Idle erratic on your old hi mileage bike? Check this . . .

[CycleRob]

Dry, fuzzy, vacuum leaking fuel injector O-rings found while working on something else. After removing the 2 allen bolts that secure the black plastic fuel injector bracket to the ThrottleBody (TB) on my 2002 model R1150R, I removed the injector from the TB, leaving it still attached to it's rigid, black plastic fuel line. There's no need to separate that joint that seals in pressurized fuel. That injector/fuel line assembly will not move very much rearward w/o risk of breaking it, so only move the assembly just enough to unplug the injector body from the Aluminum TB bore. What I found was the fat, small diameter O ring that seals between the fuel injector nozzle and the TB housing was dry and leaking manifold vacuum slightly at an idle. The dry, sealing OD surface had slightly fuzzy white powder areas that just had to be leaking air. Not having a replacement available nor willing to wait and get a new one, the old one was carefully removed for inspection and cleaning of all the sealing surfaces. That means the O ring's groove in the plastic injector body, the Aluminum bore in the TB it plugs into and the O-ring itself. Then the O-ring got greased and massaged to renew it and put back on the injector body. Use enough grease to form a visible cloth-like streak to make a good seal, but not so much it'll squeeze out and make a mess on the reinstall. Repeat the same process on the other cylinder.

The firmness I felt while axially plugging the injectors back into their TB bores told me the sealing would be really good, and it was. After completion and running the engine, even the TB synch and idle speed had to be readjusted a little. After riding the bike, I noticed a dead smooth hot idle, which I have not noticed in a long time. You get used to gradual changes and/or attribute those changes to something else, like it's almost 8 year age & 64K miles on the odometer. That wasn't it!

Washing the bike, engine heat, vibration and age all conspire to slowly degrade what looks to be an adequate design. I just renewed it. Now you have satisfying, peace-of-mind rainy day project, but only if your ride is w/o a dead smooth idle -and- your bike is several or 8 years old like mine is. Just be very careful stressing the hard plastic fuel lines.

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[ruddy]

Great tip, Rob. Thanks!

[riceburner]

Useful info - cheers.

[boxermania]

Robbie

Great catch, for as you indicate, small operational changes are hard to diagnose until one runs into things like this.

As an added note, if the O-ring is not cracked or split and there isn't a replacement available throw it into 200 F water for a few minutes and it will restore the former shape.

My 2 cents