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2007 CRF450R Carburetor Updates

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The 2007 CRF450R has some major changes to the bigger, 41mm FCR carburetor. These updates mostly focus on the accelerator pump cover and linkage that works the accelerator pump.

--The new carburetor has a revised accelerator pump linkage that "pushes" the pump diaphragm with more pressure, unlike the flexible "spring" linkages of past years. The pump timing adjustment screw now turns OUTWARDS to add freeplay, opposite from past years pump timing screw.

--There is a new cam and roller arrangement that determines the pump stroke instead of a bottoming rivet on the diaphragm. Therefore, the diaphragm is new and lacks a bottoming stud.

--The pump now has a fuel inlet on the BOTTOM of the cover. The pump's inlet check valve is located IN THE COVER, and no longer in the float bowl.

What this results in is a pump that gives an immediate, stronger squirt of fuel, which finishes it's full stroke in the first half of the throttle range. The pump force is comparable to a wired or stiffly banded 2006 linkage, with a stroke limited volume.

--The carburetor now has a different needle, with only 5 clip position, and new retainer bolt in the slide. The needle is longer and cannot fall thru the slide when the clip is removed. The retainer is more like a bolt with hex head instead of an Allen screw. The larger size requires a new top cover for the carburetor also.

Pilot jet- #42

Pilot air- #100

Needle- NJYR #3

Main jet- #178

Accelerator Pump Leak Jet- #50

See pictures at-

2007 vs 2006 CRF450R CARBURETOR PICTURES

James

Linkage- 2006 (Left) - 2007 (Right)

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Linkage Cam Roller-

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Pump Covers- 2007 (Left) - 2006 (Right)

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Pump Diaphragms- 2003-6 (long stud), 2002 (shorter stud), 2007 (flat rivet)

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Carburetor Needles and Retainers-

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The '07 CRF should not bog with some fine-tuning of the fuel screw or clip position. The response will be as good as wiring or a stiff O-ring on the accelerator pump linkage of the '02-'06 CRF's. That is, snapping the throttle open with a bike that has been ridden, and not evaluating on a stand. The pump force is as powerful as the modified pump mods described by Redbeard, Chills, Jimbo45, and Armourbl pasted at the top of the forum. In the first half of the throttle range, it makes more pressure due to the cam revisions.

The new Pump cover will fit onto older models, but the check valve needs to be removed by punching it out the bottom of the float bowl.

James

Float bowl on the '07 has no check valve (on left), unlike the '06 (on right)-

medium.jpg

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Great work, very informational. I wonder how long Factory Honda has been doing this? It's amazing how works technology slowly trickles into production. Too bad we all have to figure these things out for ourselves first! :thumbsup:

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The '07 CRF should not bog with some fine-tuning of the fuel screw or clip position. The response will be as good as wiring or a stiff O-ring on the accelerator pump linkage of the '02-'06 CRF's. That is, snapping the throttle open with a bike that has been ridden, and not evaluating on a stand. The pump force is as powerful as the modified pump mods described by Redbeard, Chills, Jimbo45, and Armourbl pasted at the top of the forum. In the first half of the throttle range, it makes more pressure due to the cam revisions.

The new Pump cover will fit onto older models, but the check valve needs to be removed by punching it out the bottom of the float bowl.

James

Float bowl on the '07 has no check valve (on left), unlike the '06 (on right)-

medium.jpg

James that is awesome.

So is a good mod to 02/06 model carbs is to fit the 07 model pump cover?

Can you explain what exactly needs to be punched out?

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To me it seems like the squirt duration is a little short. I need to get the bike up to about 4000rpm before it will accept a full throttle pull on the dyno. A properly setup 06 will pull from below 3K. It feels like the 07 needs more fuel through the AC pump, but the air/fuel reading at 4Krpm looks like it's rich enough. The first thing I'll try is changing out the 50 leak for a 35 or smaller. BTW, The bike also reads rich across the board on the AF monitor.

That needle system is going to make it a little more pricey if you want to change out your needle, as far as I can tell you can't pop the needle out of the assembly. I doub't anyone will need to change out this needle though.

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I don't have the dyno sheet in front of me, but from 4k to 5k it's around 10.5-11:1 then at 6k up to redline it hovers just below 13:1. RAD is about 97. The reading is pretty flat compared to most of the other CRF's I've worked with.

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OK I'm a knucklehead, just take the clip off to remove the needle.

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OK I'm a knucklehead, just take the clip off to remove the needle.

I was wondering what you were talking about. :thumbsup:

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James that is awesome.

So is a good mod to 02/06 model carbs is to fit the 07 model pump cover?

Can you explain what exactly needs to be punched out?

The pump cover would be a slight improvement, but not as much as increasing the pump pressure. You would need to punch the ball, spring, and brass plug out of the float bowl bottom. Remove the accelerator pump cover to see the brass plug on the bottom. This must be punched out from inside the float bowl, where the small ball bearing/check valve is visible, next to the leak jet in the picture above.

James

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question for anyone, i was wondering i have not yet did any mods to the 06 other than cosmetic bling, i was considering the a/p mod that rb and others have posted at the top of the forum. my bike is a 06 crf 450 stock, has anybody tried modifying the float bowl to the 07, along with the a/p mod in the sticky forum, and would there be any benefit by doing so? would you just do the a/p mod that is at the sticky forum only?

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will the 250f have the same setup, but just a smaller carb?

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Will the Boyeson accelereator pump cover still fit on the 07?

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has anybody tried modifying the float bowl to the 07, along with the a/p mod in the sticky forum, and would there be any benefit by doing so? would you just do the a/p mod that is at the sticky forum only?

The accelerator pump mod at the top of the forum is more important than using the '07 pump cover with check valve. The benefit of the pump cover alone is not as significant.

will the 250f have the same setup, but just a smaller carb?

According to the press releases, yes.

Will the Boyeson accelereator pump cover still fit on the 07?

The other replacement covers will not work on the '07. The new float bowl needs to have a check valve in the pump cover. None of the existing replacement pump covers will work on the 2007 CRF450R, CRF450X, CRF250R, and CRF250X.

James

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thanks james for writing back and btw i did have your kit on my 03 and it worked fantastic to say the least, it was a good purchase

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Re: 2007 CRF450R Carburetor Updates

Quote:

Originally Posted by rmhrc630

James that is awesome.

So is a good mod to 02/06 model carbs is to fit the 07 model pump cover?

Can you explain what exactly needs to be punched out?

The pump cover would be a slight improvement, but not as much as increasing the pump pressure. You would need to punch the ball, spring, and brass plug out of the float bowl bottom. Remove the accelerator pump cover to see the brass plug on the bottom. This must be punched out from inside the float bowl, where the small ball bearing/check valve is visible, next to the leak jet in the picture above.

James

Trying to think how this ( removing the check valve ) might apply to a 06 KXF 250 sea level with your leak jet kit 45 and the o ring, thats being ridden offroad. Thanks

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Emoney is the diameter of the air bleed for the main circut the same size as the earlyer carb or is it smaller you may be able to drill it a bit larger bleeding more air to the main circut causing the main circut to come in a little later shortening the nozzle has a simlar afect .the alternative to getting a smoother AF curve is installing a secondary main circut futher back in the air horn you can then lean up the main circut allowing the curve to be leaner initally and then the secoundary comes in later supplying fuel for the higher rpm range this has always been a problem with larger 4 stroke engines because of the strong signal they produce .

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Does anyone know if the 07' TRX450R got this updated carb? The part number DID change....

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