This is a discussion on 660 thermostat and fan within the Grizzly Engine & Transmission forums, part of the Grizzly Forums category; I recently bored my 660 out .080. I would like to know what the stock opening temp is for the t-stat and what part number ...
The OEM thermostat for the 660 (Part # 5KM-12411-01-00 ) starts opening at 129 degF and is fully open at 158 degF which are industry standards. As for local parts stores, I don't think ones around here can help you. Trying to find one that fits at a lower range may be a problem.
2002 Camo Grizzly 660
25" DD2 on Douglas Rhythm Wheels
Ricochet Skid Plates & Rock Sliders
Superwinch ATV2300 w/Amsteel Blue
Mad Mike Clutch Mods 2 & 3 w/orange 2ndary spring
Plano Rear Box
Rotopax Fuel Pack
Tomahawk Front Bumber w/Rigid D2's
2009 Rhino 700 Black Special Edition
27in Sedona Rip Saw on ITP Black SS108 Wheels
Viper Max 4000 w/Amsteel Blue
Yoshimura RS-8 Muffler, K&N Filter, EZ Steer Power Steering
J Strong Roof w/lights & stereo
J Strong Full Windshield
J Strong Front & Rear Bumpers
J Strong Dual Battery Isolator
US Govt survey shows three out of four people make up 75% of the total population.
The Following 2 Users Say Thank You to UpstateNYGrizz For This Useful Post:
USNY is correct. You need either Red-Line Water Wetter or Engine Ice to cool her down some. More and more brands are coming out and Evans and Be-Cool are choices as well. I have Engine Ice and it performed as stated, I'm happy w/it.
07 660, Black ITP SS108's, 28' ZILLAS, Dynatek ignition, full HMF Utility, UNI filter, Dynojet kit, Grunt clutch kit, EHS Racing air box lid mod.....
The Following User Says Thank You to El Dee For This Useful Post:
There is a little trick you can try. I used to do this on cars or trucks to help keep the temp down. Take the thermostate and drill a tiny hole on both sides of it. This way it will let the water threw without opening up fully,this will help keep it running cooler since you have a constant flow of coolant. Now, I can't tell you how big to drill them its just a trial an error thing. If you really want it to stay cool take the thermostate out. I wouldn't do that because it would probably run to cold and thats not good. I think the special coolant they have will work but probably not enough for your needs. Let me know if you try curious to see if works. I know it does for cars or trucks.
The Following User Says Thank You to RB323 For This Useful Post:
Yeah, I've drilled holes in thermostats before too. I have used the Be-Cool additive in my 73 Nova before also. Good stuff. I was hoping for a lower opening but 129 does not sound too bad. I'll have to order one I guess. Yamaha parts nation has one for $16.25 (not too bad).
What is the normal water temp on these things? I would imagine they would not need to get much hotter than 215-220 at the highest with new 50/50 coolant.
GrizzlyCentral.com is not associated with Yamaha in any way. We are an enthusiast site dedicated to the Yamaha Grizzly ATV. Our goal is to offer a place for Grizzly owners to discuss rides, events, mods, maintenance, purchasing, etc and offer help and assistance.Contact Us -
Yamaha Grizzly ATV Forum -
Privacy Statement -