Hello, I'm new to this forum aswell as the motorcycle scene.
I recently bought a 2000 Honda CB400 SF Version S, the only aftermarket thing on it is a Yoshimura exhaust and the previous owner removed the stock speedometer to install a Chinese sheitty one. The bike will idle perfectly and rev smoothly up until 4-5k. After that the bike will not rev higher it sputters and acts as if its on a rev limiter allowing me to hit only 85-90kmh on 6th gear.
The carbs have been cleaned and taken care of by a mechanic 2-3 days ago but it still has this issue.

Doing some research I found out that it may be the CDI Box, aftermarket speedo. I'm asking here if anyone ever had an issue like this so I can save a few bucks.
Thanks in advance!

(For anyone asking my mechanic is having surgery and im not able to take it back there for 2-3 weeks so im trying to see if its something i can fix on my own)

dead forum?

I wouldn't go that far, but there are very few NC39 owners on here in the first place (I'm interested in them, but I don't own one).

The obvious suspect would be the cheap Chinese clocks. Unfortunately, due to the rarity of the bike in the UK, it will be difficult to find a spare set of clocks to replace them, but you may find some in Australia or Japan. It does sound like some kind of compatibility issue between the OEM PGM-FI unit and the aftermarket clocks.

Ciao,

JZH

Have a look at the following discussion:
http://www.hondacb1.org/forum/index.php?topic=4817.0

Thank you both so much! It was the cheapy Chinese gauge. i connected the blue-orange wire with a 12+V wire and the bike is running great now.
Thank you!!!