Thermostat

KAWGRN · Oct 17, 2013

On ,my berg I restricted the bypass line with a small fuel valve I am using the 70c with the berg FE housing ,same as the KTM just shaped different to fit the hoses, and it stayed in the 13o-170F range ..this season I am going to try the 2 stroke single line 50c stat as shown in snowhawks pic ,,, in the return[/I] line of the #2 radiator, I will drill a Very small hole in the stat so it doesn't lock up on me. I'm thinking that it would slow down the cold shock when the primary stat opens so in the powder It would be like only having one radiator, thought about coming back on the trail where I have the over heating issue seen 250f with the radiator blocked off so in that case the 50c would be open and I would then have 2 radiators again. Next would be to replace the 70 with a 90c and use the 70c in place of the 50c,, any one have a 90c for the KTM housings?

PalousePoo · Oct 17, 2013

I rode in the mtns last sat, about 55 degrees out, with my 2011 yz450, (tires on!!!) and saw a max of 140 all day. Had no thermostat in. My guage was broke this summer, so didn't get to see a baseline temp on a hot day. Last winter I ran a KTM stat with bypass nipple plugged, but had drilled two 1/8' holes in side of stat. This was too much. Temps never got above 130 until you climbed, hard. I also fully enclose the front and sides of eng. with thin sheet plastic to stop the snow bath. I think trying to run 180-190 all day is unrealistic. IMO

Rush44 · Oct 17, 2013

My feeling is that the only way you are going to get the motor up to a desired temp is to cover the motor with something that won't allow the aluminum to transfer temps so quickly. When the motor gets put through a below freezing snow bath I don't think there is any thermostat in the world that would solve all of your problems. I've been thinking about a padded engine bag or something that can be zipped up over the motor to help insulate it from the cold. I keep meaning to talk with my upholsterer and see if he can make something for me that is easy to put on/take off. Skid plates simply aren't enough coverage either.

Lachoneus · Oct 17, 2013

I would be interested in something like that

thanks, great idea (easily removable engine cover of some sort)

summitboy · Oct 17, 2013

I've sent a email to Thermobob to inquire about the new housing and a 90C.

Also i have two KTM inline stat housings with stock 55C stats in them for sale as well as two brand new KTM 70C thermostats that i will not be using.

One note for the 300 crowd. You can use the factory KTM 70C stat in the 300XCW housing (stock is 55C). I tried just to test it out and it fits perfect.

Cheers

mtn-doo · Oct 17, 2013

Rush44 said:
My feeling is that the only way you are going to get the motor up to a desired temp is to cover the motor with something that won't allow the aluminum to transfer temps so quickly. When the motor gets put through a below freezing snow bath I don't think there is any thermostat in the world that would solve all of your problems. I've been thinking about a padded engine bag or something that can be zipped up over the motor to help insulate it from the cold. I keep meaning to talk with my upholsterer and see if he can make something for me that is easy to put on/take off. Skid plates simply aren't enough coverage either.

Rush, You're absolutely right. I have tested and tested the 450F and temp issues. The water temp seldom gets to the thermostat temp, so the thermostat you choose has no effect. In my tests, it never opens in the pow. The coolant temps never get high enough to open the stat. You could put in a 500 degree stat and it will still run at 90F.

The stat will only control the "high limit" of your temps. Not the low end. A higher stat will not raise your temps in the "cold pow". The engine is getting super cooled with pow and never reaches the stat opening point.

Good news though, I have observed that a 70C stat with the block off plugged will keep your temps in the 130 range when not in cold dry pow. I am speaking 4 stroke now.... 2 strokes seem to not have this issue. Reason ; The 4 stroke carries all of it's oil in the "bottom" of the case. It is super cooled all day long. That cold oil circulates through the cylinder head and draws heat away, further cooling. We must remember basic 4 stroke oil purposes, oil's primary "two" purposes is to lubricate and "cool". The cold lower cases of a 4 stroke are our issue. We must first warm the engine in order to put the stat to use! A stat will not warm our engine. The cold oil is also why it is grey and foamy. Cold soaked and full of moisture. A 4 stroke needs to reach operating temps to "burn" or boil away moisture and fuel in the form of a gas. That is why you have a case vent line. Ours do not reach that temp.

A 2 stroke seems to not suffer this condition. I feel it is because the 2 stroke has no engine oil from a cold case circulating to the head etc. Their case is bone dry. The cylinder is only lubed by pre-mix oil in you fuel. The only oil in a 2 stroke is in the trans, "gears and clutch". And that's a good place to keep cool.

The 4 strokes need to build heat in the entire engine first, then a stat can be chosen to "control" those temps.

