Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Spanner McFettler on January 04, 2023, 03:03:34 PM
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I've seen a couple of other threads that mention this but none that particularly answer my problem. Following the rebuild of my CB750K7 the neutral light stays on regardless if the bike is in gear or not. The switch is good because I've tested it, continuity is good with no shorts anywhere so I'm stumped what may cause this? When I had the engine out of the frame I did a top end rebuild but left the bottom end alone, once the engine was back in the frame I popped my little finger in the neutral switch hole and whether in or out of gear I could feel the bit that engages the ball on top of the neutral switch and it didn't seem to move. Does this sound like a gear drum selector or bent selector fork issue? I suspect this will involve getting the engine out again and looking at the transmission. The engine runs perfectly but the gearbox is a little temperamental, hard to select neutral from 1st when stopped and occasionally a bit clunky when engaging a gear, now and then I've had a false neutral too. I've probably answered my own question but would appreciate any tips, cheers.
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First its worth checking continuity in situ if you've not done that to see if it changes.
Take wire off switch, then check continuity of switch only while flipping it in and out of neutral to see if the mechanical/ electronic transfer does anything at all.
If you get a result which confirms either way, then you can go from there as to what should be checked next.
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To add, during checking it's continuity to earth via the switch connection post that you should see change when going into neutral.
After that, you can check the wire to the switch by taking the nuetral bulb out of it's holder and then checking for continuity again from the wire end that attaches to the switch across to a competent earth point. This should have no connection to earth and give you no continuity when checking like that.
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As i remember it the part that makes the neutral switch work is a machined dimple in the selector drum allowing the ball on the end of the switch to move out father and create a ground to illuminate the lamp, it is 100% impossible for this dimple to fail so you problem is either a grounded wire or faulty switch
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Try this that drove me mad once and worth a try.
On the ring crimp terminal with single wire to the switch, the ring maybe touching the outside of the natural switch causing it to earth. Slide a bit of paper under the ring clamp and see if the light goes out.
If the light does go out, then bend the end of the ring clamp away from the switch. I have found that some non original ring clamps that are a tad longer, so touched ;)
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Thanks for all the suggestions, I'll report back once I've tried them all
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Well I fixed it and in true Spanner McFettler fashion it was a ridiculously easy fix! Firstly the damned switch was not fully seated somehow, it wasn't obviously apparent without getting right under neath the bike and having a close inspection! Secondly there was paint covering the switch which was interfering with the connector that screws into the switch. Reseated the switch, cleaned all the paint off and replaced the screw, hey presto its all working! The bike is still a bit reluctant to go into neutral at times when warmed up but its fine if I select neutral before i come to a complete stop, I can live with that however and given its a brand new set of clutch plates I will get a few miles on it and ensure the clutch is properly adjusted before worrying about it too much. Thanks for the help guys, always good to get some suggestions to work with.
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Is the clunkness worse when the bike has run for a few miles?
I am far from an expert but I suspect you have a bit of clutch drag hence the clunky changes & trouble finding neutral from first.
If it does not improve after a few hundred miles I would be checking the clutch mechanism and adjustments at both ends of the system not forgetting making sure your cable routing is as it should be.
You probaly have thought of the above so sorry if my comments are a tad basic/obvious.
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I think that the selecting neutral at standstill is a 750 trait - both my 750's suffer from it. My 500 on the other hand is miles better
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Had problems with the neutral light on my 750F1 staying on not long after I bought it in 1976, tried everything to fix it to no avail, in the end I taped over the light and ignored it. It wasn't until 2005 or so when I did a total strip down and inspected the harness that I found a chafed wire was causing the problem.
I also have to select neutral before I come to a halt, otherwise when I am stationary I have to hit the kill the engine, select neutral and start up again.
Cheers
Dennis
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Can’t remember what mine is like! Not seen it for 5 months let alone ridden it. When I take it out of hibernation I will have to take note and post back finding.