Author Topic: False Neutral  (Read 730 times)

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Offline The Gurg

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False Neutral
« on: August 15, 2018, 07:40:35 am »
Trying to eliminate the false neutral I have on a shift into second. Occurs 10% of the time maybe. Usually if I’m forceful it won’t happen.

I bought new transmission bearings from Cycle X (Ken and the rest of the  Wisconsin guys are awesome!), and a new second gear. Also, replaced the broken clutch lifter plate with an OEM part.

Clutch plates and forks are within spec. I’ve read that usually the dogs or forks are the issues. Replacing second should address the dogs, I’m uploading pics of the forks. They don’t look bent to me, but I’m a newbie. The shift drum has a bend in the thin plate. Don’t think that could cause the issue, but maybe?

Offline TwoTired

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Re: False Neutral
« Reply #1 on: August 15, 2018, 09:15:25 am »
Might be helpfull to say what bike you are working on.
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Offline The Gurg

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Re: False Neutral
« Reply #2 on: August 15, 2018, 09:22:01 am »
1975 CB750 K5 38k mi.

Offline MicahDT

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Re: False Neutral
« Reply #3 on: August 15, 2018, 10:26:59 am »
I will say, I rode modern bikes before I started riding my own vintage bikes.Vintage bikes seem to have harder and longer shifting motions. If its that intermittent, it may be your technique. I struggled with it for a while on my '76 CB750 and have missed once or twice on my '74 CB550. Just food for thought.
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Offline The Gurg

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Re: False Neutral
« Reply #4 on: August 15, 2018, 01:58:38 pm »
Yeah could be that I need to be a little more forceful. But happens more with one gear, so makes me wonder if it’s something that needs to be fixed. Anything else anyone can think of that I should check?

Online jaytee-nz

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Re: False Neutral
« Reply #5 on: August 15, 2018, 02:24:45 pm »
I find that chain tension can have an effect on the first to second gear shift - a loose chain will make it clunky, to use a very technical term !
That can lead to the odd false neutral.

Offline The Gurg

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Re: False Neutral
« Reply #6 on: August 15, 2018, 02:29:59 pm »
Really, that surprises me. I hadn’t seen that anywhere. Are you talking cam chain tension? There’s no tensioner on the primary chains, right?

Offline flybox1

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Re: False Neutral
« Reply #7 on: August 15, 2018, 03:01:04 pm »
There is a tensioner on the primary, but it is fixed and not adjustable.
Loose cam chain, tight cam chain...shouldnt make a difference on gear engagement unless the crank bearings are really, really shot.
Get a good non-synthetic MC oil.
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Online jaytee-nz

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Re: False Neutral
« Reply #8 on: August 15, 2018, 05:33:16 pm »
No not the cam chain - the main drive chain to the sprocket.

Offline HondaMan

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Re: False Neutral
« Reply #9 on: August 15, 2018, 06:08:32 pm »
Take a real close look at the track for the "L" shift fork's dog (the dowel that moves it around). If the tip of the Neutral peak on that track is chipped or worn down, it can make the shift drag when it passes the Neutral and heads for 2nd. You can recognize the wear as being worn on the tip of the Neutral bump, but not down at the bottom of the groove.

Also, the L" fork will show wear on the sides of the fork where it rides in the groove of its gear, if it is bent or warped. What usually warps or bends them is: the bike falls over on the left side in such a way that the shifter gets hit and lifted, but not into gear, from Neutral. Most often, I used to call this the "car-hit-it-in-the-garage" accident, knocking the bike off its sidestand, and there was something on the floor near the shifter when the bike fell over...it happened a LOT in the day.

In the end, what happens is: the shift fork cannot push the C2 gear dogs all the way into the C5 gear's slots. Sometimes, the C5 slots may also be worn, which then tapers them and makes that gear tend to push the C2 back out while you are trying to push it in. Normally, those 2 gears should be replaced as a set, or at least the 2 of them recut together to have straight dogs and slot edges.
« Last Edit: August 15, 2018, 06:11:13 pm by HondaMan »
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Offline evanphi

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Re: False Neutral
« Reply #10 on: August 16, 2018, 06:46:16 am »
No not the cam chain - the main drive chain to the sprocket.

And also if it is too tight! I found this myself when I first had my bike... 1-2 was very easy to miss with an over-tightened chain.
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Offline PeWe

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Re: False Neutral
« Reply #11 on: August 17, 2018, 11:28:45 am »
The "false" neutral is between 4-5?
I have noticed that it is very easy to put 4 out of gear. Enough to nudge the pedal with the boot during acceleration.
Sometimes it will not gear in 5:th completely. But this is something I felt when gearing.

Better now with under cutted gears, 2-4. Now the other way, I have to release with clutch completely and shift gear more firmly, especially when gearing down.
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Offline 70CB750

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Re: False Neutral
« Reply #12 on: August 17, 2018, 11:37:16 am »
I like the Neutral between 4 and 5.  For long down hill coasting, it helps to cool the engine.

Offline robvangulik

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Re: False Neutral
« Reply #13 on: August 17, 2018, 12:12:08 pm »
I've heard about it, never could find it, never missed it. Coasting downhill is a no go anyway in a flat country like mine ;D

Offline HondaMan

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Re: False Neutral
« Reply #14 on: August 18, 2018, 07:55:45 pm »
The "false" neutral is between 4-5?
I have noticed that it is very easy to put 4 out of gear. Enough to nudge the pedal with the boot during acceleration.
Sometimes it will not gear in 5:th completely. But this is something I felt when gearing.

