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Post by sussexscooterhead on Jul 24, 2006 16:43:33 GMT -5
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Post by Jacine on Jul 24, 2006 19:43:46 GMT -5
What springs do you have in there now?
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Post by sussexscooterhead on Jul 24, 2006 21:58:00 GMT -5
I have the stock springs in it now and of course it takes off nice and smooth but I thought if it was engaging at a slightly higher RPM it would get going a little quicker.
And for so little money it seemed like a simple enough mod.
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Post by Jacine on Jul 24, 2006 22:02:23 GMT -5
True, but if the stock are 1500 rpm springs? What are the stock springs rated at?
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Post by scooterollie on Jul 25, 2006 8:52:59 GMT -5
Without a Tach it is really difficult to tell. My Roketa Fiji 150 clutch (with tach) engaged at around 2600 engine RPM and really jumped on take-off. My Bali 250 engages at a noticeably lower engine RPM. Can't say exactly what because I don't yet have a tach on that one. By feel and sound, as compared with my 150, I would guess no more than 2K. My 250 has more low-end torque and double the horsepower as compared to the 150 and it pulls strong from engagement. When you say 1K RPM springs, are you talking about clutch RPM or engine RPM? I may be showing my ignorance here but I don't yet have much variator and clutch tuning experience.
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Post by mgreenfield on Jul 25, 2006 10:01:32 GMT -5
Lots of "witchcraft" in making a CVT work just right. Complex interaction between front pulley which senses engine rpm, and rear pulley which senses torque, and clutch which senses rear pulley rpm. As rpms go up system wants to shift to a "higher gear", especially if there's no torque on the rear pulley.
Strong clutch springs can cause application of torque at the rear pulley to be delayed. This delay lets the engine wind up too much, which shifts the CVT to a higher gear, which means that when the clutch does engage you're trying to get going in "2nd or 3rd gear instead of 1st." Not good.
So, it's really easy to get in trouble as you try to tweek a CVT. Most folks just fiddle with weights in the front pulley. Some mess with the bias spring in the rear pulley. Seems to me that only serious racers/mechanics/developers mess with clutch springs.
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Post by Admin on Jul 25, 2006 12:42:27 GMT -5
I agree with mgreen. As far as the tranny system goes, you get the most bang for your buck tuning the rollers. But that pays off more in the 50cc scoots than it does in the 150's.
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Post by sussexscooterhead on Jul 25, 2006 14:43:50 GMT -5
Those are good points mgreenfield and I had been considering what to do about them.
Increasing the rpm would wear the friction material of the clutch out faster also, wouldn't it? And generate more heat?
I'm curious about the relationship between the roller weight and rear pulley spring in both the upshifting and downshifting of the transmission.
Are lighter weights equal to a heavier spring?
Is the relationship the same for both up and down shifting?
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Post by mgreenfield on Jul 26, 2006 10:04:10 GMT -5
sussexscooterhead, .....I work in Pewaukee, live in Jackson. Ride Burger400 most days to/from work. email = mgreenfield@ameritech.net. Give a holler. Maybe we meet.
AND, yep increasing rpm of clutch engagement will wear the clutch facings out faster! Especially!! if you end up asking the clutch to do some of the "gear reduction" the CVT should be doing, ....that is, slipping until the scoot comes up to speed.
Regarding the weight/spring relationship in determining CVT gear ratio: Front pulley w weights "votes" with engine rpm. Rear pulley w bias spring and helical slots "votes" with torque. And the fixed belt length makes them "agree" on the gear ratio.
Lighter weights should have very similar effect as heavier spring, but I don't know the fine points. Weights LOTS! easier to change than spring. Changing either shouldn't change final top speed because at some high rpm (with lower torque) the weights go to maximum, and this fixes the final top gear ratio.
FYI Clutch design assures gradual engagement when driven by engine, AND tendency to stay engaged once engaged. You feel this when you slow to a stop. This is especially true when (say) going down a hill where rear wheel is "pushing" the engine.
It's all an incredibly clever mechanical system. No computer control.
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