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JD Jetting '05 525 EXC w/Leaner Main, 162 main @ 2000-6000ft

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I bought my bike new and rode it one time before installing the JD jet kit. Riding at 2000-5000ft, I ended up using the stock pilot 1 turn out f/s, red needle 4th position, 170 main with the CRF pump diaphragm. I really liked the off idle response but didn't think much about the top end at the time. I made side by side pavement comparisons later to an untouched 05 525 EXC, and my bike sucked hind teat to it.

So I went home and kept reading here on this forum where everyone says how the stock bike it way too lean-which I think the bottom to mid throttle positions it is. At home, 1350ft elevation, I put the stock jetting back in, and the crisp pull all the way through to redline was back, but the off idle grunt/response was lost. I went back to Jd kit with the red needle 4th position, 170 main, and there was an absolute difference on the pull through redline-flat. I dropped the main to 162....totally cleaner and WAY harder pulling. Now I still have the off idle response and grunt combined with a way cleaner harder pulling top end. I will probably be blasted for this, but I wanted to offer this info for others to maybe at least try.

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Good advice! I tried the settings you suggested and the off-idle hesitation/bog is gone and the pull is noticably better as well.

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Shrewless, what main did you end up running? Do you think the leaner main is stronger? Is the red needle cleaner and stronger than the blue off idle?

I will say from about 6500ft and up, the needle could be leaned one step more as I was getting a slight off idle dead spot while on a very slow single track trail. Leaning the pilot helped, but didn't cure it.

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EliJoe, I ended up using 168 just because I didn't want to make major adjustments to two different circuits since I also changed to the red needle in the 5th clip position from the top as you suggested (this had been suggested by James Dean from JD Jetting as well). My bike has no off-idle hesitation/bog now and it does pull stonger and cleaner. I don't know if the improvement can be attributed to the needle or the main or if it is a combination of both but once I try the 162 main I will see there is any additional gain. I am also running the CRF accelerator pump diaphram to shorten the AP squirt duration but other that that no additional changes. I am pleased that the issue may well have been a "rich bog" since leaning it out will likely help with my other issue, fuel consumption - what a pig!! I am going to add a Power Now blade as soon as it arrives to hopefully further improve the idle-to-mid throttle snap. I'll keep you posted and please let me know if you have any additional success.

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I think the off idle snap is a result of the leaner needle, but the overall WOT pull is merely the smaller main jet. More fuel doesn't always mean more power in a gasoline engine....

Power now....I would like to try the intake stuffer and their pipe. I came off of an XR600 with a 660 kit, and I don't have the off idle chug with the 525 that I had with the 660. I think the 525 is a little soft down low.

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Now I still have the off idle response and grunt combined with a way cleaner harder pulling top end. I will probably be blasted for this, but I wanted to offer this info for others to maybe at least try.

I have an '05 450 EXC. No one should be blasted for trying something new- especially if they get results. I set mine up wayyy rich. It will get the wheel up easily, but after riding the tight stuff I killed the bike and wiped black soot out of the tail pipe. Too rich and I didn't like it. Trouble is, I am still learning to recognize the signs of a lean or rich four stroke. I will give your set up a try, as I already have the JD needle. The problem with a bike being too rich is the gas is supposed to wash the oil from the cylinder walls causing wear. I don't know if that's true or applies to some of us, but I am looking for jetting that gets the power and does a little better on fuel use. Mine is not good with the 45 pilot and 175 main. I have to check the slot on the needle.

Thanks for the tip, I ordered a Honda diaphragm and I will give it a try.

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I don't think the JD jetting would wash the cylinders, I just think that for the Ktm 4 strokes its a little too rich on the mains. Check back with your findings.

I just rode my bike with the 162 main at 1350 for a while last night.....it rips. The stronger bottom end of the JD needle works sweet with the combined hard mid-top end pull of the stock leaner main a/f ratio. Remember, the JD needle does not restrict WOT fuel like the stock needle. Hence, smaller main jet number with the JD needle to have the same WOT air/fuel ratio as the larger number main with the stock needle.

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The AP circuit is only going to come into play when snapping the thottle quickly, otherwise it will have very little effect on how rich or how lean your machine is running.

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Interesting thread. My '04 525 EXC runs very well with the JD red needle, #3 and 170 main from 3,000 to 9,000+ feet elevation, with no noticeable soot in the exhaust pipe. I have never felt the need to try a leaner main jet. Is your intake system completely stock? No Power Nows, intake stuffers, etc, and is the air filter fresh and unclogged?

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Yeah, completely stock. Drop in the 162 and see what happens. Yes. I put in a fresh filter right before I did the testing.

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I replaced the 45 pilot and 175 main with stock jets (42 pilot / 170 main). I also bought the honda diaphragm and adjusted the rod linkage per James Dean recommendations. Also, I put the clip in the middle on the red needle( also a James Dean recommendation for better fuel economy. All this to reduce a rich condition and excessive fuel use. It seems to have helped with the little testing I did.

It's important to warm the bike to check for low end grunt. With the properly adjusted linkage and 42 pilot, the bike has more than enough low end to loft the wheel over logs. I will report back on fuel use after this weeks ride.

I guess the most important (and free) mod you can check is the linkage for the pump diaphragm. It should have just enough slack to rock the plastic cam next to the throttle wheel - no more. Mine was way out, giving it that sluggish bog at the bottom, since there was no fuel to burn. I may still reduce the main jet further. James Dean posts indicate he built the red and blue needles to bridge stock jetting - in most cases. I still need to ask him questions and do some experimenting.

Looks like richer may not be the way to go.

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