I have the 50cc NSR and one of the shortcomings is the cooling system; it has no thermostat and no fans. Water flows 24/7 and temps fluctuate wildly depending on ambient temperature and movement. It's starting to get hot around here and during the day I see temps passing 80 degrees in stop and go.
I noticed yesterday a serious loss in power past that magic number. I have ignored indicators like that before and holed a piston so I am a lot less cavalier about these things. Looks like I need to beef up the cooling system.
I was interested in what temps you guys like to see in the 250s so I know what to shoot for. My bike is a pig until it gets to about 50-5 degrees and seems to run really nice between 60-75 degrees.

Then those are the temps to aim for! 80 seems to be about tops for two strokes, though obviously the gauges aren't the most accurate in the world and each bike is different.

Do you mean it was designed to run without a fan and a thermostat or that's how it's ended up?
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That's how they come. The street model NSR50 also has a smaller radiator than the NSRmini racing model, no thermostat and no fans. The temps flutuate between 70-80.
The bike doesn't come with a temp guage just an idiot light so I got a temp meter straight away. The NSR250 radiator looks like it would fit but has twice the frontal area of the NSR50 unit. Without a thermostat that could be a problem. I also don't want to buy the HRC NSR50 radiator as it does not fit my long term plans. I guess I will try flushing the system and running water wetter instead of antifreeze and clean the radiator fins.

My 28 is usually 62-68, gets to 80 at the lights. You could try a 90mm PC fan.

Whats the differents between a NSR50 and a NSRmini.

the NSRmini is a pure track bike. No lights, bigger radiator, real adjustable suspension.

The NSR50 is a street legal bike. It has a generator and battery, lights, horn etc. The radiator is thinner though and the suspension is "suspension" only in the terms that it holds the bike up.
There is not even preload adjustment on the rear. Not even that cheesy notched ramp crap budget bikes call "adjustment"; the bottom spring seat is welded in place. The upper on the forks is not a true triple clamp, the handlebars bolt down through it into the top of the fork tube. The third gen actually has a true triple clamp and clip ons, mine is the second gen.
The nose dives at the slightest hint of front brake and then bounces back uncontrollably thereby allowing the rear shock or as I call it the "spring on a stick" to show just how bad it is. Low speed stops have a predictable see-saw action that can unnerve a person, high speed is lean far back and ease into the lever. I have gotten pretty good at riding with the deficiency but recently question why I have not fixed it. I am having the forks overhauled with thicker oil and shims on the springs to try to improve the nose behavior at least. I have large plans for the future and I don't want to spend a lot on a short term fix.
The engine is the same as the mini and pretty much bulletproof with good power for it's size and typical honda reliability. I beat it mercilessly and have only eaten one piston and that was completely my fault.
The brakes are also the same as the mini, two piston up front grabbing a 220mm crossdrilled disk and a one piston in the back. Neither are floating types but the system is very effective at scrubbing off speed and honestly just needs steel braided lines to be perfect.

If you can get an NSR rad cheap, then fit it and tape up the spare capacity if it runs too cold. That's what racers do anyway - remove the stat and use tape to control the temp. That way if you're overheating you whip off the tape and get back on track!
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Water cooled go karts use the same system. Tape up the radiator and rip em off when required
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