I have read several threads on this topic and it seems there are alot of differing opinions. Today, I was riding some trails on my YZ400F and following a guy on a slow 4 wheeler. I dont know if we were not going fast enough to cool the radiators or if it is another problem. I would guess the first place to start is my radiator cap would you all agree? Arent the radiator caps on these bikes fairly universal? Couldnt I find a higher pressure cap? How would I know which one to buy? I read a thread about a guy that had my same bike and installed a radiator cap off of a KX500. Do I need to install an overflow bottle? I am running about 50/50 tap water and automotive antifreeze. The bike wont overheat on short rides, usually only when its ridden hard or really slow. Do the different types of coolant really help?

Thanks

Ebay has several high pressure radiator caps. Some are labeled 1.6 and
others list from 20 to 30 pound ratings. My manual doesnt list any information on the pressures. If I bought a high pressure cap that keeps the coolant in the engine, I have a hard time believing that the engine would get hot enough under normal conditions to cause damage, but I guess it is possible. Does anyone have any information on this?

You can pick up a cap for a KX500. Higher pressure. I did this to my old 400 and it worked like a champ.

Thanks Thump

Yamaha wanted $54 for the stock cap, I am wondering if Kawasaki is the same. I am thinking about buying one of those high pressure caps on Ebay. Do you all think that would work? I have a real moral issue with paying $54 for a radiator cap...ridiculous. Has anyone installed a temperature guage on these larger bikes? There is a place called jokersracing.com that sells a digital temp guage, mainly for racing atvs, but will fit most bikes. I am paranoid about my temperature issue now.

Also, avoid using tap water. It's quite corrosive to the internals of the cooling system. Be sure you use coolant formulated for aluminum engines too. Next trip the grocery store grab some distilled water, it's really cheap and won't corrode or form deposits in the cooling system.

I will use distilled water next time and the special antifreeze. Has anyone used those temperature strips? They have a reading from around 150 to 248 degrees and they are cheap. I suppose the disadvantage vs a guage mounted on the handlebar is that you would need to stop and read the strip.

Contact Service Honda/Kawi about the cap. They will have the best price around.

I am curious why more people dont use the temp guages. I have read several threads about engine overheating/damage on this site. The one I found for $85 is digital, small, and light. An $85 guage or $10 temp strip could prevent the damage.

I guess no one has comments about the temp guage/strips. I bought a high pressure cap and some temperature strips....I guess I will find out if that works the next time I ride.

Temp strips can only read the skin temperature of the cylinder, or radiator. There is a boundary layer between the skin and the moving fluid, so the skin temp doesn't provide much in the way of useful info.

While a temperature gauge is a nice idea in theory, it isn't very practical in this type of application. Shock, vibration, dirt, water, etc will kill it quick. Not to mention, it's next to impossible to read in realtime.

Keep the radiators clean, use the KX500 cap, fill the system with distilled water and a surfacant like Watter Wetter and you should be good to go for most MX situations that the bike was designed for.

Running slow in the woods isn't what this bike was built for and the radiators are small and light as a result. For this type of riding rigging a fan system like the Honda CRF450X uses may be necessary, or using some of the cooling system components from the WR400 might help.