Keihin cv 40 mm carburetor setting for a 1979 sportser. any ideas on the setting of this

Ahhhh..the Sporty has a rattle...or is it a ping? If your popping through the exhaust, the timing could be off and running rich (Check Spark Plug for dark sooty layer) If your engine is pinging could be advanced timing... pre-ignition happens on acceleration or under a load...loose valves will make noise all the time

Do you have the CV Keihin still? Or are you running an aftermarket carburetor ? Like an S&S?

That year Softail came with the "butterfly type" Keihin carburetor. Refer to this site for a picture of the carb. http://www.bikebandit.com/1987-harley-davidson-fxst/o/m1504#sch173168 There are several versions of this carb that were used with the latest version being the best one. It had an additional mid-range fuel port in the venturi that solved a "dead spot" problem in the RPM range where most people normally ride. As best as I can remember, Harley went to the Keihin CV type carb in 1990.

If your bike does not have an carb on it at the time and you are not particularily wanting to restore the bike to exact original condition, I'd consider an S&S Super "E" Shorty carburetor. You can purchase the complete kit to change the carb from most aftermarket dealers and some H-D dealers. The original Keihin carb was not very popular with most riders and this is the carb that a lot of them chose to put on the engine in it's place. The newer Keihin CV carb was a much better carburetor and can be installed on the engine but it will require an intake manifold change as well. You may be able to locate one of these later carbs at a swap meet for a reasonable price.

Good Luck
Steve

If your bike was allowed to sit up for an extended period of time, the gasoline in the float bowl evaporated and left behind this gummy mess. It has plugged up the jets and possibly the small fuel passageways in the carb. The carb must be completely disassembled and soaked in a professional grade carburetor cleaning solution. Then, compressed air must be used to check all the passageways to be sure they are open. No fuel is getting into the main venturi of the carb for some reason. The enricher circuit has it's own venturi and pulls fuel directly from the float bowl. This why it will run using the enricher and not run when it's turned off. I'd suggest that you take your bike to someone that knows what they are doing with a carburetor. If whoever did the carb did it right, it should run without having to use the choke. You didn't say whether your carb was the original stock carb or an aftermarket unit. If your carb is the stock Keihin CV carb and the "anti-tamper" plug has been removed from the idle mixture screw, set the screw at 3 turns off the bottom to start with and then fine tune the idle when the engine warms up. The idle mixture and idle speed are the ONLY things you can set on any carb from the outside. The fuel metering is controlled by the jets inside of the carb.

Good Luck
Steve

Before I can tell you how to lean your carburetor out, I need to know what kind of carb you have. But, there are other possible causes for your problem. The factory usually jets the original Keihin CV carb too lean to meet EPA emission requirements. The most probable cause is running the enricher too long while warming the engine up. The enricher on any carburetor provides an extremely rich mixture. So rich that it will foul plugs if allowed to run for too long. You should only use the enricher long enough to warm the engine to the point to where you can keep the engine running with the throttle grip. Once the engine will run with the throttle grip, simply idle the engine up and use the throttle grip lock to hold the throttle at this setting and push the enricher knob in. Other causes could be that the needle is not seating properly and allowing the carb to load up with fuel. If this is the case, you should have noticed that the engine is idling extremely rich and poorly. In this case, you'll have to at least drop the float bowl off and replace the needle and check the float setting with the new needle. The Kiehin CV must be positioned on an angle to set the float properly. If you still have reason to think that you need to change your carb's jetting, re-post telling me exactly what carb is on your engine.

Good Luck
Steve

It sounds like you have a bad needle in the carb allowing the float bowl to overfill. It depends on what type of carb is on the engine as well. If it's the original Keihin CV carb, you'll have to remove the carburetor from the engine and remove the float bowl, the float, and the needle. Replace the needle and reset the float height is necessary. There is a special way of setting the float height on this carb. It must be set with the carbuetor body positioned at an angle. If you'll contact me directly at [email protected] , I'll send you a picture of how to set the float level on the Keihin CV. If your bike has a different type of carburetor, let me know this and I'll try to help you with that as well. Don't forget to tell me what you need.

