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

Changed my carb on my 1979 sporty. running high idle and backfires. also keeps overflowing.

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  • dennis wagner
    dennis wagner Apr 01, 2014

    its a 99 carb 40 cv carb on a 1000 ccm sportster from 1979, with no baffle in exhaust, no leaks good plugs.


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  • Harley Davidson Master
  • 40,844 Answers

Hi Anonymous, please visit website below:
Harley Davidson CV Carburator rebuild and float adjustment ep 18 eng Roma...
Good luck

Posted on May 01, 2015

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Posted on Jan 02, 2017

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SOURCE: Backfiring

Hi, maybe its the same problem i had, i have a 1200 goldwing where your spark plug are there are holes if these become clogged the water stays there and causes backfiring, get a metal welding rod or steel coat hanger and push through the hole to clear the water, hope this helps good luck.
regards Mark

Posted on May 11, 2009

  • 3567 Answers

SOURCE: 1981 gl1100 has 4 keihin carbs bike sat 7 years

648d54b.gifWhen removing the pilot jet screw, count the number of turns to remove. Put the screw back the same number of turns then unscrew 1/4 turn.
A “very helpful” rating on this answer? Thanks!

Posted on Jul 02, 2009

  • 496 Answers

SOURCE: 2001 Honda Shadow ACE 750 idles, but won't rev up

vac leak craked boots

Posted on Jan 05, 2010

  • 4565 Answers

SOURCE: what is the float level setting on a hd keihin cv

You'll have to contact me directly for that information. The reason is that the float level is not set in the more conventional manner like other carbs. The float level is set to0.413 - 0.453' from the "bottom" of the float to the lower face of the carb body with the carb tilted at an angle of 15 - 20°. A picture is worth a thousand words in this case. For a picture, contact me directly at wd4ity at

Good Luck

Posted on May 09, 2010

  • 4336 Answers

SOURCE: My 2004 rm 125 carb has consistent gas flow out

Sounds like an inlet valve is sticking open. You have to disassemble the carb and find the cause. Overflow is too much fuel. Fix this before using or running the machine, as you are a fire hazard.

Posted on Jan 31, 2011

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Just bought a Sportster 883 2002. There's a rattle in the engine as I get higher up in rpms. Also the exhaust pops as I accelerate. Any idea as to what could be the deal. Carb maybe?

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?

May 06, 2016 | Cars & Trucks

1 Answer

What makes the diaphragms in a Keihin CVK 34 carbs work on my 1994 Kawasaki Vulcan 750

Hi, Shane for more information about your question and valuable "FREE" downloads that you will need please click on the websites below. Good luck and have a nice day.
How carburetor works Carbs explained
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Apr 06, 2016 | Motorcycles

1 Answer

Exploded view of 1991 harley cv carb

Hi Anonymous, for more information on your question please visit the websites below and good luck:
diagram of keihin carburetor Google Search

Dec 29, 2012 | Harley Davidson FXD Dyna Super Glide...

1 Answer

What type of keihin carburetor suits a FXST 1986-87

That year Softail came with the "butterfly type" Keihin carburetor. Refer to this site for a picture of the carb. 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

Sep 05, 2011 | Harley Davidson FXST Softail Standard...

1 Answer

I have a 1998 harley sporters, runs only when the choke is pulled out all the way and when I try to back it off, it stalls. I had the carburator cleaned, but it still does it..Can somebody offer me a...

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

Aug 21, 2011 | 2007 Harley Davidson XL1200R Sportster...

1 Answer

I have 1994 fxdl the plugs keep getting caked with black soot and fauling out which makes me believe its running to rich, its also backfiring,thru carb and exhaust, i want to know how to lean it out

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

Jul 06, 2011 | Harley Davidson FXDL Dyna Low Rider...

1 Answer

I have a 2003 superglide and the carb keeps building up with fuel and runs really rich and u can smell fuel .. any help

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 , 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

Jul 03, 2011 | 2003 Harley Davidson FXD Dyna Super Glide

1 Answer

When i give it some throttol it dies out.79 sporty 1000cc with cv carb.could it be fuel or timing

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

Jul 03, 2011 | 1979 Harley Davidson XLH 1000 Sportster

1 Answer

Need float specs fuel leeks out overflow on carb. hanging should it be right below the gasget at the toe or the seem?

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 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

Mar 20, 2011 | Harley Davidson XL 1200 C Sportster Custom...

1 Answer

I have a 27499-85 carburetor on a 1979 harley shovel head and am looking for the idle mixture setting-i haven't taken the carburetor off the bike yet, however i removed the air filter and don't see any...

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.

Oct 24, 2009 | 2006 Harley Davidson FXDI35 35th...

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