Better now with under cutted gears, 2-4. Now the other way, I have to release with clutch completely and shift gear more firmly, especially when gearing down.
The next time you're in that bottom end, PeWe: put a 0.25mm - 0.50mm spacer washer on the side of the gear between it and the bearing (opposite end of the mainshaft from the clutch). That should make the 4-5 shift faster and more solid, but the neutral will go away.

I'd probably miss mine if I did that, though... ;)
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.
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Offline PeWe

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Re: False Neutral
« Reply #15 on: August 18, 2018, 10:16:25 pm »
The "false" neutral is between 4-5?
I have noticed that it is very easy to put 4 out of gear. Enough to nudge the pedal with the boot during acceleration.
Sometimes it will not gear in 5:th completely. But this is something I felt when gearing.

Better now with under cutted gears, 2-4. Now the other way, I have to release with clutch completely and shift gear more firmly, especially when gearing down.
The next time you're in that bottom end, PeWe: put a 0.25mm - 0.50mm spacer washer on the side of the gear between it and the bearing (opposite end of the mainshaft from the clutch). That should make the 4-5 shift faster and more solid, but the neutral will go away.

I'd probably miss mine if I did that, though... ;)
I'll check that at next build. K1 extra engine I have, bottom.
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017

Offline HondaMan

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Re: False Neutral
« Reply #16 on: September 08, 2018, 07:39:24 pm »
The "false" neutral is between 4-5?
I have noticed that it is very easy to put 4 out of gear. Enough to nudge the pedal with the boot during acceleration.
Sometimes it will not gear in 5:th completely. But this is something I felt when gearing.

Better now with under cutted gears, 2-4. Now the other way, I have to release with clutch completely and shift gear more firmly, especially when gearing down.
The next time you're in that bottom end, PeWe: put a 0.25mm - 0.50mm spacer washer on the side of the gear between it and the bearing (opposite end of the mainshaft from the clutch). That should make the 4-5 shift faster and more solid, but the neutral will go away.

I'd probably miss mine if I did that, though... ;)
I'll check that at next build. K1 extra engine I have, bottom.

If it is an "old factory" K1 it will not have the shim option, and few of the "New Factory" K1s had it, either. This method first showed up late in the K4 engines and is very common in the F0-F3 and K7/8 engines.

In the early engines, if the neutral between 4 and 5 becomes pretty common then the bushings inside those gears may be worn, letting them wobble a bit. The New Factory used cast iron, the Old Factory used bronze in these bushings. The bronze ones live MUCH longer and have fewer issues. ;)
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 PeWe

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Re: False Neutral
« Reply #17 on: September 08, 2018, 10:58:24 pm »
The "false" neutral is between 4-5?
I have noticed that it is very easy to put 4 out of gear. Enough to nudge the pedal with the boot during acceleration.
Sometimes it will not gear in 5:th completely. But this is something I felt when gearing.

Better now with under cutted gears, 2-4. Now the other way, I have to release with clutch completely and shift gear more firmly, especially when gearing down.
The next time you're in that bottom end, PeWe: put a 0.25mm - 0.50mm spacer washer on the side of the gear between it and the bearing (opposite end of the mainshaft from the clutch). That should make the 4-5 shift faster and more solid, but the neutral will go away.

I'd probably miss mine if I did that, though... ;)
I'll check that at next build. K1 extra engine I have, bottom.

If it is an "old factory" K1 it will not have the shim option, and few of the "New Factory" K1s had it, either. This method first showed up late in the K4 engines and is very common in the F0-F3 and K7/8 engines.

In the early engines, if the neutral between 4 and 5 becomes pretty common then the bushings inside those gears may be worn, letting them wobble a bit. The New Factory used cast iron, the Old Factory used bronze in these bushings. The bronze ones live MUCH longer and have fewer issues. ;)
I'll might upgrade the gearbox with a K6 I have. I have not opened the engine yet, it might be in bad shape. The final axle will get double row bearing if cases allow it.
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017

Offline dave500

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Re: False Neutral
« Reply #18 on: September 09, 2018, 12:29:21 am »
preload the shift,take up any slack first.

Offline The Gurg

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Re: False Neutral
« Reply #19 on: September 20, 2018, 04:47:00 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.

Offline The Gurg

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Re: False Neutral
« Reply #20 on: October 31, 2018, 09:00:07 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?

Offline The Gurg

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Re: False Neutral
« Reply #21 on: October 31, 2018, 09:02:32 am »
Oh and I wanted to point out the wear on my old c5’s dogs shown in the photo. Doesn’t look like much wear to me, but maybe that’s all it takes to make going into second hit or miss?

Offline PeWe

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Re: False Neutral
« Reply #22 on: October 31, 2018, 09:43:25 am »
Undercutting the gearbox. Send the entire transmission to a shop that do 2-4 with all machined dogs and opposite gear that also is cut.

The "neutral" between 4-5 was never an issue when aware of it and knowledge what to avoid, how to shift to 5:th gear to make sure it is completely in.
2 and 4, the CB750 std out of gear sliders.
« Last Edit: October 31, 2018, 09:45:39 am by PeWe »
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Offline ofreen

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Re: False Neutral
« Reply #23 on: October 31, 2018, 10:54:01 am »
preload the shift,take up any slack first.

Yep
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Offline spotty

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Re: False Neutral
« Reply #24 on: October 31, 2018, 04:53:29 pm »
on a related but not at all honda issue, on the yamaha vmax you have rubber engine mounts ( to cut down vibration) and the engine can twist up to an inch in these under hard acceleration, this is enough to put the gear change far enough away from your foot ( which being on the rigidly mounted footpeg ) that under aforementioned hard acceleration you would only nudge the gear change instead of giving it the proper lift it needs.

fitting solid engine mounts has fixed that problem, now my hands go numb from the vibration within about half an hour..... 
and here was me thinking I'd kicked the honda habit........silly me

 

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