Thermostat selection

[Vdriveboater]

I just replaced the OEM t-stat with this one https://www.ebay.com/itm/274888683390?h ... BMyKCpwtti which doesn't have the bottom "plunger" that moves down as the t-stat opens like the OEM style has. I went for a 20 mile ride with the new t-stat and the gauge acted similarly to the one I removed (which I couldn't get to open in boiling water). What functionality am I losing with the non-plunger style t-stat? Note that I took IR gun temp readings after my ride and they back of the heads were in the 170-180F range, whereas before after a ride like that they would be around 200F. My guess is that it has something relating to the old t-stat not opening in boiling water

[triton28]

What's missing from the t'stat you purchased is the Bypass circuit open/closed spring and valve plate.
This as one can see in my photo is the spring and associated metal parts to the left of the 2 red lines.
When the engine is first started this bypass is open and not in contact with the circular shoulder of the t'stat housing thus allowing all of the coolant to bypass the radiator and the engine to warm up to operating temperature quicker.
When the coolant reaches the operating temperature the main plate opens and at the same time due to a common spindle the bypass valve moves in the direction of the arrow and closes against the circular shoulder of the t'stat body thereby allowing all of the coolant to cycle through the radiator.
Now the real question is: what effect does this coolant continuing to bypass the radiator have on the design parameters of the system? Well that would depend on the volume of the bypass line versus the volume of the main flow opening of the t'stat plate/valve since they would both be open with the engine up to operating temperature and your t'stat installed.
If the bypass is greater in volume than the main line then I would imagine eventual overheating would occur as the coolant is bypassing the system designed to cool it down to 190* or less, that of course being the radiator.
If the opposite should be the case and the bypass is equal to or less in volume than the main line opening of the t'stat plate/valve then your t'stat may function as well as any other.
Do not use the size of the pipes as a guide as it is the volume opening of the main plate of the t'stat; GPM so to speak.
It's a guess until further road testing proves one way or the other but it definitely is not as designed by MawKaw.
I hope it works for you but continue to keep an eye on the temperature gauge,
Dave

[Vdriveboater]

Thanks so much for the detailed explanation Dave. What you described is more or less what I had imagined, although not to the extent that you provided. What I concluded after comparing the two t-stat designs and the "bypass port" is that, under conditions of high ambient temps combined with extended idle or low speed driving, with the t-stat at full open, the amount of coolant flowing to the radiator vs recirculating will dictate how long the engine can run before overheating. I believe that the fleabay t-stat I installed had 60C stamped on it, which means the t-stat will open sooner than the OEM t-stat and it will probably be fully open at 70C, which should help to prevent (or at least delay) an overheating condition.

Today I purchased a Moto Rad t-stat at my local Auto Value store that looks/measures very close to the OEM Kaw unit which I'll keep on hand in case it's needed in the future. I'll post a pic and the part number soon.

[Vdriveboater]

Dave, I think this animation might be what you were describing https://www.youtube.com/watch?v=aOXz5hlKO9s
Is this how the t-stat and water flow works in the Voyager engine? The video shows the t-stat opening and the flow of hot coolant going to the water pump, but I thought it goes to the radiator on our bike?

[triton28]

Hello Vdrive;
That video was spot on and did the narrative much more concise than my poor laymans attempt did.
The video is exactly how the Voyager XII system works: the short circuit bypasses the radiator and the longer circuit, which I call the main line, flows through the radiator then to the water pump at operating temperature with the main t'stat valve open.
It will be interesting to follow your 60* t'stat install to see how it pans out for you.
Please keep us posted and thanks for the vid.
Dave

[Vdriveboater]

Here is the MotoRad thermostat part no. 328-170 that is the same design as the OEM t-stat. https://shop.advanceautoparts.com/p/mot ... rm=328-170 MotoRad also offers the UltraStat in the same model for 5 bucks more which is stainless steel and probably longer lasting. My local auto parts store found the 328-170 in stock and said that this is what is called out for the Voyager. Dimensionally the only difference is that the distance from the mounting flange to the bottom "plunger disc" is about 1/16" longer than the OEM unit, and I don't see that as creating any kind of an issue. It's rated to start opening at 170F which is slightly less than the Kaw service manual states the OEM unit opens (176F). It cost about 15 bucks which is about 50 bucks cheaper than the OEM unit from the Kaw dealer. If you prefer a warmer engine I do see that it's also available in 180 degree opening (328-180). I'm going to keep it as a spare, and if someone does try it, please share with the group how it works for you.

If I have time to put on some miles this month (weather permitting) I'll report on how the "standard type" t-stat that I installed is working out.

[GrandpaDenny]

I nominate this for the Dollar For Dollar section!