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Need some more carb advice

By BURLEY,
in WR400F/426F/450F

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BURLEY

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My new '05 WR is running poorly. As most of you know I did all the free mods and it has a ProCircuit Type 496. 48/172 jetting. It was running good. Put one desert race on it and some great trail rides. After the race, the "Yamacough" dead spot right off idle was bad. Cleaning the air filter didn't help. It wasn't "just right" and Indy suggested I go back to a 165 main. I also bought a YZ needle and proceeded to take things apart to rejet. At the same time I eliminated the AIS (had a friend weld the fitting and I capped off the other holes). I don't sence any air leaks. It will barely run now. It will start but it bobbles horribly and has this nasty nasty backfire. I put the jets back in the way I had it including the stock needle. The AIS fittings are sealed good. I can't find any vacuum leaks but no matter what I do with the jetting/fuel screw/idle etc...it runs the same. POORLY. I am searching every possiblity. Could I have taken H2O through the breather? Could I have valve issues (the bike has maybe 15 hours on it)? Doesn't this sound like a vacuum leak? I am at that point where nothing is working and I need a second set of "hands"...Thanks guys....Mike

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bikepilot

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Hey, just a wild guess, but have you checked the rubber compliance fitting between the carb and head? Maybe some foreign material in the idle port? (pull mixture screw and check the order and condition of the tiny little o-ring/washer/spring). Maybe when the carb was disassembled last time, the float got bent a little and is dragging on the side of the fuel bowl? Is the gas flowing freely out of the petcock? If not is the gas cap vented correctly? You probably already checked all this but I figured I'd toss it out there anyway... good luck.

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BURLEY

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Im guessing:

Manifold leak or your hot start is stuck open?

When you removed the carb, did you possibly damage the intake boot on the cylunder side? I wrestled a carb out once and put a rip in the intake boot.

I checked the boot. It looks good. I am still searching for leaks. When I put the bike back together the first time (after paint) I had the hot start cable routed wrong and it was stuck open. It wouldn't even start AT ALL, so I don't think that's it.

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Treebark

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When is it backfiring, after a twist of the throttle or at idling and from where the carb or the exhaust? Have you tried a new plug or checked electrical connections? I'm not familier with the AIS system so I'm not sure how that affects anything. If it's not jetting and it backfires all time then I'd check the valve clearances and change the plug.

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Rattler88

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If it's sick at idle and right off the start I would check the air screw

by removing it and cleaning it, and make sure that no dirt got in there.

Also you might want to check the float hight and make sure that there's

no crap in the little spring jet, changing the float hight on you.

Just some other opps for you???

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BURLEY

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Ok, I am back in business. I put in a new plug. Fresh gasoline and....found the plate on the slider in the carb (that the needle passes through) was upside down. It has a cresent shaped notch on the bottom and I found that notch on top. I didn't figure it would make THAT much of a difference, but my guess is that this is what the problem is. If anyone has had a similar experience... SHARE. And thanks for all the replies. I love TT. The bike is 100% now and I am SO relieved. I thought I was losing my mind.

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Indy_WR450

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Ok, I am back in business. I put in a new plug. Fresh gasoline and....found the plate on the slider in the carb (that the needle passes through) was upside down. It has a cresent shaped notch on the bottom and I found that notch on top. I didn't figure it would make THAT much of a difference, but my guess is that this is what the problem is. If anyone has had a similar experience... SHARE. And thanks for all the replies. I love TT. The bike is 100% now and I am SO relieved. I thought I was losing my mind.

There have been a lot of posts on the FCR carb on TT related to this issue. Glad you figured it out. I was stumped on your original problem. Why did you pull the slide out to rejet? ?

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Rising Star

Jackazz

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Um wait a minute here... I did'nt have to pull the slide or use needlenose pliers on my carb to get the needle out when I changed the clip position, I just flipped it over & it fell right out. ?

But then I did take off the cables & completely remove it from the bike! ??

Actually the only reason I removed it was just to "get a good look at it" & clean it up/out while I was messing with the needle. ?

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