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DR650 Main

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Hey Burned, thanks to you I got my pilot set up pretty well now. One more for you, re the main. I'm running the common DR extras (airbox opened/FMF-Q/DJ kit- with DJ165) and have noticed I spend most of my riding time in the 1/4 to 3/4 throttle range. Am I correct in thinking that the main has little influence over this range? The plugs are dark brownish when I do a plug test @ full throttle, so I'm thinking slightly rich if anything, but definitely not lean. Are there any other tests for the main other than running on a dyno or doing a top speed run in top gear to determine which jet gives me the most speed? And over summer I'll be running @ up to 4000 ft (currently sea level). Would I need to drop the main back to 160 or less for these altitudes? Tks Dave :banghead:

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yes,there is but it takes some testing.

drop the main jet 2 sizes at a time till you feel the bike noticeably struggle to rev.

go back up just till the motor revs clean.that is about as close as you can get the main jet with out a wide band a/f set up.

dont get to cuaght up in looking at the plug.modern fuels make it alomst impossible to jet that way.the plug look lean when the main jet is right.

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Thanks Burned, I might go down the dyno route after all. It pulls strongly throughout the range, doesn't bog or surge, but I just don't know whether I've optimised the thing or not. BTW, I'm running a Mik 155 which according to the comparison chart is equivalent to a DJ165. I've read in other posts that you have doubts about this comparison chart and the accuracy of it. Do you reckon it is closer to being a like for like across the range e.g DJ 155 = Mik 155? If so, I'm probably a tad lean if anything. Tks!

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ive checked dj vs mikuni jet not only with number drills but also with actual a/f ratio via a wide band sensor.they are close enoguht to interchanged.

a dyno run with a real time air fule ratio monitor will save you alot of time.

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And I've gone from a DJ 160 to a Mik 155 thinking I was going richer, whereas in reality I was going leaner, Thanks for that, I'll reinsert the 160. Thanks!

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