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redmanrandyed

To thermostat or not to thermostat?

13 posts in this topic

Alright, I am confused :thumbsup:

Is it best to run a thermostat or is it best to not run a thermostat? (XR650R) I was under the impression that the bike would run cooler if I yanked the thermostat. I noticed on the WR400's that there is no thermostat, so I took my thermostat out.

Now I read that the thermostat keeps coolant in the heat exchanger for longer periods of time to allow better cooling of the coolant.

Thermostat keeps the bike running cooler or hotter?

I noticed on SRC that he has a high temp thermostat to keep the bike cooler. For some reason, high temp thermostat sounds like the bike would be hotter?

What is best as far as keeping the engine cooler, thermostat or no thermnostat?

Thanks

Redmanrandyed

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I yanked my thermostat on my first XR650R and it never overheated once the power up kit was installed. Baja Designs suggested removing it unless you live in very cold climates. I followed that advice and only use a thermostate during the winter months. The reason I use a thermostat in the winter months is to get the bike to heat up. They run bad when they stay too cold. Removing the thermostat causes it to run cooler.

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Well--

For sure one thing we can all agree with is that the stop thermostat is very very very prone to sticking open--so there is a lot of reason to consider replacing the stocker if you live in cold climates. That said:

There seem to be two schools of thought...

Most seem to think removing the thermostat allows increased flow of coolent (less restriction)-and that should mean cooler running engine.

BUT--in recent conversations with the very very very knowlegable and helpful guys at SRCinc.net -- the Scott Summers team feels that coolent is circulating TO FAST --and that removing the thermostat only compounds that problem. They feel the coolent isnt staying in the heat exchangers long enough to sufficiently cool...and so removing the thermostat means a hotter running engine.

SO take your pick!!!!!!!!!!!!!!!!!

I have no data on this--but i am going to put in a good working reliable 180 degree thermostat. I took out the old stuck unit a year ago. BUT i run in the dez with a colder plug, have oversize radiators, and run stock pressure cap...

so many variables, so little time...

Thermostats in or out?

I dunno!

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a good working reliable 180 degree thermostat

Mike,

Autozone sells a "good working reliable 180 degree thermostat" for $4.99 that fits well in our bikes without any modification unlike the NAPA t-stat that some folks have tried. The Autozone t-stat is made my Motorad (www.motorad.com). Just ask for part number '457-180' at your local Autozone. I don't use it, but I've bought and installed it in another persons bike with good results and it's not prone to sticking open like the stocker.

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a good working reliable 180 degree thermostat

Mike,

Autozone sells a "good working reliable 180 degree thermostat" for $4.99 that fits well in our bikes without any modification unlike the NAPA t-stat that some folks have tried. The Autozone t-stat is made my Motorad (www.motorad.com). Just ask for part number '457-180' at your local Autozone. I don't use it, but I've bought and installed it in another persons bike with good results and it's not prone to sticking open like the stocker.

A huge plus about the stock thermostat is it does always stick open. I sure would hate to be on a ride with a thermostat that stuck closed. I think Honda did that delibertely. :thumbsup:

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I can't remember who to give credit to, but I remember reading on this forum "If Honda put a thermostat on the bike, there is probably a reason." Probably just worth it to get the SRC or Autozone method (thats what I did). :thumbsup:

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You can tell that the bike puts the ponies (or is that piggies) to the ground sooner with the stat in.

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Update

I picked up an oil temp dipstick from XR's only. Went for a ride up the canyon. Cruising up the dirt road the temp was around 170 degrees. 1st gear slow trail riding the temp was a constant 200 degrees. It did not go above 200.

XR's Only suggest the normal temp range is between 250 and 300 degrees.

I am going to leave the thermostat out for now, bike is running great without it.

I did not get a chance to ride for more than an hour although, picked up a nail in the rear tire :thumbsup:

Thanks

Redmanrandyed

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Update

I picked up an oil temp dipstick from XR's only. Went for a ride up the canyon. Cruising up the dirt road the temp was around 170 degrees. 1st gear slow trail riding the temp was a constant 200 degrees. It did not go above 200.

XR's Only suggest the normal temp range is between 250 and 300 degrees.

I am going to leave the thermostat out for now, bike is running great without it.

I did not get a chance to ride for more than an hour although, picked up a nail in the rear tire :thumbsup:

Thanks

Redmanrandyed

There is a difference between oil temp and cooland temp. My 650R oil temp is usually between 150-200 degrees. Air cooled XR's oil temp will get in the 250 degree range (and above).

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250-300? Seems a bit on the high side...i guess thats the numbers they get up there in the dez with Childress hitting the rev limiter...Overall i'm still going with more like 180-300...800-900 at the exhaust exit? Just a guess... i dont have a clue. It would be kinda cool to have little bits of temp sensitive tape all over the bike and come in after a ride and note all that stuff for different set ups. hmmm another thing for the to do list...maybe if i ever paint the garage floor...

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800-900 at the exhaust exit?

The exhaust gas is close to ~800F at idle and closer to ~1200F while riding based on my quick checks a ways back with an EGT sensor.

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My BRP still has the stock thermostat, but I always recomend to others that are thinking about removing one this: the "stat" has a flow rate to insure good heat transfer, and removing it usually results in the coolant flowing too fast to maintain the best heat transfer rate, so for those who are concerned that the stat might stick closed, or partially closed, take the stat, and remove all the guts, leaving a washer shaped resrictor. I also drill a small hole(.030")in EVERY stat (if I have to remove one, or when building a engine) that doesn't have already have one, to allow a small amount of coolant & air to flow past to keep air pockets from forming.

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