Topic: What makes it tough to shift into neutral?

[sammermpc]

I've got a '72 CB500 and I recently overhauled the clutch -- new lifter rod, cable, cleaned and greased the mechanisms, checked the steel plates for warping and deglazed them (light sanding) -- and then reassembled the whole deal.

It works a great deal better than it did, and I'm pretty happy -- but I'm curious, what are the factors involved in making it hard to find neutral when the bike is hot? It gets progressively more difficult as I ride. I generally can find it with some fiddling, but I don't really understand the mechanism. The clutch is disengaging, obviously, but the lifter pedal either won't budge, or clicks heavily past neutral.

[martin99]

Make sure it's in a good state of tune and that the carbs are synched.

[sammermpc]

Yeah, I think I've finally done enough stuff to synch the carbs -- I guess I don't understand the theory, here -- what would having your carbs synched have to do with finding neutral?

[Tews19]

PM dave500.... or Two tired or RB550FOUR..... All experts for your bike and all willing to help.

[martin99]

+1.

I suggested carb synch because it certainly has a positive effect on my bike (750) with finding neutral and it's one of those things that can be done relatively easily to rule out uneven idle as a causatory factor.

I've just done a quick search and there appears to be several threads on this, all with good info. Sometimes these old girls need a bit of coaxing into gear at the best of times though, not like modern bikes.

[sammermpc]

Yeah, I know that it can be tough to find neutral, in general, and there are a lot of posts where people are working on their plates, etc., particularly on CB500s -- I just don't know enough about bikes to know why this would happen.

For example -- let's say I'm pulling up to a stoplight. I've got the clutch pulled in, and I'm breaking steadily. My clutch, I believe, functions well, so the pushrod is being pressed through, the pressure plate lifted, and (because I am slowing down to a stop at a light, and the engine won't bog when I'm stopped there) -- power isn't being delivered to the rear tire anymore. So theoretically, at least, the clutch plates aren't stuck, as I'm not stuck in a specific "gear".

Maybe what I'm asking is how the lifter pedal works, and why having hot oil, lousy friction disks, whatever, would make it hard to find neutral -- as it seems like the clutch plates itself are just delivering power to the transmission -- yet most of the advice about finding neutral tends to be about warped/worn plates, the wrong oil, etc.

I can definitely go through the appropriate steps, I am just confused about why this is the case. I'll PM those fellows, see what they can teach me.

[TwoTired]

If it shifts easy when the engine is stopped and still hot, but not with engine running and hot, then it is a dragging clutch.

Oil selection can make difference.  Also, did you soak the frictions in oil before assembly?

[sammermpc]

It shifts easily and well while riding, even as it gets hot. I notice it mostly when I'm coming to a stop.

Yeah, I soaked the frictions, but they are pretty old and are some weird aftermarket configuration. I measured the springs and they're within spec according to the Clymer, but I should probably just pick up a new set as well. David Silver seems like has some nice looking ones.

A dragging clutch means that the plates aren't fully disengaging?

[MandEms]

I have a hard time finding neutral on my 76 CB550F on occasion as well.  Thanks for the thread Sammermpc.

Like Sammer, it seems, to my basic understanding, that finding neutral would simply be a mechanical function.  I don't understand how carb synch comes into play.  But again, I haven't looked at the actual shifting mechanism very closely.

[tlbranth]

I'd agree with the 'dragging clutch' diagnosis. I think it's the nature of motorcycles. I have 4 bikes and neutral is not findable on any of them with a hot engine. I wouldn't worry too much about it.

[MandEms]

Thanks.  I have plenty of other things to worry about.

[TwoTired]

It shifts easily and well while riding, even as it gets hot. I notice it mostly when I'm coming to a stop.

That's not info I was seeking.
Get engine hot, stop it and then try shifting through the gears. Does it make the first shift easily?  Or, is it difficult to get the shifter to move?

Yeah, I soaked the frictions, but they are pretty old and are some weird aftermarket configuration. I measured the springs and they're within spec according to the Clymer, but I should probably just pick up a new set as well. David Silver seems like has some nice looking ones.
Weak springs may make it slip under full power/loading.  But, they don't cause clutch drag.

Did you check the steels and discs for flatness warpage?  Was there discoloration on the steels' surfaces?

A dragging clutch means that the plates aren't fully disengaging?

That's correct.
Because of their proximity there can be some fluid coupling (oil between the steels and frictions).  This is usually not enough to cause a shift problem.  But, if some of the plates still touch, power will be transferred plate to plate.

The transfer of power preloads the gear train, making the shift dogs difficult to move out of their slots.  With no preload, the shifter should have no hinderance for moving the dogs into or out of their slots.

Clutch drag is hard on the shift dogs (they can round off), shift forks, and shift fork slots.  With enough wear, the trans will take itself out of gear when under power.   The only thing holding the dogs in place are the shift forks.  These fit into a slot, which can wear wider as well. At first, shifting becomes "sloppy".  Later, it jumps out of gear, and/or becomes difficult to get all the way into gear.

You can mitigate some of the wear by anticipating what gear you will use next, and shifting while the bike is in motion and everything inside is still turning.  If coming to a stop, down shift and get it into 1st or neutral before completing the stop.  (There's a good argument for safety anticipating next gear selection too,  so that you can use power as an avoidance procedure alternative to braking.)

If the bike jumps and clunks badly when selecting a gear from neutral, this is another sign of a dragging clutch.

