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bigtooth

Carb Settings

7 posts in this topic

I have done a search on this and found a lot of usefull information, but none that pertains exactly to me. I have a '91 xr600r, I run the twin air filter cage and filter, and most of the time I have the baffles out of the stock exhaust. The bike has a bog when you hit the throttle hard, I understand that this is natual for a stock carb, but I would like to minimize it as much as possible. I have never rejetted a carb before, but I'm going to give it a try. I was hoping that you guys could give me some advice on what settings to try and perhaps point me to some literature that could teach me what they all mean. thanks! :excuseme:

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If you still have stock jetting, it needs to be richer on the bottom. Try a 68 pilot. The play with the screw adjustment to get it to work best. Without a pumper carb, that bog will always be there. Try not opening it quite so fast.

It could also use a step or two richer on the main jet, but that has nothing to do with the bog.

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So whats the idea on this? Is it to run the bike as rich as possible? Do you know what the stock jetting is?

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For a 91 the stock jetting is

main 152

pilot 62

pilot screw 2 turns out

needle 3rd clip

I think that I have a 68 pilot and a 158 main. The bike comes setup on the lean side. When you remove the snorkle and the exhaust baffle, it gets even leaner.

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Well I took a look at my carb tonight, I found the jets on the bottom of the carb, under the float. It looks like I have a 155 and 68 in it, but I couldnt figure out what you guys mean by clips on the needle. Can you guys try and explain that to me.

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The bog may be because you removed the backfire screen. This is a common mistake on XRs. Even scott Summers, Mr. XR. leaves his backfire screen in because American Honda couldn't get the thing to stop bogging off the bottom when it was out. Also go to the next richer pilot, and one clip higher on the needle. Take the carb top off, look down into the carb, you will see the top of the needle in the center of the slide. Pull it streight up and out, there is a little C clip on it in a slot in the top of the needle and there are like 5 slots in the needle. With the pointy end of the needle pointing DOWN move the clip (carefully) to the next position down towards the pointy side, this will raise the needle, it richens the off idle circuit that is the transition between pilot jet and slide/ main jet. Does nothing about bog but gets the bike a little richer. This may not be necessary for kust an un corked stock pipe but try it anyway. For the big, put the backfire screen back in...that will get rid of the bog.

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Hey thanks for the great advice. The problem with the backfire screen is that I dont have one. My bike never had one, I got it with just a k&n on it. Any place that I can get a new one?

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