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Author Topic: False Neutral  (Read 751 times)

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Offline HondaMan

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Re: False Neutral
« Reply #25 on: November 03, 2018, 09:58:36 am »
Still trying to diagnose this issue. Realized I misspoke before: I got a c5 gear from Cycle X not a c2.

1.) do I need to have c2 cut to receive the undercut dogs from Cycle Xs c5 gear. (I have photos attached of both the old and new c5.)

2.) should I have a machine shop fix the bent plate on the shift drum. Honda discontinued the shift drum, Yamiya carries it but it’s really pricey. I could order an oem plate from eBay, but the screw on the drum has the sides stamped down. Not sure how to remove the screw.

3.) anything else I should be looking/considering. The shift forks and everything else looks good to me, but I am an amateur mechanic. Would you guys reassemble once I address questions 1 & 2?

How about if you PM me your mailing address? There looks to be a chip on the Neutral bump on the shift drum, probably caused when it jammed and bent the pin flange. I have drums: what is the serial number of the crankcases?
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Offline The Gurg

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Re: False Neutral
« Reply #26 on: November 07, 2018, 08:29:04 am »
So here’s where I’m at:

I’m thinking that the undercut c5 dogs and c2 slots from Cycle X will fix the issue. And that the broken clutch lifter plate was a big contributor (which I’ll replace).

No one seems to think the shift drum plate being bent is an issue. I’m still struggling to understand the exact mechanical purpose of the plate. Would love some insight. I have a machine shop straightening the plate. But the shop is going to try to do it without removing the screw or plate. Makes me question what the integrity of the piece will be after bending back. So, I also ordered used SOHC 1975 CB750 (should be an exact match) shift drum and forks from ebay for $40. Should I use the machine shop unbent drum or the used eBay drum?

Also, planning on doing a dry run (with some assembly lube) of the transmission. Peter Anderson has a pretty cool trick on how to do that.

Go to the 34 minute and 52 second mark:


Offline HondaMan

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Re: False Neutral
« Reply #27 on: November 07, 2018, 07:26:24 pm »
Here’s a few more photos of the shift drum. Hondaman thought that could be the issue. Got the 2nd gear in from CycleX with undercut dogs.

The Neutral Bump looks to be OK, but the bent alignment flange, not so much. This will tend to bind and drag the rotation when it comes up against the spring detent wheel, making the shift action stall out and miss the full shift. This essentially holds it in-between the gears when that happens. The "crisp" shift these bikes are known for was due to a combination of the dry sump, the large gears and loose dog tolerances, so there is a lively difference between them when they negotiate the final dog-in-slot move, making the clunk we all know so well. This also makes the wear marks you see, and since 1-2 happens a LOT in this bike, they wear the most for it.

The wider Neutral detent yours has indicates it is a late K3 or later type "improved" shift drum. These have a little slower 1-2 shift but a more easily-found Neutral on a hot day, as it holds the fork's dog in-between the gears a little bit longer in travel.
The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: http://forums.sohc4.net/index.php?topic=65293.0

Link to website: www.SOHC4shop.com

Offline The Gurg

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Re: False Neutral
« Reply #28 on: November 08, 2018, 08:00:07 am »
Is this the neutral bump on the L track?

Offline PeWe

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Re: False Neutral
« Reply #29 on: November 08, 2018, 10:00:25 am »
Neutral switch will extract into this hole (dimple) and lit the green pilot indicator lamp.
See yellow arrows to the right.
« Last Edit: November 08, 2018, 11:46:35 am by PeWe »
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017

 

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