Need help with 99 400F carb

[SpceSpff]

I have had this bike for a long time, but it has sat quite a bit since I had kids.  I want to start riding again, but I have a carb issue.  The carb leaks gas like crazy.  Apprears it comes out from the bowl gasket, not sure.  Several years ago, I took it apart and cleaned up up real good, even filled it with water, to see if it would leak.  Seemed like I fixed it, until I remounted it (after the water dried, of course).  Still leaks. 

 

What are my options?  I read a few threads and it sounds like the carbs are junk anyways.  Parts are hard to find, etc.  Is there a direct replacement I can buy? How much more would it cost to upgrade to a 450 carb? 

 

Thanks in advance for the help.

[Thommo_400f]

True

The '99 carb is crap

Look for an '02 onwards. Much better setup.

Plenty show up at wreckers / ebay if you search a bit.

[SpceSpff]

Thanks for the reply.  How easy is the '02 and up carb to adapt?  Direct swap?

[grayracer513]

The '02 carb is the simplest because the complete hot start is self contained on the carb.  then you have only to block off the ports for the external HS on the 400 with common vacuum caps (glued and safety wired).

 

With the '03 and later, the matter is complicated by the need to add a cable and lever to the conversion, as the hot starts on all of these are handlebar mounted.  If you use an auto decompression cam, you can use the decomp lever with an OEM cable and such.

 

With any of these, the only other thing is that the newer carbs are slightly shorter, so the air boot has to be stretched a little.  The simple solution is to clamp the boot to the carb first, then push it forward into the mounting socket and clamp that.

 

The best carbs to use are the '05 and later YZ450 carbs.  They have more sophisticated internal circuitry and include a leak jet for cleaner low speed operation.  You will need to use the throttle cables appropriate for the year model carb you select, and as much of the hot start assembly (cable, plunger, etc.) as you can get with it if buying an '03+.

[WrightStuff]

The '02 carb is the simplest because the complete hot start is self contained on the carb.  then you have only to block off the ports for the external HS on the 400 with common vacuum caps (glued and safety wired).

 

With the '03 and later, the matter is complicated by the need to add a cable and lever to the conversion, as the hot starts on all of these are handlebar mounted.  If you use an auto decompression cam, you can use the decomp lever with an OEM cable and such.

 

With any of these, the only other thing is that the newer carbs are slightly shorter, so the air boot has to be stretched a little.  The simple solution is to clamp the boot to the carb first, then push it forward into the mounting socket and clamp that.

 

The best carbs to use are the '05 and later YZ450 carbs.  They have more sophisticated internal circuitry and include a leak jet for cleaner low speed operation.  You will need to use the throttle cables appropriate for the year model carb you select, and as much of the hot start assembly (cable, plunger, etc.) as you can get with it if buying an '03+.

 

Gray... ever counted up how many times you've typed this out? ?

 

I grabbed an 07 450 off eBay for $150 with both throttle cables and the hot start cable and lever. With a little work you can get it on. To mount the hot start lever, I ordered the back side of the clutch perch for the 07 450 from the dealer - $8.00.

It bolted right up and looks cool! Now I just need to get the bike running.

Edited August 29, 2013 by WrightStuff

[SpceSpff]

Thanks so much for the informative replies! Great info and I am happy to get started on this fix.  I love this old 99.  Starts after sitting for months at a time, with only a couple kicks. 

 

Gray, thank you very much for the rundown.  So when you say the hot start is contained in the carb on an 02', does that mean the red knob also?  Here is an eBay link to a "02' carb".  But I see the reb knob on the outside, just like my 99'. 

 

http://www.ebay.com/itm/141048705968?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

[Thommo_400f]

That is an '02 in the picture.

The '99 carbs had hot start mounted on the frame behind the carb.

[SpceSpff]

That is an '02 in the picture.

The '99 carbs had hot start mounted on the frame behind the carb.

 

Oh man, I'm an idiot.  Been so long since I've been on the bike! 

 

I am going to have to think about this one.  Decide if I want to use an 02' or get an 05' and up and get it to work...

[SpceSpff]

Hey, need some advice. I got a 06 carb and installed it today. Bike runs, but needs tuning. I didn't check how it was jetted before install. Too excited But the bike does have a full Dr. D system. So, it will run, but only at high idle (choke on). There is a decent amount of popping. Rode it up and down the street once, bike died while stopping (clutch in). But at idle and while riding, it's a bit rough. I reused the 99 throttle tube. Aluminum over plastic, right?

1. Hot start- the actual lever wasn't included, so the cable is zip ties to bars for now. That ok?

2. Stock hot start. Just reinstalled it for now, since I had nothing to plug hole on block or airbox. Think that's affecting operation?

3. What jets should I be using (assuming I need to rejet)?

4. What can I do now to tune, before opening carb? The pilot screw on the bottom of carb right?

5. Sometimes while kicking, I can't get a full kick. I reset the decompression lever and try kicking, but the kick starter stops halfway or three quarters through a full kick, as if I hadn't hit decom lever. Is that normal?

Thanks for the earlier advice, especially greyracer. And thanks in advance for help for my new questions.

[Yz400f Jeff]

I would take the carb off and give it a good cleaning and check the jet sizes should be around 45 pilot 65 starter and main should be around 180. The hot start(s) shouldn't be the problem. Popping and only running with choke on is a classic plugged up pilot jet and or passage way ( running lean )Take the jets out clean them up really good with some carb cleaner ( don't get it on any rubber parts) and fishing line and push some line up into the passage ways where the jets sit to see if they are plugged up with junk. Lightly seat your fuel screw and turn it out 1 1/2 or 2 turns out and go from there should fire up if all is good I still run my stock carb I don't no anything about the 06 carb but it shouldn't be a whole lot different. About the kick start locking up mid kick sounds like your giving it throttle?? No throttle needed. Maybe one or 2 twists before the kick but not during might hurt your foot I learned the hard way.

[Yz400f Jeff]

Just noticed the bike is not new to you sorry if I was no help lol

[SpceSpff]

No, Jeff, there was some good info in there.  I am going to check out the things you mentioned.  I think the throttle cable may be too tight, resulting in throttle being applied during kicking.  Good advice, thanks!

[Mike15870]

A while back I was looking to replace my FCR on the '99 YZ400F, using an Edelbrock carb.  This seemed like the absolute best for easy adjust, install, etc.  But Now I can't find one with LOTS of searching.  Reading above in the thread the '02-'09 carbs look to be the best fit.  Any input on this Edlebrock ?

[grayracer513]

 

main should be around 180.

 

What??