Hi guys, i have just recently bought a beloved CBR400RR-L (1991) which someone has attempted to transform into a streetfighter . When i got the bike it had what seems like a miss-fire, anyways i am now at a loss to its cause. The back starts first time/everytime and idles fine, as soon as i rev it splutters and coughs and if anything gets worse the more revs i give it. I have replaced the plugs and leads, to the ones stated in the haynes. I have checked for sparks and all 4 in working order. I have tested coils (primary and secondary) for resistance all ok. I have checked pulse generator and that tested ok. I have checked the TPS and i cant get a resistance between the outer 2 pins (as stated in manual a 4-5ohm resistance is expected). Thing is when i test the outer 2 pins back to the CDI there is continuity, so there no break in the cables. Could my CDI unti be causing the miss-fire, or should i be thinking its a timing concern. I have inspected the CDI visually and it looks fine...one thing to note there are no colour stickers and info on the CDI unit? Please guys if you have any suggestions fire them to me and hopefully i can get to the cause and start to rebuild the bike to its former glory. Failing that if anyone knows of a decent repair garage in the north east of england let me know. My local garage said that miss-fires are hard to find and even if the cause was not found they would be charging me the £48p/hr rate for as long as i ask them to investigate..hence the reason for my self diagnosis. I dont mind paying as long as i feel confident they could repair it.....
Rant over, cheers guys.

Ps if anyone submits info that leads to the rectification of the bike i will happily reward there paypal handsomely.

The most common cause of electrical problems on these Honda 400's are the Japanese 112MPH speed restriction, if damaged or tampered it sends the bike into a limp home mode where it cuts the spark to two cylinders @ 5,000 RPM, if the wire's been damaged, unplugged or not been bypassed properly this could be the cause of your problem, failing that are you sure its electrical? you could also have blocked jet's in the carbs or a faulty fuel pump
Simon

sorry for bringing up an old post

did you get this sorted?

Yeah mate, turned out to be a fault TPS switch.

Nice one mate. I'm waiting on a chain and sprocket set and I should be ready for a ride out if you're up for it.
You dont happen to have a chain splitter/angle grinder do you? Struggling to take old chain off!

Hadrian

yeah got both mate....to be honest though angle grinder maybe the easiest way but ts gonna be messy

Aw nice one. I would be eternally grateful if I could borrow it please :)

I finish work at 5 so if you wanted to come over mine to collect it you could?

That'd be great mate. Pm me your address please. Thanks a bunch
Hadrian