I have had my latest build up and running for about a month now (29" kent Genesis with a 66cc Skyhawk and SBP shift kit) and have had lots of trouble with a lean condition over 25 mph. I have cut many intake gaskets for the cheap china intake, did not help. Added O ring to NT carb inlet, did not help. Removed screen in the gas tank petcock, did not help. broke motor down and replaced all the seals and gaskets, did not help. Drilled out jet in NT carb one size larger with an indexed drill set, that made some difference but engine would four stroke at low to midrange and run ok at WOT. Still not the performance I have on my other bike and my wife's bike. I had to make a custom intake because the air cleaner hit the seat post and top frame tube so I figured that the custom intake was too long and small of a diameter for the distance the fuel/air mixture had to travel ( the 7" L x 5/8" ID intake I made did not have any leaks as I pressurized it under water with no bubbles).

I purchased a CNS carburetor from Spooky Tooth Cycles, a expansion chamber from SBP, and a Boost Bottle from Boost Bottle Industries for the 66cc size engine. The CNS carb intake size is a bit larger than the NT Style carb by 4mm (there is a shim but I wanted to utilize the larger size of the CNS carb bore) so I had to remake the intake and switch sides of the carb to the left from the original position on the right side of the seat post to install the expansion chamber on right in the upward posision. Now the intake size is 5 1/2" L x 7/8" ID and is a closer match to the port size of the head so when I port matched the intake it was a perfect match. I also port matched the expansion head pipe to the exhaust port of the head with a dremel tool, took about 5 min per port. The boost bottle is still on its way so I will install it later but I may not need it now because this monster has sooooo much low end torque it doesn't even seem like the same bike. Before upgrades my bike struggled to reach 25 MPH (moped speed limit in Nevada is 30 MPH) and now a SCARY 45+ mph with plenty of throttle left and still had one more gear to go. The 29" wheels come to life with a twist of the throttle with no assist from pedaling (before upgrades I would have to pedal like a madman just to get going). She used to bog and pop before, now she just says "how fast do you want to go". I am sure 50+ mph is not out of the question but 30 is plenty fast on a bicycle.

I am not a speed demon by any means but I do like to have the power when I need it to stay up with traffic when making turns from the left hand lane and not becoming road kill from stalling out or climbing the hills at the edge of the valley. Not to mention my 125 lb 5'2" wife leaving me in the dust and laughing because she can. All the products I have installed on my new 29er are well worth the money and thanks to Spooky Tooth cycles for the super fast delivery on that CNS carb.