10pyro10 Posted April 1, 2010 Does anybody know the factory sizes of the main jet and pilot jet on the stock carb and also the needle position? I believe the carb is a Mikuni BST33SS. Thanks folks! Share this post Link to post Share on other sites
jcalis Posted April 1, 2010 pilot: 37.5 main: 127.5 needle: non-adjustable, one position only Share this post Link to post Share on other sites
10pyro10 Posted April 1, 2010 Thanx jc. My clymer 1990-1994 repair manual is showing (page226) a 135 main jet on the DR350S. That sounded too big for my bike. But a 127.5 main jet is more in line what I was thinkin. I didn't know the needle was fixed though. I'm lookin at a FMF powercore4 slip on (with quiet core insert) for my bike. I was just on the phone with FMF and they said jetting was not needed. He said maybe a turn of the fuel screw but that's it. The jetting center of the FMF site shows these settings for my bike......... Main Jet: 127.5 Pilot Jet: 37.5 Needle: STOCK Needle Position: 3RD Power Jet: N/A Air Screw: N/A Fuel Screw: STOCK Comments: Remove airbox lid snorkel I'm afraid it will be too lean esp without the snorkel but I think I'm just gonna try that slip on and see what happens. If I buy it, I'll report here with the outcome. I'm sure I'm not the only one going through this. Share this post Link to post Share on other sites
jcalis Posted April 1, 2010 Main jet should be around a 135 if you have an open airbox and aftermarket exhaust. The pilot jet should be fine, just tweak the idle mixture screw for best, smooth idle. 1.5 - 2 turns out from lightly seated position works best for most bikes. Clymer may be quoting the "Dirt" model when talking about the adjustable needle. Share this post Link to post Share on other sites
10pyro10 Posted April 2, 2010 (edited) By the way, my airbox isn't opened up. I don't mind removing the snorkle if I have to but I'm trying to avoid cutting into my air box. I want to be able to go back to stock should I not like this powercore. I was hoping to just slip on the new one to see how I like it. I know it will run a tad leaner but I was hoping the fuel screw would fix that. I figured I'd post this here as a good source of info for others too. Hope the pic comes out ok... This is for 1990-1994 bikes! I don't know if these specs are the same for later years though. Edited April 2, 2010 by 10pyro10 Share this post Link to post Share on other sites