A dragging clutch can also be a product of improper adjustment.  It's not just full engagement to adjust, but, also complete disengagement.  I've noted some who focus on the clutch lever position.  This is supposed to be done AFTER the clutch engagement/disengagement extremes are adjusted.  I admit, I am more familiar with the Cb550 clutch mechanism than the Cb500.  But, I have gotten some sage advice about the CB500 from a couple of long time Honda mechanic from that era, who did a lot of warranty repair work on them before the improved CB550 come about.

[sammermpc]

Get engine hot, stop it and then try shifting through the gears. Does it make the first shift easily?  Or, is it difficult to get the shifter to move?

Yeah, sometimes it takes a fair amount of force/play on the lifter to get it out of first when hot. It sometimes makes a pretty good 'thunk' too.

Did you check the steels and discs for flatness warpage?  Was there discoloration on the steels' surfaces?

I did -- they had a sort've black gum on them -- this is before I lightly sanded them down. They definitely were pretty clean when I mounted them back in, and I checked for warping on a sheet of glass. Seemed ok.

Because of their proximity there can be some fluid coupling (oil between the steels and frictions).  This is usually not enough to cause a shift problem.  But, if some of the plates still touch, power will be transferred plate to plate.

The transfer of power preloads the gear train, making the shift dogs difficult to move out of their slots.  With no preload, the shifter should have no hinderance for moving the dogs into or out of their slots.

This is exactly what I was looking for -- so if I understand correctly, even though the plates are disengaging well enough to allow for normal shifting, because there is some *slight* drag, the gear train is under enough pressure to make it difficult to move the dogs. And that translates into a clunky or difficult-to-move lifter lever? Why would neutral be more affected than the other gears, in general? Sorry for all the questions -- I find that I do a much better job fixing stuff when I understand how it's actually working. More fun too.

[TwoTired]

they had a sort've black gum on them -- this is before I lightly sanded them down. They definitely were pretty clean when I mounted them back in, and I checked for warping on a sheet of glass. Seemed ok.

The surface imperfection will actually help when the plates/discs are engaged.  But, will also add friction when they aren't being forcefully pressed against each other.

You could try some High power Drag race type starts to try to wear-in the matting surfaces and make them more slippery. 
As mentioned, oil type can also be a factor.  In my experience thicker oils usually increase clutch drag.  I only use the recommended 10W-40 on these bikes.  And Semi synthetic seems to make the clutch and shift mechanism smoother on my Cb550's.

This is exactly what I was looking for -- so if I understand correctly, even though the plates are disengaging well enough to allow for normal shifting, because there is some *slight* drag, the gear train is under enough pressure to make it difficult to move the dogs. And that translates into a clunky or difficult-to-move lifter lever?

Yes. In fact, the entire shifting mechanism is under more stress just to overcome the drag.

Why would neutral be more affected than the other gears, in general?

Because the driven gears aren't moving/spinning and the driving gears are.  This is when maximum drag forces are greatest.  If you try to shift under power without full clutch disengagement, the shifter is similarly hard to move.

That's why I told you to stop the motor (the driving gears), to see if the shifter operates easily.  If so, dragging clutch is the likely cause.

There are some details about the shift drum that can cause sticky shifts.  But, a dragging clutch is more likely until the shift drum grooves and pins wear.  Clutch issues can lead to trans/shift issues if not addressed in a timely manner.

[K_Kalynuik]

is there a way to measure your shift forks to check to see if they are indeed bent? I currently have my cases split and would like to check the shift forks for being bent or worn. Any info might help.

[TwoTired]

I don't know what the new clearances are supposed to be, offhand.  It would be a matter of inserting them in the slots and measure the gaps.  I would think less is better and long as they slide.  If they are bent, the fork engagement face wear patterns won't be evenly distributed across center of contact.

I see service data in the Honda shop manual Chapter 13.  It has service limits of the Gear shift drum, and shift forks listed there.  You'll need a micrometer to measure the bits in question.

[K_Kalynuik]

I don't know what the new clearances are supposed to be, offhand.  It would be a matter of inserting them in the slots and measure the gaps.  I would think less is better and long as they slide.  If they are bent, the fork engagement face wear patterns won't be evenly distributed across center of contact.

I see service data in the Honda shop manual Chapter 13.  It has service limits of the Gear shift drum, and shift forks listed there.  You'll need a micrometer to measure the bits in question.

  Thanks Twotired! I was secretly hoping you would chime in.

[Ecks]

Did you make sure to install the clutch plates all facing in the same direction?  The plates are stamped out of a big sheet, and as such, have a bit of asymmetry to their edges (since the stamping press bends the edge a wee bit as well as shearing it)... Anyway, the plates all have to face the same direction, otherwise they'll make the clutch prone to dragging.

If it hasn't already been said, just adjusting the clutch can yield benefits.  By taking up the "slack" in the cable, a pull of the clutch lever will get the clutch plates further apart, reducing clutch drag.

Hope this helps.

[Puntas13]

My 500 shifts easily into neutral every time no matter how long I've been riding. Its got 20k miles and is still sporting the factory clutch as far as i know. I use Honda GN4 20w/50 if that matters
 
On the other hand my 750 would not shift into neutral at a stop after the engine was warmed up.

I'm not sure if its works with the 500/550s but i fixed the issue with my 750 by drilling several more holes in the clutch basket. Theres a how-to in the Tricks and tips forum.

Like a few others said make sure your steel plates are all facing the same direction.