Modern Buddy

Have a Roughhouse with Prima Performance Kit #1. Installed an NCY 68cc ceramic cylinder. Can someone help me figure out the appropriate jetting? I Have a stock carburetor and Scooterworks racing air filter. So far what I have seen is people running a 40 for the pilot jet and 125 main jet. Then they have taken the stock air filter and drilled 7 holes on the back side of it. For those that have his set up I mentioned..... How has it worked for you performance wise? Also how many miles per gallon are you getting? Thanks.

I am running that kit, but not with a stock carb. So I can't help with jetting. However, look up the Uni brand airbox vent holes. Its a little 1 1/4" filter that plugs into a hole you cut. The way to go if you want to keep the airbox.

What carburetor are you running with yours? I think I would like to run a 21mm or is that too much. Also the air filter is 38mm so ideally I would like to find a carburetor that matches what I already have. What pilot jet and main jet are you running?

Whether or not I run the stock carb or get a new one doesn't really matter right? I can compensate for the stock carb by the jetting I use and air filter. Am I right when I say that?

115-125 range sounds about right to me. I think I have a 110 in mine with a malossi iron kit, prima stage 1 pipe, and the airbox lid drilled.

Although it will run hot with the stock carb. It's considered restrictive. Most people recommend a 19mm. A 21mm will work as well. I still run the stock carb but do Not cruise over 45 mph indicated.

What 21mm carburetor is compatible with the roughhouse. Also, if I change he carburetor won't I also have to change the intake manifold and get performance reeds? The others thing I will add is.... I am not racing with this bike. This is my only means of transportation so I need it for everyday, practical use. The idea of the big bore was to increase top speed. I want that bike to be able to do 60mph ideally. At the same time, I don't want to dimish bottom end speed. Didn't think his would turn into a few hundred dollar more process.

Oh, forgot to mention that I have the scooter works racing air filter which is 38mm so I would like this carburetor to be compatible preferably.

At 60 mph I don't see the crank lasting very long. Rpms will kill. You need to understand that your engine will not last as long. Mine went 9k miles on the stock top end before it blew the rings, the wrist pin bearing also had pitting and nearly ruined the crankshaft. The prima pipe and rollers were the only modification. It was jetted fat to run as cool as possible. Currently has the malossi iron kit and it's also jetted fat. It soft seized trying to cruise at an indicated 52mph. It survived but I'm more careful now. I have a local friend that commutes and he blew up three different kits, 2 on a Zuma and one kymco super 9. The stock kits will live a long happy life running wide open. To kit a 2 stroke properly you need: 70cc kit, pipe, performance reeds, carb and a lower gear ratio. Sometimes intake manifold . Sometimes an air intake.

I am running a 21mm carb. The 21 mm carb is great for top speed, BUT you use more fuel and wear parts.

The stock carb jetted right will do the trick. The torque of the 70 kit will keep you at normal speeds up steep hills. The bigger carb will really give you the top speed, but you run it hard all the time.

So the bigger carbs will raise the top speed at the expense of increased RPM, is that what I am reading?

Correct Todd. I believe the set-up I have with the expansion chamber and 21 mm flat slide will run harder than the parts can last. Its okay if it breaks because this one is for fun, but I think its a bit much for a "daily-driver". If you keep it under 50-55 it should stay together.