Installing a '07 WR450 carb on a 426, what to do?

Acv valve is under this cover? Photo jpeg above isn't working. attachicon.gif20160926_104839.jpg

 

Yes and I wouldn't use Yamabond.

If you plug up the ACV you need to use a YZ450 pilot air jet.

What size is the yz450 pilot air jet and what do you suggest to plug it up with?

I used Epoxy. You should look up the jet part number for a 07 YZ450. I think it is a 100 or a 110.

Why not gasket sealer?

Air jet?1474911194350.jpg

Yup

Why not close off the Acv valve with gasket sealer?

Why not close off the Acv valve with gasket sealer?

Because it can get sucked in the carb.

110 paj

 

Use nothing.

 

Just cut the pin on the ACV plastic floating valve .

Ok, I will try that.

While I am at it, the accelerator pump cover looks like it is aftermarket with the Boyeson symbol, any validity?1474918649194.jpg

Ok, installing the JD Jetting jet kit and calls for me to use a #168 main jet. Think this is too rich for the 426 to use on the 450 carb?

Any help about richness?

Any help about richness?

I'd suggest checking this forum's jetting database for other 426's running at your altitude.  You might have to experiment a little bit, but all you need is a screwdriver, a 17mm wrench and a 6mm socket to change your main.  One the benefits of the steel frame if you ask me :)

Any help about richness?

 

168 should be fine

 

A boyesen cover helps with cavitation, but it does not solve the basic apump problems of a weak linkage spring, a short throw diaphragm, and a short push rod.

 

Honda sells a kit to upgrade all FCR MX carb Apump to 2009 specs

Tokyomods, Merge Racing, and R&D all sell stiffer linkage springs

 

  http://tokyomods.com...arburetion.html

  http://www.crfsonly....roducts_id/3932

Thanks guys!

 

I have the Tokyo Mods spring, #100 air jet(valve closed), Jd Jetting jet kit, using the smaller O-ring on the throttle valve mod, ready for install in the morning. Hoping it all works. If still bogging, I will try the CRF updating mod.

 

Can't wait!

Do you seen any performance changes with the upgraded carb or does it just make it easier to dial in and keep running smoothly? I used the JD jet kit on my 426 and it seems to be running like a champ but if there is more power to be gained...... 

Edited by nateb1583

Do you seen any performance changes with the upgraded carb or does it just make it easier to dial in and keep running smoothly? I used the JD jet kit on my 426 and it seems to be running like a champ but if there is more power to be gained...... 

 

 The newer carb runs 'cleaner' at all rpms, and is built better.

It also has an upgrade path the really takes it to the precipice of FI. 

Ok, how does the Tokyo mods spring fit into the pump? Where do the hooks go?

No instructions.1475294640318.jpg

Ok, how does the Tokyo mods spring fit into the pump? Where do the hooks go?

No instructions.attachicon.gif20161001_000027.jpg

 

 It doesn't fit into the pump.

That silver spring is for the diaphragm

 

The red spring is for the apump linkage under the throttle wheel cover

It replaces the stock linkage spring.

 

http://www.crfsonly.com/howto/keihin-fcr-carb/honda-crf-merge-racing-acelerator-pump-spring/merge-racing-installation-honda-crf.pdf

 

The trick is to ignore installing the second hook until you have the circlip back on, then use a curved dental pick to 'hook' the second hook in place.

 

....same questions for 10 years...     http://crfsonly.com/forum/viewtopic.php?t=36526&sid=0ca6f37d6c959c960b251134b21d5207

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