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YZ400 -YZ450 Carb

8 posts in this topic

Hi all I've got a 99' yz400 and I bought an 08'450 carb. I've just about got all the parts for the swap and had a few questions. I searched the fourms for all the info on this mod and noticed that everyone has installed them with stock jetting my questions have to do with jetting and options. Has everyone stayed with the stock jetting and or settings or have they tried JD jet kit, Factory pro Emusion tube or other mods and what were your results. I've owened the bike since new it's dual sported and has a DSP pipe. I live in socal I ride a little where I live (1200 ft) but mostly ride in the dessert Cal city, Jawbone and those areas. Any info would be greatly appreciated.

Roger

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I would run the stock 450 jetting at least at first to see how it works out. Most of the time, it's pretty close. Certainly don't waste your money on jet kits and trick parts.

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I'm planning on running it stock first for a base line then play with it. I picked ut a JD jet kit at CG by my house on clearence for $25.00, the jets are worth that.

Roger

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I got 30 hours with my 450 carb now, with stock jetting, and have no trouble at all, its very close to perfect. It pops a bit when really warm (1 hour + of constant riding) but I guess thats just how it is =)

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I got 30 hours with my 450 carb now, with stock jetting, and have no trouble at all, its very close to perfect. It pops a bit when really warm (1 hour + of constant riding) but I guess thats just how it is =)

Thank You

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I would run the stock 450 jetting at least at first to see how it works out. Most of the time, it's pretty close. Certainly don't waste your money on jet kits and trick parts.

Hey all - Just wanted to give an update - had been following a 99 400 carb flooding thread trying to get my 99 400 running.  I got a 2008 450 carb off the net and installed it.  After a few struggles in 'just bolt in on' issues. the bike is running like a top, like it was new.  Starts on the first kick !!!

 

Just a few notes on 'bolting it on'

  • I had to loosen the air box to pull it forward enough into the intake.  - re bolted it back up after really tightening the air box side of the carb.
  • I also pulled the brass piece out of the intake carb mount.  It allowed me to get a better grip on the engine side of the carb.
  • Make sure you plug the hot start tube on the intake AND the hot start 'tube' on the air box.
  • Lastly and I really think this was a big rookie mistake on my part - make sure that the fuel screw is installed correctly BEFORE you hook up the carb.  I didn't and the fuel screw fell out during testing and really put me in a tail spin trying to diagnose what the F happened to my well idling bike.  Installed a new Moose Zip Ty screw and this bike sings now !!!

Big Thanks out to Greyracer !!!  Your advice really helped and thanks for answering the same questions a thousand times in the threads.

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Thanks for the follow up.  All to often we see advice given, but don't hear how everything played out.  It's always helpful, and yes, a little gratifying, to hear back about the results.

 

On the air box thing, that's a different approach, but it works.  I normally tell people to try clamping the carb in the air boot first, then push the whole thing forward into the mount sleeve.  I'm now wondering whether the air boot from an '02 YZ426 would remedy the problem.

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Hi Guys,

grayracer513 & Mike15870

I have a 99' YZ 400 that I hated. This bike almost got thrown in the trash. I tried everything. Finally I found your post on TT and took your advice and put an 08' 450 carb on it.

My bike runs absolutely perfect. This bike was a pain to start and only liked to run WOT.

One twist of the throttle, no choke, 1 kick starts every time when the temp is above 60.I dropped one size from the stock 450 pilot jet and I have no issues with poppingbog,hesitation. Now it is a great woods bike.

I live in OH. 850ft above sea level.

Definitely take the brass spacers out of the rubber manifold hose clamps to get a tighter clamp on the carb like Mike stated. My bike started to run very lean on a long ride one day and I noticed the carb had pulled out of the manifold. No problems since I removed the spacers.

Throw the stock carb in the trash where it belongs!

I also put an aftermarket compression release cam in that works great. I think this old YZ will be around for awhile!

Thanks again.

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