yz400 carb swap?

Could I swap a 426 carb onto my 400?

You could. The 426 carbs are FCR-MX39's, as are the 450 carbs, but the '05 and up YZ450 carbs are a revised, improved version that works considerably better overall.

But the 426 carb comes with the hot start built in, which is inconvenient, but relieves you of the time and expense of setting up for the bar mounted HS. If you find one that's in good condition without a lot of wear in the nozzle or slide plate, you'd be way ahead compared with the FCR on the 400.

You could. The 426 carbs are FCR-MX39's, as are the 450 carbs, but the '05 and up YZ450 carbs are a revised, improved version that works considerably better overall.

But the 426 carb comes with the hot start built in, which is inconvenient, but relieves you of the time and expense of setting up for the bar mounted HS. If you find one that's in good condition without a lot of wear in the nozzle or slide plate, you'd be way ahead compared with the FCR on the 400.

Thanks for the info!

So could I swap a 450 carb from a bike up to 09 on my 400? This would be great because components are so much cheaper on the newer carbs.

You'll have some "problems" doing that. One is that you'll need cables for the bike your carb comes from, but they'll work in your throttle.

You'll need to plug off the vacuum port at the head where your current hot start goes, as well as the hole in the air boot for the same item.

If you use a YZ450 carb, you'll want to get it with as much of the hot start stuff as you can, from the lever down to the plunger, or you'll need to piece it together.

Lastly, the carb's a little shorter, so here's the trick: clamp the air boot on first, then push the whole thing forward into the carb mounting sleeve. Piece of cake.

Do you think the jetting would be similar from one bike to the next? I wonder if I could use the jetting from the 400 carb in the 450 carb?

The only real reason I am considerng this so strongly is because the rebuild kits for the 400 carb are very expensive and parts/gaskets for the 450 carb are cheap. The rebuild kit from sudco for the 400 carb is like $130.

Stock 450 jetting normally works. The improvement in overall performance is worthwhile regardless of the cost either way.

Well I found/bought a 2006 yz450 carb off of fleabay today. I'll have to score the throttle cables and hotstart stuff but I got the carb pretty cheap so I hope it doesn't add up to too much.

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