I just added small baffles on my 84 straight pipes and she seems to stumble a little on cracking on the throttle do u think that accel pump or air mixture out of wack easiest way to adjust. thanks

 

on my late 84 with a cv carb,
when i put my baffles in i back my air mixture screw out about a 1/2 turn seems like it needs alttle more fuel with the baffles,

 

My late 84 with S @ S Shorty "E" , 40" drags, put 2" cheapo baffles had to back out air 1/2 turn.

 

From S&S:
Cams and exhaust systems can make some engines difficult to carburate. S&S has found that certain cams and exhaust systems cause poor performance at a specific rpm, and attempts to correct problem with carb tuning usually degrade carburation at other rpm ranges. A combination of cam overlap, reversion, and back pressure, or even lack of back pressure, can cause mixture dilution at certain rpm. This will result in loss of power, engine roughness, or misfiring.

Drag pipes - For knucklehead, panhead, shovelhead, and ironhead Harley-Davidson® Sportster® models, 13⁄4" O.D. drag pipes with straight cutoff end 28" to 30" long will work well with almost any camshaft or other performance modification. 2" O.D. drag pipes are not recommended for any application except very large competition engines.

The use of drag pipes is not recommended for Evolution motors in street application.

Mufflered exhaust systems - A good, economical street exhaust system consists of stock header pipes with cross-over tube and low restriction mufflers such as S&S® slip-on mufflers. This system typically produces 10 horsepower more than drag pipes in midrange, where vast majority of normal riding occurs. Contact S&S for current exhaust recommendations.

Not convinced yet? Here's more...

If you have an existing 2-into-2 system that uses slip-on style mufflers, whether it is an OEM or an aftermarket system, we recommend the new S&S slip-on mufflers. S&S dyno tests achieve almost 8 more horsepower and 5 ft. lbs. of torque on a stock Twin Cam 88 engine using stock header pipes and S&S slip-on mufflers, and S&S Super Sidewinder engines have produced 1-1.1 horsepower per cubic inch using stock style exhaust and S&S slip-on mufflers. These mufflers will allow your engine produce more horsepower and torque than straight-through drag pipes in street and highway driving, and work equally well on both stock and large displacement engines. If you don't already have an exhaust system that accepts the S&S slip-On mufflers, and you need to buy a complete exhaust system, the RevTech staggered dual, or Python 3 systems work well.

Exhaust selection is critical for optimal performance. Open drag pipes work reasonably well for peak horsepower numbers on some engines but limit low speed performance on the street and can be nearly impossible to carburet. S & S has not had good results with baffled drag pipes due to the increase of exhaust gas restriction (back pressure). Special low restriction Cycle Shack XP baffle is available through most retail suppliers, and will help with tuning in some cases. Overall, drag pipes are a poor choice for street use.

Drag pipes offer nothing to break up the reversion wave pulse. This wave goes down the pipe and then the wave returns back up the pipes. When this wave is in proper time sync to hit the exhaust valve when it is open (pipe length affects the rpm that this happens) it allows the wave to enter the cylinder and when the intake is open during cam overlap it travels across the top of the piston (it is near top of the cylinder at this time) and out the intake valve. This wave continues out the intake through the carb where the next intake stroke draws it all in again. Each time this wave passes through the carburetor the venturi adds gas and makes the next incoming charge richer creating a flat spot or stumble or worse a blubber at this rpm. The longer the duration cam the worse this situation is. Also larger diameter drag pipes and fishtails seem to make this situation worse.

 

I stated to play with the air mixture now i don t know where it was so now i will start the process all over. When i crack the throttle is where it happens no popping or stalling just hesitation What is the easiest way to adjust the accel pump and air mixture thanks

 

Here are my Pilot Screw Setting notes. These are written for a Keihin butterfly style carb, but the principles and procedures are the same ...

Setting The Pilot Screw on Your IronHead

If the carb is old and dirty the pilot screw passage may be gummed up such that you will not be able to "gently seat" the pilot screw reliably. If this is the case remove the carb from the bike and clean it up. Some guys try to do carb work with the carb in the bike. IMO this is a very bad idea.

