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XR650L stumbles at highway speeds after DynoJet kit

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It's a stock 2008 and ran great stock but after installing the DynoJet needle and spring the bike cuts out at 50mph and above when loading it up an incline, cuts out quite badly actually and wont build additional speed unless you give it all and downshift. I did not install the actual Jet(s) because my stock one appeared pressed in and non removeable. From a slow roll the bike will pull notebly harder than before until 5th gear when it begins cutting out.


any direction would be appreciated.

mixture screw.jpg

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That picture looks like a broken off air adjustment screw :cry:  :cry:  :cry: Good luck getting it out so you can adjust it. You will probably need to take a dremel cut off wheel to it to get a slot cut into it so it can be removed for inspecting the o ring and cleaning. Off course it could just be a brass anti-tamper plug which needs to be removed. It looks like someone tried to do something to it but I'm not sure without a more detailed picture.

Edited by tom00013

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PULL the jet kit out........put in keihin jets so we can help you better...try 52/155 or 55/155 to start...


so you put in the needle and spring only eh,,,,they do not work with OE jets...



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That's your fuel/air screw. Use a left hand 1/8" drill bit and the broken piece will come out.

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I have not owned and worked on a bike in 30 years so, yes I will go back in the carb, get better pictures first and certainly consider the Keihin jets too. Just need a sub 100 degree day. Thanks for the info. By the way that's my son in the Avatar in case the 30 yr statement wasn't adding up to ya.

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That looks more like a capped screw than a busted one, but I thought they didn't do that until just a couple years ago.


The DJ kit might not bring all the goodness of the standard mods, but it shouldn't make it run worse, either.

You did put in the DJ main jet?

Made sure the slide diaphragm was properly in place?

Edited by XR650L_Dave

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Happy Dynojet Kit customer here. I'm pretty sure I know what's happening with your bike, but I am assuming some things: otherwise stock carb, stock exhaust, unaltered airbox, and stock filter (is that correct?)


The symptoms you describe tell me your bike is jetted way too rich. For some reason (probably ignition mapping) 5th gear is where you really see the effects of rich jetting. The dynojet needle is way preferable to the stock needle even with Dave's mods but it has to be on the right clip to work.(if Dave's mods have been done, don't use the DJ spring, put the modded spring back in.) If you don't want to uncork the airbox, you should drop the needle until it runs correctly. This is time consuming because you have to adjust, test and repeat. If you don't want to through all of that, I suggest the following:


Let the engine breathe

-take the snorkel out of the airbox

-Open up the rest of the top of the airbox. (Move all the wires out of the way and use a hole saw or utility knife to make as big a hole as possible in the part of the airbox right above the filter. I suggest removing the air filter and stuffing a rag into the boot before you do this.)

-Get a Uni or Twin Air filter


Jet correctly

-get that plug out of the fuel screw hole and get a new fuel screw long enough so that you can actually use it.

-put the 160 DJ main jet in

-set the needle clip in the middle position


To set the fuel screw position correctly, warm up the engine and set the idle a little higher than normal. Start with the fuel screw at 3 turns out and slowly turn it in (righty-tighty, etc.) until the engine RPMs drop just a little. Then turn the fuel screw back out 3/4 of a turn (or 1/2 turn if at high elevation). This also assumes that the correct Keihin slow jet is in there. I think I have a 52 in mine. This does not come with the DJ kit.


You should be happy with it now.

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