My NC30 keeps spitting out all the coolent when running around 8000rpm and up. It all comes out of the overflow, then overheats. Below this it is fine. Has a new radiator cap, but someone told me these bikes need a longer (deeper) spring in the cap then other bikes, is this true?

If I stop and refill the system it works fine for another 30 minutes, then spits it out again. Anyone had this issue?

Bit bizarre, I'd have said rad cap which you've already changed. Maybe thermostat.

mick.mh2racing wrote:Bit bizarre, I'd have said rad cap which you've already changed. Maybe thermostat.

Is the NC30 radiator cap a standard size as used in most other bikes?

Yep standard size - I'm running a Yamaha item with no probs. What pressure rating is marked on your rad cap?

had exact same problem. fitted a new genuine Honda NC30 rad cap and said problem went away immediately.

Cheers, i figure it is the cap. Will try to get my hands on a honda genuine article and see if this fixes it. Will up date when/if I have success.

Standard Nc caps are 1.1 bar rated. On the race NC30 we raced last year we ended up using TZ or KTM radiator caps as they were rated to 1.2 bar preasure. Also check that the radiator cap seat is clean.

fingers crossed

.....so I managed to get hold of an original NC30 radiator cap, 1.1 bar. The tep was stable up until I started running at higher speeds and reving in 3rd, 4th and 5th to 11 and 12 rpm. Then It started spitting coolant and overheating. Actually the air kept the temp stable, but as soon as I stopped, it overheated and coolant was coming out of the overflow tank. Do you think a higher pressure cap will fix it? Could it be the water pump or thermastat?

How have others solved this issue?

jacknell wrote:Standard Nc caps are 1.1 bar rated. On the race NC30 we raced last year we ended up using TZ or KTM radiator caps as they were rated to 1.2 bar preasure. Also check that the radiator cap seat is clean.

fingers crossed

Did this solve the problem for you on the track?

GCD wrote:

jacknell wrote:Standard Nc caps are 1.1 bar rated. On the race NC30 we raced last year we ended up using TZ or KTM radiator caps as they were rated to 1.2 bar preasure. Also check that the radiator cap seat is clean.

fingers crossed

Did this solve the problem for you on the track?

Yes it solved are problem. with them being race bike the caps were on and of all the time to check coolant levels and i think the alloy filler neck was getting a bit worn. So tidying the radiator filler neck and fitting a tz250 cap worked for us.

Lets hope its not a head gasket. Check the colour of your plugs and the condition of the oil for signs of moisture in the oil.

kev.