Author Topic: Clunky shifting, then not clunky shifting... (Read 8248 times)

phil71 · « **on:** March 21, 2011, 01:05:39 PM »

Hi everyone,
My 71 CB750 K1 sometimes will 'clack' into 1st and into 2nd.
shifting under very hard acceleration can result in hitting neutral on the 1/2 shift.
Then, at times, it's smooth as glass. Probably about 50/50. Clutchless shifting is like butter, so I feel like the synchros might be alright.
Other details:
*Shifting carefully and slowly will always make it shift fine. Haste makes noise, in this case.
*20w50 seems to make it act better than 10w40(the shop manual says either is okay)
* The clutch (11kmiles) is a little (and very little) rattle-y at idle when not engaged, and quiets down when pulled.
any thoughts?
thanks!

climbingaz · « **Reply #1 on:** March 21, 2011, 01:15:58 PM »

I've noticed my 750 gets a little difficult to shift from neutral into first when the engine is hot (stop and go traffic). Not sure if this is normal either?

MCRider · « **Reply #2 on:** March 21, 2011, 01:50:42 PM »

Synchros? We don't need no steenkin synchros!

There are no synchros in a motorcycle transmission. It is a "bash box". As the name implies, it will bash occasionally and technique is important. I woldn't do clutchless shifting very much as you'll wear out the engagement dogs quicker, whether it feels good or not. And that's from someone who loves to power shift.

The clutch rattle is the signature noise of a CB750, as long as it goes away when you pull the lever, everything is OK.

MCRider · « **Reply #3 on:** March 21, 2011, 01:54:49 PM »

As long as it isn't hopping out of gear into a false neutral, after having shifted into gear, like second from first, you are probably OK and just need to shift with skill to minimize bashing.

Climbing: also common. Try to avoid stop and go, you're clutch plates are swelling and sticking. May need cleaning, if it gets badder, replacement. Be sure its adjusted so you get a full pull, and try to get it into the gear you want before you stop rolling.

phil71 · « **Reply #4 on:** March 21, 2011, 02:12:09 PM »

I knew that about the synchros.. just an old habit. I didn't powershift so much as relax the throttle till the gear slacked and gave up the shift drum,then the shifter would go smoothly into the next gear. I really only did that twice to see if the gear profiles might be smacked up. I don't think they are.
It's not hopping into neutral, just sometimes it's possible to miss the shift from 1/2 when you're really thrashing it.
When you say 'Full-pull', you mean full disengagement, right? It doesn't 'lurch' when i put it in first, if that's what you're asking.

Coyote13 · « **Reply #5 on:** March 21, 2011, 02:21:53 PM »

I miss 1/2 regularly when really getting on it. My buddy laughs hysterically as he blows by me on his Sportster (pretty sweet ride btw). Just gotta be diligent (sp?)

TwoTired · « **Reply #6 on:** March 21, 2011, 02:23:51 PM »

Quote from: phil71 on March 21, 2011, 01:05:39 PM

*20w50 seems to make it act better than 10w40(the shop manual says either is okay)

Are you comparing worn out 10W-40 that has lost much of its friction/viscosity modifiers, to brand new 20W-50 that has them still intact?

Gear clunking is often a function of how much drag or fluid coupling is occurring in the clutch pack.
So, you have to pay attention to oil temp, as well.

With new oil, it behaves as the lower weight rating when cold, and the hotter weight when hot.
Oil that is worn out loses it's ability to behave at the higher weight.

Still, you can expect some trans/clutch sluggishness when the engine/trans are cold.
When the oil is worn out, it may not get thick enough the allow the clutch plates to glide easily.

Alternately, worn out 20W-50 should still behave as 20W. When hot, this weight would work better in the clutch than worn out 10W-40 which can only behave as 10W, and is too thin for a hot engine. (10W is superior to 20W in a cold engine.)

Cheers,

phil71 · « **Reply #7 on:** March 21, 2011, 02:30:19 PM »

In this case, I've changed the oil&filter 4x in under 300miles, because the thing sat for 27 years. I wanted to get anything out that might have been in the system. So, none of these symptoms were with oil any older than 100 miles. The 20w50 is definitely smoother, cold and warm.

MCRider · « **Reply #8 on:** March 21, 2011, 03:20:55 PM »

Quote from: phil71 on March 21, 2011, 02:12:09 PM

I knew that about the synchros.. just an old habit. I didn't powershift so much as relax the throttle till the gear slacked and gave up the shift drum,then the shifter would go smoothly into the next gear. I really only did that twice to see if the gear profiles might be smacked up. I don't think they are.
It's not hopping into neutral, just sometimes it's possible to miss the shift from 1/2 when you're really thrashing it.
When you say 'Full-pull', you mean full disengagement, right? It doesn't 'lurch' when i put it in first, if that's what you're asking.

All good. The 1-2 shift is the hardest to hit, and you just have to stay with it. Too easy with the shifter causes multiple jump outs and will eventually taper the engagement dogs to where it jumps out on its own. Multiple aggressive inputs will eventually bend the shift fork to where it won't engage 2nd all the way and again it jumps out. Can't win. The gear and fork involved have been replaced to the point Honda has run out of stock and we are reduced to trusting for "good" used parts, or paying $700+ at Yamiya for replacement parts.

