Author Topic: SHIFT PATTERN WRONG  (Read 334 times)

0 Members and 1 Guest are viewing this topic.

Offline bama7

  • Full Member
  • *
  • Posts: 13
SHIFT PATTERN WRONG
« on: April 01, 2019, 06:27:05 am »
First off I know very little about the internals of the 750A transmission. The only thing I did was install the stick shifter. I did not go into the transmission at all. To shift into low gear the lever has to be pulled completely to the rear.  The lever must be pushed full forward to get into high gear. The neutral position or park what ever it is called is between the low and high position. That means I can't shift from low to high while the bike is moving. What could cause this problem? The motor runs great. Also, while in neutral when racing the throttle the rpm will not increase to full rpm. It seems to be wanting to move the bike. HELP!! 

Offline raymond10078

  • Moderator
  • Expert
  • *****
  • Posts: 752
  • Just learnin' as I go . . . .
Re: SHIFT PATTERN WRONG
« Reply #1 on: April 01, 2019, 06:23:31 pm »
This is curious.

The CB750A has two shafts, only an inch or two apart.

The rearward shaft is for shifting.  The pattern is N-L-D, from bottom to top (clockwise direction).

The forward shaft is a safety mechanism, tied to the kickstand.  Counterclockwise rotation is safety off. 

Which shaft did you connect to?

Pic?

The shifter in the CB750A is not like a CB750.  No mechanical gears or dogs begin moved by a gear cam.  The CB750A shifter is a hydraulic valve, and allows oil to be ported to either the Low or High clutch pack.

I don't believe that the pattern can be changed.
1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline bama7

  • Full Member
  • *
  • Posts: 13
Re: SHIFT PATTERN WRONG
« Reply #2 on: April 01, 2019, 08:04:16 pm »
Thanks for the reply. The shift lever is connected to the correct shaft. I need to check the position of the forward shaft, safety mechanism, to make sure it is in the proper position. Nothing about the pattern makes any sense to me. I don't know how it could be assembled wrong. I am hoping I will find something simple I have overlooked. For some reason I can't load a picture. I am going to try again and load  picture of the shifter and safety shaft. Thank you
When I try to post a picture message says it is too big. I was able to load the avatar picture the other day with out any problem.

« Last Edit: April 01, 2019, 08:37:19 pm by bama7 »

Offline raymond10078

  • Moderator
  • Expert
  • *****
  • Posts: 752
  • Just learnin' as I go . . . .
Re: SHIFT PATTERN WRONG
« Reply #3 on: April 04, 2019, 10:09:52 am »
send me the pic personally, and I'll upload it.

raymond10078@gmail.com
1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline bama7

  • Full Member
  • *
  • Posts: 13
Re: SHIFT PATTERN WRONG
« Reply #4 on: April 04, 2019, 12:52:14 pm »
I just sent you an email with three pictures.  Forward is H middle is N and Back is L. The shift lever does not stay in a position as such. When you put it in gear or in N the lever springs back to where it was, but it is in gear. It will not rev the motor while in N acts like it is in a bind or something.

Offline raymond10078

  • Moderator
  • Expert
  • *****
  • Posts: 752
  • Just learnin' as I go . . . .
Re: SHIFT PATTERN WRONG
« Reply #5 on: April 04, 2019, 01:55:49 pm »
More text from the OP:

Forward is H middle is N and Back is L. The shift lever does not stay in a position as such. When you put it in gear or in N the lever springs back to where it was, but it is in gear. It will not rev the motor while in N acts like it is in a bind or something.

Pics from the OP are attached.
1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline raymond10078

  • Moderator
  • Expert
  • *****
  • Posts: 752
  • Just learnin' as I go . . . .
Re: SHIFT PATTERN WRONG
« Reply #6 on: April 04, 2019, 02:13:45 pm »
One of your statements - that it seems "bound" is troublesome.

I'm going to assume that the high and low is determined by driving your bike (i.e., not with the rear wheel off the ground).

Given that, the ONLY way that I know that the transmission can be bound - is if the two gears are simultaneously engaged.  In this engine, each "gear" is selected by applying oil under pressure to one of two clutch packs (one clutch pack for each gear).  I'm going to GUESS that your selector valve is messed up - and is applying oil pressure to both clutch packs at the same time.

If it were me, I'd pull the left cover off and watch the selector move in response to the gear shaft.  I haven't personally messed with this part of the bike - yet (crossing my fingers), so take my input as a guess.

1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline bama7

  • Full Member
  • *
  • Posts: 13
Re: SHIFT PATTERN WRONG
« Reply #7 on: April 04, 2019, 03:12:57 pm »
Your guess is much better than my experience. You are referring to the manual selector valve correct? I hope to do that tomorrow. Thanks again.
« Last Edit: April 04, 2019, 03:16:30 pm by bama7 »

Offline raymond10078

  • Moderator
  • Expert
  • *****
  • Posts: 752
  • Just learnin' as I go . . . .
Re: SHIFT PATTERN WRONG
« Reply #8 on: April 05, 2019, 11:07:39 am »
I'm sharing my off-line discussion with the OP:

OP said:  I found a big flat washer covered in grime laying sideways between the shift valve and the other mechanisms.  Absolutely crazy.  I will jack up the trike and see what happens after I see where the washer should go.  Maybe just a spacer.
1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline raymond10078

  • Moderator
  • Expert
  • *****
  • Posts: 752
  • Just learnin' as I go . . . .
Re: SHIFT PATTERN WRONG
« Reply #9 on: April 05, 2019, 11:09:20 am »
Short video of OP's bike and valve in action.
1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline raymond10078

  • Moderator
  • Expert
  • *****
  • Posts: 752
  • Just learnin' as I go . . . .
Re: SHIFT PATTERN WRONG
« Reply #10 on: April 05, 2019, 11:11:53 am »
No washer shown in service manual.

If you look at the service manual, pay attention to section 2.  The valve, how it works, how it is supposed to stroke, all covered.

In the video, your valve strokes properly.  Fully extended is N, valve plunger down one position is L (or 1), valve plunger down to second position is H (or 2).

From my understanding, the valve has no seals, just tight tolerances.
1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline bama7

  • Full Member
  • *
  • Posts: 13
Re: SHIFT PATTERN WRONG
« Reply #11 on: April 05, 2019, 02:13:39 pm »
I am getting some parts from eBay around Wednesday. I am in hopes the problem will be fixed then.

Offline bama7

  • Full Member
  • *
  • Posts: 13
Re: SHIFT PATTERN WRONG
« Reply #12 on: May 08, 2019, 01:39:36 pm »
A MIRACLE HAS BEEN PERFORMED!!!  My buddy changed the parts I got from ebay, but no change in the shift pattern. After some thought he checked the parking brake shaft and internals. Someone had taken it apart and did not put it back together correctly. I really don't know what exactly was wrong and don't care at this moment. I am just happy it works as it should. I hope to get it tomorrow and ride some. Very happy!
Got the Trike this morning and it worked great.
« Last Edit: May 09, 2019, 10:37:20 am by bama7 »

 

;