The most critical add on items

[90GTVert]

For those looking to improve on the performance of your scooter, here is the very first thing I'd consider. Install a tachometer. You can get a very simple to install Tiny Tach or SenDEC tach for around $40 and they are invaluable for performance monitoring and tuning. I wouldn't even consider doing any weight tuning without one since it will tell you exactly what the engine thought of the changes you just made. Most of the GY6 150 engines like to run in the 7500-8000 rpm range when wide open and on level ground, but how else do you know you have your engine in its "happy place"? Consider that your weight, altitude and terrain all affect the variator weight, carburetion and engine performance, and you'll see why I think this is the very first performance item you should add to your scooter. You can also use them to monitor any performance drops in advance of a part failure in many cases. They are readily available on eBay. Stan

[mike65072]

Great advice Stan. There are several models of these small tachs, which models work with the GY6 150 engines? Thanks.

[scooterollie]

mike65072;
In the "Tiny Tach" brand, you want model #TT226R-2C found here:

www.tinytach.com/tinytach/gasoline.php#

[kabala]

Hey Stan great advice,

How would you advise on how to adjust this WOT rpm, if it isn't between 7500 - 8000 rpms? I think you mentioned changing roller weights before. But whats the weight to rpm ratio?

For example if I'm using 10 grams now, what rpm increase can I expect if I drop down to 9 grams?

Or is there somekind of adjustment governor screw on the engine which allows me to increase the top end rpms.

[90GTVert]

If you want to raise the RPM's decrease the roller weight, and if you want to lower the RPM's increase the weight. I've found that if you drop 2 grams ( from say 12 gr to 10 gr weight) you will add around 5-600 RPM's, but this can vary based on a lot of factors (altitude, rider weight, terrain). You can also mix the weights (evenly spaced to stay in balance) to get finer adjustments. Most 150's come with around 13 gram weights, so if you have a couple sizes on hand, you can make a lot of combinations to get where you want to be. The more power you produce, the heavier the weights will need to be to keep the variator in balance with the power band of the engine.

Keep in mind that these engines are capable of higher RPM's, but unless you do some modification, anything beyond the 8k range is just adding wear and tear on the engine and cutting it's life span.

There are no governors on the engine other than the intake and exhaust flow restrictions from the OEM parts. Stan

kabala said:

Hey Stan great advice,

How would you advise on how to adjust this WOT rpm, if it isn't between 7500 - 8000 rpms? I think you mentioned changing roller weights before. But whats the weight to rpm ratio?

For example if I'm using 10 grams now, what rpm increase can I expect if I drop down to 9 grams?

Or is there somekind of adjustment governor screw on the engine which allows me to increase the top end rpms.