High speed gear installed

[sformal]

After a lot of hesitation, I decided to installed a 8:1 high speed gear on a stock G15-A...

The G15-A is a Japanese Yamaha which is a mix of several for the US:

• The engine/ignition is the 301cc (G16-A);
• The transmission is G11-A;
• The rest is more similar to G9-A;
• It is a 4 seater (limo) with 4 drum brakes.

Prior to this installation:

• Primary sheave (front clutch) from CPP (CPP05);
• Secondary sheave with power spring and spacer from CPP (DPK101);
• The sliding sheave of the secondary is the machined one from CPP (see following note);
• Severe double clogged belt from GBoost.

Please note, original wheels (8" rims) are in place and no lift kit.

As there is no 8:1 kit for the G11-A, I ordered for G9-A. If the small gear is exactly the same, the center hole of the large gear must be increased a bit; I had it done in a machine shop...

Once all installed, here are my first remarks:

• I have absolutely no trouble with torque; I cannot say I see a difference but before I was using the original sliding sheave;
• I hit 48 Km/h (30 Mph) without trouble, probably more if I over RPM a bit (playing with the governor).
• All the region is almost flat here.

I was hesitating installing such gear as I never found someone who did it without swapping a bigger engine and my conclusion is that it is something to do, even on a cart with the stock engine!

From there, I do not really want to hit the highest speed, and let say 40/45 Km/h is really the best for the region. I use this cart daily as my main transportation mean.

For different reasons, I shall put back the original sliding sheave and see what it does. Of course I shall post about it later... I did not test neither this new configuration with 3 "heavy passengers" () but shall post as soon as I try...

Would you have any question...

[ironmonkey17]

Did you have a chance to clock your speed before all the changes?

[sformal]

Yes, I was 28 Km/h (17 mph), but around 4,500 rpm...

...BUT to remove the transmission and put it back, we must remove the governor so its setting, of course, becomes different after the operation! Now there is something I did not think about is that I have a RPM in the engine compartment so tomorrow, I shall see at what rpm I go, but I suspect I was around 3,750... I shall see tomorrow (night here).

Anyway the purpose of this post - and I would have liked to know it before, I would not have waited more than a year - is that we can install a 8:1 with the original engine, it easily support it.

...and it is, by far, more efficient than to change the wheel size!!! For me, it was different, the frame/suspension/steering are totally different than US versions. To create a lift would have been a nightmare and, by the way, I use it in town and do not like the lifted look.

[sho305]

Putting 22-23 tires on is about the same as 8:1 gears and stock tires. Yes, about 30mph.

The cut sheave will help at very low speeds say 0-5mph. It gives a lower low gear when you take off, tow, or climb very steep hills. Otherwise it does nothing much different at high speeds. So it should be ideal for your HS gears and give you back nearly the same power at 0-5mph as you had with stock gears. The HD kevlar belt will also do that a little because it is slightly wider and rides little higher on the secondary.

[sformal]

Not really the speed calculator of this site calculates:

• 3500 rpm
• 12.5:1 ratio
• 18.5" tire diameter
• -> 15.4 MPH (24.8 Km/h)

• 3500 rpm
• 12.5:1 ratio
• 22" tire diameter
• -> 18.3 MPH (29.5 Km/h)

• 3500 rpm
• 12.5:1 ratio
• 23" tire diameter
• -> 19.2 MPH (30.8 Km/h)

• 3500 rpm
• 8:1 ratio
• 18.5" tire diameter
• -> 24.1 MPH (38.8 Km/h)

This being said, I am not surprised by their calculation, according to Maths:

• 1 turn of wheel 18.5" = 58.11946409 inches of distance
• There are 63,360 inches by Mile
• So to make 15 miles in an hour, the wheels rotate (15 x 63,360) / 58.11946409 = 16,352.53 times
• With a wheel of 22", the distance at each turn will instead be 69,11504 inches
• The total distance during the same time (same rpm) will be 16,352.53 x 69.11504 / 63360 = 17,83784 Miles during the same hour

It is very clear than changing the gear ration from 12.5:1 to 8:1, is BY FAR more efficient than changing the tire size (not talking about the cost difference)!

[sformal]

After almost 2 months, no trouble when we are 4 persons plus a child onboard , the engine is powerful enought.

Having installed back the original sliding sheave instead of the machined one, I cannot see much difference concerning the torque...

IMHO, a waste of buck$ but again, the region is flat!

[walte1fr]

Anyone installed this on a lifted 23” wheeled lifted tire?


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[cgtech]

Torque will suck with high speed gears, stock engine, huge tires.

[Rooster59]

Agreed. The 23" versus 18.5" tires will tax the stock engine enough. The gear change might even lower top speed if the engine can't pull it.

I didn't install 8:1 with 23" tires until I installed a 23hp engine.

[walte1fr]

Ok I figured so but was hoping. Haha


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