Author Topic: Won't shift into FOURTH??? updated 12/5 - fixed  (Read 10218 times)

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Offline KB02

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Won't shift into FOURTH??? updated 12/5 - fixed
« on: October 27, 2009, 05:06:14 am »
So over the weekend I was doing some carb tuning on my hot-rodded '78 750 (attempting to anyway) which was followed by some short little test rides for my road and back (about 100 yards or so). While I think I have managed to get the carbs relatively synced and adjusted, have run into the problem that my bike does not want to shift into second gear.

I have checked the obvious stuff and it is not a clutch issue. No matter how hard I pull up on the shifter, I canot get the bike to shift up into second All I have is first an neutral.

What should I look for? I have to take the shifter side cover off anyway as I have a small oil leak that I have to address. Might it be something in the linkage behind that cover that is binding up?

I tried a search but only came across clutch issues.
« Last Edit: December 06, 2009, 03:16:36 pm by KB02 »
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Offline Bill/BentON Racing

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Re: Won't shift into second???
« Reply #1 on: October 27, 2009, 05:39:59 am »
First place I would look,Good Luck,Bill
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Offline MCRider

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Re: Won't shift into second???
« Reply #2 on: October 27, 2009, 05:49:23 am »
First place I would look,Good Luck,Bill

Yes, you'll need to study that monkey mechanism beneath the cover that turns the shift drum and see if its not doing its job. With the cover off, you can re-install the shift actuator and pedal and see how its supposed to work, run it thru its paces.  Don't force it though and rock the rear wheel back and forth to get the gears to engage. It either goes in or it doesn't. Forcing it won't fix it, and will likely harm it more or differently.

Did it used to shift OK? What's happened to it since then. Were you (or someone else) powershifting on your test rides? Has it been dropped on the left side?

The real common issue is usually it will go into second but won't stay there. It pops out when throttle is applied. That's usually a certain symptom for a bent shift fork and or worn shift fork slot in the 2/3 gear. Usually a result of abuse. And I use that term not in a bad way, as i like to powershift as well. we just pay the price eventually.

You could have a bent or badly worn shift fork, which just coincidentally started acting up at this time.

Shift forks are a "pull the engine" fix.

« Last Edit: October 27, 2009, 05:53:28 am by MCRider »
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Offline BurtonWarpup

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Re: Won't shift into second???
« Reply #3 on: October 27, 2009, 10:03:36 am »
I bought a 750 real cheap because the guy had dropped the bike on it's left side and it got stuck in second gear. When I pulled off the transmission cover I found that the "gear shift arm spring" had fallen off. I put it back in place and everything has worked great since. Might want to check for that.
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Offline ron.cieri.313

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Re: Won't shift into second???
« Reply #4 on: October 27, 2009, 10:33:07 am »
Same problem...I'm at the "pull the engine fix"...see my post on the current status of my project

http://forums.sohc4.net/index.php?topic=59158.0
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Offline nobody

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Re: Won't shift into second???
« Reply #5 on: October 27, 2009, 11:01:50 am »
I'm unfortunately in the same "pull the engine" boat and am following Ron's thread very closely. I need to bribe a friend or two to come over and help me get that hunk of metal out one of these coming nights.
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Offline KB02

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Re: Won't shift into second???
« Reply #6 on: October 28, 2009, 05:10:41 am »
Yeah, I'm really hoping that I don't have to split the cases. I'm just really hoping that it is a linkage problem. We'll see. I have today off from work, so I'll be looking into it a little bit today to see what I find. Time for first oil change anyway.  :)

As for history, I really don't know. The bike was a non-runner when I got it. The shift forks appeared to be within spec when I had the engine apart and things seemed to move correctly before I put all the linkage back in place (I remember that being a pain in th a$$, too, so that could be where my problem lies...).
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Offline cb650

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Re: Won't shift into second???
« Reply #7 on: October 28, 2009, 05:53:04 am »
One of my 650's did this long ago and it was just a spring on a lever outside the case but under the cover.   Only time it has ever happened.
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Offline MCRider

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Re: Won't shift into second???
« Reply #8 on: October 28, 2009, 06:00:28 am »
Yeah, I'm really hoping that I don't have to split the cases. I'm just really hoping that it is a linkage problem. We'll see. I have today off from work, so I'll be looking into it a little bit today to see what I find. Time for first oil change anyway.  :)

As for history, I really don't know. The bike was a non-runner when I got it. The shift forks appeared to be within spec when I had the engine apart and things seemed to move correctly before I put all the linkage back in place (I remember that being a pain in th a$$, too, so that could be where my problem lies...).
Get a microfiche/parts diagram and follow closely. I'm voting on a missing piece, especially the wound springs that returns the selector to the "next gear please" position. Known as "spring, positive stopper", on the fiche.
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Offline ron.cieri.313

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Re: Won't shift into second???
« Reply #9 on: October 28, 2009, 06:58:43 am »
Don't want to hijack the post but in my case, I've gone over the shift mechanism a few times quite thoroughly and I don't think I'm that lucky...but here's hoping that all it is for u!...of course, you will miss all the fun of tearing your bike totally apart.
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Offline Tower

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Re: Won't shift into second???
« Reply #10 on: October 28, 2009, 08:42:42 am »
A betting man would place his bet on the gear shift return spring (maybe the drum stopper spring.  Not enough tension on these springs will prevent the shift spindle from returning far enough to engage the lower cog in the shift drum stopper.

