Re: Av7 74CC or Av10 50CC (persuade me)

I have the same set-up on a 40t, 45 all day, you'll be happy. I tried the 4-ball guide with 2-balls trick in my variator. It was fun/faster for awhile, but switched back to a stock 3-ball setup. I didn't like the bike screaming at 5000 rpms going 25 through the neighborhood (it didn't variate to 2nd ratio until about 35mph). The stock exhaust can easily be modified to take advantage of the 74cc kit and you don't have the linkage/clearance hassles.

Re: Av7 74CC or Av10 50CC (persuade me)

> Kenneth Hill Wrote:

> -------------------------------------------------------

> I have the same set-up on a 40t, 45 all day, you'll be happy. I tried

> the 4-ball guide with 2-balls trick in my variator. It was fun/faster

> for awhile, but switched back to a stock 3-ball setup. I didn't like the

> bike screaming at 5000 rpms going 25 through the neighborhood (it didn't

> variate to 2nd ratio until about 35mph). The stock exhaust can easily be

> modified to take advantage of the 74cc kit and you don't have the

> linkage/clearance hassles.

Does the variator essentially "shift" to a second diameter at a certain RPM?

I thought it was gradual, slowly enlarging the variator diameter throughout the RPM band. But it's essentially like 2 speeds?

Re: Av7 74CC or Av10 50CC (persuade me)

yeah you're right it doesn't shift abruptly, there is a clutch engaging, variator closing, spring resisting engine movement.

all 3 elements contribute to tuning, you can mess with spring shimming to fine tune the shifting action, but unfortunately the av7 style variator doesn't give you many options for improved performance.

Re: Av7 74CC or Av10 50CC (persuade me)

@kenneth hill

Did you do rebel moby's exhaust mods?

What did u do to modify it?

Thanks

Re: Av7 74CC or Av10 50CC (persuade me)

My variator makes an awful noise when I spin it by hand.

I'll probably take it apart and see.

Re: Av7 74CC or Av10 50CC (persuade me)

Graham, question for you.

I just watched Tomahawks new vid about the launch lever.

For greater acceleration you want small sprocket in front and a larger rear sprocket.

The variator essentially starts out as a small sprocket. As you gain speed, the variator creates a larger sprocket (essentially) so that you gain top speed.

The launch lever allows you to compress the spring and pull the motor back.

Let's say you're at a red light and you want optimal acceleration. You press the launch lever. It pulls the motor back. I thought that the motor should be in that position when you're at a top speed. How does that help at low speed?

Does it allow motor to hit higher rpm faster? You push launch lever and now the belt is "loose" since the motor is closer to the variator. So that allows the motor to spin quickly and then you drop the clutch lol? (drop the launch pedal lol)

Re: Av7 74CC or Av10 50CC (persuade me)

> Francois Labat Wrote:

> -------------------------------------------------------

> My variator makes an awful noise when I spin it by hand.

>

> I'll probably take it apart and see.

if it spins easy but sounds like metal balls clunking around on metal then.... its totally normal.

Re: Av7 74CC or Av10 50CC (persuade me)

the launch lever is pushing the motor forward.

the variator has balls in it which fling out and push the cheeks closed, as the cheeks close the belt rides up and makes it a bigger pulley.

the springs that hold the motor in place are like a big clothespin lookin spring thing, those resist the force of the cheeks closing by pushing the motor forward.

so, the engine 'shifting' is a combination of how much the balls weigh, how much the spring pushes it forward, and the geometry of the variator parts.

the launch lever forces the engine forward, acting like a a stiffer spring and delaying the shifting so you rev up faster. you'll probably be surprised once you are setup with the kit and 2 ball variator, that thing will be a rocket comparitively. 70 cc kits in general don't need the launch lever as much as 50's because they make better low end torque and don't have to be revved up to a million to make power.

Re: Av7 74CC or Av10 50CC (persuade me)

Thanks Graham!

Makes a lot more sense if the lever is pushing the motor forward.

Prevents motor from going backwards and the variator going up in pulley size.

Getting a way better understanding of the whole system now.

Awesome. I understand why its popular on the 50CC builds. It also doesn't seem that hard to make... Cheap mod if you got metal and linkage laying around.

I'll stick without for now. Keep the complexity low.

Welding the shock mounts tomorrow. (edited)

Re: Av7 74CC or Av10 50CC (persuade me)

I enlarged the holes in the internal baffles (you can bore them out with long scrwedrivers) and added an additional "escape tube" in the end cap. I used a rear bicycle quick-release axle kept almost full-length, I'm sure any small-diameter tube that you can weld in or use the cone and nut hardware of the axle to affix to the cap. (edited)

mobyv7e5bn.jpg

Re: Av7 74CC or Av10 50CC (persuade me)

It is kinda "gradual" (the variation) just takes a lot of rpms to get it moving. The more instant acceleration at just about all but top end is entertaining, but expect to burn lots of gas even just tooling around.

Re: Av7 74CC or Av10 50CC (persuade me)

the 103 exhaust is similar and i did some messing with that years ago, a larger diameter 'back pipe'- the one that sticks out the end, but keeping a long length, provided my favorite tone.

i drilled the end cap out to fit a 1/2" conduit and bored one of the middle welded in baffle plates, nice and throaty, maybe a little louder than you would want but about the same as a performance pipe.

i agree that the launch lever is un-necessary on a mild kitted build, torque wont be your problem, nothing wrong with taking off quick but the bikes i build these days i'm all about smooth acceleration.

Re: Av7 74CC or Av10 50CC (persuade me)

I have tried the blunderbuss on 70cc av7 with the mentioned mods above and did not think it was enough. Is the end tube that sticks out on the removable cap big enough for the 70cc kit?

Re: Av7 74CC or Av10 50CC (persuade me)

well.... its a moped so maybe its never enough. getting to 45 quick and creeping its way up to 50 top speed, with all pretty standard parts and total sleeper stats, good reliability... i'm not sure what else ya need out of a moped. yeah its not a crazy piped high rpm screamer but its a lot cheaper and less hassle.

i left the stock tube when i built one of these, jeez, back in 2009 or 10 probably... but like i said on the peugeot i put in a bigger pipe and it gave it a deeper tone, not sure if it made much difference.

Re: Av7 74CC or Av10 50CC (persuade me)

Some time ago I modified one with the ball type. I straight up PMed Rebel Moby and asked him how to modify the one with the ball on the end. It was hard to find info on that style. He said you could trim off some of the outlet pipe on the inside and start drilling eight 1/8 inch holes on the inner ball. Using the brass tube designed for a house lamp(the one with the 2 nuts that allow the wire to go from the base to the socket) drill another hole in the outer ball and use that for a second exit. To get it tuned right you can keep drilling holes on the inner ball until you start to lose performance. Once you feel the power drop off, after you made one too many holes, you can simply rivet the last hole shut.

I love the idea but I did not want to spend all that time removing the ball, dilling a hole, putting the ball back on, taking it for a ride, letting it cool, and then repeat. I figured I would be happy with just close. So I cut the inner tube off so I had two pieces that were the same length. Drilled a hole next to the existing exhaust exit. Angled the pipe so one faced each way. Then welded it in place. I drilled twelve 1/8 inch holes. Lightly packed the ball with some exhaust packing and it gave me the performance we were looking for.

I miss reading Rebel Moby’s posts. Hope he is doing well. (edited)

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