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Need carb knowledge quick - Please!

910 Views 9 Replies 4 Participants Last post by  ShawnCT450R
Bike is a 2007 DRZ400SM with stock carb. On the forward end of the carb, center, underside, there was a screw with a large knurled knob on the end of it. I believe this was the fuel mixture screw (???). It fell out while I was riding today (bike shut off on it's own - had to have wife bring the truck), and I just discovered that it is gone. Am I correct as to what that screw is? Also, I need to replace it, and quickly. Track day this weekend. What should I replace it with (aftermarket or stock), and where to get it. Much thanks in advance!!!

BTW - not talking about the idle adjust knob.
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Did you buy the bike used? I don't think the stock fuel screw has a big knurled head. Someone will chime in but if it was fuel screw, get aftermarket with the large knob so you'll be able to make adjustments easy
Thanks for the quick reply. The knurled head was actually not very big. Just trying to provide a good mental picture for you. I did buy it used, a couple years ago. The screw that was in there was stock from the looks of it.
You're fuel screw fell out. I would get another aftermarket one so you can still adjust it. Don't forget the spring and the o-ring that goes on the screw where it goes into the carb (I hope that makes sense lol). One thing to remember and this might be why this happened. Do not go more than 3 turns out on the screw. More than 3 turns and you'll need to go up a size or two on your pilot.
I vote fuel screw. You can get sweet anodized ones with numbers for reference for pretty cheap. Might want to squirt some carb clean through it just invade something in it with the screw gone. You'll need a spring, o-ring, and tiny washer that go with it.
Exactly what I thought guys. Thanks for the confirmation, and the extra tips about the spring and orings and stuff. Who do I get it through? SMJ sell it, or maybe thumpertalk? Do they sell a kit with the screw, spring, orings all in one? Thanks again!!
You are gonna need to order the spring and O-ring from OEM parts. I think TT have Oem parts now, if not, Bike Bandit has OEM stuff.
Ordered the fuel screw directly from kientech today. Excellent customer service, and they knew exactly what I needed. Including the oring, washer, and spring, and express shipping (I need it by Friday), it was half of what just a stock screw was from the dealer. Can't wait. Also, picked up my old style honda XR gas cap today to replace the crappy clark gas cap on the big tank. Need to go test fit it. I'll let you know how the needle works for me when it gets here.
From head to tip it goes spring, washer, o-ring
Just a follow-up here. Got the fuel screw from Kientech. Had all the little parts with it. Put a little black mark on the shaft (to count turns) and put it in. 2 turns out, and the bike fired right up and ran great. Rang it out a good bit at the track on Sunday. No issues. Great service from Kientech, and they knew what they were talking about. Cheap fix.

Also, we had a guy named Kenny with us this weekend, who is a prior racer, and was the original R&D tester for the new BMW S1RR superbike. Great guy. Gave us lots of tips on riding. Brought one of his race-ready S1RRs for us to oogle and drool on. Really sweet bike.

Also, the other pro with us had two of his racing supermoto minis with him. He was following us around the track and giving us tips as well. Not gonna lie. He and I went out for a few laps, and my 400 had nothing for that little 140 kit. Hehehe

Great day, all in all.
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