Offline ron.cieri.313

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Re: Won't shift into second???
« Reply #11 on: October 28, 2009, 08:59:16 am »
http://www.mrcycles.com/fiche_section_detail.asp?section=125612&category=MOTORCYCLES&make=HONDA&year=1976&fveh=2991

The darn springs aren't labelled on this fiche site...can you tell me which one you are referring to?...thanks.
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Offline KB02

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Re: Won't shift into second???
« Reply #12 on: October 28, 2009, 09:31:09 am »
Don't want to hijack the post but in my case, I've gone over the shift mechanism a few times quite thoroughly and I don't think I'm that lucky...but here's hoping that all it is for u!...of course, you will miss all the fun of tearing your bike totally apart.

Oh, I've had the bike totally apart. Check out my build thread in my signature.

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Okay, so a little tearing apart and here is what I have:
   I took this picture just after I took the side cover off. The bike was in, what I believed to be, neutral. Tell me, does this look right to you?


The things that look out of place to me are the two areas circled in red. Should the one on the left be down in behind the plates on the shift drum, or riding on the disks? Should the piece in the right be in the indent, circled in blue, while in neutral?


After playing around a bit, I think my problem is different. I put the shifter back on and played with things a bit and I was able to keep shifting down.  ??? I then got this with the rear wheel spinning freely. I think that I am now truly in neutral.

I kept shifting and playing around and it looks like I am actually able to shift from 1st through 3rd BUT it still would not go any higher than that. Does any of this make sense? Should I change the title to "Won't shift into fourth???"

I really don't want to pull this engine out. I JUST got it in...
« Last Edit: October 28, 2009, 09:33:19 am by KB02 »
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Offline KB02

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Re: Won't shift into second???
« Reply #13 on: October 28, 2009, 09:38:52 am »
http://www.mrcycles.com/fiche_section_detail.asp?section=125612&category=MOTORCYCLES&make=HONDA&year=1976&fveh=2991

The darn springs aren't labelled on this fiche site...can you tell me which one you are referring to?...thanks.

Try using www.crotchrocket.com They list ALL the parts on the fiche, available and unavailable. (Gear Shift return spring in #20)
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Offline MCRider

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Re: Won't shift into second???
« Reply #14 on: October 28, 2009, 09:39:58 am »
http://www.mrcycles.com/fiche_section_detail.asp?section=125612&category=MOTORCYCLES&make=HONDA&year=1976&fveh=2991

The darn springs aren't labelled on this fiche site...can you tell me which one you are referring to?...thanks.

I use motogrid.com
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Offline ron.cieri.313

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Re: Won't shift into second???
« Reply #15 on: October 28, 2009, 10:46:21 am »
Thanks guys...after your posts I realized BikeBandit must list all the parts too...much better...I will quadruple check that spring but my engine comes out tonight!...can't wait now.

Your shift mechanism looks good and is in neutral in the bottom pic but if the likes of MC and others have chimed in then no need for me too.

I think typically the gear shift mechanism is the the most likely culprit but believe me, I wouldn't tear out the engine unless I've tried everything..several times...still would love to be wrong but I believe/hoping?...I'm going to see worn dog gears or a bent middle shift fork.
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Offline nobody

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Re: Won't shift into second???
« Reply #16 on: October 28, 2009, 11:16:19 am »
That's sort of my fear as well. What if I get in there and it all looks fine? "oh hell... what now?"
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Offline ron.cieri.313

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Re: Won't shift into second???
« Reply #17 on: October 28, 2009, 11:20:36 am »
Lol...don't think about it...or tell urself the universe must be trying to send you some kind of message
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Offline nobody

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Re: Won't shift into second???
« Reply #18 on: October 28, 2009, 12:43:33 pm »
hahaha "Matt, you are not destined to own a motorcycle, let your girlfriend use the garage"

I'd tell the universe to shove it.
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Offline ron.cieri.313

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Re: Won't shift into second???
« Reply #19 on: October 28, 2009, 01:41:25 pm »
exactly...that y u split the cases anywho
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Offline nobody

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Re: Won't shift into second???
« Reply #20 on: October 28, 2009, 01:51:32 pm »
You make a valid point. I suppose most people would make a "perfect project bike" post on criagslist.
74 cb750k

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Offline KB02

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Re: Won't shift into second???
« Reply #21 on: October 28, 2009, 02:58:26 pm »
Lol...don't think about it...or tell urself the universe must be trying to send you some kind of message

If life hands you lemons, make lemonade. If life hands you tomatoes, make tomato soup. If life hands you a box of hand grenades... well, now... THAT'S a message!!
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Offline nobody

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Re: Won't shift into second???
« Reply #22 on: October 28, 2009, 03:02:41 pm »
hahahaha, that's going in my signature.
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Offline bryanj

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Re: Won't shift into second???
« Reply #23 on: October 29, 2009, 11:02:24 am »
Both gearbox shafts need to rotate to get all the gears, not just the back wheel
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Offline KB02

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Re: Won't shift into FOURTH??? (updated 11/1)
« Reply #24 on: November 01, 2009, 08:44:26 am »
Well... like ron.cieri.313, it looks like I may be in for a teardown.  >:( :'(

I checked everything out, re-did my shifting linkage a little bit (much stronger now) and re-tested the bike. I now successful have gears ONE thru THREE. When shifting up to where fourth should be... I just get a second neutral.  :( :( ???

What I have learned so far from my playing with it:
- The bike can start from a dead stop in third gear.
- The bike shifts hard.
- Neutral is difficult to find (It's a new bike - that will just take time to learn).
- I may have to tear down the engine.
- I suck at carb tuning. I may have to bring it to someone who is better with carbs than I am.
- Those pipes JUST SOUND KILLER!!!
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