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05 WR450F DJ kit - can't figure this one out

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Matt's has an 05 wr450F, all the normal mods with a White Bros MX4 exhaust and the dynojet kit with the boyeson accelerator pump cover. I had his bike jetted well up til mid Jun then it started to sputter some. We figured it was due to the warming weather and would need to make a jetting adjustment, but he hasn't rode his bike since mid June when he broke his collar bone, but his buddy took it out last Sunday. It was sputtering up a storm and would cough when you blipped the throttle.

I rode his bike yesterday and the bike is terrible from bottom to top of the throttle. I thought with the cooler temps and lower humidity the bike would have cleaned out some but it spits, sputters, surges some, cuts out but doesn't stall, acceleration is rough, and constant cruise at various throttle positions causes the bike to surge, & sputter. It's acting like it's rich and lean but at different times.

The needle is on clip position #4. We had installed a DJ150 mj originally, so I tried a 160 MJ. The problem seemed to get worse when testing a WOT run in 4th gear. I didn't have the road room to run the bike in 5th. The problem actually seemed worse. I started going leaner, 146, 142, 138. It was getting a little better but the bike was still cutting out. I didn't think a 142 and lower mainjet would be large enough. Pretty much there was not a mainjet that gave me a clean top end run.

I kicked the bike 20 times with the ignition off to see if I could get fuel to flow from the over flow tube. I wanted to see if the float was too high. I couldn't get any fuel to leak from the overflow hose.

I also disconnected the TPS and it made absolutely no difference in how the bike ran.

Before I go tearing the carb completely off the bike and clean it thoroughly I was going to try a few things.

1. I was going to check for air leaks around the carb using wd40 spray. When Matt first installed the jetkit he cracked the black housing where the hot start lever cable enters the carb. I was thinking this may be causing an air leak.

2. I was going to try using the JD setup I am currently running in my bike to see how the bike runs. I was hoping to eliminate or pinpoint a carb problem.

3. Throw away the DJ kit (just kidding, but considering it since my 06 wr450f is running great with the JD kit)

4. Remove and clean the carb and check the float level. I thought the floats might be too low and it's a fuel starvation problem. He did wreck pretty hard could the impact of wrecking caused the floats to go out of adjustment?

Does anyone else have any suggestions that could possibly be causing his bike run so poorly? I'm a bit lost, just when you think you have this jetting stuff down pat, you get thrown a curve ball. If there is any other information you may need let me know.

Thanks Greg.

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What about the top end? I couldn't get the bike to clean up top end to test whether the main was the correct size or not.

By leaning out the needle are you saying I will get a cleaner picture of how the bike runs at WOT. I think it makes sense what you say, I run WOT and the second I roll back to 3/4 throttle I hit the rich condition caused by the needle taper hence giving me the false rich condition?

Eddie, is this what you are getting at?

When you hit the rev limiter does the bike cut out, or does it act more like a rich stutter? It may have been I was hitting the rev limiter in 4th gear, then hitting the rich condition when I rolled back from WOT. I'm just trying to make sense of it.

I going to move the needle clip to position 2 with the 150mj dynojet says to install with an aftermarket slipon pipe.

Thanks Greg

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Thanks Eddie.

I put the clip on needle position 2. I put the DJ 150mj in with the stock 45 pilot.

The bike ran well, but I had to set the fuel screw to 2-3/8 turns for clean throttle response and the engine idle rpm just cleaned out at 2-3/8. I put the 48 pilot back in and I think she should be good to go.

Eddie, thanks once again. I learned something new while jetting this time. When you can't seem to find a mainjet what works try leaning out the needle a clip position or two and test again.

Someday I will be as smart as you :thumbsup:

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In the original Kehein application I beleive it had a "D" series (3rd letter) needle? They have so little taper that they come fitted with a large main jet but the main is blocked by the needle. The JD needle has more taper thus the main has some effect. What it sounds like you have here is the DJ needle has more taper yet causing the main to need to be smaller yet and the needle height to be more criticle

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Install the NCVQ needle from the YZF 450. I have found that either raising the stock needle 2 clips richer or installing the "motocross" version of these enduro types work very well. Sometimes going up one or two sizes on the pilot is also needed.

I have also installed the Edelbrock carb. on YFZ 450's,YZF 450's and DRZ 400 with excellent results. Runs great and if an adjustment is needed, no changing jets. The adjustments are external.

I will not run another motor without this type of carb.. Just way to simple and they work great!

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I don't know why people waste their time on the any jet kit for this bike when the 48 pilot, YZ needle, and 165-168 MJ pretty much dial it in.

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I don't know why people waste their time on the any jet kit for this bike when the 48 pilot, YZ needle, and 165-168 MJ pretty much dial it in.

! :ride::thumbsup:

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