What radiator cap do you use??

I know about the Summers choices, isn't there a Kawasaki cap that can be used?

Could someone explain how a high temp themostat makes the BRP less likely to boil over??

I run a 1.8 Rad Cap from Baja Designs. Got it for $25 semolians. You can try to get a KX 80 Rad Cap, I believe they are 1.6 which supposedly works fine. When I checked the dealers in my area for the Kawie cap they were more expensive. Baja had the best deal for me in my area. The stock cap is a 1.1. The 1.6 & 1.8 caps are rated to handle higher pressure before barfing fluid. It puts more pressure on the hoses, but so far so good. Every Pig Bud I ride with runs the 1.8.

I did have some boil over issues, but didn't want to jack up my coolant system pressure, my logic is that there is less chance of a radiator poping a hole if it takes a hit from falling down, a whack from a branch....I did change over to that "Engine Ice", and it seems to have less boil-over now.

Kawasaki KX80 (1.6) cap fits nicely. Higher cap rating is needed when running (racing) without the overflow bottle attached. Changes the pressure/temp (not equal) at which coolent will spew. Hopefully that mud bogged radiator, or slow going up that crowded enduro hillclimb-that would have pushed the stock cap to bubble, isnt enough to get the 1.6 to pop its top. Not sure what the threshold temps are. Anyone?

OK I let my buddy ride my prized machine (XR650R) so I could show him how to ride his DR350E in deep sand with bald tires - bad idea. After a 45 min. hard ride he let my bike idle for about 2-3 minutes watching me turn around after a failed hill climb attempt. Then it happened - the ill fated boil over. I was not HAPPY. Bottom line it can happen when you least expect it and no he will not be on my bike any time soon. I will probably go with the 1.6 cap, water wetter and or EG based coolant per PHYSDON. Question if a 1.6 ATM cap = 23.52 PSI what does the stock cap =? Any luck getting a cap at the local Auto Parts?

My XR650R never boils over, even when other bikes in our riding group used to and I still use the stock rad cap. It will idle for 30+ minutes in warm weather and not boil over :)

I have never experienced a boil over on my bike. It has the stock cap. I don't idle the bike very long in one place and I try to keep it moving.

I have a couple of rides with the Summers cap and thermostat now. My bike has Devol guards and they look like they may restrict air some but they have paid for themselves many times over up here in nothern woods.

So the first thing I tried after installing the high pressure cap was to duplicate the conditions where "Betty" has puked up her coolant in the past - the cap is the fix, big difference.

The new thermostat works well also in that the bike warms up faster and doesn't "flame out" at stop lights as we are heading out of town on our way to the woods.

Question if a 1.6 ATM cap = 23.52 PSI what does the stock cap =?

The "1.6" refers to 1.6 times normal atmoshere pressure, which is 14.7 psi. The stock cap is 1.1 times 14.7 = 16.7 psi.

This is why I don't run a high pressure cap, because I don't want to put that much more pressure on the cooling system, we are talking almost 50% more pressure.

If I knew where to get a slightly higher then stock cap, say a 1.2-1.4, then maybe I'd give it a shot.

Loufish my fellow xr-er you must be an engineer or PhD. I will now impress my buds with my new found knowledge on what in the world pressure 1.1 equals. I asked the guys on the cr450 page about running a higher number cap and they all reply against it. small sample but all neg. Now for the good news. I have tried to get my bike to boil again after a long hard run in the deep sand and no spillage. I even let it idle for 2-3 minutes (after the run) while turning my air screw out to 1 1/2. it now runs like --- darn good with the 72 pilot.

I don't know where all the "boil-over" stories are coming from. My bike has the usual power-up kit installed, and after 2 1/2 years of riding it now, it has never boiled over, or even gotten hot enough to not be able to touch the cylinder. Unless the bike is stock, how does it get so hot?

Of course, I never let it sit and idle for more than a minute or so, except for the usual 2 minute warm-up when cold. The bike doesn't have a fan, don't let it sit and idle, ride it. Even riding it up 1st and 2nd gear steep mountain trails with the 160 jet, never had it boil over.


I don't know where all the "boil-over" stories are coming from.

My bike boils when it was at a 1.1 cap. But I also ride Glamis. With the 1.8 it's only boiled once due to an ill-fated wheel spinning knobbie tire attempt at a huge dune.

Normal riding in any heat... it's not boiled over with the 1.8 Not everyone needs that cap. But my bike would boil at a street light (in sunny San Diego, CA) with the 1.1 SOOooo, tell me what I'm doing wrong?!! From what I know, nothing. Boil overs happen due to all the elements.

I won't ride the XR any longer in the dunes... but that's only cuz I was able to buy a CRF. It just plain abused the XR due to it's weight...etc and my riding style.

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