Choke Cable Repair
You may have noticed a slight decrease in your fuel mileage. Or you may have noticed the bike doesn't run quite as good as it used to. Or you might notice a slight increase in RPM's at idle. And your bike, being a carb'ed model, is a few years old and has a few miles under its belt.
Well, these are all signs that your choke cable is going, or has gone bad. Almost always it is the plastic fitting at the carb end of the cable. If you've done a lot of tweeking with your carb settings lately, such as changing jets or adjusting the fuel/air mixture screw, the cable could be loose or disconnected from the carb. Then, when you push the choke knob back in, the choke needle won't close. Or the plastic on the fitting could have softened and it no longer clamps onto the steel elbow at the end of the cable.
On CV carburetors, the choke is actually a needle valve that opens to add fuel after the slide, hence why it's actually called an enrichener. When you pull the choke knob, the cable attached to the knob pulls the needle valve open. There is a small spring between the needle and a fitting attached to a steel elbow at the carb end of the cable. When you push the knob back in, the spring seats the needle closed. Between the steel elbow and the needle is a threaded plastic "nut" that connects the cable to the carb. When this plastic nut fails, the spring pushes the cable away from the carb and doesn't seat the needle fully. If the needle doesn't close, it allows gas to flow, reducing your mileage and possibly fouling your plugs.
"Don't Panic" for there is an easy way to check.
First is the feel when you push the choke knob back in. If it feels "spongy" toward the closed position and wants to push back out just a little, then it is likely that you have a problem at the carb end of the cable. If you've removed the cross over air tube, you should be able to look between the cylinders from the left as you pull and push the choke cable. Look at the right side of the carb where the choke cable connects. If you see the steel elbow moving toward and away from the carb about 1/8" or more, then you have a bad cable.
If there's a problem, pull the carb off the intake manifold and try to tighten the plastic nut to the carb. Do not put too much torque on this nut as it will break easily - it's just plastic! If it's already snug, then look for a crack anywhere along this plastic part while moving the choke knob in and out. If it's cracked, you'll have to replace the cable.
Probably the more common problem is the clamp "fingers" at the end of the plastic nut that clamp onto the steel elbow have lost their strength and allow the elbow to slip in and out of the nut. This prevents the choke needle from fully closing and will cause your bike to run rich, fowling plugs and dropping your gas mileage. Pull the rubber off the end of the plastic nut and check the location of the groove in the steel elbow relative to the fingers. Most likely, fingers are not engaged into the groove like they should be.
To fix this problem, buy a 3/8" diameter hose clamp or the smallest clamp you can find. This is one time where zip-ties won't work. Position the clamp over the fingers with the steel elbow engaged and tighten the clamp as snug as you can. Check by moving the choke knob several times. If the steel elbow stays in place, you've got it fixed. Re-install the carb and enjoy your properly jetted ride with better mileage.
Here's a diagram of the CV carburetor for a D1 1500 Classic. Part 16016 in the upper right corner is the plastic "nut" connector that we're concerned with.
Here is a photo of the steel elbow with the loose "fingers". It's right behind the rubber hose and the vent line connection and under the carb cap in the upper right corner of this picture.
And here's a photo with the clamp in place. Notice it overlaps the fingers and the elbow.
Well, these are all signs that your choke cable is going, or has gone bad. Almost always it is the plastic fitting at the carb end of the cable. If you've done a lot of tweeking with your carb settings lately, such as changing jets or adjusting the fuel/air mixture screw, the cable could be loose or disconnected from the carb. Then, when you push the choke knob back in, the choke needle won't close. Or the plastic on the fitting could have softened and it no longer clamps onto the steel elbow at the end of the cable.
On CV carburetors, the choke is actually a needle valve that opens to add fuel after the slide, hence why it's actually called an enrichener. When you pull the choke knob, the cable attached to the knob pulls the needle valve open. There is a small spring between the needle and a fitting attached to a steel elbow at the carb end of the cable. When you push the knob back in, the spring seats the needle closed. Between the steel elbow and the needle is a threaded plastic "nut" that connects the cable to the carb. When this plastic nut fails, the spring pushes the cable away from the carb and doesn't seat the needle fully. If the needle doesn't close, it allows gas to flow, reducing your mileage and possibly fouling your plugs.
"Don't Panic" for there is an easy way to check.
First is the feel when you push the choke knob back in. If it feels "spongy" toward the closed position and wants to push back out just a little, then it is likely that you have a problem at the carb end of the cable. If you've removed the cross over air tube, you should be able to look between the cylinders from the left as you pull and push the choke cable. Look at the right side of the carb where the choke cable connects. If you see the steel elbow moving toward and away from the carb about 1/8" or more, then you have a bad cable.
If there's a problem, pull the carb off the intake manifold and try to tighten the plastic nut to the carb. Do not put too much torque on this nut as it will break easily - it's just plastic! If it's already snug, then look for a crack anywhere along this plastic part while moving the choke knob in and out. If it's cracked, you'll have to replace the cable.
Probably the more common problem is the clamp "fingers" at the end of the plastic nut that clamp onto the steel elbow have lost their strength and allow the elbow to slip in and out of the nut. This prevents the choke needle from fully closing and will cause your bike to run rich, fowling plugs and dropping your gas mileage. Pull the rubber off the end of the plastic nut and check the location of the groove in the steel elbow relative to the fingers. Most likely, fingers are not engaged into the groove like they should be.
To fix this problem, buy a 3/8" diameter hose clamp or the smallest clamp you can find. This is one time where zip-ties won't work. Position the clamp over the fingers with the steel elbow engaged and tighten the clamp as snug as you can. Check by moving the choke knob several times. If the steel elbow stays in place, you've got it fixed. Re-install the carb and enjoy your properly jetted ride with better mileage.
Here's a diagram of the CV carburetor for a D1 1500 Classic. Part 16016 in the upper right corner is the plastic "nut" connector that we're concerned with.
Here is a photo of the steel elbow with the loose "fingers". It's right behind the rubber hose and the vent line connection and under the carb cap in the upper right corner of this picture.
And here's a photo with the clamp in place. Notice it overlaps the fingers and the elbow.
posted by James Vierkant at 9:59 AM
1 Comments:
This comment has been removed by a blog administrator.
Post a Comment
<< Home