Cautious uncorking

I have read about the many advantages of uncorking a stock XR650L, that a "Beast" resides within...thus with my curiosity drawing nearer - I wrestling with the decision to uncork my new toy. Currently the only mods / improvements I have made are a Baja designs skid plate, acerbis fork and disc brake guard and a Uni air filter.

IF I uncork it - may only the smog block off kit and carb rejet kit be used with the stock pipe. I don't want it loud - with an aftermarket pipe. Can you use just the smog block off kit without rejetting? I know you have to grind off the tab that prevents you from adjusting the air / fuel mixture screw, what is the adjustment for it after you remove the tab. Thanks in advance for all answers / advice etc :)

Yes you can run the stock muff. with larger jets. I used the dyna jet kit and it made a big diff. The only problem I had was that the kit came with out a larger pilot (slow) jet. Once I replaced the stock pilot with a 55 pilot,my sparkplug turned coffey brown and the poping from being to lean went away. As far as the smog kit goes I found no impovement. May be it runs cooler? Just do a search for Daves mods and you will save money and your motor will be better for it. I have just ordered the xrs only complete exaust system (header tail section) in stainles steal. I have been told its not to loud.

The stock jetting is designed for the stock airflow, which is restricted by the air box snorkel and the stock exhaust. You will need to rejet for a new level of airflow when you change the configuration of the air box and/or the exhaust system. The three items, intake, jetting, and exhaust need to be tuned as a system. If you rejet without changing the restrictive air box and exhaust system, you could end up with problems. If you do a lot of searching of this forum and read what is available on you will find out what configurations have worked for others. I am no expert, but I followed the (Dave and Brian) procedure with anew BigGun "Quiet Series" exhaust system, and had great results. The BigGun Quiet Series is a little louder than stock, but not bad, and it meets US Forrest Service sound requirements.


Get a White Bros E-Series S bend, and add the Quiet Core adds mad power over stock and you lose that big ugly bazooka that looks like a WMD off your BRP.

Most guys run a 58/158 jet, shim the needle, and drill the slides to 5/16, then turn the screw out 2.25-2.50 turns. So much better !

check out Supertrapp IDS2 quiet core pipe (XR600 model fits the 650'L') , ... about same loudness as stock pipe, affordable, too ... remember, when you upgrade your exhaust pipe, you probably will need another (richer) jet change to compensate for the better-flowing pipe ... enjoy

My standard advice- try it with the stock pipe first.


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