clutch mods

[ron9969]

Hi, im new here and thought this might help people.I have a dune 150 with the gy6 engine,the buggy weighs 500 some pounds and the engine was originally for a scooter,or so i read.Anyhow shimming the clutch or buying a stronger spring and changing variator weights all helps bring the motor alive and helps keep the clutch alive.Im guessing the ATV,s have the same setup and its something to consider.I just put a one quarter inch spacer behind my clutch,helped out alot.I read an article about doing this to snowmobiles and then polaris ATV.S. Im amazed i havent read about peoples kids burning up clutch,s.Seems to be a major topic on buggy sites.

[Reveeen]

The final drive ratio within the crankcase is different between a scooter and a buggy. The buggy engine I bought has a 3.07:1 final ratio, scooters are typically 2.11:1 to 2.78:1.

Pic here:
http://www.partsforscooters.com/Vehi...e-Transmission

I could not find a 3:07:1 (13/40) listed in the conventional scooter ratios, so I'm assuming it's specifically for buggies.

So, unless you changed the chain and sprockets, your final drive is too high.

[Weldangrind]

I presume that you mean too high numerically. A 3:07:1 would provide awesome low-end grunt.

[ron9969]

Originally Posted by Reveeen

The final drive ratio within the crankcase is different between a scooter and a buggy. The buggy engine I bought has a 3.07:1 final ratio, scooters are typically 2.11:1 to 2.78:1.

Pic here:
http://www.partsforscooters.com/Vehi...e-Transmission

I could not find a 3:07:1 (13/40) listed in the conventional scooter ratios, so I'm assuming it's specifically for buggies.

So, unless you changed the chain and sprockets, your final drive is too high.

Wow you went somewhere else,dont atv,s have a centrifigual clutch?all i had to do is stiffen the big spring with a spacer,others buy a stiffer spring.

[Weldangrind]

Yes, GY6 based quads have a centrifugal clutch, just like your buggy. GY6 buggies also have a gearset at the driven end of the belt (so does your buggy). If you look at the rear of the engine, to the rear of the left side belt cover, you'll see a fill plug at the mid point and a drain plug underneath. I'm not sure what gear oil is spec'd, but I used Castrol Syntec 75W90.

Reveen's point was that your gearset is buggy-specific, even though the rest of the design is based on a Honda scooter (first used in the Honda Elite, I think). A scooter engine in a buggy would be geared too high (low numerically) for climbing and quick starts.

[Reveeen]

There isn't anybody that will give you straight answers about this stuff, it seems to be a combination of ignorance, and the set-ups are so application/load specific that what works for one will not necessarily work for another.

Clutch springs:
Heavier increases the engagement RPM. A GY6 clutch (stock) seems to come in at around 1000 RPM. When/as you modify your motor you move your power band up, so unless you stiffen your clutch springs, your clutch will "hit" out of the power, and your machine will bog. The downside to heavier clutch springs is heat, when you increase your engagement RPM the clutch has to slip more to get things moving, slip=heat, too much heat and you will fubar your clutch, so be careful.

Variator weights:
As the engine RPMs climb the weights are thrown out changing the drive ratio. You want to keep the engine in the power, so you juggle the weights to do so. Lighter weights will hold the engine to high RPMs, heavier will drop the RPMs for a given speed. You can mix and match weights to give an overall result.

Take up spring (or the big spring in the back):
Typically you leave this one alone unless:
1) you are compensating for too heavy a set of variator weights
2) you are "fixing" the condition where you let off the throttle, then "get back on it" and the transmission has not shifted down, resulting in bog.
3) you are having belt slippage (heavy black marks on the variator faces)
Too heavy a rear spring will "eat" belts, as will too light a spring.

[Weldangrind]

Originally Posted by Reveeen

2) you are "fixing" the condition where you let off the throttle, then "get back on it" and the transmission has not shifted down, resulting in bog.

Excellent description Reveen. I understand the clutch principle from studying torque converters, and variator weights have a similar effect to distributor weights but I hadn't thought of modifying the Take-Up Spring. That would be useful in hill climbing; once you back off the throttle, it's difficult to regain momentum uphill. 8O

[Reveeen]

Modifications to the variator system should take place one at a time, in the order I've listed, unless you know what you are doing, "shotgunning" a bunch of mods at once really doesn't accomplish much.

Both 2 strokes, and 4 strokes, behave differently, what works for one doesn't necessarily work for the other.

There are claims that the GY6 is good for 12,500 RPM, I don't know, never had a tachometer on one.

[ron9969]

Im not sure about the gearset,i could only imagine a engine ment to power a scooter pushing a 500 pound plus buggy,kinda tough.My gutless wonder,well i put the quarter inch big spring shim,then added 10 gram rollars to the variator.Then after reading so many articles about burnt clutches and feeling that i was about to burn mine up,i put a bigger back sprocket on.its ok now.my buggy kinda screams along,i can max the rpm,s out in about twenty feet.i think my buggy goes around thirty mph tops.

[Reveeen]

Well Ron we got the thing reversed, you got a scooter motor for a buggy, and I got a buggy motor for a scooter. (I'm ok geared low, it will just keep the tickets down)