In the pilot screw passage there should be, in this sequence: screw, spring, washer, o-ring. [Often POs have installed these parts in the wrong sequence; remember that the purpose of the washer is to protect the o-ring from being damaged by the spring]. The screw usually comes out easily. The other parts may require some work. The best technique is to stick a pipe cleaner in the hole, twist it around, and, like magic, out come the other parts on the end of the pipe cleaner.

EDIT: The above info on the pilot screw applies to 1979 and newer carbs. For 77 and older there is nothing in the passage except the screw itself.

1. You need to have easy access to the pilot screw, easy enough to reliably judge "screw it in until gently seated". Loosen the front fuel tank mount bolt; remove the rear fuel tank mount bolt; prop the rear of the fuel tank up on a piece of 2X4; on some bikes this will not be necessary.

2. With the engine cold [so you do not burn your fingers] turn the pilot screw in clockwise until it is gently seated. Count the number of 1/4 turns as you do it; write the number down. Back it out to the original setting. You may need to return reliably to this setting after experimenting.

The "normal" starting point for this process is 1,1/4 [according to the 79 - 85 FM] or 1,1/2 [according to usual practice] turns out.

EDIT: An old HotXL magazine article recommends for Keihin butterfly carbs between 1/4 and 1,1/4 turns out. My experience is that this works best. If you are more than 1,1/4 turns out your pilot jet is too small.

3. The engine must be at full warm up. It will have very hot parts; to avoid burned fingers have a well lighted, comfy place to work.

4. Set the engine idling at about 1000 RPM. You want it to be idling at the slowest speed that is consistent with a smooth idle so that you can hear or feel slight changes.

5. Turn the pilot screw in clockwise until the engine idle becomes worse; tending to stall. Count the number of 1/4 turns as you do this. Then turn the pilot screw out counter clockwise until the engine idle gets good, then becomes worse, tending to stall. Count the number of 1/4 turns as you do this.

6. The best setting for your bike will be somewhere between these two settings. The FM says to use the leanest setting [most screwed in] consistent with a good idle quality. Some guys say to go between the two settings.

It should be between 1/2 and 1,1/2 turns out from gently seated. If it is not within this range you should change the slow jet.

EDIT: I follow the advice from the old HotXL mag article - set it between 1/2 and 1,1/4 turns out.

7. You may have to adjust the idle speed.

8. Make sure that the spark plugs are clean, then ride the bike around your neighborhood for 10 minutes. Keep it under about 15 MPH so that you are on the "idle port", not the "idle transfer ports", the "mid range port", or the "main jet" [see carb diagrams in FM]. Hopefully the plugs will come out a nice medium gray or tan color. If they are too dark you can screw it in another 1/4 turn; too light screw it out 1/4 turn, and try the ride again.

9. If they are really light or really dark the problem is not with the pilot screw setting. For example, too light might mean an intake or exhaust leak, and too dark might mean the pilot jet is too large [among other possibilities].

10. My experience with this process is that after making a change i have to clean the plugs and go for a good ride [say, a half hour or more] before i can trust that the new results are reliable.

 

You do have the Shorty "E" dont You?
If so,turn the pump all the way in till just seated.
Then adj Your air, After Your happy with the idle,turn the pump screw out a quarter turn at a time till the hesitation goes away..Your done.Ride it,just maybe You will need to open up pump another 1/4 turn.

 

yes I do Shorty e I am going to try this tommorowthanks

 

Where is the accel setting usually mine was set at apprx 2 1/2 out

 

1 3/4" pipes with straight cut ends and 28"-30" length works best for drag pipes? Is that with or without baffles or washers in them? I understand drag pipes aren't the best choice but that is what I have. One set is 1 3/4" , the other is 2", both are 40" long. I do have a set of 1 3/4" gooseneck pipes that are old and rusty and crusty. Maybe I could do a little testing with them. I can cut them off at say 29" and rattlecan them flatblack or Kentucky chrome with some high temp paint and give that a try just to compare them.