"Not recommended," by whom?I said, not recommended.
Watt-man will sell you a 195 deg. F. t-stat and o-ring for the T-bob 2 which fits the stock t-stat housing. I bought one from him. Although, I had previously fabricated and installed a bypass for an application unrelated to temperature control, so mine is sort of a T-bob 1-1/2.
#1,"Not recommended," by whom?
I have a "Normk" model higher-temperature thermostat; may drop it in just to see what happens. Please warn me of any danger, describing the failure/malfunction mechanism. Thanks!
[Further thanks to Normk for obtaining the higher-temperature thermostats and allowing me to purchase one.]
I don't have a gauge overlay, but I know that the center of the scale on my gen2 is 210 degrees F. and each quarter scale is 30 degrees F. So, 1/4 scale is 180 deg. and 3/4 scale is 240 deg.GoMotor, do you have a gauge overlay if so what temps are you running on the road after the stat change and 1/2 bob job?..................:
The plumbing system you have shown here is very similar to the one I used. I tapped into the head on top between the temperature sensor and the thermostat making it a little easier to manage the drill and tap swarf with a piece of cardboard through the t-stat opening and under the drilling location. I now think it might be possible to put a tee on the existing sensor opening and use it for both the bypass and the sensor. This would eliminate the need to drill and tap the head. I soldered a 1/4" barbed coupling on to the side of a 3/4" barbed coupling to make a tee for the pump inlet hose, but I like your tap into the pump housing better.If someone wishes to do my bypass system, it's only about $30.00 for thermostat, elbows , fittings and hose.
Here's some info on my bypass design. IMO, it's simple as pie:
Most eloquent and well-reasoned brief, Normk; thanks!The KLR thermostat is 160 F but Sega scooters have a 160 F or 180 F thermostat. I had 195 F thermostats made in China to fit the stock KLR housing.
The problem I see with running higher than 160 F is concern regarding theromoshock to the system. One might note that all of the non-thermostat bypass systems in motorcycles use only 160 F.
Chrysler were one of the last auto manufacturers I know of who used a non-thermostat bypass cooling system. It was used in the Neon, 2.2 & 2.5 engines which were all notorious for head gasket failures. My hypothesis is that the rapid and significant change in temperatures when thermostat opened caused significant changes in the expansion rate of the head versus the block. This seems to match the head gasket problems which seemed to be from the head and block sliding over the head gasket rather than expanding and contracting together.
I have the same concern regarding the motorcycle engines. A bypass system simply recirculates coolant within the engine to maintain the engine at a uniform temperature which reduces issues such as the head gasket wiping issue, cylinder deformation due to the huge difference in temperature between bottom and top + increases the thermal mass involved in thermostat cycling.
A major problem with an non-bypass system is that the thermostat only reacts to the temperature of the coolant surrounding it. In the case of the KLR, 40 degrees is not an unusual temperature difference between the spark plug and thermostat....in what? 3 inches?
What happens is that the coolant pocket around the exhaust ports heats up more than other areas of the head and far more than lower down the cylinder. When the small pocket around the thermostat reaches 160 F, the thermostat swings close to wide open and a rapid loop or coolant cycle occurs, bringing cold coolant up from the bottom into the thermostat pocket. The thermostat slams shut and then the pocket begins heating again. One can match the cold air flow and engine load so as to see the temperature gauge swing wildly.
When there is a bypass passage/hose the coolant within the engine cycles through the passage/hose from the thermostat pocket to the water pump inlet and up through the engine. This constant mixing (keep in mind that the water pump pressure with the thermostat closed can be 65 PSI) maintains the coolant at a constant temperature which encourages more even engine temperatures.
Rather than heating only a small pocket quickly to thermostat opening temperature, the entire coolant volume within the engine must be heated and cooled in order to cycle the thermostat. As a result, the thermostat tends to simply open the amount which is required to maintain a constant balance of flow through the radiator and bypass to balance the cooling needed. The gauge sits in one spot unless other factors intervene.
Once the thermostat is open, the pressure in the engine drops to about the radiator cap level. Since the engine heat isn't changing wildly, the engine isn't in a state of dissimilar expansion and contraction so the head gasket isn't in so much danger.
This allows use of a higher thermostat which is why I chose the popular 195 F as the temperature. The difference in engine operation is well documented. The KLR engine is designed to operate at 250 F+ so clearances are better at higher temperatures.
I don't recommend simply installing a higher temperature thermostat as outlined.
The Thermobob2 is a kit using the smaller, stock sized thermostat. Bill sells thermostats separately as Thermobob3 so that's what I recommend. I didn't want to deal with sales or to cut in on Bill so connected him with the supplier.
If someone wishes to do my bypass system, it's only about $30.00 for thermostat, elbows , fittings and hose.
Here's some info on my bypass design. IMO, it's simple as pie:
I was curious when I saw that coolant was piped to the carburetor on Australian models.I forgot to ask if you have thought about the Ozzie carb heater plumbing and why they may require that in their climate?
Just to clarify, Normk, are you saying the temperature of the coolant at the bottom of the cylinder may be 60 degrees F., while the temperature at the thermostat may approach 160 degrees F.? At nominal engine operating temperature? After circulation? For how long?The temperature at the bottom of the cylinder, according to Bill Watson's measurements and my rough attempts to confirm, are often very close to ambient so not unusual to see 60 F at the bottom and a bit over 160 F in the exhaust port area. That means that the cylinder is tapered fairly significantly under many operating conditions.
I was curious when I saw that coolant was piped to the carburetor on Australian models.
Some air planes I had were equipped to provide heated air to the carburetors to prevent icing in the throats of the carburetors. I wonder why my motorcycles don't ice when I ride them at altitudes higher than that at which the planes iced.