[Samir72]

My silencer just fell off as I crossed some railroad tracks and it's gone.
Aside from the noise, will riding w/o a silencer do any damage to the engine?
Since the silencer has been on backorder forever, can someone recommend another source?

Thanks

[1 Thump]

Depending on how much baffling was present in the muffler you will be running lean to very lean. Lean is not good for these bikes. Mufflers are cheap:
http://www.nichecycle.com/ncs/index.php/categories/exhaust/mufflers.html

[Samir72]

Which way do I turn the screw to get richer? I looked at a few posts and people are not in agreement about the direction. If it's an airflow screw, closing it should restrict air and make it richer I think.
I have a CV Carb BS29 on an AVL Bullet Chrome 2009.

[tooseevee]

Which way do I turn the screw to get richer? I looked at a few posts and people are not in agreement about the direction. If it's an airflow screw, closing it should restrict air and make it richer I think.
I have a CV Carb BS29 on an AVL Bullet Chrome 2009.

       It's not an airflow screw. It's a fuel flow screw.

        Clockwise will lean it out.

         Counterclockwise will rich it up.

          You might not be dangerously lean because you still have the very restrictive hot tube in the header pipe, but I'd keep the cruising at highway speeds for lengthy times to a minimum.

[KB8ANY]

Baffling affects 2-stroke engines but not 4-stroke engines.  So it won't do anything to your engine.

When the piston pulls in the fuel-air mixture, the exhaust valve is closed.  Then, when the piston pushes the waste gas out, the intake valve is closed.  In between both valves are closed.

Good luck.

Paul

[tooseevee]

Baffling affects 2-stroke engines but not 4-stroke engines.  So it won't do anything to your engine.
Good luck.
Paul

             If you want to believe that, fine, but it is totally not true.

[High On Octane]

Baffling affects 2-stroke engines but not 4-stroke engines.  So it won't do anything to your engine.

When the piston pulls in the fuel-air mixture, the exhaust valve is closed.  Then, when the piston pushes the waste gas out, the intake valve is closed.  In between both valves are closed.

Good luck.

Paul

That is incorrect.  Running any 4 stroke motor without a baffle will burn out your valve train and can damage your pistons.  4 stroke motors NEED back pressure in order to scavenge power from the exhaust.  NOT running some type of muffler will damage the motor.

Scottie

[ERC]

I'll second those opinions.  ERC

[Ice]

 4 Strokes can be run successfully with open exhaust I.E. no restriction IF they are jetted for it.

 Removing the muffler from an otherwise correctly jetted bike creates an incredible lean condition. Not good at all and like Scotty J said it damages valves and pistons.

[KB8ANY]

Yo y'all:

The exhaust gasses that have gone down the tube have no effect on the intake.  They can't - the exhaust valve closes before the intake valve opens and the pressure in the cylinder at TDC is almost exactly neutral.  It has to be, or otherwise the whole thing wouldn't work.

The fuel air mixture comes in is because of the partial vacuum created by the piston going down - and that is the only thing it "sees," so to speak.  The incoming fuel air charge doesn't even know there is an exhaust valve or anything - it is chasing the vacuum.

Sure the jetting affects performance.  Sure obstructions in the exhaust ("baffling" by definition is not an obstruction) affects the engine performance.  But these are different things.

When I changed the exhaust in my scooter I had to change the jetting - but that is because it is a two-stroke, and by design relies on the back pulse (what I think you mean when you say back pressure ) to push the incoming charge back into the cylinder just before the piston port closes.  But that is the way two-strokes work.

(Dare I say) Good luck ?

[D the D]

KB8ANY,
Run your Enfield without a muffler and no rejetting for the rest of the year.  Well, until you hole your piston, which you will.     Then when you post asking about replacing it you can explain as to why it had nothing to do with the lean condition induced by removing the muffler. 

