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FJR Motorcycle Forums
Technical & Mechanical Problems
Drive train "crashing" when engaged on a cold engine
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<blockquote data-quote="Fred W" data-source="post: 1461057" data-attributes="member: 3828"><p>Just read through this thread. The one thing not yet mentioned, but I assume a lot of people think when they hear the “kerchunk” (term worth googling on this forum) is that it is not your gears that are meshing violently to make that irksome noise. The gears on a motorcycle gearbox are known as a “constant mesh” (think there is still a forum member by that name) design. So the opposing gears are always fully meshed. They slide side to side on their splined shafts during engagement, and there are what is known as “dogs” that stick out laterally from the gear wheels that do the gear to gear engagements. They are much rougher, tougher, and less prone to chipping than the gears themselves. </p><p></p><p>My old 1st Gen 2005 kerchunked from the day I bought it until it left 100k miles older with it’s new owner on it. I tried varying oil many times, cleaned the clutch plates and oil soaked them, but nothing ever affected the cold shift kerchunk. During that time I often led groups of FJR riders on rides. I observed that they all did that at that time.</p><p></p><p>Imagine my surprise when I bought a brand new FJR in 2014 and that bike didn’t kerchunk even when cold. Every great once in a while it does make the noise if I rush into 1st, but what is most noteworthy is that most of the time it just snicks into gear. </p><p></p><p>My old ‘05 never snicked into first cold in it’s life. Even hot It was a non-snicker. I just got in the habit of always starting in gear once warm, as others have mentioned. I still always started in neutral cold so as not to put undue load on the wimpy starter motor.</p><p></p><p>No idea why my ‘14 doesn’t kerchunk. I did eventually put a slipper clutch in it, but it always snicked from day one even before the clutch upgrade. YMMV.</p></blockquote><p></p>
[QUOTE="Fred W, post: 1461057, member: 3828"] Just read through this thread. The one thing not yet mentioned, but I assume a lot of people think when they hear the “kerchunk” (term worth googling on this forum) is that it is not your gears that are meshing violently to make that irksome noise. The gears on a motorcycle gearbox are known as a “constant mesh” (think there is still a forum member by that name) design. So the opposing gears are always fully meshed. They slide side to side on their splined shafts during engagement, and there are what is known as “dogs” that stick out laterally from the gear wheels that do the gear to gear engagements. They are much rougher, tougher, and less prone to chipping than the gears themselves. My old 1st Gen 2005 kerchunked from the day I bought it until it left 100k miles older with it’s new owner on it. I tried varying oil many times, cleaned the clutch plates and oil soaked them, but nothing ever affected the cold shift kerchunk. During that time I often led groups of FJR riders on rides. I observed that they all did that at that time. Imagine my surprise when I bought a brand new FJR in 2014 and that bike didn’t kerchunk even when cold. Every great once in a while it does make the noise if I rush into 1st, but what is most noteworthy is that most of the time it just snicks into gear. My old ‘05 never snicked into first cold in it’s life. Even hot It was a non-snicker. I just got in the habit of always starting in gear once warm, as others have mentioned. I still always started in neutral cold so as not to put undue load on the wimpy starter motor. No idea why my ‘14 doesn’t kerchunk. I did eventually put a slipper clutch in it, but it always snicked from day one even before the clutch upgrade. YMMV. [/QUOTE]
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FJR Motorcycle Forums
Technical & Mechanical Problems
Drive train "crashing" when engaged on a cold engine
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