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The dreaded off idle bogg

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I have a z400 quad with the following mods; drz e base gasket, hotcams intake and exhaust cams, an fcr 39 of a yfz 450 quad, a 10k srp ignition box and a pro circuit full pipe. My set up runs great without the exception of the off idle bogg. I have even switched back to the stock gearing as I was hitting the rev limiter in 5th!

I started out with a 165mj a 45 pilot and 2 turns out on the fuel screw. This was way too rich as it would start and run cold without the choke on. So I changed out the pilot for a 42 and set the fuel screw 1 ¾ out. This cured the rich idle but it still had a slight bogg. After doing a search here I adjusted the acc pump screw a ½ turn in to soften it up a bit, I was still thinking it was lean. This helped, as it will free rev without a bogg. After riding 54 miles of trails this weekend it still has that damn bogg. It’s a real pisser when you want to lift the front end to blast through a puddle. I had better response with the bsr. With this modded set up it’s a fight to get access to the carb. Is there any short cuts, something I’m missing? Thanks

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The sources of the bog are legion, but if you feel you've got it jetted correctly, then you need to adjust at your accelerator pump squirt.

You need to determine if your YFZ carb has a tab in the proper place that will allow you to do the BK mod OR you need to determine if your YFZ carb has leak jet.

One or the other of these changes can be used to adjust the duration of your AP squirt. I personally prefer the leak jet method, because it avoids drillling holes in an expensive carb. See the sitemap at www.thumperfaq.com for details.

The AP screw you adjusted is intended to set the timing of the squirt in relation to the twist of the throttle. You'll need to dig a little deeper to affect the duration.

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