Hello, I have read and tried the methods of allmost every topic before. But I have not seen somthing like that. I need your advice on a huge problem I have. I own a cb 400 super four version R (1995 japan grey import model to Greece) , the faired version with the square headlight and the TPS on the carbs, recently my bike started having the rev limiter at 12000 rpm ( instead of the 14000 as it is made and as it did all those years before, red starts at 13000). and it does that only if I am on the open road and slowly raise rpm with sixth gear.
THE great mistery!!!, if I just pull the throttle having the cluch pulled or even when I am in neutral it stops revving and it is like it hits the rev limiter at 6000-7000-8000 rpm and instantly the needle goes crazy and jumps again and again everywhere in the rpms. ALSO if I pull the throttle slowly in neutral but really slowly then it revs up until 10000 rpm and then jumps around in rpms. It started doing this out of the blue without to do something on the bike or change something not even the headlamp which is a HID 35 watt with ballast the last three years. I also have installed a scorpio (sr i 900) alarm 5 years ago and I have uninstalled it now just to eliminate the possibility that the problem starts from there. carbs are cleaned and the valves adjusted also! and all these just to eliminate factors. Can you, please, help me I love my bike. Thank you in advance. p.s.: I have replaced the TCI (I think it is not CDI) control unit and the TPS from the carbs but the problem didn't stop(in all the possible combinations.) from a friends bike same year same model. I have checked the clocks for damaged cables or contacts and everything is ok and cleaned every contact with electronics contact cleaner and also checked as much cables as I could for continuity. It has happened again a month ago but I had just unplugged and then plugged again the ECU( tci, cdi I am not sure what do I have) and the problem solved until recently that the unplug and plug again trick didn't work....I have also checked the coils, spark plugs (iridium NGK the last 2 years) also tried some copper ones, the tips from the coils to the spark plugs, fuse box, battery, regulator rectifier. It has no problem to move it, charges battery ok I have also made a trip one day and also go to work every day. it has not lost power on the revs that it works but the problem is still there!!! please help me.

You talk very casually about revving the engine to its redline speed while it is in neutral. This in not a nice thing to do to your engine. The operational specification for redline engine speed in an internal combustion engine is not intended to be regularly attained in an "unloaded" condition.

And the danger of accidentally "zinging" the engine past the redline and into valve-float territory (past the point where the valve springs can keep up and safely close the valves, which can result in their touching the rising piston tops) is very much more likely to happen during an unloaded rev condition than a loaded rev condition.

Regarding your odd RPM-limit problem: The only component you haven't mentioned in your post is the Signal Generator (also known as the Pulse Generator or Ignition Trigger or Toothed Wheel Sensor or Variable Reluctance Sensor).

This is the sensor (really just a magnet wrapped in copper wire) that generates an electrical signal as the individual teeth of the engine's toothed wheel pass by it. This toothed wheel is located on the left-hand end of your Honda's crankshaft, under the left-hand engine crankcase side cover. The two wires that run from this sensor to the CDI box come out of the very top of the crankcase side cover.

The Signal Generator itself (the copper-wound magnet) is very robust (they are factory-sealed in very hard epoxy resin) and it is highly unlikely to ever fail. But the wires that run from it to the CDI box are small and relatively easy to damage. Plus there's a quick disconnect plug between the Signal Generator and the bike's main wiring harness assembly.

Gavé toi fecked Alm thé earthi.g points? Twats us dell Woerth a look.

Well the above is what happens when you hit the change language key on your phone without realizing!
It was French by the way.

What I said was have you checked all the earthing points, it's well worth a look.

Thank you very much for your replies. Earthing points checked. I dont usually rev it in neutral, it is since I discovered the problem, that I do it. To check if it has gone. You are correct about the free revving. 737 I am aware of this mechanism in the left side of the bike. So beside continuity of these two cables there is nothing else I can do to this eye mechanism. But I have to open the case right? Thank you again my friend you are very helpful to all your posts. I ll post back with results. You dont think it has to do anythink with other components that complete the TCI, right. But we will talk about this after I check these cables.

I just opened the left side cover and also undone the bolts that hold the sensor so that I could measure continuity for as long as possible of the lenght of the cable and they are ok too. I have also removed the airbox so that i could measure any other cable and they are all fine. I am so much confused with all these. Can you suggest me anything else?. I dont want to give up on my bike. Its my bike , I kinda love this thing. Please any suggestions or ideas would be very much appreciated!!!

After lots of hours spent on the bike, I am tired, but I will not give up. I know we can solve the problem. I do not know what else to check. I read a post of 737 that explained how the TCI motorcycles operate but I cannot fully understand, due to lack in knowledge about electronics and electrics, how can I check if the problem is in the clocks and it is so well hidden that I cannot find it by just checking cables and cleaning contacts , (also the two springs behind the needle move freely and also the needle with the other components that roll around a shoe horse style magnet plate, no marks or debris or anything bloking move there) or if it is in somewhere else... How does the rpm limiter engages in my bike? I wonder. Why does it engages the rpm limiter in diferent rpms, depending on ,not how fast I twist the throttle, but on how fast the rpms rise. The slowest the rpm rises, the higher in thousands of rpm the limiter engages...

I am persuaded, by eliminating every other possibility, that the problem is in the clocks of my bike. The thing is that I cannot find an other pair to test it and also I cannot locate exactly where it could be in the clocks.… Does any one have any advice or idea?
I would also apreciate if someone could teĺl me if there is some other aftermarket tachometer that works with this bike, aftermarket I mean, or if I could eliminate somehow the tachometer without mess with the good working of the engine. I think I cannot just unplug it and have no consequenses for the rest of the bike. Thank you.

To clarify is it just your rev DISPLAY having a problem?
Or does the bike itself rev weirdly

Anyhow,
I just replaced my cb400 project big clocks with a KOSO rx2n.

Superb upgrade! Best to get a mechanic to help you out with the wiring, but if you're handy with wires and stuff you could probably do it yourself in an afternoon.

I just took my bike on the free way and clock works beautifully!

The other alternative was a used clock ($300) or a brand new old stock ($450)

I got the koso meter for much less, and it's way more functional

Hi Sprockett if you kind enough to share a picture how it looks like after installation of that KOSO it will be great thanks


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