I bought a well-used 2006 Rev-3 270 that had fried main bearings and in general a worn-out motor. I just did a total engine rebuild (top end, crank, bearings, seals etc). Bike starts and runs great! Stock Mikuni VM26 carb with #140 main, 27.5 pilot, needle clip 3rd position (middle), air screw 1.0 turns. Unleaded premium fuel with Maxima 927 at 60:1 and stock heat range spark plug (NGK BP7ES) stock ign timing. Motorex pre-mixed coolant. Waterpump housing, seal and impeller in good condition.

I ride at sea-level mostly and have run about six tanks of gas thru the bike riding around the property, the majority of the time crawling around in 1st and 2nd gears, ambient air temps 70F to 85F. Whenever I first start the bike from cold the fan doesn't run until I've been riding for 10 minutes or so. After that the fan runs constantly while riding. I'll shut the bike off for five or ten minutes and upon re-starting the fan is running. I haven't yet been able to intersperse slow speed riding with any faster riding (3rd thru 6th gears) to see if more air moving thru the radiator will cause the fan to shut off?

My question is; how often/long should the radiator cooling fan run? Is this normal for this bike or do "they all do that" ?

Any info appreciated!

Thanks, Dorian

The fan usually runs like that. Have you checked the water level since the rebuild. And a 140 is just a little lean at sea level. I would suggest a 145. 150 was stock.

My rev 3 was exactly the same, the fan motor gives a much lower output than say that of a gas gas, when running on tick over or low revs, the fan speed on these bikes increases greatly as the revs are increased, so if you rode a trial, the blast between sections would normally be enough to cool the bike, still not convinced?

I wasn't either, but had all the volt outputs measured, they were all fine, had the bike 2 years it was fine.

Still got mine since 2006 and once warm the fan is hardley ever off. been like it since new and never had any problems.

add some water wetter to your coolent..

Thanks heaps for the feedback all - very helpful!

Coolant level fine since rebuild. I'll bump the main jet up to a #145. Will check into Water Wetter also.

I'll see how it goes once I get a chance to ride it in a meet or higher gears/speeds.

Thanks again! Dorian

http://www.redlineoil.com/Products.aspx?pcid=10

just keep in mind...its not an ant freeze...its a super coolent...i used GM Dex cool mixed with this stuff...works well in alloy engines,

just keep in mind...its not an ant freeze...its a super coolent...i used GM Dex cool mixed with this stuff...works well in alloy engines,

Thanks for the link. Wow, based on their info a little goes a long way! My 600cc capacity cooling system will only need ~1 oz.

I'll pick some up this week.

- Dorian

Ya there are several companies making this stuff

Funny thing is.....it's just a surfactant, kinda like your dish washing detergent, as far as the science goes its really cheep and simple stuff but it actually works

Mostly it works at the point when the fluid boils and small bubbles form on the hot parts of the engine, when the bubbles form the coolant is no longer in contact with the aluminum, its insulation

The surfactant breaks down the surface tension so the bubbles are much less likely to form