[Skno]

(This is why I was thinking Too rich. I have a 95"TC with a 195 and 45 slow. I am running the CS slash slip-ons and have my mixture screw out 2 1/2 turns. I have a burble on decel. I just ran it down my street up to 45 mph in 2nd gear then closed the throttle. Lots of burble and some popping but nothing loud. No backfiring.)post by habenaro kid


hab if this is true how do you explain the pop/backfire stops when the enrichner is out a little?


(I was told that the lack of baffling in my Samson exhausts is the problem)post by mtucci

That is basically what i was told




(I've gone as rich as a #50 slow jet and 3 turns out on the idle mix screwand the problem gets better the richer I go but then idle performance suffers because It's too rich.) post by pauliediesel

Bingo! with the twin cam/ I think to get this bike the way i want it i will have to change the exhaust. for now i will deal with it

thanks for the input/any further input would be helpful to those experiencing this problem. As common as it is someone has to have a definitve reason.



skno

 

[BaggerDad]

About a year ago, I got the below explaination about exhaust popping from either an exhaust site or Mikuni carb site.

It is normal for many high performance exhaust systems to moderately backfire or pop after the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.

The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.

Why This (normally) Happens:

1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is delivered to the engine by the pilot (idle) system.

2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.

3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.

4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires.

5) Completely stock Harleys do not do this until open-end mufflers, such as the popular Screamin' Eagle slip-ons, are installed. The exhaust must be both free-flowing and have an open exit for the popping to occur.

Other Causes:

Air Leaks:
Any source of fresh air into the exhaust system can create or worsen the conditions that bring about exhaust backfiring. The most common entry point is the junction of the header pipes and mufflers. Even a small air leak can dramatically increase the intensity or likelihood of exhaust system backfiring. A high temperature silicone sealant, as can be found in many auto parts stores, may be used to seal the pipe/muffler junction.

Lean Carburetion:
While (high performance) exhaust system popping may be considered normal, it is certainly made worse by and overly lean idle circuit.
Be sure that your carburetor's pilot jet is the correct size and that the idle air mixture screw is correctly adjusted before looking for other causes of popping. The procedure for adjusting the pilot circuit is covered in the Tuning Manual.
Ignition:

If exhaust system popping is very loud, very irregular and accompanied by loss of power, then you should suspect that the ignition system is not performing as it should. If, for some reason, the ignition sometimes fires at the wrong time, then exhaust popping can become very energetic (loud). Look for failing high tension leads (plug wires), failing ignition coil(s), switches or connectors as possible causes.

 

[bigblock455]

Well my backfire is cured. I installed a V&H Pro Pipe HS today and the backfiring has stopped. I can't get it to backfire at all. I got the pipes new from ebay for $300 delivered................what a deal. The exhaust note is better than the Cycle Shack slip-ons too. All in all I love 'em. Later

 

[mtucci]

Exhaust Popping

BigBlock455

Looks like the exhaust was at fault. Yes?

I have a 2003 carbureted Road King with a K&N Hi Pass air cleaner,
stock CV carb with a 48 slo jet, and Sampson Silver Bullet slip-on's.

Experience slight popping on decel and deal with it by applying
slight throttle when slowing down.

I'm considering putting on the BuB Sleeper exhaust for H-D FL's. Since
these run $425, I'm not rushing into a purchase until I know how they
sound. My Sampson's have a rich idle sound but are too brash/loud/
annoying/whatever, when cruising. Annoying and tiring when doing
a lot of throttle ups/downs for traffic . So they're going to be replaced
eventually.

Since I do quite a bit of cruising, I need a Harley sound but not a lot of
noise making that the Sampson's put out.

 

[bigblock455]

Yes I would say the Cycle Shack slip ons were the problem. Seems like the bike runs smoother and accelerates longer in each gear with the Pro Pipe. I can't give you any advice on pipes since I'm a 2 into 1 kinda guy but if it was me V&H Pro Pipe or the D&D Fat Cats. I don't care for the way the Thunderheader and the White Bros loop the front head pipe around the nose cones but if you like it those are good pipes too . Later

 

[gtkenney]

I know this is an old subject, BUT.... has anyone solved this crap?

I have a 2003 FXDL (Dyna Lowrider) - new Cycle Shack slip on mufflers. #48 Slow Jet, new needle, tried changing the 190 main to 200. No matter what you do, it backfires on deceleration.

Is the solution to move to new mufflers, or a new carb ? ? ? Has anyone successfully fixed this condition?

 

[mtucci]

exhaust popping

gtkenney

Seems once you remove the stock exhausts off the H-D bikes, all models,
and put on less restrictive exhausts, then the popping problem begins.
I've heard that this is common with carb bikes, injected seem to do better
or not have the problem at all.

I had Samson Silver bullet exhausts and they popped hard. After listening
to all the supposed problem solvers I decided to go with Bub sleeper
slip-ons for my 03 FLHR Road King which is carb.

While I still get some pops, not as bad as Samson and the pops are more
muffled or deeper sounding, so it's not like a crack sound. I've accepted
the fact that popping is with this bike and will live with it. I don't feel like
spending all sorts of cash for fixes that don't work such as carb adjusts,
needle changes, jet changes, etc. Besides I get great mileage 45/47 mpg.

 

[HDWRENCH]

It is normal for the most part. Ihad a set of Supper Trapp mean mothers and they had one of the nastyest crackling on decel I have heard.

One thing that many do is instead of dwon shifting to come to a stop many just pull in the clutch and let the bike glide. My buddy has a set of sampson fish tails on his springer heritage. He loves the sound of normal driving but not the popping soooo.. He just pulls in the clutch . I really dont see the need to be down shifting and letting the bike rev up??

Sounds cool maybe?? not sure I do not do it as it is very hard on B motors, from the one that I have fixed all where damaged on decel.

Lite down shifting is ok but for some they dow it two or three times.

But again normal for most.

 

[mtucci]

Dealing with the Pops

HDWRENCH

Yep, funny how we all deal with the exhaust pops. Not all the time, just
as I feel at that moment I do any one of the following:

Stay in the highest gear I can as I slow down and rely on braking rather
than gearing down to reduce my speed. Eventually though, I do have to
gear it down.

Keep a little throttle on when going down hills.

Then, you get "I don't care if it pops or not" and just ride without doing
all this other stuff.

As I mentioned in an earlier post, my Bub exhaust is quiet as far as pops
go as compared to the Samsons. Any pops I experience now are low in
sound when they do pop.

Bike is a 03 FLHR Road King (carb) with Bub FL slipons.

 

[bigblock455]

Going to the V&H Pro Pipes got rid of all but 10% of my pops. In addition they are way quieter when they do happen. Later.