Hello, On my 650's the needles are exposed but on this 81 400 I'm going over they are covered. Can someone give me the location of the plug. On other bikes I've used Dyno Jet kits but they don't seem to make one for the 400. Any help would be appreciated.
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Locating factory plug covering needle
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you'll have to dig out the plug on top of the intake stub. use a self tap screw and pull it.
no dyno kits for this bike, dyno time to sort out fuelling
no dyno kits for this bike, dyno time to sort out fuelling
OliverB
XS400 Junkie
Yep, that's it. The factory inserted the plug to keep folks from tampering with the factory (too lean) idle mix setting. You can carefully drill out the plug to expose idle mix screws below. You probably already know that the factory setting was 1.5 turns out but should be 3-3.5 turns out for better idle and low rpm performance. You also probably know that the very tiny "O" rings around the base on the idle mix needle jets will be hardened by now so you should replace them.
cturek
XS400 Addict
The plug is made of brass and is about 2-3 mm thick. Be carefull drilling a hole to get a screw started to pull out the plug. The top of the idle screw is close to the bottom of the plug and will be easily damaged if you drill just a little too far or screw in your "pull out scew" a little to far.
I'd get new anyway along with the O ring!
OliverB
XS400 Junkie
If the plugs were in place then, yes, a VERY SMALL o-ring should be at the bottom. Won't not be around the tip of the jet screw but stuck way down in the bottom of the hole and difficult to see. Sometimes you have to use something very small and hooked to get the o-ring up and out. If nothing is there, could be someone installed another screw and plug but not the o-ring.
OliverB
XS400 Junkie
Who knows but the kits from Mikesxs do come with new plugs - aluminum, IIRC.
gotcha. i removed the blind, and unscrewed the screw and spring came with it. no washer, no o-ring. the blind was brass, so id assume it was stock. i have no issues adding washer/o-ring, i just dont know the orientation, and furthermore, do not understand why mine was absent. ill peek into the carb body this afternoon and see if its jammed in there.
