engine running problems CB400

[skoerbin]

Hey,

Ive got a 95 CB400, having a coupl of running issues. It is fine and smooth at idle and through the early stages of the rev range then at about 2/3 throttle has some surging and running rough and then it seems to sort it self out when it gets past that. (I'm unsure of exact RPM as I have a non standard dash on at the moment and the techo doesnt work)

Ive done a few things with my limited mechanical knowledge to narrow the problem down. Ive checked the plugs and cleaned (small amount of white, indicating running slightly lean), checked the spark and seemed to be fine, then moved to the carbs. As im not the most mechanical person i decided that if i pulled the out and appart i wouldnt be able to get them back together so used some subaru upper engine cleaner though the air intake to try and clean them out. Unsure if i did this correctly as not as much smoke came out as i had expected. and I cleaned the air filter.

These things seem to have fixed the issue a little bit however it is still noticeable. I did go for a ride around the block with the air filter out and the side cover off slightly and seemed to run a little better than before i started.

So in sort, any ideas what the problem could be? eletrical from the dash? carb related? air intake? or air fuel ratios? and whats my best steps to resolve it?

Thanks in advance

Scott

[BANDITROD]

sounds like a carb prob to me mate maybe take out carbs and give a good clean the only way to learn is to dive in head first mate

[Redmohawk]

Indeed sounds like a carb issue to me to mate, Watch trying to read plugs for lean rich etc with unleaded its very difficult to read plugs without lead in fuel ,as that was what gave you the white in the tail pipe and on your plugs etc. Black carbon buildup is still a sign of rich but usally will run ruff before it shows on the plug much. Better to use a Oxy sensor or take it somewhere than burn a hole in a piston.

You can pull a oxy sensor from a late model car in the wreackers and mount it in a tube to shove up the exhaust for testing, and use a cheap lean rich meter from autopro/supercheap/ebay instructions on the box are simple enough to wire it up. there are only 3 wires to worry about 5 if you connect the heater element.

[livewire]

New set of plugs is always a good start

[el sammo]

hold it flat then at peak rpm put youre hand completley over the carb mouths 1 at a a time,if nothing else its terribly amusing and if its just water or something easily unblocked the vaccum will suck it out of the carbs into youre engine solving the problem

or if youre not a lazy bodgy cunt..and its not a customers bike lol
then youre gonna have to pull the carbs off and clean them out properly

if it blows up then its youre fault for taking advice from the internet

[skoerbin]

haha cheers, i had the day off yesterday and pulled the carbs appart, they looked clean enough to eat off but i gave them a good clean anyway. didnt seem to do much, then i decided to google it and found something saying that bikes from japan have a speed limiter fitted factory and that if you break the wire it thinks you are hitting 180 when the revs hit 5500, gave a quick solution using a resistor and some wire. i think ill give it a go and see what happens, if not its back to the drawing board again.

thats the website http://www.rrzone.com/forums/showthread.php?t=6075 (dont know if its appropriate to post a link to other threads but its quicker than copying it then pasting it)