Worn or cracked rubber intake boot fix
Use high temp silicone hose to cover the existing carburetor holders
If you have worked on bikes long enough you have run into this problem. An older bike that has been sitting and certain rubber parts have dried out and cracked. The most frustrating parts that this happen to is the intake boots or also known as the carburetor (carb) holders. Cracked or rotten carb intake holders can cause tiny vacuum leaks that can lead to a whole host of problems, difficult tuning/jetting, unstable idle, overheating, to potential engine damage.
Depending on the model and year of the bike sometimes these are still available from OEM parts distributors such as Rocky Mountain ATV/MC. However even if available new they can be pricey and with multi-cylinder engines this cost can add up. Sometimes when in the begining stages of restoration you just want to get the bike running before spending the big dollars on replacement parts. Well here is a low cost solution to help fix those nasty carb boots so you can properly tune your machine.
The solution is to measure the outside diameter of the carburetor holder and the outside diameter of the carburetors mounting flange. Use this to pick the correct size of silicone hose that will fit tightly over the intake boot and fit snugly over the carburetor flange. The silicone hose will stretch a little and if necessary use a little bit of heat from a heat gun. Use small worm type hose clamps to secure both ends. If this is more of a permanent solution you may want to use a little bit of high temp RTV silicone sealant around the intake boot before slipping the hose on. One thing of note, because you now be mounting the carburetors to the new silicone hose and not the carb holder/intake boot itself you will be elongating the intake runner by about 3/4 inch or so, this may affect the ease of installation of the air box and boots associated with it. Usually the boots from the air box to the carburetors have enough give and room for the added length, however some situations might make this fix less desirable for fitment reasons.
Depending on the model and year of the bike sometimes these are still available from OEM parts distributors such as Rocky Mountain ATV/MC. However even if available new they can be pricey and with multi-cylinder engines this cost can add up. Sometimes when in the begining stages of restoration you just want to get the bike running before spending the big dollars on replacement parts. Well here is a low cost solution to help fix those nasty carb boots so you can properly tune your machine.
The solution is to measure the outside diameter of the carburetor holder and the outside diameter of the carburetors mounting flange. Use this to pick the correct size of silicone hose that will fit tightly over the intake boot and fit snugly over the carburetor flange. The silicone hose will stretch a little and if necessary use a little bit of heat from a heat gun. Use small worm type hose clamps to secure both ends. If this is more of a permanent solution you may want to use a little bit of high temp RTV silicone sealant around the intake boot before slipping the hose on. One thing of note, because you now be mounting the carburetors to the new silicone hose and not the carb holder/intake boot itself you will be elongating the intake runner by about 3/4 inch or so, this may affect the ease of installation of the air box and boots associated with it. Usually the boots from the air box to the carburetors have enough give and room for the added length, however some situations might make this fix less desirable for fitment reasons.
Installed: notice the slightly added length to the intake
Now for obvious reasons you would not want to use this solution for a complete factory accurate restoration, but it can be a life saver in the beginning stages of getting an old bike running again. Also old dirt bikes can benefit from this cheap solution to keep that old bike running and on the trail.
Automotive silicone radiator hose can be found online or at specialty automotive parts stores and speed shops. Use your imagination, this is just one way to solve a frustrating problem with bikes that have been sitting for a while and the rubber carburetor boots are all cracked and dried up.
For more tips like this and other helpful information for keeping your motorcycle running, visit the video pages by navigating at the top.
If you like this or have any other questions please leave a comment, no need to register to comment.
Automotive silicone radiator hose can be found online or at specialty automotive parts stores and speed shops. Use your imagination, this is just one way to solve a frustrating problem with bikes that have been sitting for a while and the rubber carburetor boots are all cracked and dried up.
For more tips like this and other helpful information for keeping your motorcycle running, visit the video pages by navigating at the top.
If you like this or have any other questions please leave a comment, no need to register to comment.