Topic: Shifting issues

[oldfett]

I have a 1975 CB750K that I ride quite a bit. The main issue I have with the bike is shifting. When shifting I have to hold in the clutch and wait for the engine to drop down below 3k RPM's before I can shift. When out on a spirated drive hitting 6k plus RPM's this can take a few seconds. Otherwise I am grinding. If I wait for it to fall below 3k RPM's it shifts very nice and smooth. My only question is why? I have done some research and I am thinking that the clutch is not fully disengaging. Possibly due to warping, oil starvation or maybe even age. Does this make sense or does it sound like transmission problems?

I have adjusted the clutch just as the service manual suggests.

[oldfett]

Anyone have any ideas?

[Tower]

I don't think this is a clutch problem.

Sounds like a shifter dog or transmission gears issue.  I'm assuming its all gears? 

[oldfett]

It's most prominent in 1st to 2nd but yes it does it in all gears. I am of course hoping its not a transmission issue but it might be. Its a confusing issue none the less.

[Tower]

Ensure your are changing gears properly.  i.e clutch all way in before lifting gear lever in one firm motion.

Follow the shop manual procedure for adjusting the clutch to get your clutch to its peak adjustment...
1. Turn the adjusting bolt at the lever all the way in to loosen cable
2. Turn adjusting bolt at housing to fully loosen the cable at the clutch housing
3. Remove clutch cover
4. Loosen lock nut, turn out the adjusting screw a few times
5. Turn screw back in until you feel resistance, then turn out 3/4 turn, lock it down with nut
6. Tighten the cable at the at the housing
7. Adjust handlebar lever so there is about  1/2" to 3/4" free play at the lever (before clutch starts to disengage)
8. Replace cover.

Now that your clutch is reset, test run. If problem persists do an oil change.  10w30.

Let oil heat up and take it for a spin.  If problem perists, inspect shift spindle for broken springs or worn spindle or cogs. Replace any broken or worn parts.

Finally, if all else fails, repair the transmission.

Transmission problems will consist of one or a combination of:
a) Worn shift fork (most likely dogs) or worn shift drum
b) Damaged gear(s)
b) Worn bearings causing misalignment of shafts
Note: Shift drum has a lot of play, but if there's too much it will cause shifting problems.

[oldfett]

I've ridden enough bikes that I think I have the sifting down pat.    I also always shift with the clutch, I have never even tried to shift without the clutch. This is the way I was taught, some don't, but I do.

I also did the clutch adjustment just like you stated and there is about a 1/2" of play at the lever.

The oil was changed twice this summer, the last time was about 100 miles ago. Although I tend to run mine on 20w50.

I have not checked the shift spindle, I will have to do a little bit of research and check into this.

I'm worried that it may indeed be the transmission my only qualm about this is thus, it does it going into every gear. Because of this I doubt that it would be damaged gears or shift forks as they would all have to be damaged correct? It may be the bearings causing the shafts to be out of alignment. I would hope that this wouldn't be the case with 24k miles.However the previous jackhole may have done something.

Thanks for your help!

[shizzomynizzo]

I'm no expert, but I hardly think its the clutch. I had a clutch cable snap on my bike, and i drove it home, about 30 miles, no clutch. it didn't grind at all when shifting and i was well above 3k when shifting. I have shifted my car sometimes with no clutch.

[TwoTired]

When standing still in neutral and the clutch pulled in, does the bike jump or grind when selecting a gear?

[oldfett]

When standing still and shifting into 1st there is a prominent click and the whole bike jerks a little.

[TwoTired]

That sure sounds like clutch drag.  Do you also have difficulty finding neutral when stopped? (Also a pointer toward clutch drag).

Had the bike sat idle for a long time? (allowing the clutch springs to squeeze the oil out of the frictions?)

Has the bike had the clutch hub mod to push extra oil in between the discs?

What oil have you selected for use, and how old is the oil.  Did you notice any change in behavior after the last oil change?

[oldfett]

By stopped do you mean in gear with the clutch lever pulled in and in another gear? If so yes it is nearly impossible I 99% of the time have to shut off the bike and then put it in neutral. Occasionally I can get it into neutral from 2nd otherwise it shifts straight from 2nd to 1st or 1st to second. And yes I am very gently pulling up or pushing won looking for neutral.

I have no idea how long this bike has been sitting. When I bought the bike 6 months ago the guy said he rode it regularly and gave it full tune ups, which I later found out was BS. So there is a strong possibility that it has been sitting.

I have never had the clutch apart so I don't know of any mods. I was just looking for some input before I started tearing into her.

I have been running 20w50 and have changed it twice this summer. I changed it when I bought it as the oil was NASTY. I changed it 200 miles later (about 100 miles ago) just because it was so nasty when I drained it out the first time. As I have been riding the bike in general it has been getting better, I think, but nothing noticeably better no.

[TwoTired]

By stopped do you mean in gear with the clutch lever pulled in and in another gear? If so yes it is nearly impossible I 99% of the time have to shut off the bike and then put it in neutral. Occasionally I can get it into neutral from 2nd otherwise it shifts straight from 2nd to 1st or 1st to second. And yes I am very gently pulling up or pushing won looking for neutral.

Seems like a classic clutch drag to me.
Could be warped plates/discs.  Or, lack of oil in the clutch.
The plates/discs are fed oil from the inner drum.  I know Hondaman has a mod to add holes and improve clutch oiling.
You might try:  (I'm making a logical projection)
Ty wrap/bind the clutch lever to the bar grip and run the engine so oil pressure/circulation gets to the clutch hub and distributes through the plates. then let it sit overnight to see if the oil can re-saturate the frictions.
The theory is that the clutch springs have at some point squeezed most of the oil out of the friction pads.  If they haven't glazed and sealed themselves, maybe they can swell up and work right again...maybe not. ??  Don't know, but it would be easier than changing a clutch. 

If the steels/discs are warped, or if the basket fingers are knicked/grooved or the drum grooved to prevent full disengagement of steels and frictions, oiling won't help.

[Tower]

Maybe start by changing oil to the one that Honda recommends, or 10w30 as its slightly thinner at operating temp.  It will make a difference.

[SKTP]

I have a 1978 750K it has just recently started shifting really 'clunky' in first and second but is smooth as silk on the way down and up into 3rd to 5th...I'm starting to think its my chain tension?

I can get into netural...not sure if these symptoms are related to what you have going on..but I will keep you posted if I make any 'clunk' elimination progress

[oldfett]

Maybe start by changing oil to the one that Honda recommends, or 10w30 as its slightly thinner at operating temp.  It will make a difference.

My CB750 has a sticker suggesting 20w40 and 20w50 right under the seat. As I was riding in the warmer summer months I opted for the 20w50. This was the correct choice I thought, or am I wrong?

[BVCB650]

Stickers don't usually lie, but in my book, it suggests you use a weight of oil depending on the ambient air temp, not engine temp, or 10W40 for idiots.