be careful when prying off the carbs as the aluminium they are made of is very easily damaged.. and I mean VERY! Use penetrating fluid and make sure that the airbox is as far back as it will go. On mine there were two pipes passing behind it that when removed gave me another half inch to play with.

When you move the airbox back, the rubbers joining it to the carbs will pop off and expose a very delicate part of the carbs (like a 2 inch diameter tube at the intake of the carb ) which they will rest against so be very careful to work slowly and delicately. Carb parts can be very expensive to replace.

To remove the carbs from the head, I found it easier to lift the rear part of the carbs upwards and sort of pry them off slowly. Again they will probably be very stubborn to leave their beloved engine so work slowly and use just the right amount of brute force :p

when they finally come off you will need to remove several pipes so make a note which came out from where. You must also take care of a small sensor on the right hand side. This is identifiable by a wire from the no4 carb to the wiring harness and covered by a small black plastic cover. it is easier to remove the 3 screws holding it on the bike rather than disconnecting the connector halfway along the wire. after removing the screws and sliding it out take care of a very small plastic part inside which will probably fall out if you are not careful. Remove it yourself and mark it with tape so as not to lose it. Take your time to observe what happens inside there when you twist the throttle so that you know how to put it back together.

You will probably be able to put in or remove your restrictors without removing other stuff however if you take the carbs out altogether you will need to remove the push/pull throttle cables (these can be very fiddly to assemble back) and also the choke cable.

Hope this helps and please excuse my far from perfect english,
Chris

That's a good piece of information to know.

Wow, top advice, thanks a lot! You definitely make it sound a lot more involved than I'd hoped - but I reckon I can just about manage all that with a bit of patience.

chricol wrote: ...and please excuse my far from perfect english,
Chris

And I'd say your English is pretty much perfect Chris - better than a lot of actual English folks even :)

I'll let you know how it goes :)

https://www.facebook.com/media/set/?set ... 205&type=3

these are some pictures from a recent overhaul I carried out. You might find them useful.

I belive my honda cb400sf 1992 NC31 is restricted in an electrical way, she rides great till I get into top gear then she won't climb up the revs and really struggles going past 70ish mph.

I've had digital clocks put on her I just can't seem to get to the bottom of the issue, could anyone help me please.

Stratty wrote: Mon May 18, 2020 1:31 am I belive my honda cb400sf 1992 NC31 is restricted in an electrical way, she rides great till I get into top gear then she won't climb up the revs and really struggles going past 70ish mph.

I've had digital clocks put on her I just can't seem to get to the bottom of the issue, could anyone help me please.

Did you get anywhere with this by any chance. I have a similar top speed issue and am waiting for a dyno near me to open so I can get some baseline info. My bike is the same era and has similar top speed issues. I also have aftermarket clocks fitted.

Cheers

Stratty wrote: Mon May 18, 2020 1:31 am I belive my honda cb400sf 1992 NC31 is restricted in an electrical way, she rides great till I get into top gear then she won't climb up the revs and really struggles going past 70ish mph.

I've had digital clocks put on her I just can't seem to get to the bottom of the issue, could anyone help me please.

I would suggest that the issue is your clocks and that you might need to have a look into whether there is the same restriction on that bike as there is on my NC30.

When you have disconnected the clocks - on an nc30 for sure - then there is a signal missing to the CDI and it cuts ignition at 5500rpm. This to prevent people removing clocks to bypass the 180kmh Jap speed restriction

So, for both you guys with a loss of power - and probably a dead obvious issue at 5500rpm - I would suggest refitting your clocks just to troubleshoot it.

The other fixes are to sodler in a restrictor to the circuit that is checking for the clocks - this is what the M-MAX boxes and all that overpriced shit did for you. You would also remove the 180kmh restriction of course..

