i've had my cbr400 nc23 for a while now and it's being a bit of a slow on-going project. Anyway it's running and i've balanced the carbs.
Only when i was balancing the carbs it did get a little hot!

Thought nothing more of it and let it cool down. I then decided to do the clearences. Drained the coolant off, dropped the rad and did the clearences.
Got it all up and running yesterday. Poured some coolant in, brimmed the rad and started the bike to bleed the system. Here's the problem, when i rev the bike the coolant rises and overflows! I presumed this was because the waterpump was spinning faster due to the engine spinning up.
So i put the cap on, and decided to bleed it another way. I put a little coolant in the expansion bottle revved the bike up so as any coolant sent through would bring air with it and then the coolant in the expansion bottle would travel back up to the rad to compensate for the space the air took up.

I then went out for a ride on it. At first it was really spluttery and wouldn't go past 5k, then 7k, then 8k etc etc. Anyway it all cleared out and went up the rev range fine and i put it back in the garage.


Now i've just read on another forum that rising and overlfowing coolant on the header tank when revving the bike means that the headgasket is gone.... true??

The thing that is scaring me though is that with these being gear driven cams surly you can't have the head skimmed? and what if it's warped from when i got hot?
So it could be a new head jobbie....???



Thanks guys.

Hi,
Unless you have oil in the water or vice versa I wouldn't worry too much, just keep an eye on the temperature. You can skim the head a little as long as you introduce a little backlash into the cam gear train. If it comes to that I'll explain what to do, but fingers crossed you'll be ok.
Cheers,
Mike

blueflag wrote:Hi,
Unless you have oil in the water or vice versa I wouldn't worry too much, just keep an eye on the temperature. You can skim the head a little as long as you introduce a little backlash into the cam gear train. If it comes to that I'll explain what to do, but fingers crossed you'll be ok.
Cheers,
Mike

I've had the clutch end casing off to replace the oil pump chain and sprockets and the oil in the sump is perfect, no orangey gunk anywhere on the engine.

Fingers crossed all is good then :D

Like i say i rode it yesterday and although it was spluttery at first (i put that down to it not being used in 7months, will be condensation in the intake, the chambers etc etc) but after a few quick blasts up the street it cleared out and revved all the way up the range (well to tell the truth i could only get it to 10k before i ran out of space, but im sure it will go all the way) and it was smooth.... in fact a hell of alot smoother than i expected from a restricted 400 :D

if when you first fill the rad up start the bike an rev it the water starts to over flow check the thermost , it maybe stuck in the open position are not be there all ,someone may have pulled it. At hight RPMs the bike will run hot with no thermostat