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phibes4000
07-05-2007, 06:59 AM
I've been running a 2G Clutch for about 500Km with the standard 1.6mm springs. I'm changing my clutch bell (to malossi), spring (trying red @ 70cc) and putting a malossi torque driver in (prob waste of time).

Like all Polini instructions, there's some serious pidgin english happening; so I'm confused. Can someone confirm that "in order to improve of 500rev/1' ... decrease of 1mm the dimension ... of the springs assembling" means 'tightening the spring tension by 1mm will increase the point at which the clutch engages by 500 RPM'?

Does this only affect take off? Given that I have a lot of mods should I go to a stronger spring (1.8mm)?

BTW, has anyone out there (other than Kyle H) got good speed out of a 70cc Polini kit using a red spring - I was only getting 88km/h on White/8.1g...

Ciudale
07-05-2007, 10:30 AM
Reducing (tightening) the lenght of the clutch spring will give you 500 RPMs more at take of. This will make you bike start stronger. It depends on the pipe you have on your bike, if the powerband is high or not. Setting the clucth to a high level will reduce the time it reaches the good RPMs level.
By the way 8.1g with a white spring seems quite heavy. I don't know whats your setup but you should probably go lighter.

phibes4000
07-05-2007, 06:35 PM
My setup is 06 PureJet NRG - Polini 70cc; Yasuni R (deristricted); Gear Kit: Polini Secondary; Polini Variator, Polini 2G Clutch; Polini Reed Cage, Carbon Petals, ECU Stage II Map; Malossi Winged Clutch Bell; Red Sponge; Malossi Torque Driver

I did have the White torque spring and 8.1g rollers (std in Polini Speed Control Kit). I've seen some say the white spring is best, but the fastest 70cc here seems to be Kyle's who's running Red/6g. Don't know what to believe but am getting Red and Yellow springs (just realised the ones I ordered are the wrong size).

It would be good to hear from someone with a 70 who's tried the yellow, red, white springs - it would be good to have a constant so I can just play with Roller weights.

Ciudale
07-05-2007, 08:03 PM
Man is it a joke, with the setup you have you don't know how works the variation? Let me laugh ! Is it your friends bike? Thats not a question of "that spring works better than this one" !
Do you know what is the purpose of a contra spring? You can't say that the white works better than the yellow, or the red, as its a matter of combination between spring AND rollers. Just for the idea, 5gs with a white spring can give you the same effect that 9gs with a red one. You add some thickness at the spring, but you run heavier rollers so you have approximately the same behaviour.

phibes4000
07-05-2007, 08:19 PM
HA HA HA - yes it's mine, yes I think I understand how it works but all my tuning experience is with cars and vintage scooters - i.e. not this style of transmission. I just wanted a constant so I didn't have to try every combo. I just realised that for me the options are white/blue/green/purple - red/yellow no fit.

I thought the spring did make a difference - you seem to be suggesting it's all about the ratio; but as I understand it the strength of the spring may affect durability and if too strong/weak push the pulley closed/open too quickly past a point the weights can compensate..

Ciudale
07-05-2007, 10:13 PM
The way the variator opens/close is only due to the combination rollers weight/spring thickness. Some people have their theory about using 5g/white instead of 9g/red, but at the end it remains the same, cause the ratio is equal. For example I use a very used white spring, even more stiff than a new one, but with very light rollers, and I get as many RPMs as with a red one and heavier rolls. The thing you got to find is not what kind of spring to use, but what ratio spring/weights the setup.

phibes4000
07-06-2007, 12:24 AM
Well; I've gone 7g/Green Malossi - a lot better for me than 8.1/White Polini for acceleration; but could squeeze more RPMs out at top speed. I need to do some research to figure out the powerband for the Polini 70cc + Yas R and where I want to settle at WOT.

Ciudale
07-06-2007, 01:27 AM
The R has a quite high powerband, so try lighter rolls. As you have an upgear kit and that the Polini variator is not an "accel" one, try something around 5gs with the white spring. A good way too check if the variation works at its best is to put a mark on the variator's pulley. If you have too lights rollers, they won't have enough force to push the belt to the top of the variator and the mark will remain. Then go for heavier rollers until the mark disappears. There you have the good weight for a good balance between accel and speed.

phibes4000
07-07-2007, 05:31 AM
Ah, the mark would have been a good idea; but I've already changed weights. I left the green spring in - I believe the white is too soft; and went with 3x 7.1g and 3x 5g. I improved the air intake as well; mostly clearing obstructions and the suspiciously small hole at the end. I just got up to 93 km/h on flat, relatively short distance, in rain, with a headwind.

I think I've gone as far as I can without getting into polishing, playing with squish etc. May put on a dyno at some point to figure out whether it's too lean/rich but after pulling out plug to index it looks nice. If I get bored I'll do a carb conversion; although hopefully there's a re-flash for the ECU before then...

I think the limiting factor for RPMs is the cylinder kit - there's an interesting review at scooterattack that suggests the Stage6 goes better with the Yas R - although it's a carbed bike/kit my Polini seems most powerful round 8K too...
http://www.scooter-attack.com/index2.php?main=/pskurven/kurve.php%3Fs%3D%26id%3D504

Anyway thanks for your help and I'm glad I made you laugh...