'11 WR450 loosing spark/cutting out intermitantly

Hoping somebody has seen this before.  I have a '11 WR450, properly jetted, FMF exhaust.  Ran fine last time I rode last week. This time It acted like the spark was cutting out. Happend at any throttle position.  Would loose all power/acceleration for about a second or so and come right back on again.  Did not do this all the time, very intermittant.  Did it for about 20 minutes then problem went away for about an hour and a half of riding then returned.  It actually totally died at one point, was very difficult to start.   Full tank of fresh fuel, fresh oil, occured on both ON and Reserve.  Choke off.  69 degrees ambient and dry.  When it wasn't doing this cutting out it ripped just as before the problem set-in.   Problem was not affected by duration of riding, engine heat, bumps, up hill or down hill.  Bike was washed w/ garden hose after last ride, but has had plenty of time for water to dry out of the bad places.


Is there any part in the ignition system that typcially fails like this?  Any help is appreciated.     

Edited by Taxgod4u

Pull off the seat and tank and headlight and check all ground then harness connections.

I will go check the connections now.  More info:  it seemed to only cut out when on the flat and smooth roads between trials.  Do these thing have a low oil switch that could be misreading?

update, cleaned all of the plugs along the spine and under speedo.  Replaced spark plug (very rusty from washing bike)  Still died on me after about 2 miles or street riding.  Checked the track side shorty gas cap vent and it was totally clogged.  The check valve must have frozen shut.  Zero air flow in or out


Now riddle me this...  how was the tank getting air while I was riding?  It only cut out while on level flat ground and no issues while MX'n for an hour and a half.  It had to get air from somewhere.  Gas expansion from the agitation???

Those caps always plug up eventually.

Get rid of it.

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