrifugal clutch. For the same price as a normal clutch set up. the only thing is you would have to buy the cranks that are wide enough, so you can peddle.
On ebay. They come up from time to time, but I don't think they sell as well because of the fact that you have to buy wider cranks.
 
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