Ron Brown

This is keeping me up late....

While I understand that a car or motorcycle can be placed in neutral, and can spin

indefinitely, how can a moped, which has only one gear (always locked on) , take the shock of jumping off the kickstand, or coming to a stop sign. So the engine is huffing and puffing, but I always believed attached to the piston arm, and therefore to the drivetrain. What am I missing here? Thank you.

Re: In 2 words


Re: In 2 words


I have no clutch, that's part of the mystery. Thank you for your response.

Re: Ron Brown

That is to say, beyond a starting clutch.

Re: Ron Brown

i think you have an internal centrifugal clutch ... my minarelli does.

Automatic transmission.. centrifugal clutch

A moped... of the style allowed in the US... has a centrifugal clutch built inside.

Do you shift your automatic tranny on your car into neutral at a light? No

Do you put a snowmobile into neutral? No... there is no neutral

Does a chain saw chain saw continue to run at low RPM? No

All these engines have a centrifugal clutch which has an outer "drum" which is stopped while the vehicle is stopped.

And an inner "hub" which rotates whenever the engine is running.

As engine RPM rises ... shoes on the rotating hub push outwards from centrifugal force and begin to engage the outer drum and begin to propel the vehicle.

The car auto tranny actually uses a "fluid clutch".. not quite the same as a centrifugal clutch... but the principal is similar.

...And.... then.................. there is Fred Flintstone.

Re: Ron Brown


Thanks for your response. I'm sorry about my cranky responses;

but an "internal clutch" seems far out to me. I think this machine has only a starting clutch. I'm assuming the "starting clutch" --enough to turn the engine over and suck some fuel into the cylinder. Other than that, it rides on one gear. What are the piston, and axle doing while I'm sitting at a stop sign?

Re: Automatic transmission.. centrifugal clutch

Again, I appreciate all responses Miguel and Fred,

So you're saying with the "centrifugul clutch", as rmps rise there's "catch" in the system due to expanding something or other. This makes sense, other than that I don't know when the machine would understand this point, as we would ,shifting a normal car.

Re: Automatic transmission.. centrifugal clutch

yes, the vehicle "understands" this. that's why it's "automatic" centrifugal. as fred explained, at a stop sign, you simple brake an automatic car. the clutch slips in and the car is fine. you only have to hold the clutch down in a manual transmission car.

but moped have automatic centrifugal clutches. they're simple yet complex. what lovely little machines they are!

Re: Automatic transmission.. centrifugal clutch

It is not a "catch"... it is just like the brake shoes in a drum brake.

The clutch shoes are flung out by centrifugal force against the force of springs holding them back... the stronger the springs the higher RPM it takes to fling them outwards and engage the outer drum.

That is called "clutch tuning" by the snowmobilers.

Snowmobile drag racers use stronger springs so the clutch doesn't engage till the engine is at almost maximum RPM... and they... BLAST... out of the hole.

Trail machines engage at much lower RPM because they use weaker springs.

And I would like to hear your definition of a "starting clutch" as you call it.

Re: Ron Brown

Ron Brown /

Thanks, Jim, Miguel and Fred.

Fred, I think what Rick describes as a starting clutch is that mechanism which connects the engine to the pedals when you pedal fast enough. My Motobecane, like many other peds, uses this starting system. Strange, you would think they could arrange for this to engage at a certain engine rpm and avoid all these automatic clutches you guys are talking about.

Ron :-)

we doan need no steeenking clutches!

We just start eet onn de stand and rev eet up and roll eet off the stand and do a smoky burnout as wee leeev!

Speaking of smokey burnouts ... Ron... you ever been to "bike nite" in Royal Oak ?

I was there Thursday... quite a sight to see.

Re: we doan need no steeenking clutches!

Ron Brown /


Not for a couple of years. Especially not on the pink Honda, too close to Ferndale.


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