Max rpm question By lencho (Read 2,793 times)

[lencho]

I have a 150cc scooter and the tach shows the redline at 9000 rpm. At WOT on a flat road the engine will rev over the redline, as high as 9500 while traveling at 60 mph. I have read here that the max rpm should be limited to 7000 - 8000 by changing the weight of the rollers/sliders. If I install heavier rollers and decrease the rpm, will I still reach 60 mph? Is there some magic spreadsheet or chart that can help me keep from spending $200.00 on trial and error and ending up with 8 extra unwanted sets of rollers?

Lencho

[Alleyoop]

The magic is as follows:

Rollers= For every gram up or down your rpms will change by 500-600 rpms.
Sliders= For every gram up or down your rpms will change by 200-350 rpms.

So knowing what to expect from those numbers and weighing your current weights you can dial in whatever rpms you want to run at Wide Open Throttle.
Alleyoop

[lencho]

Should I decrease the WOT rpm, or am I ok as long as I keep it at or below 9000 Rpm? If I increase the roller weight to decrease the rpm, will that also decrease the mph or will the heavier weights also cause the variator to shift into a higher gear resulting in a similar max speed?

Lencho

[petrol42]

You probably will lose some top speed using heavier weights.

If you're going 60mph @ 9000 RPMs, most likely your variator is at the highest position it could go. This means you're getting to 60mph thru your engine's RPMs and not thru the CVT "gear ratios".

[Bashan]

Some folks run their GY6 150 up to 10 and 11K RPM and seem to do fine. Obviously that's pushing the envelope and around 9K is a decent redline. I wouldn't trust that tach just like I wouldn't trust the Chinese speedo. Get a Tiny Tach or one like it to fine tune your RPMs. Heavier weights push the inner pulley plate out quicker so you shift into higher "gears" quicker. You'll lose hill climbing ability but may reach a higher top end IF the inner plate wasn't making it out all the way. If it was then you were at your top end anyway as petrol42 pointed out. Some folks opt for the 115mm inner plate which allows the belt to go higher on the outer plate which equals more top end at lower RPMs. It sounds to me like you're at a pretty good setup with 9K at 60 MPH. It's a 150, you should only expect to run at 55 MPH most of the time. Rich

[lencho]

When alleyoop shared the ratio of weights to rpm, I assumed he was referring to WOT rpm. In my mind, the only way to do that is for the heavier weights to move the variator inner gear further resulting in a higher gear. After reading the other responses I now wonder if he was referring to rpm at which the variator starts to shift.

I marked my variator and ran up the engine (on the center stand, not driving it) and the attached pic shows the result. Does it look like there is unused high gear I could take advantage of with heavier weights?

Lencho

[tvnacman]

what is the diameter of the inner pulley . I sell one that is 115mm in diameter , most stock not all are 107mm . What size is the belt ?
A 12g roller will put you at about 8000 to about 8500 rpms depending on the engine . I would go with 13g roller will drop the rpm down a little (13g is my preference) if I run the lighter rollers I will destroy the engine quick . So I need the engine to protect itself .

John

[lencho]

Not sure of the pulley diameter and I'm out on town so I can't measure it. The belt is 835 20 30.

Lencho

[tvnacman]

Post the engine number you might be able to go to 842 .

John

[Alleyoop]

Yes I would say the belt should rise higher than that, that looks like a 1/2 inch left on the Variator You should try the next longer belt and or little heavier weights. You see that line on the Variator with it all nice and shiney You SHOULD at least be to that line.

About the weights and rpms results, I am saying for example:

If your current weights are say 14g rollers = RPMS 9000K:

If you go heavier than 14G WOT RPMS DROP:
1. If you put in 15g rollers = RPMS=8500
2. If you put in 16g rollers = RPMS=8000

If you go ligther than 14G WOT RPMS RISE:
1. If you put in 13g rollers = RPMS=9500
2. If you put in 12g rollers = RPMS=10000


Petrol42 is correct currently your getting your top end speed with HIGH RPMS which is NOT what you want your motor will not last.

You want to run at those Speeds with a lot less RPMS so you have to tune your CVT to reach those speeds at a much lower RPMS.
Things to do is try a longer belt and heavier weights if still not enough then your last resort is Taller Tranny Gears.
Alleyoop

[lencho]

So, let me share with you what fixed it!

I took tvnacman's advice and went to the scooter shop to buy a longer (842) belt. I was smart enough to bring my old belt with me (not normal) and immediatly noticed the new belt was much wider. My old belt had worn down from 20mm to about 17mm.

My thought is that the shorter belt (835) was too tight and caused excessive wear on the side of the belt. With a worn belt I was not taking advantage of high gear since after the variator moved all the way into high gear, the belt wasn't wide enough to ride on the outermost part of the drive pully.

With the old belt I ran 60 MPH at 9500 RPM
With the new belt I run 65 MPH at 8200 RPM

Much better!!!

Thanks for the help guys

Lencho

[tvnacman]

did you measure the diameter of the variator pulley faces ?

John

[lencho]

I didn't measure the pulley face, I will have to remember to do that next time I have it apart. I did weigh the rollers and they are 13 g.

Lencho

[Alleyoop]

That Variator is a hair over 4" in diameter. A performance Variator is 4 1/2 inchs in diameter.
Alleyoop