CYYJ
Michael
Way back in 2001, when the earth was still cooling down and we used 300 baud modems to connect to the interweb, fellow forum member Roger Heap and I were trying to figure out ways of solving the 'hot left leg' problem on our ST 1100s. At the time, I wrote up a post about it on Steiner's forum.
I still have the pictures from that effort, and perhaps it might be helpful to other ST 1100 owners if I wrote up our modifications here.
There are three different modifications involved. I did all three of them, and it solved the heat problem.
1) Installing a second cold air hose
When the ST 1100 first went into production, Honda installed cold air deliver hoses on both sides of the engine. Around the second year of production, Honda stopped installing the hose on the left side of the engine. Folklore has it that this was because of carburetor icing problems, but I think that is just folklore. I measured the ambient temperature in the carburetor area of my ST 1100, and it was always higher than 100°F once the engine had warmed up. If the motorcycle was left idling for a long period of time (the condition most conducive to formation of carburetor ice), the ambient temperature surrounding the carbs was as high as 150°F. In any case, I haven't encountered carburetor ice problems in the 17 years since I added this hose.
The hose, Honda part number 64280-MT3-000 ("Duct, Cold Air Intake"), is the same part for both sides of the engine. When you order it, you'll need to order two small screws to attach it to the front fairing. The screw part numbers are 90114-KW7-900. The hose costs about $35 USD.
Installing the hose is pretty straightforward. Routing and attachment of the hose is a mirror image of the OEM right side hose. You'll need to remove the false fuel tank cover, and remove a little bit of Tupperware at the front of the bike. It helps to have a couple of tie-wraps on hand to secure the hose in place once you install it, this will prevent it from blocking re-installation of the false tank cover, and also prevent the hose from getting in the way of the left side fairing pocket when you remove and replace the left side Tupperware.
2) Removing the two plastic panels at the front of the false fuel tank
For reasons unknown (perhaps to keep dirt or water out of the front of the engine, or perhaps to route more air up behind the windshield), Honda installed two plastic baffles on either side of the steering stem of the motorcycle.
If these baffles are removed, the airflow that was previously directed up the large opening where the forks are is now permitted to flow straight back under the false fuel tank cover, and from there down either side of the engine, aft of the ventilation openings on the side panels.
I removed both baffles. I've since ridden over 120,000 miles, and never had any problems with water or dirt entering the area behind where these baffles used to be.
The photo below shows the baffle in place (each one is held on by one screw), and the photo below that shows both baffles once removed from the moto.
3) Secure the rubber flap (heat shield) above the carburetors with Velcro
Honda provides a rubber heat shield that fits across the frame at the front of the motorcycle. Unfortunately, the rubber is not secured to the frame tubes, which means that quite a bit of hot air can migrate upwards.
I attached Velcro to the frame tubes and the bottom of the heat shield, this to prevent hot air from migrating up past the shield.
Before modification
Velcro Installed
Together, these three modifications have resulted in a considerable drop in temperature of the false tank cover and of the Tupperware panels that go down each side of the motorcycle towards the rider footpegs.
Michael
I still have the pictures from that effort, and perhaps it might be helpful to other ST 1100 owners if I wrote up our modifications here.
There are three different modifications involved. I did all three of them, and it solved the heat problem.
1) Installing a second cold air hose
When the ST 1100 first went into production, Honda installed cold air deliver hoses on both sides of the engine. Around the second year of production, Honda stopped installing the hose on the left side of the engine. Folklore has it that this was because of carburetor icing problems, but I think that is just folklore. I measured the ambient temperature in the carburetor area of my ST 1100, and it was always higher than 100°F once the engine had warmed up. If the motorcycle was left idling for a long period of time (the condition most conducive to formation of carburetor ice), the ambient temperature surrounding the carbs was as high as 150°F. In any case, I haven't encountered carburetor ice problems in the 17 years since I added this hose.
The hose, Honda part number 64280-MT3-000 ("Duct, Cold Air Intake"), is the same part for both sides of the engine. When you order it, you'll need to order two small screws to attach it to the front fairing. The screw part numbers are 90114-KW7-900. The hose costs about $35 USD.
Installing the hose is pretty straightforward. Routing and attachment of the hose is a mirror image of the OEM right side hose. You'll need to remove the false fuel tank cover, and remove a little bit of Tupperware at the front of the bike. It helps to have a couple of tie-wraps on hand to secure the hose in place once you install it, this will prevent it from blocking re-installation of the false tank cover, and also prevent the hose from getting in the way of the left side fairing pocket when you remove and replace the left side Tupperware.
2) Removing the two plastic panels at the front of the false fuel tank
For reasons unknown (perhaps to keep dirt or water out of the front of the engine, or perhaps to route more air up behind the windshield), Honda installed two plastic baffles on either side of the steering stem of the motorcycle.
If these baffles are removed, the airflow that was previously directed up the large opening where the forks are is now permitted to flow straight back under the false fuel tank cover, and from there down either side of the engine, aft of the ventilation openings on the side panels.
I removed both baffles. I've since ridden over 120,000 miles, and never had any problems with water or dirt entering the area behind where these baffles used to be.
The photo below shows the baffle in place (each one is held on by one screw), and the photo below that shows both baffles once removed from the moto.
3) Secure the rubber flap (heat shield) above the carburetors with Velcro
Honda provides a rubber heat shield that fits across the frame at the front of the motorcycle. Unfortunately, the rubber is not secured to the frame tubes, which means that quite a bit of hot air can migrate upwards.
I attached Velcro to the frame tubes and the bottom of the heat shield, this to prevent hot air from migrating up past the shield.
Before modification
Velcro Installed
Together, these three modifications have resulted in a considerable drop in temperature of the false tank cover and of the Tupperware panels that go down each side of the motorcycle towards the rider footpegs.
Michael
