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Hey Folks,


got a little question.

I currently have an annoying problem with my CB450s.

All gears work fine, but as soon as the bike has run for a while 5-10 min it's difficult to go into neutral.

It still works when I'm rolling towards the traffic light, but when I stopped I can't engage neutral anymore.

Any idea what I need to check?


Thanks
 

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Sensei
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27,171 Posts
Yes...

These are constant mesh transmissions without synchronizers, the gears NEED to be rotating to effect smooth shifts...
IF your engine is running, that keeps the gears spinning IF the clutch is engaged...
When you pull the clutch lever, (disengaging the engine rotation via the clutch) the shafts/gears quickly stop rotating and may be left under slight "locking" pressure by the dogs
The transmission shift drum is also slightly bound UNLESS its DETENT WHEELS spin freely and drop fully into the "star pockets"
The latter is likely the problem as the larger detent wheel is notorious for wearing out of round on its rivet "axle" and causing this "sticking" condition....
Phone and I'll explain further if necessary....
 

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This is an amazingly timely post - I've got the exact same problem but it's on an SL350 K2. At a standstill (power off), gears all move fine. Run the engine and first will engage but won't disengage without a real fight. Other gears seem to be much less problematic.

I know the detent problem on the 450 is pretty common, but it hadn't occurred to me this was likely to be the cause of my problems on the 350. I've bought a spare for the 450 already, just in case.

Sprint - am I right in thinking the part on the 350 that's likely to cause this trouble is part #8 on this diagram:

honda-sl350-motosport-1972-k2-usa-shift-drumshift-arm_bighu0025e0015_9276.jpg

I'm gonna have to pull then engine to fix a top end leak, so I might as well sort this out while I'm in there.
 

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Sensei
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27,171 Posts
This is an amazingly timely post - I've got the exact same problem but it's on an SL350 K2. At a standstill (power off), gears all move fine. Run the engine and first will engage but won't disengage without a real fight. Other gears seem to be much less problematic.

Sprint - am I right in thinking the part on the 350 that's likely to cause this trouble is part #8 on this diagram:


I'm gonna have to pull then engine to fix a top end leak, so I might as well sort this out while I'm in there.
Could be/might be, but also might be a "square" ball (#26) or part #13 is too tight (#23 o-ring crushed or missing)....
 

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Just to be clear about the OP's bike... are we actually talking about a DOHC CB450, or an '88 CB450S...? a quick look at his other posts seems to indicate he's talking about the SOHC 450
 

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I gotta say I (possibly wrongly) assumed it was the K series 450 the OP was referring to.

Sprint - thanks very much for that. The ball - or something in that location - sounds like a more likely candidate than the fork right now, given that everything else moves without too much trouble. Both the washer and o-ring are there, but it's fair to say the o-ring has lost some of its elasticity; it's looking pretty flat. The bike's been standing for a while, and it's entirely possible that age, coupled with me maybe giving it a bit too much in the tightening stakes when it came to part #13. I couldn't detect too much in the way of out-of-round in the ball itself, but I'll roll it on a very flat surface tomorrow and see how it behaves.

Meantime, and apologies for being a bit slow on the uptake, why would over-tightening that assembly make shifting out of first so problematic? I can see how it could cause the selector drum to get stuck in neutral because the ball would sit in the locator in the drum and not want to move out again, but I can't figure out why that would lock up first (where there is no locator). Is it because the assembly being too tight would put unnecessary pressure on the drum at a point where it needs to rotate freely? I should add that I over think a lot of this stuff . . .

At the very least, I'll replace the o-ring while I'm waiting for a gasket kit to arrive . . .
 
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