Jump to content

honda cb400n wont rev past 5,000k under load


Ant132
 Share

Recommended Posts

hi, my bike was fine and ran great but i took it out monday and i couldnt get past 5,000 rpm, as soon as it got to 5,000 it kinda went pop,pop,pop,pop, until i knocked it up a gear and it would go again, until the same would happen again once the revs hit 4/5k.


Ive been working the last few days to fix it to no avail, ive cleaned the carbs, checked the connections to the cdi, generator, ignition coil and cdi pick up. and generally checked the connections of the whole loom, and also checked for any air leaks.


The bike revs up fine in neutral, but wont go past 5,000 under load.


I have now found out that i can get to 6,000 in 1st, 5,000rpm in 2nd and 4/5,000 in 3rd, 4,000 in 4th etc. etc.


Any ideas. thankfull to any help from experience!!!


Bike is honda cb400n superdream, air-cooled 4-stroke twin cylinder. I also replaced the rocker cover gasket in the same day, then took it out to find this problem.


thank you

Link to comment
Share on other sites

Bike is honda cb400n superdream, air-cooled 4-stroke twin cylinder. I also replaced the rocker cover gasket in the same day, then took it out to find this problem.


thank you

how was it before your repairs?

Link to comment
Share on other sites

Bike is honda cb400n superdream, air-cooled 4-stroke twin cylinder. I also replaced the rocker cover gasket in the same day, then took it out to find this problem.


thank you

how was it before your repairs?

 

Absolutely fine, the one and only thing i did replace the rocker cover gasket.


Thanks :cheers:

Link to comment
Share on other sites

Bike is honda cb400n superdream, air-cooled 4-stroke twin cylinder. I also replaced the rocker cover gasket in the same day, then took it out to find this problem.


thank you

how was it before your repairs?

 

Absolutely fine, the one and only thing i did replace the rocker cover gasket.


Thanks :cheers:

It has to be something from your repair, did you refit the breather and pipes correctly?

Link to comment
Share on other sites

Everything fitted correctly mate!! To tell the truth since posting this yesterday ive now found out some more information on similar problems etc. and im led towards generator failure.


There is apparently two parts on the superdream generator, one that controls starting and upto 4/5k and another that controls rpm over that. So it is likely that the generator has failed due to them being a weak point in the superdreams electrical system.


If it is the gen, then chances are it is just some mad kind of coincidence :lol: as honestly, every last thing i could have checked to do with the simple gasket fit has been checked and re-checked by me and my dad who was helping me yesterday.


What you reckon to this mate? Is it worth me splashing out on the gen or am i barking up the wrong tree?

Link to comment
Share on other sites

I just guessing but if it doesn't rev past 5000 only under load, then I would have thought it would be a fuel or air problem, not an electrical problem.


Don't take my word as gospel though, I ain't no expert

Link to comment
Share on other sites

Everything fitted correctly mate!! To tell the truth since posting this yesterday ive now found out some more information on similar problems etc. and im led towards generator failure.


There is apparently two parts on the superdream generator, one that controls starting and upto 4/5k and another that controls rpm over that. So it is likely that the generator has failed due to them being a weak point in the superdreams electrical system.


If it is the gen, then chances are it is just some mad kind of coincidence :lol: as honestly, every last thing i could have checked to do with the simple gasket fit has been checked and re-checked by me and my dad who was helping me yesterday.


What you reckon to this mate? Is it worth me splashing out on the gen or am i barking up the wrong tree?

i would search the site for Regulator or rectifier, i posted a link from the Katana Club site regarding checking them, and you'd need a multimeter to measure amps/volts

http://www.thegsresources.com/garage/gs_statorfault.htm

Link to comment
Share on other sites

hi, my bike was fine and ran great but i took it out monday and i couldnt get past 5,000 rpm, as soon as it got to 5,000 it kinda went pop,pop,pop,pop, until i knocked it up a gear and it would go again, until the same would happen again once the revs hit 4/5k.

 

just dug out my old haynes manual for the 400n, it states that engine fade under load is due to preignition and typically faulty plugs. it's listed as an explicit example in the fault finding section :!:


i also looked at the alternator part. the cdi pickup is integrated with the alternator but it makes no reference to there being two parts opperating at different RPM (it would be odd if there were). what you do have is the cdi pickup in the alternator operating the ignition advance device.


i would suggest you check/replace plugs, check the state of your HT with a spark gap tester (checking for a spark on the end of a plug isn't enough). then double check the cdi pickup connector on the alternator (make sure the spade connectors aren't corroded or pushed back inside the connector housing and that the pickup is mounted securely)


(remember, you would of disconnected the HT when taking the rocker cover off. it's possible you bent an HT lead and the insulation cracked or the connection came loose at the coil or plug cap ends. the HT lead just screws into the connector!)


if all that is ok, should check/replace the cdi pickup. haynes doesn't even list a test method. just says change if thought to be faulty. if you have access to a timing strobe, you can check it quite easily i'd of thought.


hope that helps... :)

Link to comment
Share on other sites

Thanks Ross, some good advice there. Will keep me busy this afternoon! :cheers:

 

Hi Ant,


up to 5k revs is everything okay? i.e. normal power etc?

 

Yes mate, the same as before. Still starts great and idles fine, the power under 5k is the same. No power loss or anything. :cheers:

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

  • Welcome to The Motorbike Forum.

    Sign in or register an account to join in.

×
×
  • Create New...

Important Information

Terms of Use Privacy Policy Guidelines We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.

Please Sign In or Sign Up