[Bullet Whisperer]

KB8ANY
There are whole chapters in books about exhaust systems and their 'tuned lengths' etc for best performance from 4 stroke engines. After many hours on the dyno with various Royal Enfields, including our race machines [both of which have won numerous races over the years], testing all sorts of stuff including exhaust systems, I can assure anyone who thinks otherwise that the exhaust system should be considered to be part of an efficient, well set up engine. No exhaust pipe at all on our race bikes would knock at least 25 percent of the power off and send the various other settings all to cock.
 As for the incoming charge not even knowing there is an exhaust valve, all 4 stroke engines I have encountered have a thing called 'valve overlap', where, at the 'other' TDC, both valves are partially open and tuners can take advantage of this even more so than manufacturers - the incoming charge can be pulled in with the aid of the outgoing exhaust charge in a number of ways [which the whole chapters in various books explain].
 No exhaust on a machine designed and set up for one = less power and less engine life. Take it from me, if not, maybe 'Ace' will see this and say something you will accept.
 B.W.

[tooseevee]

Yo y'all:

The exhaust gasses that have gone down the tube have no effect on the intake.  They can't - the exhaust valve closes before the intake valve opens and the pressure in the cylinder at TDC is almost exactly neutral.  It has to be, or otherwise the whole thing wouldn't work.

The fuel air mixture comes in is because of the partial vacuum created by the piston going down - and that is the only thing it "sees," so to speak.  The incoming fuel air charge doesn't even know there is an exhaust valve or anything - it is chasing the vacuum.

Sure the jetting affects performance.  Sure obstructions in the exhaust ("baffling" by definition is not an obstruction) affects the engine performance.  But these are different things.

When I changed the exhaust in my scooter I had to change the jetting - but that is because it is a two-stroke, and by design relies on the back pulse (what I think you mean when you say back pressure ) to push the incoming charge back into the cylinder just before the piston port closes.  But that is the way two-strokes work.

(Dare I say) Good luck ?

           Yo?

           Your understanding of engine theory is just totally confused & you are just plain wrong on what exhaust systems can do to & for engines & you don't know what you're talking about. You keep on with this & all you're doing is confusing those new riders who are trying to learn how to get the most out of their learning about engines.

          The stupidest thing you keep saying is that baffling or not baffling has no effect on 4-strokes, only 2-strokes, is just plain ridiculous & you also don't seem to know valve timing theory or pressure wave theory.

            If you want to believe what you're saying, fine, but you're just muddying the water here with for new riders. 

[ace.cafe]

KB8ANY
There are whole chapters in books about exhaust systems and their 'tuned lengths' etc for best performance from 4 stroke engines. After many hours on the dyno with various Royal Enfields, including our race machines [both of which have won numerous races over the years], testing all sorts of stuff including exhaust systems, I can assure anyone who thinks otherwise that the exhaust system should be considered to be part of an efficient, well set up engine. No exhaust pipe at all on our race bikes would knock at least 25 percent of the power off and send the various other settings all to cock.
 As for the incoming charge not even knowing there is an exhaust valve, all 4 stroke engines I have encountered have a thing called 'valve overlap', where, at the 'other' TDC, both valves are partially open and tuners can take advantage of this even more so than manufacturers - the incoming charge can be pulled in with the aid of the outgoing exhaust charge in a number of ways [which the whole chapters in various books explain].
 No exhaust on a machine designed and set up for one = less power and less engine life. Take it from me, if not, maybe 'Ace' will see this and say something you will accept.
 B.W.

I agree with BW and the others about this.

I also agree that the hot tube restrictor in the end of the header pipe will act to somewhat mitigate the effects of losing the muffler.

It's best to either put another muffler on there, or re-tune the carb mixture to compensate for the change in exhaust system.

[KB8ANY]

Ace:

Sounds too exotic for me.  I would be afraid of the piston hitting the exhaust valve at the top of the exhaust stroke, even with cutouts in the top of the piston.  I also don't understand how, if both valves are open on the intake, part of the incoming fuel air mix isn't simply pulled out the exhaust and down the tube by the partial vacuum created by the outgoing exhaust, since there is nothing to stop that.  But like I say, too exotic for me.

I'm sure the instructors at our local technical college will have some enlightening comments for me about this thread.

Thanx & good luck.

Paul