Q My Yamaha R1 is buzzing... but not in a good way

Motorcycle News (UK) - - Mcn garage -

When I turn the ig­ni­tion on for my Y-reg Yamaha R1 I can hear the fuel pump start up, but the EXUP valve doesn’t move and there is just the sound of a buzzing, arc­ing, noise from the EXUP mo­tor. The EXUP valve it­self is turn­ing freely and when I turn the EXUP mo­tor with a pair of grips it does re­set when I turn the ig­ni­tion on, but then it just sits mak­ing the afore­men­tioned noise. Mojo67, MCN fo­rums

An­swered by Charles Marvell, Fl­itwick Mo­tor­cy­cles The EXUP mech­a­nism is sited in the most hos­tile en­vi­ron­ment on the bike with rain­wa­ter, dirt, salt and heat com­bin­ing to at­tack it, and the slight­est fric­tion in the EXUP hous­ing will be enough to stall the valve. Al­though you say it is turn­ing freely, can you flick it through its range of move­ment with your fin­ger­tips? The valve blade can get out of align­ment and the only sure­fire way to re­cover its pro­file is to spin it up on a lathe. Maybe a pre­vi­ous owner had to use heat to loosen the bolts and that has been enough to dis­tort the hous­ing too, so you may need to pol­ish that as well.

Sounds like the blade on your EXUP valve has gone out of align­ment

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