Good Luck
Steve

If the engine is running, it's not a timing issue. If the engine is running and the timing is not right, it would continue to run when you give it some throttle but maybe not run well. I'd suspect the carb. If you've put a later model Keihin CV carb on the bike and it dies when you give it throttle, you could have either a bad accelerator pump diaphragm or a hole in the vacuum diaphragm that controls the slide. To check the accelerator pump, remove the air filter so that you can see inside the mouth of the carb. With the engine OFF, crank the throttle to wide open. Watch for a stream of fuel to squirt out of the brass nozzle just inside of the mouth of the carb. If you do not see the shot of fuel, your accelerator pump in not working. You need to drop the float bowl off the carb and check the diaphragm and fuel passages to make sure they're open. To check the slide vacuum diaphragm, with the air filter off and the engine running, rev the engine up a bit and watch the slide in the carb. It should move up and down. Do not get your face too close to the carb. If it spits back through the carb, it could cause you some injury. If the slide does not move up and down, you may have a hole in the vacuum diaphragm. In order for you to install the Keihin CV carb on this model Sportster you had to have changed the intake to one specially made for this installation or you had to use an adaptor. Make absolutely sure you have no vacuum leaks. Look on the backside of the carb for a vacuum port that you may not have connected to the VOES switch.

Good Luck
Steve

I would suspect that your problem is something other than the float setting. If your carb has been running properly until recently, there may be trash in the needle and seat. Float settings don't just change by themselves. Once they're set, they stay that way until someone changes it. I'd be glad to send you the float settings but you didn't tell me what kind of carb you're running on the bike. Harley riders are noted for changing the type of carburetor they run on their bike. If you're running the stock Keihin carb, the float level has to be set with the carb on an angle. To illustrate this, I'd have to send you a picture. I'd be glad to do so if you're contact me directly as this forum only allows a file size of 150Kb or smaller. Contact me at [email protected] and I'll send you a picture of how to set the float level of the Keihin CV. If you are running a different type of carb, let me know and I'll send you information on that one as well if I have it.

Good Luck
Steve

This is not the original carburetor that came on the bike. The orignial was a Kehien "butterfly" carburetor. This carburetor is a later "CV" version with the large square looking top on it.

I'll tell you how to access the idle mixture screw on each model. The "butterfly" carb had it's idle mixture screw in a "tower" on top of the carb just forward of the carburetor mounting flange. The square topped "CV" carb has the idle mixture screw underneath the carb at rear of the float bowl.

They both came from the factory with an "anti-tamper" plug of about 3/16 inch diameter (5mm) pressed in over the adjuster screw so that the owner could not mess with the idle mixture.

To get access to the idle mixture adjustment screw, you must drill a small hole in the "anti-tamper" plug. Be very careful not to drill too deeply or you will damage the brass screw underneath the plug. Drill just enough to go through the plug with a small drill bit. Screw a sheet metal screw or start a tap in the hole. If you use the sheet metal screw, use a pair of pliers or something to pull the plug out. If you're using a tap, once you get the hole tapped screw a screw into the hole and use the pliers to pull the plug out.

If your bike will idle at all, start the bike up and allow the engine to warm up. If it won't idle, screw the idle mixture in until it just barely "bottoms" in the hole. Back it out 1 1/2 turns on the "butterfly" carb and about 3 turns on the "CV" carb and start the engine. Adjust the screw to obtain the highest smoothest idle. Then use the throttle stop screw to set the idle speed of the engine. Once you're finished, put a small dab of RTV sealant in the hole over the screw. If you don't do this, water will seep down by the fine threads permanently seizing the screw making it impossible to adjust the idle mixture in the future.