Coolant and 1.8 bar cap?

[wence]

Hey guys,
Just put on a new 1.8 bar radiator cap to replace the old bent cap I had.
Since putting the cap on it has boiled over twice after a warm up ride. I have refilled to top of the radiator and assume that the boiling over is only due to this as it did not do it before.Does this sound correct?
The boiling over does not continue and there is water still over the fins of the radiator.
Next question:
I have very watered down coolant in the bike. Is the coolant type and mixing a problem with bikes as it can be for cars?
I don't know what the previous owner used , hence why the water top ups.
What is the best type to use in this situation?
Do I need to flush the whole system thoroughly?
I very rarely ride in places that are below 5degrees celsius.
Thanks in advance ,
Mark

[GMP]

Mark,

Yes, you are likely boiling off the overfill of the system. About 10mm over the core is correct.

The less antifreeze in the mix, the better heat transfer BUT lower boil point. 60/40 water/coolant is a good mix, or just use a premixed coolant like engine ice. Don't use automotive coolants(Toyota coolant is OK) as they usually contain abrasives for cleaning the cooling systems during long term use. Just drain, flush with water, and refill.

For 4-strokes with boil over problems in tight woods we have run the EVANS waterless coolant with great results in several bikes. Its the only stuff I'd put in a new 4-stroke.

[Nick]

Just covering the core inside is sufficient, the rest will boil off.

[jostby]

Use a "extended life" coolant. They have the additives to keep the aluminum/steel contact areas from corroding.

[GMP]

My bike was run for a season, sat the next out, and run half of last season on the the same engine ice. When I pulled the top end apart this winter the cooling system surfaces were spotless. I've never seen any corrosion in a GG motor using good coolant.

[wence]

Thanks guys,
I'll go and purchase this week and change on the weekend while changing oil.
Cheers Mark

[wence]

Just wondering where I would get engine ice in Australia?
Who actually makes it?
I can readily get two types of motul coolant.Are these any good?
Cheers Mark

[GMP]

Any MC coolant is fine.

[wence]

Thanks to all,
Ended up finding and buying Engine ice.
Cheers Mark