Slow riding/when is hot too hot?

i went to evans NPG-R (400 deg boiling point @ 7 psi) and use two2cool oil treatment(clutch safe) i can't make it boil over if i tried (and i have) :naughty:

I switched to NPG-R as well and it seems to work as NCMountainman claims and I run Two2Cool also! :naughty:

Good point mountainman!!

myself and several others have realized less performance from engine ice than with 50/50. in the tight twisties 1st and 2nd gear mostly. i think engine ice works o.k. if you have a good continuous airflow(such as desert or MX) but get in a tight muddy harescramble and it evacuates faster than a floridian during hurricane season :naughty:

Agreed! :naughty: That NPG-R stuff is AWESOME! If team AmPro Yamaha and Ty Davis use it that's good enough for me. Haven't ordered the Two2cool yet but will be running it soon. You will not boil over AND it has superior heat transfer abilities compared to everything else I have tried.

Ok. I've spent nearly two days reading posts regarding overheating (boiling) issues. I thought I would ask my questions in this thread, instead of starting another.

Since tempatures climbed to the high 90's my bike just fails on the trails. Over the past week it has boiled three times. I know, some of you will tell me to put the piece of metal under the shade and wait for the cooler part of the day. But, yesterday I was riding with a buddy that has the same bike (98 WR400). I boiled and he didn't. Is something failing on my bike? I pulled out the Clymer manual and read the section on the cooling system twice. Should I pull the pump apart? Replace it? Stuff the radiater with ice (just kidding)?

I am going to try the Evans product and am very curious about the Boyesen high flow water pump. But, could something be wrong with my bike? :applause:

Most likely you are have old coolant and leaner jetting then your buddy. Time to replace the stuff and make sure your bike is jetted on the rich side of perfect for hot weather. :applause:

Thanks, Indy. I will give it a try.

I use 100% evans npg-r and have never boiled anything out. I replaced standard coolant in January 05 and still have 10mm over top of core. Im running hare races and temps are around 100 w/ 70% humidity. That stuff is awesome. Put it in and forget about it. :applause:

What is the down side of running Evans NPG-R ? (not meaning hotter boiling point)

i went to evans NPG-R (400 deg boiling point @ 7 psi) and use two2cool oil treatment(clutch safe) i can't make it boil over if i tried (and i have)

ncmountainman or indy..... I checked here on TT and they have the two2cool but not the NPG-R. Rocky mountain didn't show it either. Where are you ordering it from :applause:

you lost it,toll free 888-990-2665 or press the secure online order button

you lost it,toll free 888-990-2665 or press the secure online order button

Geeee thanks for the confirmation. I feel much better now that I have given up all hope :applause:

Hey Mountainman, I just ordered 22cool and NPG-R. I'm trusten ya man! :applause:

I am sick of boil over, or is my bike sick of slow rid'in?

Hey Mountainman, I just ordered 22cool and NPG-R. I'm trusten ya man! :applause:

I am sick of boil over, or is my bike sick of slow rid'in?

just be sure to get the evans flush and do it twice(theres plenty for that) fill it,run it awhile,drain it,repeat(be sure to tip the bike to the left,almost laying it down to get the air pockets out). it will run a little warmer while the flush is in there. you won't regret trying it :eek: and the 22c seems to work well with the evans also,must help the heat transfer?

I have K type thermocouples in the radiator inlet and outlet and I have seen my bike at 180F when doing low speeds as you mentioned and at this temp I could feel the heat like you, no worries, by the time you grab 4th in a drag race acceleration the bike cools down to 135F or so on a 75 degree day. Ted

Your post is a bit old but do you still run those thermocouples? What kind of gauge do you connect them to?

you obviously don't race! it's not just that the NPG-R doesn't boil t'ill 400' but it avoids nucleate boiling inside the cylinder and does a much better cooling job when things do get hot. i was continually boiling out products that are supposed to have a 250-260' boiling point. and my head is just fine (the bike's anyhow!) i'm pretty sure my bike sees 300' regularly. just because technology has held us to 220-250' does not mean that the motor cannot handle more heat than the coolant. i would say that it would take more than 400' to warp a head (as long as the coolant was still circulating) which only the evans could make possible. norman sees these these temps in his testing very often. and yes i've got the boyesen water pump,and the jetting is right,valves are adjusted. it's just that the 50/50 coolants just don't do it for me. better to run hotter and keep your coolant in the bike than to spit it out and have half what you started with? :worthy:

Now wait a minute...

