Ideal crusing rpm

[Rhompin45]

As it it when I'm going along at 50mph my Rpms are at 6200 if I go wot its about 58 mph at around 7200 rpm. I'm not looking to race this thing but I am think I need new variator weights since they are getting old. I don't know if I should go maybe one size lighter to slightly raise the rpm or just get the same. I want the motor to last so I don't want to go to high but it's just as bad for a motor running to low of Rpms so what's the sweet spot of these motors? As I am excelerating the Rpms go up to 5000 at around 25 maybe and increase slowly from there.

[gitsum]

Most generic GY6 150cc scooter engines are tuned to make their best horsepower around 7000 rpms and peak torque about 1000 rpm's lower. There are exceptions and variations of course, but the majority will fall into this profile.

Tune your variator with weights (I prefer sliders) that allow the engine to rev between 6500 - 6750 rpms during WOT acceleration. Ideally you want to reach maximum speed on level ground around 7000 rpms, 7500 at the maximum. If you are revving the engine above 7000-7500 rpms at top speed but staying at 6500 - 6750 rpms during acceleration, you need taller gearing. This can be done by using a larger diameter rear tire, shaving the variator boss (you may need to adjust the variator weights slightly lighter to maintain optimum engine speed during acceleration), an aftermarket variator, or a taller gear set in the transmission.

I have three parameters I strictly adhere to for running an air-cooled GY6 in regards to reliability and longevity.

1. At sustained cruising speeds the rpm's should not exceed 7000.
2. The engine cylinder temps remain under 350 f, 375 f for a short period of time (like less than 10 minutes)
if climbing a long grade.
3. If pushing the scooter regularly at higher speeds/temps, change the engine oil every 500 miles (gear oil 1500 miles) and keep the valve clearances in spec. For a Taiwanese or Japanese air-cooled scooter valve checks/adjustments every 2500 miles or so, for a Chinese scooter I would check more like at 1500 miles.

Most carbureted air-cooled GY6 scooters are tuned almost too lean to pass emissions. The carb needs to be properly tuned and jetted, and should have an air/fuel (pilot) screw for adjustment. On some carbs this is blocked off (you can remove the blockage). There are a few carbs that don't even have an air/fuel adjustment screw, I would suggest replacing it with one that does.

I don't worry so much about sustaining WOT for high speed cruising as I do engine temps.

Following these guidelines I fully expect my Taiwanese scooter to last a long time without premature engine wear or an engine failure. The top end should go at least 25,000 miles, perhaps as many as 50,000 miles.

[Rhompin45]

Thanks for the info. I have been good about changing the oil every 1000 km so like 600 miles. I put a uni filter on drilled out the stock exhaust like half inch pipe the stuck out the back i went up to an inch and welded a 1 inch pipe back it( helped more than I thought actually. And I went to a 115 main jet. It's the biggest I can go with out it bogging down. I wanted to run rich to help keep the motor cooler. I am conserned about temp I live in Phoenix az and it gets up to 115 a few days in the summer. But I don't use it to commute its just my toy so I mostly ride it at night when it's summer. I commute on a Suzuki tu250 which is also air cooled but it seems to stay cooler. Ill have to play with some weights to to see what I can do. I like tinkering with it anyways. It has helped build my motor skills because if I run into a problem there is a pretty good following of these things if I have questions. Like your self thanks for all of the info.

[gitsum]

Trail Tech has a cylinder head temp gauge with a sensor that goes on the spark plug for about $40.

I also had a TU250X, it was a great little bike. I had a CHT gauge installed on that too.

On every scooter I've owned (quite a few) I drill a half circle of holes in the CVT cover just behind the clutch.
It makes a big difference keeping the temps lower which greatly increases belt life and reliability.

[Rhompin45]

Ill have to check out that gauge that's a good idea. Do you have excess dirt/ road debre that finds its way in the cvt? That is my only concern with that.

[gitsum]

No extra debris, if anything there is less build up of belt dust.

The CVT was not sealed to begin with, it has small vents and an intake at the front.

The holes are drilled to face the rear because it inhibits water and dirt from being directly scooped inside.
The variator fan is supposed to draw air from the front intake which is much larger than the stock vents in the bottom or rear of the CVT cover.

[CarefulRider]

Wonder if I can revive this by asking the question with a different objective:

Have posed this question in other forums & have got one reply. I'd like your opinions as well to arrive at a general consensus.

I have a 2007, Sunl, Adventure, LB150T-12; 157QMJ, with a 150 cc GY6 engine. The scoot is equipped with all stock parts. No modifications of any kind. I just attached a tachometer to the scoot, as this model didn't come with one.

Now I wonder what the most economical RPM is to operate the scoot.

[Rhompin45]

That's a good question. I would think it would be economical speed along with rpm. Because wind pushing against you at higher speeds decrease it also. But I would think leaving it stock and cruse below say 40 45 would be your best bet. But don't take my word as this is my best thought. Although running at said speed it would be nice to be in the lower end of the upper hp range if that makes sence ? It would be nice to see a dyno of one of these motors but even stock gy6 motors seem to vary some. So there is a lot of variables. I hope this somewhat makes sence.