Author Topic: Will not shift to 3 - really resolved :) (Read 11909 times)

70CB750 · « **on:** April 22, 2015, 05:24:03 AM »

or 4 or 5.

1978 CB750SS engine. The problem is, on the road, it will not shift from 2 up. When I pull the cover, all the linkage seems to be "normal" no broken or loose springs and with the cover off I am able to get it to 5 and back again with some rear wheel rocking for the upshift.

The clutch is adjusted and working well, 1st goes in easily.

My plan is to take all the shifting linkage out, clean it, check for oddities and put it back together lubed, but at the first glance, there is nothing wrong.

I will also take out the Neutral switch and check it, since that was one of things pointed out in the case of flybox's missing 5th.

Any suggestions? There is really no block to shifting, it moves reasonably well when doing it by hand.

evanphi · « **Reply #1 on:** April 22, 2015, 07:36:49 AM »

I was reading one of my old threads (over a year ago) and you mentioned you were skipping second to go to third for the past few years. Did this get fixed?

Something to do with being under a load. Maybe bent shifter forks?

70CB750 · « **Reply #2 on:** April 22, 2015, 07:40:40 AM »

Quote from: evanphi on April 22, 2015, 07:36:49 AM

I was reading one of my old threads (over a year ago) and you mentioned you were skipping second to go to third for the past few years. Did this get fixed?

Something to do with being under a load. Maybe bent shifter forks?

That's the K0, 2dn is toast, this is the built (78 engine in 73 frame). I got the engine as a deal, never heard it running, but it would turn smoothly and shift.

Hmm, should have opened the case up while it was on the bench.

flybox1 · « **Reply #3 on:** April 22, 2015, 09:19:41 AM »

Bummed to hear of another F3 engine with shifting issues.

I hope its easier than finding you have a bent shift fork $:-\$

I'm still without 5th

I rode for an hour last Sunday. Bike runs perfectly, but when I upshift from 4 to 5, there's nothing there. No gear teeth chatter, no restricted lever travel, nothing. I just get revs after I let the clutch out.
I even pulled over and lowered the shifter lever a notch from where my foot likes it. Still, nothing. My clutch works as it should.
Back in the garage, I can rock the rear back and forth and get all gears, including 5th, to engage.
I took the shifter cover off and checked the birdcage and shift linkage. Its all there and again, it shifts fine into ALL gears.

I'm about ready to bribe/challenge some of the PNW'ers with beer and brats to ride on up and help me figure it out

Let me know how yours goes. This might help...

Bailgang · « **Reply #4 on:** April 22, 2015, 02:37:47 PM »

Quote from: flybox1 on April 22, 2015, 09:19:41 AM

Bummed to hear of another F3 engine with shifting issues. I hope its easier than finding you have a bent shift fork $:-\$

I'm still without 5th

That really blows Flybox, I'm glad I kept my enthusiasm down to a minimum when I got the trans in my F2 working like it should because I was really hoping you'd have the same results as I.

flybox1 · « **Reply #5 on:** April 22, 2015, 02:46:50 PM »

Quote from: Bailgang on April 22, 2015, 02:37:47 PM

Quote from: flybox1 on April 22, 2015, 09:19:41 AM
Bummed to hear of another F3 engine with shifting issues. I hope its easier than finding you have a bent shift fork $:-\$

I'm still without 5th

That really blows Flybox, I'm glad I kept my enthusiasm down to a minimum when I got the trans in my F2 working like it should because I was really hoping you'd have the same results as I.

No worries, Scott. I'm happy you got yours sorted.

Im gonna find a big ufcking hill, rock it into 5th, and push off, Knievel-style

Sorry Prokop....hijack over

70CB750 · « **Reply #6 on:** April 23, 2015, 03:43:54 AM »

NP

On the plus side, I can assemble the shift linkage without thinking, without picture. Knowledge is power

martin99 · « **Reply #7 on:** April 23, 2015, 11:26:17 PM »

Had this exact same problem a while ago on my F2. Went into gear up to third, but no further. I disassembled the shifter linkage.

I found the PO had placed a washer between the pivot post (#8 in the schematic - http://www.cmsnl.com/honda-cb750f2-super-sport-england_model14689/partslist/E18.html#results) and engine. I reassembled it correctly, but I honestly didn't think that washer made any difference.

While I was in there I got some needle-nose pliers and tweaked the plate on the selector drum (#11) so it was nice and straight. There was a slight bend in it.

Reassembled the linkage and no problems since. I've often wondered what it was that I did that 'cured' it, I think in my case it was a combination of that misplaced washer which very slightly misaligned everything, combined with the out-of-true plate which allowed things to get hooked up in there.