.

summitboy · Oct 18, 2013

So Bill at Thermobob will not have a 90C stat for the new small housing. They have never been able to find a small 90C stat. Too bad for the 4 stroke guys. They will have to use the larger unit if they want a 90C. Sorry

J&L Snowhawk · Oct 18, 2013

I will be using the M456 thermostat on my aprilia sxv. I was thinking if I run coolant from rear cylinder back to water pump then run front cylinder to t stat then radiator it should keep my temps up real good. Anyone think that will b a problem?

summitboy · Oct 18, 2013

Isn't the M456 a LPG thermostat ? Its like a 3/8 in/out is it not ? Also thats only 55C. Seems like that is not quite enough for a 4 stroke and a 2 stroke according to people than ran 70's and 90's. Cant see that being a worthy solution. What bike runs 3/8 coolant lines ? Saw a pic of one on the subframe, just can't see that working way out there. Correct me if i'm wrong ??

dooman92 · Oct 19, 2013

m456

Summitboy, I see on the helmar web site they have a 5/8 hose inline M456. I called with questions and was advised someone would call me back, but yet to hear from them. I will try them again.

Do you know the part numbers of any KTM's that take the 90C stat??? Thanks

summitboy · Oct 19, 2013

No i have never found a small 90C yet.

summitboy · Dec 5, 2013

Here is a couple CR500 stat pictures. Rode in -23C weather today. A little snow not deep by any means. Temps were in the 140-150F range with dual 55C stats.

.

KAWGRN · Dec 6, 2013

My berg has a bypassing thermostat on the right radiator, and my bypass line is now restricted with a valve which I am going to remove as 98%,the flow comes out of the motor and will now be bypassing both radiators,I made a tee fitting right at the pump inlet, so in bypass I get no flow to the rads
,Im now installing the KTM single line stat in the out let of the left radiator with the direction flow towards the engine,so if the main stat does open it's sends water to both sides but since the right radiator is unrestricted, it will get a bulk of the flow, the left rad won't flow at all as the thermostat at 50c won't really open until the left rad is up to that temp,basically shutting the left radiator until she's good and warm, I'm am hoping that my 3 stage radiator scenario will work out, time will tell
Stage1 is bypass full flow
Stage 2 is right radiator flow modulated by the stat
Stage 3 is right radiator flow and left radiator controlled at 55c in the return line so if the right is hot ( doubt it ) it will eventually get to open the left stat but since it's in the return the radiator would be hot and minimize the cold shock to the engine

I have been able to keep the engine temps in the 160 range with the initial set up using the valve in the bypass but when I got back to the trail it boiled over, I would then pull the rad block offs and it would cool back to about 130, work in progress!

KAWGRN · Dec 6, 2013

Here's another thought!,

Till built is on the right path

turbo the buitch and let it make heat!

summitboy · Dec 6, 2013

I know lots have tried bypass without much luck. Too cold sometimes. One thing that is a problem with these bypass systems is the stats have the small holes in them to allow fluid to bypass the stat a little. I think Thermobob has it figured with his bypass lines and having the little holes completely blocked. This would allow the bypass to do its job correctly.

I noticed on my bike with these stats water just circulates all the time and once it gets up to engine temp the stats don't do much because so much fluid is still circulating.

Will be interesting to see the difference. You can see when the stats open and instantly you have a drop in temp. Shock cooling effect. I think with proper bypass one can get a more consistent running temp. Just measuring the temp at the outlet doesn't give a true representation of what the entire engine is running at. With a 55 to 70 with proper bypass in the deep snow the 2 stroke temps should be close to the 130-140 range.

JTAB · Dec 6, 2013

Thermo Bob

I just made my first trip with the Thermo Bob Thermostat last weekend.
held 190's all weekend no engine covers and outside temps were 20's to 40's.
This is the only time I have ever been able to hold temps the real test will be in deep powder. Last year I rode with a bike that had one and was holding 165 in deep snow!

I am very pleased and think it is the way to go......

summitboy · Dec 6, 2013

Does your temp seem very stable ? Or does it fluctuate a lot ? Which bike are you on ? I assume its a 4 stroke with the bob 190 in it ?

JTAB · Dec 6, 2013

KTM 500 XC-W KMS TURBO temp stayed in the 190's never moved more than a few degrees.

summitboy · Dec 6, 2013

Huh. Few degrees. So that Thermobob is working just like it is supposed to. Nice. I just hope a 70C isnt to much now lol

JimBridger · Dec 7, 2013

Anyone have any pics of a KTM 70c thermostat installed on a 2010+ yz450? I either put mine in backwards or I have a sticking t-stat. shoots over 195* (coolant temp in head) and keeps climbing. stat never opens. It should open around 155-160 right?

Thermostat

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