How to 10HP for clone?

I have a 6.5 clone in my doodlebug and need more power!

So far I have a custom exhaust. Removed governor. Removed the airbox but I am still with the stock filter. Royal Purple synthetic oil.

I wish I had a dyno!

What would you guys suggest for a 3.5HP boost?
That header should be worth 1hp alone.
Aftermarket carb, 1.2 ratio rockers, 18 lb springs, and advance the timing to 28 degrees
WOW 1HP for the header! Oh wait I am slowly remembering what the piece of crap stock one looked like and 1HP is totally believable.

What carb would you recommend?


Active Member
I have a NR-Racing package 1 motor dyno'd @ 9.2hp @ 4500rpm that literally screams for the is under rated @ 8hp on their site. I did some checking:hammer::thumbsup: before I bought themotor on another site ( which I'm having trouble finding) that dyno'd the blue clone with only the governor removed @ 7.2 hp @ 4200 rpm.Another mini I have I put a low restrictive air filter on and header from NR, rejetted and it made a huge difference !!!
You can also mill your cylinder head and cut every other fin off the plastic flywheel fan, every little bit counts.
I thought about doing this, as I seen it on I wasn't sure if it would be safe. I guess if the cooling system was designed for a engine that would just sit there it might be okay to do since the mini bike isnt static and air flows over the motor too.
If you are gonna mill the head make sure you port it as well. Just milling the head cuts down on flow.
yep there is quite of bit of meat that can be taken out of the ports, especially where the bowl area flows into the port itself, get rid of all the hard edges, flow the port floor towards the valves so there aren't any drastic drop offs....

One thing else about milling the head, depending how much you mill and if you go with a flat top piston or not the sparkplug might hit the piston..... I never gave it that much thought until I assembled my clone after having .080 taken off the head and using a flat top piston..... I screwed the plug in and turned the engine over by hand a few times to see how the compression felt under a slow spin..... I pulled the plug out and the gap on the electrode was closed tight, it just barely hit the piston but it was enough to flatten the air gap.... I see places selling short plugs for this situation but thats not a real good idea as the spark will be up in the threads in the head, instead I'm gonna get some spark plug washers (indexing washers) and shim the plug up enough so it doesnt come in contact with the piston yet keep as much of the spark in the combustion chamber as possible....