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Discussion Starter · #1 ·
My 1971 450 slips at 3500rpm for just a second when accelerating in first gear. This is under “normal acceleration” speed, as in smooth acceleration from a stop light- not racing someone. It is worse up hill and tends to slip closer to 3000 and again around 4500. This ONLY happens in first.
I have new steel plates (except for the tapered one closest to the engine, new friction discs, new springs. I have replaced the shiftdrum, the detent roller, the shift forks, and a few of the gears. The transmission was inspected by Bill Lane and verified to be in good condition. I use 10 W40 motorcycle oil. The clutch is adjusted according to the book and is not too tight. I am out of things to check. The basket seems ok. I don’t know if there could be a problem with the pressure plate.
Any ideas?
Ian
(I posted about this before and thought I had fixed the problem....I didn’t)
 

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The springs are new but did you check the spring length is correct? Are they honda OEM friction plates or EBC? Tried Barnett kevlar frictions plates? You could source a 6 spring clutch basket and pressure plate from a K0 if all else fails.
 

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The clutch is adjusted according to the book and is not too tight. I am out of things to check.
The book is not clear about how to use the adjuster on the sprocket cover. But, if you posted about this before, you should know to disconnect the cable at the lever, and set the adjuster so that it just touches the lifter rod, then back it off a small amount - maybe 1/16" of the outer edge of the adjuster. If it is too tight, it won't let the clutch fully engage.

Also, did you check the steel plates to be sure that they are actually flat? Any wear notches in the clutch basket, where the plates lock into it?
 

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My 1971 450 slips at 3500rpm for just a second when accelerating in first gear. This is under “normal acceleration” speed, as in smooth acceleration from a stop light- not racing someone. It is worse up hill and tends to slip closer to 3000 and again around 4500. This ONLY happens in first.
I have new steel plates (except for the tapered one closest to the engine, new friction discs, new springs. I have replaced the shiftdrum, the detent roller, the shift forks, and a few of the gears. The transmission was inspected by Bill Lane and verified to be in good condition. I use 10 W40 motorcycle oil. The clutch is adjusted according to the book and is not too tight. I am out of things to check. The basket seems ok. I don’t know if there could be a problem with the pressure plate.
Any ideas?
Ian
(I posted about this before and thought I had fixed the problem....I didn’t)


I question your choice of oil I would suggest that 10/40 is intended for modern bikes not our 40+ year old bikes. Doubt if this is the cause of your clutch problem, but I am sure it is not the recommended oil for a CB450
 

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I know you said you're using 10W40 motorcycle oil but did you actually check to make sure the oil is rated for JASO MA or JASO MA2 ? If not that's your problem right there.
Not all motorcycle oils are safe to used with wet clutches.
 

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It is odd that it only happens in first gear. Every slippy clutch I have encountered (cars mainly) first present themselves in the higher gears where it takes more torque to move the bike down the freeway. I would go find a piece of road where you can run it around 4500 RPM in fourth gear. Then crank it on, that should make it slip.
 

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Discussion Starter · #8 ·
I am using motorcycle oil.
I have tried multiple weights and brands of motorcycle specific oil with no change in the problem.
I do not know the sprocket size. I will check.
The springs are new and within spec- I checked.
The new friction discs AND the new steel plates are OEM Honda gear.
I did not know the thing about disengaging the clutch cable for adjustment. I will try that.
I am considering a new basket and pressure plate. Will a K0 work on a K4?

Thanks for the ideas.
 

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The K0 uses a six spring basket and the five speed bikes have four. I don't know why Honda changed, but the four spring clutch packs work fine.
 
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