Carburetor Questions About My FCR

Hey, All!!!

I've been doing some "Winter Maintenance" on the '06 YZ450F. I'm cleaning the carburetor now, and have a question or two about these FCRs....

I've been kinda going somewhat by past experience working on 2-stroke carbs, and with my manual. Since my bike has had the "Zip-Ty Mod" done to it, I figured this article from Dirt Rider Magazine might help me.

That article kinda became the source of one of my questions. The text for picture number 5 says:

"05 The slide has a wear plate that lifts off. Some companies recommend changing it every 25 hours. It is an expensive part, but replacing it can make a big difference in how crisply and cleanly the bike runs down low."


One of my questions is: Does anyone ever replace this wear plate? My local Yamaha dealer, for some reason, sells parts around 20-30% discounted if you purchase online. P/N 5JG-14546-01-00, VALVE, NEEDLE is $105. :thumbsup::ride: Has anyone ever replaced this part to help solve a carburetor problem? Now, my bike didn't have a carb problem before I tore the carb down (but the day is still young, hee hee..... :lol: ), so I feel it's not necessary to replace it. It runs fine. But, it does have over 60 hrs. on it, and there is some visible wear on the part of the plate towards the intake port, as well as some "blistering" on it.....

Also, can anyone explain to me what function the "Starter Jet" plays? I'm gonna really go out on a limb here, and guess that it ties in with the choke knob, and is only used for starting, when the choke knob is pulled out. Does it factor in with any metering at, say, low throttle openings, or only starting??

On most 2-stroke carbs I've worked on, and the non-A/P 4-stroke carbs I've worked on, I've always been able to look at the casting tunnels & plugs, and could make a pretty good educated guess on how air & fuel travels thru the carb of the various circuits. But this Starter Jet circuit is a little tough for me to follow in my FCR, & figure out.....

Thanks for any help & advice you guys may have!


The plate on the back of the slide is misnamed in the parts fiche. It's actually called the vacuum release plate (by Keihin). It's usually OK to run it as long as it isn't cracked or missing a corner, and you should be fine with what's there. If you think it needs replacement, you can get the same part for a CRF450R through TT OEM for $59 (16037-MEB-671), and you can also check with Sudco and ask for a Vacuum Release Plate 35-41mm, (PN 1609-809-2100 Sudco order number 021-725; have them double check the number). Sudco ships orders over $25 for free last I heard.

The starter jet is what meters the fuel that flows through the "choke" (actually just an enrichening valve). There's normally no need to change it unless you ride in really, really cold weather. It plays no role in anything except when the choke is used.

Cool!!! :ride:

Thanks, Grayracer513! :thumbsup:

You confirmed what I thought about the starter jet, and I really, really appreciate the scoop on what I call "the Wear Plate"! I've got a new seal coming for that, but figure that alone should be "Good Enough!" for the time being. Like I said above, the bike runs GREAT, so I see no need to replace it, or lighten my wallet. I also finally found a post about it in the Jetting/EFI forum by Eddie Sisneros that, basically, said they seldom needed replacing....

Side note: Is that Vacuum Release Plate made of some sorta thermoplastic? It's not magnetic, and I really didn't wanna hit it with a file to see if it was metal. I'd thought about possibly having it plated with Roguard, or something similar, like was done on one of my 1911 pistols I shot in matches awhile back. That plating wears incredibly well (in a handgun application), but I don't think it could be plated if it's plastic...... :lol:


Edited by Diesel Goober
misspelled a word....

I would leave it alone. If I'm not mistaken, it's aluminum with some sort of coating, but I've never really bothered to investigate that thoroughly.

As far as plating it, I would guess that might cost as much as the $59 for a new one, but I could be wrong. As witness the grill work on most modern cars and trucks, plastic can ceratinly be "plated", but it's a much different process than electro-plating metals is.

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