70CB750 · « **Reply #8 on:** April 24, 2015, 03:00:07 AM »

Thank you, Martin, as a matter of fact, my #11 has a slight bent to it too.

In all my efforts, I did not take apart the end of the drum yet, maybe it's time.

edwardmorris · « **Reply #9 on:** April 24, 2015, 02:50:06 PM »

Quote from: 70CB750 on April 24, 2015, 03:00:07 AM

..........In all my efforts, I did not take apart the end of the drum yet, maybe it's time.

Be very careful if you do end up needing to take that apart, I ended up destroying my shift drum entirely when I tried to remove that staked in 6mm screw...

robl8 · « **Reply #10 on:** April 25, 2015, 08:13:57 AM »

This video was pretty helpful in replacing my Shifter fork, which is much simpler than what you will go through, but he doea a pretty thorough build.

70CB750 · « **Reply #11 on:** April 30, 2015, 04:08:23 AM »

Oil makes problems with the clutch, right? Not with the actually gear movement?

I am using Mobil Delvac, use it in the K0 every winter without problems, could not imagine the F engine would not like it.

flybox1 · « **Reply #12 on:** April 30, 2015, 07:42:22 AM »

Any update on your shifting issue?

70CB750 · « **Reply #13 on:** April 30, 2015, 08:09:54 AM »

I polished and lubed all moving parts from the linkage, it did not make a difference.

On the road and 1 and 2 only. With some effort I was able to get it in 3, not sure how, just being brutal I guess and it was 2 and 3 only again.

More and more convinced something else is wrong, not the linkage.

How is your 5?

flybox1 · « **Reply #14 on:** April 30, 2015, 08:25:17 AM »

The search for 5th has been temporarily shelved for a charging issue

http://forums.sohc4.net/index.php/topic,147341.0.html

Hondamans book listed shifter fork width measurements (all three stacked on the fork rod to measure outer edge of engagement)
Did you check this before they went in?
This only measures width of the group. It does not measure the distance relationship between forks, or their angle off the fork rod(to check for twist, etc)

70CB750 · « **Reply #15 on:** April 30, 2015, 08:41:42 AM »

Thats the thing, I did new rings and rebuilt the head but never opened the bottom.

The engine seemed to be in good shape, except the F3 valve guide problem.

flybox1 · « **Reply #16 on:** April 30, 2015, 08:57:36 AM »

Dissapointing. I was hoping for you it was birdcage/shift lever issue.
Apparently we both can stack those in our sleep

ekpent · « **Reply #17 on:** April 30, 2015, 11:05:21 AM »

Did you ever see that engine running on the road ? I recently finished stripping down an unknown F0 bottom end thinking I could salvage the lower end gears etc for my stash but they were messed up pretty bad. Probably the reason it ended up outside the bike half torn apart.

70CB750 · « **Reply #18 on:** April 30, 2015, 11:21:01 AM »

No, it was parted out motorycle - got engine, wheels, harness, forks...

atm cycles · « **Reply #19 on:** May 01, 2015, 09:52:57 PM »

Was the neutral switch removed? Make sure it is seated all the way. I had a k6 with the exact issue. I could shift through the gears with engine off no third while running.Ended up breaking a dog off. Splitting cases replacing gears all to find same problem when all back up and running. Then I noticed switch wasn't seated. Big lesson learned!!!!!

70CB750 · « **Reply #20 on:** May 02, 2015, 01:42:23 AM »

I used thinner o-ring with the neutral switch, to mke sure it sits all the way, made no difference.

atm cycles · « **Reply #21 on:** May 02, 2015, 04:03:53 AM »

I would think your not going to get to the bottom of this till you split the cases. Knowing you from your threads you more than enough talent and knowledge to fix this one

70CB750 · « **Reply #22 on:** May 03, 2015, 08:31:43 AM »

Thanks atm

Anyway. I got her on the road today. Just for kicks and giggles I doubled o-rings at the neutral switch, clamped it down and took it for a spin.

And the daughter of unwed parents shifted like new.

The neutral light is on all the time, but I will deal with that later - new switch or whatnot.

70CB750 · « **Reply #23 on:** May 03, 2015, 08:40:42 AM »

She runs so well I got carried away and run out of gas making loops around our home.

I had to limp home but made it just about.

BPellerine · « **Reply #24 on:** May 03, 2015, 05:15:31 PM »

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Author Topic: Will not shift to 3 - really resolved :) (Read 11909 times)