Help with rad. cap and overflow bottle...

I have found that I do not do enough long rides to use any of the coolant from the overflow bottle or at least I think I don't :-)

That being said, if I remove the overflow bottle, all the hose up to the radiator cap, do I need to change out the cap? If so, will the YZ cap work?

Or could I get away with leaving some of the hose off the cap and running it down the frame and dumping it by the skid plate?

Getting tired of seeing all the dripping onto my swingarm from the bottle too...

Thanks for your help with this.


I'm not sure what you mean by "use" on a long ride. If your coolant system is working properly, the level in the bottle should increase as the bike warms, and return to the lower fill line when it cools. If you are having problems overheating, try adding some water wetter, and make sure your reservoir is not too full to begin with.

As for changing the cap, the KX 500 cap fits the WR and is rated to a higher PSI.


The YZ cap is has the same pressure rating as the WR (1.1 I believe). You can get higher pressure caps at an auto parts store also. Stant is a common brand:

1.1 = 15.6 PSI

1.4 = 19.9 PSI

1.6 = 21.8 PSI

P.S. I haven't had any trouble running my 99' WR4 with the stock cap and bottle removed.

P.P.S - I ordered one of the 19 PSI (1.4) caps from Baker Precision, but it never came. They were less than stellar in the service department. I ended up getting it from a local autoparts store.

[This message has been edited by Heywood (edited 03-30-2001).]

I wouldnt recommend moving to a higher pressure if I could avoid it. The higher pressure would be good for higher elevations mainly as water boils at 212 Degrees F at Sea level and around 200 at 5500 ft.

Now, with that in mind.. This is an important thing to mention. Adding 1 lb to your radiator cap will boost your boiling point 3 degrees, and wont kill your Cooling system.. But.. Its important to consider that the simple raising of pressure in your System will both, weaken Hose connections of coolant.. and will INCREASE the likelyhood of radiator Damage with an Impact!

More pressure.. Soft aluminum..Mixed with Heat..Coolant..And now More Pressure.. Not worth the Change. Unless its at High Altitude where Air pressure is Lower.. THEN and only then should you consider a higher pressure cap. :D

This is from 7 Years of Automotive Knowledge working in a busy Parts Store to those that thought changing to a higher cap would improve cooling. It Does nothing of the Sort. It mearly Changes boiling points of the coolant.


Yep, I agree with that statement Jemtec. I would keep the cap the same pressure unless at really high altitudes. Leave it as it is.

I know of quite a few guys over here who have simply dumped the bottle and lines with the stock cap. Bear in mind though that it is handy if you boil it badly at the bottom of some great hill on a hot summers day!

i converted my overflow bottle into extra gas tank on my 98 wr.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now