Carb jetting w/ oem muffler

[pds00]

I'm getting my buddies buggy running that was sitting for a few years. Dune 150 w/ everything stock. The air box looks like it got run over so I put a UNI on it. I know i need to rejet however I don't want to destroy the OEM muffler. He isn't looking for performance since his kids are 10 and 12 yrs old. Any thoughts, jet sizes, would be appreciated. If i have to drill the muffler out i will to get the engine to run properly.

[Johnny 5]

you would need to clean the pilot jet or replace it. Our dune 150 buggies have 34 pilot jets and 122 main with modifacations. I opened the muffler a little from stock 5/8 to 3/4 of a inch. I drilled the stock tip off the mufler and welded a pice of 2 inch long bmx bike handle bar end that I had in the garage. I did not want to open the exhaust too much because the back presure is good for low end take off. Also you should have at least 6 inches give or take from the carb to the air filter. I used 1.5 inch sink drain pipe from home depot and a radiator hose to make a custom intake pipe. Stock 114 main jet will work if you dont open the muffler. When you open the muffler always jet up 117.5 or 120 at sea level. I tried a 125 main jet with no mods and the buggie would not get out of its own way. This is my experiance with jetting. Always check your plug after jetting for lean or rich. Black rich white lean tanish brown good.