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2007 450 EXC Problems Please Help!!

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I have a 2007 450 EXC with a bog / dead spot. If to go from no throttle to full throttle it cuts off. It is fine if you are already in the gas and hit it full throttle. I have a JD Jet kit installed w/a 170 main jet & Stock Pilot jet. I installed a R&D adjustable accelerator pump as well with no luck on the problem. I have talked to the people @ JD & have everything installed to their specs. i have also tried adjusting the needle multiple times. I am starting to think it may be something other than the carb. Please let me know if you have any ideas.

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I had a similar issue and in my case it turned out to be a small flake of junk blocking the pilot circuit port. I had used carb cleaner several times to clean the carb with no luck. I then took a pen light and inspected the ports. The pilot port was partially obstructed. I had to take a index drill bit the same size as the port and force the piece of junk out.

You may also have an issue with the AP. I am not familiar with the R&D AP kit so I would be no help there getting that tuned.

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The pilot has to be clean and throttle linkage set up for low end response. Your needle should not be an issue directly off the bottom.

For AP adjustment it's best to remove the carbs and witness the fuel squirt going under the slide as you rotate the throttle wheel. Use throttle linkage screw for CCW for max fuel squirt at earliest opportunity. If it hits the slide turn screw CW. After that you do that, set up the accessory AP kit, and work on the needle position.

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Have you tried to put a honda diaphram in.I did that to my old 05 (which is really the same bike).Because of the emmisions the diaphram that comes stock puts too much fuel when you hammer the throttle.

Also i wired the ac pump arm.When you have the ac pump cover off and still on the bike when you move the throttle you can see the lag in the ac arm.If you wire it they work together.

Like others said clean the jets out realy good before doing any mods.Take a bread tie with the coating off and clean the jets out.

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Thanks for the responses. I have put a suzuki 450 diaphragm in it & I removed the subframe & watched the fuel spray and have it timed like everyone says. It just dies still if i slam on the gas. Maybe the honda diaphragm is what i need. My friend has a 2006 with the Suzuki diaphragm and it runs great???? This makes me love my YZ250 right about now....

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At the risk of sounding like a moron;

Most carbed 4st do not like snapping the throttle open especially while on the milkcrate. They just do not behave like a 2st in this manner.

Now if your are aggressively rolling on the throttle while riding and having a bog while not unheard of it can usually be tuned out.

The JD kit is basically a total tunning package with detailed instructions that will work very well with most common setups. Mix and matching with other tunning parts somewhat defeats what JD is offering.

I would go back to basics;

Be sure the valves are correct.

Replace the pilot jet with new as they can be hard to clean fully.

Set the carb up per JD.

Be sure the accelerator pump if fully primed

Turn the idle speed up a little

Roll the throttle open, not "snapping" it open

Bruce

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I have checked the valves, The jets are clean I run a bike shop in maryland. also I have spent time talking to the people over @ JD to make sure I had everything set up to their specs.

It will run if you roll on the power, but when you need to blip it to get your front end up over a rockl ledge or tree trunk it dies. I almost wet otb a few times. I have raced motocross & hare scrambles for the last 10 years, so for someone new to riding this problem may not be such a big deal, But for me I need that immediate response. My buddy has a 06 and its awesome!! I am taking a trip to hatfeild mmcoy this weekend and planning on bringing my YZ unless I can find out whatever I am overlooking.

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I have set up a few of these bikes now and what works for me is a 42 or 45 pilot a OCEMP Sudco needle and a 158 or 160 main with a 1 second AP discharge, same as honda and maybe the suzuki. We have done afew 450s,525s and 530s with this setup and they all run awesome.

Ed

Edited by no1clyde

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I have set up a few of these bikes now and what works for me is a 42 or 45 pilot a OCEMP Sudco needle and a 158 or 160 main with a 1 second AP discharge, same as honda and maybe the suzuki. We have done afew 450s,525s and 530s with this setup and they all run awesome.

Ed

the above is the go-to jetting for the 400-505cc RFS bikes along w/ the Honda diaphram and o-ring mod. :thumbsup::thumbsup:

ur not mixing the R&D adjustable accelerator pump w/ a non-stock diaphram are you?

TPS is plugged in?

proper bowl fuel level?

how many hours on the bike?

many of the gurus suggest installing a new pilot jet when there is a stubborn carb problem no matter how clean it appears...this has fix'd the problem in many cases. :ride:

cheers

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My buddy has a 06 and its awesome!! I am taking a trip to hatfeild mmcoy this weekend and planning on bringing my YZ unless I can find out whatever I am overlooking.

Barrow or swap your buddies carb and see what happens.

Bruce

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