[xlint89]

I would love to see you build a monster engine. I try to help guys out using the least amount of $$ possible.

If you're looking for HUGE HP gains, a built GY6 might be a let down. I think they make 9 HP stock. You're prob going to see 15 HP at the most with a maxed out engine build.

Might be worth looking into an engine swap at that point. ATV or sled engine would have much more RELIABLE HP available.

HOWEVER: with the built GY6 you have no fabrication needed to make the engine fit. You can easily install reverse onto it. It already has electric start. And no need to fabricate a cooling system.

Plus the Yerf is one of the lightest buggies produced. They didn't use heavy gauge steel. And as you up the HP, you're going to find that the frame and axle will need beefed up as well. Not to mention the brakes should be upgraded as speed increases too.

So, now you see why I'm not gung-ho on the monster build?

It's a yard cart that is fun. Can it be made reliable? Yes
Can it be made more durable? Yes
Can it be made more powerful? Yes

Is it worth it to you?


Addressing the Chinese parts. Yes, that's most likely what's in there already. Not the best quality controls. That's why there's so much performance gain available from just cleaning up casting flaws and port matching. The engines run reliably because they are not high strung and adding more stress on the parts like you're looking to do.

You really do get what you pay for with cheap parts on this stuff.

When boring the cases for a big bore cylinder the spigot gets really thin in spots. This is why Tom likes a steel sleeved cylinder to aid in support of this area. That's not going to be a $50 cylinder and piston I'm sure. I have been fortunate enough to not have issues with my NCY Nikasil plated 62mm cylinder and it was prob around $90 for it.

I can't comment on the crank, but mine was around $200. Ruima 2.2mm and it was way beefier than the stock connecting rod. I had pics of the comparison, but Photosuckit blocks the pics from coming through now.

The head i used was a Taida large valve $160 and then cleaned it up a little myself.

The TK exhaust I used was pretty expensive. I want to say almost $300 but is supposed to be one of the best. I had good results with the stock header and a FMF silencer before the build. Not sure how good that header would be once the engine size was increased.

I didn't see your carb listed. The stock 24mm would prob be holding you back. I like flat slides myself, and went with the Mikuni 28 and have had great results. Around $100 for it.

UNI air filter $20

A12 cam shaft $35

Plus the cylinder spacer for the stroker rod, longer timing chain, quality (USA made) valve springs, etc.....

You might be able to build an engine for under $300, but I seriously doubt you will get longevity out of it using cheap parts.

I bent the valves on my head once, and completely broke them and the piston another time. That was before I got the GOOD American made valve springs.