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hksimpson

Cracked Throttle Valve -- Carb options for 99 YZF400

13 posts in this topic

My 1999 YZ400F that I just got did not idle well so I tore the carb apart and of course if was dirty, but after putting it back together, it still did not idle that well.

I looked at is closer this time and found that the thin part that makes up the throttle valve is cracked:

http://home.csumb.edu/s/simpsonhenryk/world/carb.gif

It is the part that looks like a lid on the skateboard that combined is the throttle valve.

Anyone think this might be the problem? Above idle is rips just fine but at idle is dies and if I keep the throttle on to keep it running, it seems to pulsate.

Anyone ever seen this and I am thinking of getting a newer carb for the bike, so can someone tell me what fits/works?

Oh, and great to meet all of you in this forum. Been around in the DRZ forum, but when I got back into the dirt, the YZ was a lot less than getting a DRZ and seemed like fun.

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My 1999 YZ400F that I just got did not idle well so I tore the carb apart and of course if was dirty, but after putting it back together, it still did not idle that well.

I looked at is closer this time and found that the thin part that makes up the throttle valve is cracked:

http://home.csumb.edu/s/simpsonhenryk/world/carb.gif

It is the part that looks like a lid on the skateboard that combined is the throttle valve.

Anyone think this might be the problem? Above idle is rips just fine but at idle is dies and if I keep the throttle on to keep it running, it seems to pulsate.

Anyone ever seen this and I am thinking of getting a newer carb for the bike, so can someone tell me what fits/works?

Oh, and great to meet all of you in this forum. Been around in the DRZ forum, but when I got back into the dirt, the YZ was a lot less than getting a DRZ and seemed like fun.

Get that thing replaced NOW before it breaks off and gets ingested into the top end - big $$$$ if that happens. Go to Sudco. com for a replacement. Here's one other persons experience with the same problem: http://www.thumpertalk.com/forum/showthread.php?t=148719

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That is the perfect answer and one I could not find when I searched. I will not ride the bike (damn -- got a week off starting tomorrow!).

What other year YZ carbs will fit?

Thanks

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That is the perfect answer and one I could not find when I searched. I will not ride the bike (damn -- got a week off starting tomorrow!).

What other year YZ carbs will fit?

Thanks

I ride a 99 WR400 - essentially the same as your bike - and I have an 04 WR450 carb in it. It fits right in (the rubber boot on the air box side has to be stretched a bit but the clamp holds it in place just fine). You will also need the 04 throttle cables. I just capped the hole in the carb (with the plunger mechanism inside) for the hot start cable and use the stock hot start pull-knob set-up.

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No need to replace the entire carb, just get a new slide plate. Make sure that if you replace the plate you don't install it backwards or upside down ( I have read several threads in the WR forum about this happening http://www.thumpertalk.com/forum/showthread.php?t=340488&highlight=slide+plate ). It definitely needs replaced before it breaks off. Good luck! :thumbsup:

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I checked every dealer in the area (3) and all are saying a week to ten days, I go to Sudco and they say they can't get it, and the big online retailers have really long "processing" times and can't even confirm if they have the part in stock until I place the order.

Man, what does a person need to do to be able to ride! I am off next week and my bike will just sit there.

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Did you try the TT OEM store?? Great prices and great service.

Just shows you how much of an idiot I am! I ordered all my DRZ stuff from them and it was great. I will look into it.

I want to ride so bad I am looking at bikes locally that I can buy, ride next week, then sell.

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I checked every dealer in the area (3) and all are saying a week to ten days, I go to Sudco and they say they can't get it, and the big online retailers have really long "processing" times and can't even confirm if they have the part in stock until I place the order.

Man, what does a person need to do to be able to ride! I am off next week and my bike will just sit there.

Where in California are you located? If you are some place in Socal come on by (Huntington Beach) and I'll loan you mine from my 99 400 carb (I'm using a 04 450 carb in my 99) until you can buy a new one.

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Where in California are you located? If you are some place in Socal come on by (Huntington Beach) and I'll loan you mine from my 99 400 carb (I'm using a 04 450 carb in my 99) until you can buy a new one.

WOW!!! Isn't TT full of great people. What a stand up guy.

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Where in California are you located? If you are some place in Socal come on by (Huntington Beach) and I'll loan you mine from my 99 400 carb (I'm using a 04 450 carb in my 99) until you can buy a new one.

I am in Monterey so it is a bit far for the part, but as already mentioned, your offer is what makes Thumpertalk and most of the people I meet when I ride so cool.

After finding the prices on the parts, I am going to go with a used 450 carb because my cables are on the worn side anyway, so with he valve, gasket, cables and the other seals I want to replace, I am near $200. That goes a long way towards a newer carb.

BTW, other than the cables being different and deciding what hot start to use, was it easy to do the swap? Did you change the jetting on the newer carb?

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I am in Monterey so it is a bit far for the part, but as already mentioned, your offer is what makes Thumpertalk and most of the people I meet when I ride so cool.

After finding the prices on the parts, I am going to go with a used 450 carb because my cables are on the worn side anyway, so with he valve, gasket, cables and the other seals I want to replace, I am near $200. That goes a long way towards a newer carb.

BTW, other than the cables being different and deciding what hot start to use, was it easy to do the swap? Did you change the jetting on the newer carb?

The carb bolts right up but is a little shorter than the 400 carb so the rubber boot has to be stretched to go over the intake bell. Make sure you have a good seal in this area. I used Indy's jetting guide (found in the Jetting sticky on the WR side) to jet the carb. This carb truly is an upgrade over the 400 carb and woke the bike up. BTW, I paid $150 for my carb (purchased used here in the TT classifieds) but it was missing some parts - about $50 worth - so when all was said and done I was out $200.

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yep, the 98' & 99's wr carb had tis very common problem, i didnt noe the yz carb also have tis problem, get the post 2000 carb but metal parts will still wear out,

:thumbsup:

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