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General Minitrail Talk
Projects/Builds
1975 CB125S
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<blockquote data-quote="69ST" data-source="post: 186887" data-attributes="member: 5"><p>Interesting, as the only stuck plates I've seen with the 49 & 72cc horizontals were due to rust...and those were rare exceptions that had ingested water. </p><p></p><p>Could very well be that automotive oil formulations reached a tipping point ~25 years ago. If you recall, in the 1970s, the changes were almost yearly but for the better. Zinc & phosphorous levels weren't seriously hammered until 2006 but, friction modifiers have been evolving for decades now. I agree with you, GN4 is cheap insurance; I've also seen tech analysis, it's better quality than most realize. I imagine that any JASO-spec/wet clutch compatible, bike oil, should be a safe bet. As cjpayne has mentioned, 20W50 Valvoline motorcycle oil delivers slightly (but noticeably) better shift feel.</p><p></p><p>As for bead blasting, or sandblasting clutch plates, that will work. I just don't know for how long. Some clutch plates have dimpled friction surfaces, with a very precise pattern...easy to do, for an OEM. OTOH, I've seen glazed clutch plates that caused no problems. Wet clutch operation is very similar to automatic transmission clutch packs in automotive & truck applications. Clutch friction material composition is the realm of engineers. Two basic principles I do understand are dynamic friction and static friction...a.k.a. as "sticktion" (no joke) to engineers. The former describes parameters involved with engaging & modulating clutch engagement as from a standing start. The latter describes how much force a clutch can withstand, before the onset of slippage, once fully engaged. Most of this is above my pay grade. There aren't many choices in replacement parts anyway...a good thing, imho, as it could be mind-numbing. </p><p></p><p>When dealing with a slipping clutch, I just replace the discs & plates, springs too if available. Gotta teardown the clutch pack either way. So, it's the same amount of work, oil and gaskets...only real difference, once you've gone this deep into the clutch...is the price of plates + discs.</p></blockquote><p></p>
[QUOTE="69ST, post: 186887, member: 5"] Interesting, as the only stuck plates I've seen with the 49 & 72cc horizontals were due to rust...and those were rare exceptions that had ingested water. Could very well be that automotive oil formulations reached a tipping point ~25 years ago. If you recall, in the 1970s, the changes were almost yearly but for the better. Zinc & phosphorous levels weren't seriously hammered until 2006 but, friction modifiers have been evolving for decades now. I agree with you, GN4 is cheap insurance; I've also seen tech analysis, it's better quality than most realize. I imagine that any JASO-spec/wet clutch compatible, bike oil, should be a safe bet. As cjpayne has mentioned, 20W50 Valvoline motorcycle oil delivers slightly (but noticeably) better shift feel. As for bead blasting, or sandblasting clutch plates, that will work. I just don't know for how long. Some clutch plates have dimpled friction surfaces, with a very precise pattern...easy to do, for an OEM. OTOH, I've seen glazed clutch plates that caused no problems. Wet clutch operation is very similar to automatic transmission clutch packs in automotive & truck applications. Clutch friction material composition is the realm of engineers. Two basic principles I do understand are dynamic friction and static friction...a.k.a. as "sticktion" (no joke) to engineers. The former describes parameters involved with engaging & modulating clutch engagement as from a standing start. The latter describes how much force a clutch can withstand, before the onset of slippage, once fully engaged. Most of this is above my pay grade. There aren't many choices in replacement parts anyway...a good thing, imho, as it could be mind-numbing. When dealing with a slipping clutch, I just replace the discs & plates, springs too if available. Gotta teardown the clutch pack either way. So, it's the same amount of work, oil and gaskets...only real difference, once you've gone this deep into the clutch...is the price of plates + discs. [/QUOTE]
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