The full pull comment was directed at the post from Climbingaz, but yes you got my meaning right.

Coyote13 · « **Reply #9 on:** March 21, 2011, 05:06:58 PM »

Holy balls, 700 bucks? Better get workin on that "diligence" I was talking about earlier

camelman · « **Reply #10 on:** March 21, 2011, 05:35:47 PM »

I pulled a clutch basket off a cb450 a while back to help a friend out. He was having missed shift issues, really heavy first gear clunking and uneven clutch engagement. I found the clutch basket fingers had shallow grooves from the clutch disks contacting them. The disks were hanging up in the grooves and causing all of the issues mentioned above. He didn't want to buy a new basket so I just smoothed the fingers off with a file. The issues disappeared 100%. This might not be your issue, but it is easy to check.

Camelman

MCRider · « **Reply #11 on:** March 21, 2011, 06:02:14 PM »

Quote from: camelman on March 21, 2011, 05:35:47 PM

I pulled a clutch basket off a cb450 a while back to help a friend out. He was having missed shift issues, really heavy first gear clunking and uneven clutch engagement. I found the clutch basket fingers had shallow grooves from the clutch disks contacting them. The disks were hanging up in the grooves and causing all of the issues mentioned above. He didn't want to buy a new basket so I just smoothed the fingers off with a file. The issues disappeared 100%. This might not be your issue, but it is easy to check.

Camelman

Yes there are some issues, differing from K to K. As I mentioned, often the plates get gunked up with an aluminum broth, a good scrubbing with solvent perks them up. HondaMan addresses several clutch hub issues that when upgraded work better.

I just cleaned my well used high mileage barnett clutch plates in my solvent tank. A stream of grey goo came off of them for minutes before they were fully clean. There was no visible damage or wear. I expect better performance.

nancy · « **Reply #12 on:** March 21, 2011, 06:05:45 PM »

Camelman,
I agree - after reading a magazine article written by an old bike mechanic/expert in the UK - the article was a short story on clutches. He mentioned the basket and the wear as you mentioned being a cause of grabbing and other unpleasant actions. I recently aquired a Triumph Sprint ST - I can't say the shifting is hugely better on that. I still clunk a bit and have to hit it right.
Regards
Mark

DH · « **Reply #13 on:** March 21, 2011, 06:08:10 PM »

This may help? http://forums.sohc4.net/index.php?topic=78643.msg877816#msg877816

Tricks and tips/how to's
Engine section
Oil pressure+ easier shifting walk thru

nancy · « **Reply #14 on:** March 21, 2011, 06:09:34 PM »

dead link DH...

DH · « **Reply #15 on:** March 21, 2011, 06:14:37 PM »

Quote from: nancy on March 21, 2011, 06:09:34 PM

dead link DH...

Updated, typo the first time. Sorry bout that...

splitt · « **Reply #16 on:** March 21, 2011, 06:59:22 PM »

Has the clutch been replaced? Here's an excellent article about clutch rebuilding:

http://hondachopper.yuku.com/reply/18868#reply-18868

This applies to all motorcycle clutches.

nancy · « **Reply #17 on:** March 21, 2011, 10:42:26 PM »

DH - thanks for that link,...that is a cool article... nice work by that man.
Regards
Mark

Coyote13 · « **Reply #18 on:** March 22, 2011, 07:06:43 AM »

Quote from: nancy on March 21, 2011, 10:42:26 PM

DH - thanks for that link,...that is a cool article... nice work by that man.
Regards
Mark

x2....guess I know what I'm doing when I get some down time

DH · « **Reply #19 on:** March 22, 2011, 05:17:22 PM »

I'm gonna try it too. I still have a clunky transmission, even after updating to a k7 clutch. Hoping the o rings will stop pressure losses.
Three of the o rings that go on the oil pump are the same part that goes on the oil filter bolt (and come with every new oil filter). Since I use mine over, and only change 'em out after several oil changes, I have three "in stock"

Just need the small one now, and good to go. That other link to the post on Hondachopper.com is good as well. The guy who wrote that post used to be a member here several years ago. Best of luck guys.

Duke McDukiedook · « **Reply #20 on:** March 22, 2011, 09:54:14 PM »

If all is good with your dogs and oil and clutch issues I find a little pressure on the lever before I engage the clutch helps me with shifting- specifically from 1-2.

DYSKORD · « **Reply #21 on:** March 22, 2011, 10:05:47 PM »

I was having intermitent shifting issues until I replaced my worn chain. I am by no means an expert so maybe somebody else can verify or falsify my belief that it helped.

MCRider · « **Reply #22 on:** March 23, 2011, 05:44:26 AM »

Quote from: Industrial-sized Dukiedook on March 22, 2011, 09:54:14 PM

If all is good with your dogs and oil and clutch issues I find a little pressure on the lever before I engage the clutch helps me with shifting- specifically from 1-2.

Pre-loading the shifter, taking out the mechanical slop of the shift linkage, before a shift, is part of the "technique" of shifting a bash box, for smoothness and completeness of the shift. IMO

phil71 · « **Reply #23 on:** March 23, 2011, 03:02:04 PM »

You guys are dead on, pre loading the shifter makes a big difference...
i'm not going to worry much more about this for now.

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Author Topic: Clunky shifting, then not clunky shifting... (Read 8248 times)

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