S&S motor with CV carburetor ; it start and run idle very good, but no power or aceleration

Carburetor [A200774] for Lawn Equipment ' eReplacement Parts might have it but be where they have discontinued most carburetor parts good luck

Check your jets to make sure nothing is damaged. What type of carburetor? Slide, CV (Slide and butterfly), or Fixed Venturi (Butterfly only) Carburetor? If its a CV check the diaphragm. Also look at your throttle cable routing and make sure it isn't getting caught on anything or routed so tightly the cable can't maneuver through the sheath. If none of that works your fuel mixture screw/idle adjusters all all out of whack and it will need to be adjusted. Cheers!

Why don't you balance the carburetor. It seems that the mixture is not correct when you push the throttle. Had it been timing it would act rough even on idle.

This sounds like a couple different things. Lets start with the easier idea first. You need to locate the fuel filter and remove it and blow into the end that points to the carburetor. Point the other end at your hand or in a cup and catch the gas that comes out. If there was a good bit of debree then replace it and see if it fixed the problem. If it did buy a new filter next time it starts acting up, If not then it would be wise to check all the vacuum hoses for leaks or if one has come loose. If you can't see any leaks or loose ones then get a can of carburetor cleaner and as the engine is runnoing spay short spurts around the motor area. If the engine revs up to a faster idle then there is a leak. Do not spray right at the throat of the carburetor intake. That will rev for sure and there is nothing wrong there when it revs up. It would be like giving it gas.
If you find and trace down the leak stop it up or repair it. If nothing can be found then to the next step.
This also acts like a caburetor acereration pump. That is inside the carburetor and is a piece of rubber type diafram that moves back and forth and aceleration is given to the vehicle. These can get a pin hole or harden after time and you will need a carb rebuild kit. The kit should be under twenty bucks at schucks. Let me know how it turns out. I wish you well. The Raz

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.

have you tried an engine idle relearn?

start car don't touch a thing, encluding brake. Let idle for 2 fan cycles. and see how it works from there.