Have a look for speedo restrictor mod - that'll sort it surely :)

unkul79 wrote: Fri Jun 12, 2020 9:07 pm

Stratty wrote: Mon May 18, 2020 1:31 am I belive my honda cb400sf 1992 NC31 is restricted in an electrical way, she rides great till I get into top gear then she won't climb up the revs and really struggles going past 70ish mph.

I've had digital clocks put on her I just can't seem to get to the bottom of the issue, could anyone help me please.

Did you get anywhere with this by any chance. I have a similar top speed issue and am waiting for a dyno near me to open so I can get some baseline info. My bike is the same era and has similar top speed issues. I also have aftermarket clocks fitted.

Cheers

Now then - quoting you so you can see the reply :)

CMSMJ1 wrote: Mon Jun 15, 2020 12:38 pm

Stratty wrote: Mon May 18, 2020 1:31 am I belive my honda cb400sf 1992 NC31 is restricted in an electrical way, she rides great till I get into top gear then she won't climb up the revs and really struggles going past 70ish mph.

I've had digital clocks put on her I just can't seem to get to the bottom of the issue, could anyone help me please.

I would suggest that the issue is your clocks and that you might need to have a look into whether there is the same restriction on that bike as there is on my NC30.

When you have disconnected the clocks - on an nc30 for sure - then there is a signal missing to the CDI and it cuts ignition at 5500rpm. This to prevent people removing clocks to bypass the 180kmh Jap speed restriction

So, for both you guys with a loss of power - and probably a dead obvious issue at 5500rpm - I would suggest refitting your clocks just to troubleshoot it.

The other fixes are to sodler in a restrictor to the circuit that is checking for the clocks - this is what the M-MAX boxes and all that overpriced shit did for you. You would also remove the 180kmh restriction of course..

Have a look for speedo restrictor mod - that'll sort it surely :)

Hi Thanks for the reply. I dont have original clocks fitted. Ive been trying to get on a dyno to see how accurate my after market clocks ae but my gut (and ears) tell me that im revving much higher than 5500 rmp. Also i did te resistr mod (i assume this is what you mean) and saw no change in performance. My other thread can be seen here viewtopic.php?f=24&t=55476 . It highlights my situation and a few other members have been really helpful. ATM im at a bit of a deadend as the local dynos near me arent open.

Cheers

unkul79 wrote: Mon Jun 15, 2020 2:03 pm

CMSMJ1 wrote: Mon Jun 15, 2020 12:38 pm

Stratty wrote: Mon May 18, 2020 1:31 am I belive my honda cb400sf 1992 NC31 is restricted in an electrical way, she rides great till I get into top gear then she won't climb up the revs and really struggles going past 70ish mph.

I've had digital clocks put on her I just can't seem to get to the bottom of the issue, could anyone help me please.

I would suggest that the issue is your clocks and that you might need to have a look into whether there is the same restriction on that bike as there is on my NC30.

When you have disconnected the clocks - on an nc30 for sure - then there is a signal missing to the CDI and it cuts ignition at 5500rpm. This to prevent people removing clocks to bypass the 180kmh Jap speed restriction

So, for both you guys with a loss of power - and probably a dead obvious issue at 5500rpm - I would suggest refitting your clocks just to troubleshoot it.

The other fixes are to sodler in a restrictor to the circuit that is checking for the clocks - this is what the M-MAX boxes and all that overpriced shit did for you. You would also remove the 180kmh restriction of course..

Have a look for speedo restrictor mod - that'll sort it surely :)

Hi Thanks for the reply. I dont have original clocks fitted. Ive been trying to get on a dyno to see how accurate my after market clocks ae but my gut (and ears) tell me that im revving much higher than 5500 rmp. Also i did te resistr mod (i assume this is what you mean) and saw no change in performance. My other thread can be seen here viewtopic.php?f=24&t=55476 . It highlights my situation and a few other members have been really helpful. ATM im at a bit of a deadend as the local dynos near me arent open.

Cheers

That is interesting = gave you some of my pennies worth of thoughts! Hope it might help