Hey guys just bought my NC35 RVF400, it runs a little hot for my liking, stopped at traffic lights it sits just and i mean JUST below the very hottest it can get, start cruising and it goes back down to half way. How can i bleed the cooling system if there is any air in it ? What would u guys recommend ?

RVFwheelie wrote:Hey guys just bought my NC35 RVF400, it runs a little hot for my liking, stopped at traffic lights it sits just and i mean JUST below the very hottest it can get, start cruising and it goes back down to half way. How can i bleed the cooling system if there is any air in it ? What would u guys recommend ?

Is the coolant in good condition?

Id flush the system if it looks dirty, you can actually get antifreeze testers.

The lower rad tends to get crudded up, if you soak it overnight in degreaser it will usually clean up nicely, if its blocked it will slow your cooling down.

to bleed the system, start the bike without the rad cap on (remove cap when cold) and let it warm up to about half way, rev the bike to 5000 rpm 3 or 4 times by snapping the throttle and any airbubbles should make their way out, gentle squeeze of the hoses might help.

turn off, let cool and fill up to top, replace cap.

Is the fan coming on,Are the radiator fins clear,

I was going to say the same about the fan, it should come on before the needle goes into the red.
Also when squeezing the radiator pipes DON'T squeeze the exhaust by mistake...........

Thanks guys! ill check out the fins tonight.. the fan comes on but only when its closer to the red, not at halfway like most bikes. Tip take @dobbslc ill make sure i dont grab the exhaust haha!

RVFwheelie wrote:Thanks guys! ill check out the fins tonight.. the fan comes on but only when its closer to the red, not at halfway like most bikes. Tip take @dobbslc ill make sure i dont grab the exhaust haha!

it only comes on near the top, its just the way the gauge is made up.

The bikes run hot in traffic, as long as its not spewing water everywhere it should be fine.

You can wire up a switch to turn the fan on/off whenever you want, basically on the left hand side of the bike, wire up a toggle switch it makes/breaks the fan-motor-to-frame-earth connection.

There's some instructions here: viewtopic.php?f=24&t=1053&p=6675&hilit= ... +mod#p6675

One thing to be careful of if/when testing this out initially by putting wires to the frame by hand, the voltage is high enough that there can be little sparks for a fraction of a second when you ground the connection and the motor starts up. So don't have open containers of petrol lying around...

I dont see the point of the switch though, the fan switch turns the fan on when it gets too hot.

turning it on earlier might keep the temperature a bit lower but since Honda designed the fan switch to come on at specific temperature there is no trobule to the engine, only a psycohological thing for the rider.

if everythings ok the fan will stop it overheating.

turning it on earlier might keep the temperature a bit lower but since Honda designed the fan switch to come on at specific temperature

In principle I agree with what you're saying, but I don't think the Honda-designed temperature is low enough. Mine overheated twice last summer, once when I'd been caning it down the motorway and come off into heavy traffic, once when I'd been booming down an A-road and suddenly there was a 5-mile queue due to road repairs with guys holding up stop-n-go lollipop signs. That second one was at night and it still overheated, I had to sit there by the side of the road waiting for it to cool while all the cagers I'd just filtered past crawled by me in the queue having a look. Both times the bike cut out cos it got so hot, I was quite worried. So keeping the temp that bit lower with the fan in advance of situations like that seemed sensible to me so I put the switch in.

At the moment I'm rebuilding the entire cooling system with new aftermarket radiators so hopefully won't need the switch, cos as you say it should come on automatically. But then again, having it there gives a safety net if the temperature sensor or radiator switch packs up, so I'll probably just leave it as it is.

yea the switch is a good idea might have a look into that! tried to undo the radiator cap the other day and literally could not get it off, gonna take all the fairings off tomorrow and see if i can get it undone again. Also going to look at some new top and bottom radiators and hoses as ht ones on there at the moment are looking a bit worst for wear!
http://www.ebay.com.au/itm/L-R-Aluminum ... 0c6&_uhb=1
something like them!