Update 11/22/13: The original plastic tee had a catastrophic failure after less than 2 years. It has been replaced with a more durable metal part. The original part was a Doorman# 47112 (3/4" x 3/8" x 3/4" tee).
Motorcycle coolant systems are rather crude relative to cars. If any of you are familiar with the KLR 650 There is a popular cooling system mod to help better regulate engine temperatures. I am basically adapting this as a cheaper DIY mod for the Vulcan 500 engine. Unless you ride in cold temperatures, this mod is most likely a complete waste of time. This mod will help even out engine temperatures which is a good thing for longevity. Also the engine and oil will get up to temperature quicker.
How the stock cooling system works: Our bikes use a 71C (160F) thermostat. This thermostat has a small "weep" hole to allow a very small amount of coolant to keep circulating. As the thermostat opens cold coolant in the radiator flows into the hot engine and the thermostat shuts. This continues until a somewhat stable temperature is obtained. This works fairly well for warm summer weather where engine temps will eventually stabilize in the neighborhood of 190-205F. The bad part of this system is that in very cold weather The top of the engine may warm up but the bottom is constantly shocked by cold coolant when the thermostat opens. This may prevent the engine oil from warming enough to drive out any moisture that may have gotten in.
How the modified system works: The thermostat is replaced with a 91C (195F) thermostat that has no "weep" hole. A small bypass hose is installed before the thermostat and ties back in just before the water pump thus bypassing the radiator. This is how most modern automobiles work. The bypass keeps coolant circulating evening out engine temperatures and the higher temp thermostat will keep the engine at a more ideal temp.
If you want more information just google "thermobob KLR650" I give the guy a lot of credit who designed this. He did quite a bit of homework that I wouldn't have. I just think most of the parts in his kit are unnecessary. I reused the existing thermostat housing, put a hose barb in it for the bypass, and used a cheap plastic tee in the bottom radiator hose. There are aluminum "tees" to add an inline coolant temp sensor, but they are expensive and take up more room than the plastic one actually quite the opposite the aluminum one is smaller (shorter). On to the mod.....
Parts list:
- I am using a 195 degree thermostat for a '94 Chevy Astro, Federated autoparts# 203-195. $5
It's actually shorter top to bottom than the OE Kawasaki. Also notice there is no weep hole.
- A few feet of 3/8" ID SAE 30R7 fuel hose for the bypass line(-30 to 257F and 50PSI working). $5
- Two hose clamps for suitable for 3/8" hose. $2
- Two oem 18mm hose clamps for lower radiator (hose clamps for 3/4" ID heater hose also works). I bought practically new hose from a 2009 off fleabay as it had the hose clamps and a spare hose in case things don't work out. $15
18mm Koso temp sensor adapter to be used to splice in the return line. It includes the 18mm hose clamps. $28
Two 1/8" NPT to 3/8" brass hose barbs. I had to order this from amazon.com as I could not find them locally. $1.18 ea, These have gone up significantly in price!
Necessary "specialty" tools. I had these so I didn't need to buy, but I mention here since many people may not have them:
- 1/8" NPT tap.
- 11/32 drill bit.
I drilled and tapped the thermostat housing for the bypass line. I put the hole a little closer to the temp sensor than I had wanted to. Also you technically shouldn't need teflon tape for the 1/8" - 27 NPT fine threads, but I figured better safe than sorry. Being able to use a hole in the bottom of the housing would have been better, but I felt the material was too thin. Be CAREFUL when drilling the hole. When the drill bit punches thru, it will grab the uneven inner surface. I simply used a dremel and a file to open up the hole.
Note: See Vulcan 500 LTD section below for the metal "tee". Pictures below show the failed original plastic part.
I cut and spliced the lower radiator hose with the tee as shown. I spliced fairly close to the radiator so that I could aim the 3/8" hose under the cam chain tensioner and then route it up by the radiator to the thermostat. Original hose shown for comparison.
Final installation of lower radiator hose. Before anyone gets confused, yes I have a Franken-bike, part EX500, EN500C, and mostly EN500A. I trimmed the "spring" at the Tee.
Installed Thermostat with bypass.
Total cost was about $35. It would have been cheaper had I not bought a spare hose. I'll update this when I've had some saddle time in. This was done on an EN500A The bottom thermostat housings for both generation Vulcan 500's are the same, so I would imagine this could also be done on a EN500C.
This mod made much more of a difference on my LTD than my first gen. I suspect that the pod filter and carb mods on the first gen. done by a previous owner minimize some of the improvement. After the mod my LTD warms up much quicker and stays warmed up. I went on a 5 mile ride when it was about 58-60F (40-45mph speeds). After I stopped I felt the bottom of my radiator. It was ice cold. The metal output tube of the water pump was almost too hot to touch. So it was working, I was surprised that the coolant hadn't gotten warm enough to open the thermostat. I have noticeably more low end torque. Ie I can actually use 2-3k rpm occasionally with out completely bogging down the motor. I speculate a warmer engine will better vaporize the fuel and give me better fuel economy. I've only had a couple tanks thru the LTD and the temperatures have been up and down so it's hard to gauge if my cold weather mileage has improved or not. I see no downside to this mod and am very pleased. I've had a few morning rides in the 20's F and I only use full choke while I'm putting my helmet on then switch to low choke setting when I ride off. After the first stop sign (200 yards) I turn the choke off. Before I would ride a mile or so before turning off the choke.