Has anyone put a 4-valve head on an old 150

[waspmike]

As you can see I'm new to this forum.

I'm considering a new-old-stock carburettor G-Max 150.

I do like tinkering so I figure it needs a 4-valve head partly because this comes with cam already. Has anyone done this before?

I am at the end of the supply chain so I need all my ducks in a row before commencing.

For instance the 4-valve inlet at 25.2mm is that bigger than stock so will I need a new inlet. Etc, etc.

I would appreciate some insight.

BTW the 220 is not available here before anyone suggests it. Nor is the 150i.

[babblefish]

Answered your PM, but thought there might be some general interest in this.

Although I have not had any personal experience with 4-valve heads, I have been told by a couple of very knowledgeable people in Taiwan (scooter capital of the world, I think!) that a 4-valve head will give you more top end power at the sacrifice of low end torque. A 2-valve head is better for low end power and all around riding. It is possible to get most of the benefits of a 4-valve in a 2-valve without losing too much bottom end by using slightly bigger valve sizes and a bit of porting work. All of this makes sense to me (old hot rodder/engine builder). Looking at it from a port-flow point of view, the more port/valve area one has (as in a 4-valve head), the less velocity there is at lower RPMs, hence less power in the bottom end. I guess it all boils down to what you're after; high RPM power or low end grunt and everyday driveability. In the end, I went with the 2-valver with bigger valves and port work. Unfortunately, due to time constraints, I haven't been able to finish building my engine yet, but hope to do so this winter.

Oh, and welcome to MB!

[waspmike]

Wes,

Found it. Have a read of this?

http://www.billzilla.org/2v4vpage2.htm

The next question: Is the 4-valve head designed for 125 or 150 GY6? I ask because of compression ratio.