Posted June 28, 200717 yr Have a 1980 XS400GS @ high speed 50-60 it loses power i.e. run @ 60 for a minute then drops down New plugs,wires & had Carbs Cin'ed
June 28, 200717 yr Does it happen no matter what gear you are in? Whats you throtle position and what RPM are you at. You might need new coils or condenser. If you're tuning it you might as well get them for added peace of mind they're fairly cheap. go to MikesXS.com. A lot of parts for the xs650 will work with the 400. I checked the part numbers for the coils and they are the same between the two bikes. And if you're running point make sure to get non resistance or 1ohm resistance plug caps, you need as much spark as you can get with points.
June 29, 200717 yr Author 55 @ 5000 RPM the plugs coil wires & coil wire end are new from yamaha the throttle is open all the way
June 29, 200717 yr Moderator 55 @ 5000 RPM the plugs coil wires & coil wire end are new from yamaha the throttle is open all the way check fuel flow from tank and it is venting (replacing the space left by the fuel with air) then check float heights in each carb
July 1, 200717 yr check the timing is set correctly, it could be slighly out which is commn on the 250/400 regards
July 3, 200717 yr Author Just a add-on in 5th gear can run it to 6500 PRM = 55MPH but thats it if I shift to 6th gear it drops to 5000RPM = 50 PRM & no more power
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