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FJR Motorcycle Forums
Technical & Mechanical Problems
Loud knock at cold idle
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<blockquote data-quote="Wee Willy" data-source="post: 627823" data-attributes="member: 17731"><p>My '08 will do the same thing on rare occasion. I believe now, having experienced it about 5 or so times in the 5 months I've owned the bike, that this is very like a detonation event when the motor is running at low RPM under the engine control system's (ECS) choke settings. Only happens right after the bike is started cold and if I'm running regular fuel and I'm not in the loop twisting the throttle. If I go to a higher grade of fuel (mid or premium which I will run occasionally just to see the difference) it never happens. Detonation usually requires a hot engine, high compression ratio and low grade (low octane) fuel but such an event can also happen if the ECS fires the spark (timing) at or before a certain point in the compression stroke. My solution that seems to solve the problem is to use small throttle blips to surge the RPM from idle to 2500 at about 1 cycle every 2 seconds and do so for about 10 seconds after a cold start. This "bump" hasn't happened since.</p><p></p><p>Cheers,</p><p></p><p>W2</p></blockquote><p></p>
[QUOTE="Wee Willy, post: 627823, member: 17731"] My '08 will do the same thing on rare occasion. I believe now, having experienced it about 5 or so times in the 5 months I've owned the bike, that this is very like a detonation event when the motor is running at low RPM under the engine control system's (ECS) choke settings. Only happens right after the bike is started cold and if I'm running regular fuel and I'm not in the loop twisting the throttle. If I go to a higher grade of fuel (mid or premium which I will run occasionally just to see the difference) it never happens. Detonation usually requires a hot engine, high compression ratio and low grade (low octane) fuel but such an event can also happen if the ECS fires the spark (timing) at or before a certain point in the compression stroke. My solution that seems to solve the problem is to use small throttle blips to surge the RPM from idle to 2500 at about 1 cycle every 2 seconds and do so for about 10 seconds after a cold start. This "bump" hasn't happened since. Cheers, W2 [/QUOTE]
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FJR Motorcycle Forums
Technical & Mechanical Problems
Loud knock at cold idle
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