Center/Clutch springs

[diopwrd]

hey everybody....can anyone explain to me how these springs funtion?

[Arnadanoob]

Both the center and clutch springs do different jobs but keep in mind that it's the entirety of the transmission (boss, pulley, weights, ramp, belt, rear pulley, center spring, clutch, clutch weight and clutch springs) need to all work together in order to run properly.

The center spring is nearly a tension spring. It's job is to control the rate in which the belt drops down (which results in going into a higher gear).

When the bike is at rest, the center spring keeps the belt on the outsides of the rear pulley which is like 1st gear in a car. If you look at a mountain bike, notice the rear cogset, the biggest gear on the rear rim is the low gear. Conversely the smallest cog is the high gear. The spring strength controls the rate in which it switches gears.

A stronger center spring will allow the belt to drop into the pulley into a higher gear at a slower rate than a softer center spring (because it'll cause the rear pulley to resist pulling apart to allow the belt to drop down lower towards the center for a higher gear). If you use too strong of a center spring, your rear pulley will keep the belt in a lower gear (great for climbing but bad for higher speeds) for a longer period of time. The end effect is similar to using lighter weights at the front pulley (variator).

If you use too soft of a center spring it'll switch to a higher gear too quickly making it much harder for your engine to accelerate your moped. A softer center spring might be more useful for when you're on relatively level terrain and in need of a higher gear sooner (especially for you high mileage cross-country riders). The end effect is similar to using heavier weights at the front pulley (variator).

Strong center spring = upshifts slowly, downshifts quickly. For you technical peeps, the stronger spring resists compression (which allows for a higher gear) but is very willing to expand (which allows for a lower gear).

Softer center spring = upshifts quickly, downshifts slowly. For you technical peeps, the softer spring doesn't resist compression much (which allows for an easier upshift in gears) but is slow/lazy to expand (which determines the rate of downshifting to a lower gear).

You need to remember that you need to balance this out with your front pulley (variator) and the weights. Generally when you go with a stronger center spring, you use more weights. If you go softer on the center spring, you can use lighter weights. This isn't the rule, but it's a good way to start tuning.



The clutch springs are simple, it's the timing of when it engages the clutch. If you have it engage too soon, you'll have no power and it'll likely bog off the line. If you have it too high, all it'll do is rev up your motor more than necessary and it'll likely fly off the line. If you've driven a car with a manual transmission, I'm sure you can relate to letting out the clutch at 2000 rpms versus at 4000 rpms. The latter will take off faster because the engine will be at a higher power band. However this would be great for you big and heavy guys.

Lighter weight of rider = can use softer clutch springs (2000-3000 rpm)

Heavier weight riders = might need to use stronger clutch springs (3000-4000 rpm)

[noiseguy]

Nice post; that went into Adv Tech Docs too.

[PimpinSpree]

Lighter weight of rider = can use softer clutch springs (2000-3000 rpm)

Heavier weight riders = might need to use stronger clutch springs (3000-4000 rpm)

i don't know if your refering to the clutch springs as what rpm the clutch engages, but the aftermarket ones are sold by how high they engage over stock. So, i think we're on the same page here, but a lighter rider would want stock or 1k springs, and a real heavy rider would want 1k or 2k springs. Any higher than that and you'll probably wheely whether you want to or not

[Arnadanoob]

You're right, that's the general idea but it all depends on the moped's setup. See in Hawaii a lot of us are running strokers and the riders are like 200 pounds and up. 2k clutch springs won't cut it when you see those bikes with Arrow chamber pipes or Scorpions.

The clutch spring type is usually based off of how your moped takes off, for my bike I'm running a stock crank with a Corsa 72cc with a PG Long pipe. The PG is not the best take-off (low end) pipe for my application so if I use a softer clutch spring, it tends to bog a little during take off so I need the higher rev to compensate. I'm not a heavy rider at 155 pounds but again it's all about how your setup is.

If your bike is near stock, I'd normally leave it stock unless you're a big dude then you can go a little higher. A modded moped almost never runs stock or 1k springs, 2k is usually where most people start tuning. 3k is what I'm currently running and 4k is for the big boys.