Heterogeneous Nucleate Boiling (very small bubbles that form on the metal surface then immediately collapse) actually improves cooling. The tiny bubbles from nucleate boiling break up the laminar flow layer that forms against the engine metal and improves the heat transfer rate into the bulk of the coolant channel. Even Homogeneous Nucleate Boiling (very small bubbles that form in the coolant bulk) improve cooling by increasing convection in the coolant bulk. Thus, nucleate boiling = cooler engine temps.

But to clarify further, nucleate boiling is not Bulk Boiling. Bulk boiling is when large bubbles form in the coolant bulk that don't collapse. With nucleate boiling, the coolant bulk is a liquid that remains below the boiling point of the coolant.

It's when you transition from nucleate boiling (Departure from Nucleate Boiling or "DNB") to film boiling that you start to isolate the engine metal from the coolant (since it's between the metal and coolant, it's the heterogeneous type of DNB). That's a bad thing no matter what coolant you're using.

I'm not going to knock Evans' no-H2O products - at least not in this post. I will say that for me, I like that I can run a "50-50" product like Engine Ice and not feel like my engine is excessively hot and not have the bike puke coolant. (And don't use siloxane surfactants in your coolant on bikes...)


why R vs +?

R is life long + is annual replacement not that is a big deal

the specs do not seem that different?

just want to understand the thought why you made your choice ?

I also boil with engine ice but this is the land of 112 air temps


Evans NPG+ Waterless Coolant is the recommended coolant for all gasoline and diesel engines. NPG+ is a stand-alone lifetime coolant that does not freeze, or boil over. NPG+ controls detonation, cavitation, and is non-corrosive. Installing NPG+ requires the radiator, engine block and heater core to be drained completely and then filled 100% with NPG+. NPG+ meets or exceeds both the ASTM D 1384 corrosion test and the ASTM D 3306-94 specifications.

Boils 375°F @ 0 psi

Freezes -40°F

Viscosity 2.3cp @ 212°F

Surface Tension 44dyn/cm

$32.50 per Gallon

Evans NPG-R Coolant


NPG-R is specifically formulated to handle the extreme conditions of racing and high performance automotive, marine and motorcycle applications. The reduced viscosity of NPG-R makes it more compatible with small tube copper-brass radiators while providing the superior cooling of Evans Waterless Coolants. Although NPG-R is safe for all metals and contains no water, an annual coolant change is suggested for racing vehicles. For maximum corrosion protection, high performance street driven vehicles running NPG-R should change coolant every other year.

Boils 400°F @ 7psi

Freezes -10°F

Viscosity 2.0cp @ 212°F

Surface Tension 46dyn/cm

$32.50 per Gallon

Fwiw, I don't believe in the "lifelong" hype of coolants. In order to do that, they have to be loaded with corrosion inhibitors well in excess of what you need for the annual/bi-annual coolants. There's no free lunch, so "something" has to be displaced in the mix - coolant, water (none in NPG), surfactants, buffers. I'm going to guess coolant in this case.

The other issue is that we're limited to a few chemicals that can be used for corrosion inhibition. Thus, lifelong coolants can't be loaded with silicates or they'd fall out of solution and fill your rads with little "rocks" (you'd know it if you saw it), so NPG/+/R pretty much has to have an Organic Acid (OAT) or a hybrid OAT/low-silicate (HOAT) corrosion inhibitor. Even OATs and HOATs have limited lifespans (5 years or so), so I have no idea how Evans can claim that NPG+ is a "lifetime" coolant. I wouldn't do it.

Given the choice, NPG-R has a lower viscosity and should be easier on the water pump (which seems to be the weakest link in the WR cooling system).

I also have NPG-r and it seems to work fine in the Phoenix area but the only issue I have with the stuff is how do you know if the bike is hot if it doesnt boil over?

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