Shorty Cocktail Mufflers

[mitchp]

I have got my 1976c model running pretty good. Accelleration is good, no flat spots. The plugs are starting to show a coffee with cream color. So far im very happy with how this old nail is shapeing up. Now my question, the bike is doing the backfire sound of those Hardly Dividsons with the chopped shotgun exhausts, on decellaration (engine braking) i think the backfire sound sucks. The bike came to me with aftermarket mufflers. They are rather short, and i believe they are called cocktail shakers. They look kind of cool and maybe period correct, Are these mufflers causing the backfire becouse they have very little backpressure, or can i make a carb jetting adjustment to quiet this beast down. I am running 127.5 pilots. Intake manifolds are nicley sealed. Im running the stock 38s with the stock airbox. Mitch PS Is it possible to find a original new set of S/W shocks?

[grizld1]

Carburetion may not be your problem, Mitch. If you look closely at a head pipe you'll notice that there are two holes in the outer wall, one near the head and the other near the outlet. The holes are there to vent off expanding air when the pipes heat up. If the clamped area of your muffler doesn't seal the hole near the outlet tightly, air will be sucked into the mufflers, and the exhaust will pop under engine braking. The "tell" for the condition is often a bit of soot near the muffler clamps. Try cleaning up the outlet ends of your pipes and refitting the muffs to cover the holes. If they still give you trouble, there's a product called Chamber Seal that may help.

[pamcopete]

If your stock headers are double walled, the functional pipe is inside the outer pipe, so if you are going to use the stock headers with an after market muffler, you need an adapter that will connect the muffler to the smaller inner pipe. And, yes...the outer pipes do have holes in them, so if you just clamp the muffler to the outer pipe, the exhaust will leak out of the holes .

The outer pipe may also leak at the head flange as well. The outer pipes were not designed to flow any exhaust, so there is no guarantee that they are gas tight from end to end.


I used this adapter on my '81/H:



This is a 1 1/2 X 1 3/8" adapter available at most auto supply stores, #548520. The small end will fit tightly around the outside of the inner pipe. Clamp the muffler around the large end. There is no way to clamp the small end around the inner pipe, but it fits real tight, so you can either wait for the carbon buildup to seal it or apply some Permatex muffler sealer.




The small end is completely hidden inside the header, the big end is completely hidden inside the muffler.

This is what it looks like when installed.

[grizld1]

That's the case only for late 1-piece pipes with welded-on mufflers that have been cut off. On earlier pipes the OEM mufflers were attached with a compression nut and the ends of the inner pipes were flared out and welded to the outers, sealing them. There's no need to cut off the ends and cram in an adapter unless the pipes are so nasty that a seal can't be achieved under the clamps.

[pamcopete]

grizld1,

Yeah, I thought that the earlier pipes were different. Thanks for the explanation.

[Tom Graham]

Mitch,

A bit of micro debris may be plugging or partially plugging an idle jet. Quick fix is to remove the mixture screw and spray carb cleaner in teh hole to blast the idle jet plugging dirt back to the float bowl.

Tom

[mitchp]

I have just installed my new carbs and am ready for new mufflers to replace the short cocktail units. I want to run the stock headpipes for now. I see Mikes has a few different styles and lengths, all of which have a description of sound levels such as nice tone, good sound etc. My short mufflers which are on the bike are mechanicley baffled and in my opinion are a bit to loud. I like a good throaty sound within reason and would be nice to pick up a couple of horsepower. Anyone like to weigh in on this subject. Mitch

[grizld1]

The very inexpensive Emgo Road Hawk wide mouth bell muffs (they closely resemble the OEM muffs on late Specials) are excellent value for the money on a stocker. Flow characteristics are close enough to OEM that I've never had to alter jetting for them. Baffles are fixed mechanical type and may be quieter than what you want to hear, but you can always open them up a bit.

[mitchp]

Where can i get these Emgo units?

[grizld1]

Most of the major suppliers have them: the Emgo number is 80-84013. I bought a pair for a D-model I was refurbishing a couple of years back from www.powersportssuperstore.com ; the muffs are currently out of stock there, however. A Google search will turn up some sources for you. The big distributors offer the Emgo line as well, you might be able to order them locally.

[mitchp]

Hey Griz, thanks for your input. My local vintage shop Rusty Riders can indeed get Emgo muffs, Message to Tom G, please post a pic of your 77D model, i would love to view it. As i told you before, my home shop is right down the road from you. Mitch

[Tom Graham]

Hi Mitch,

Sorry, I don't have a good picture to post but we can get together this spring at Woodland's Tavern on 3rd Ave. just east of Northwest blvd. in Grandview. Happy Hour all night, $2 for any 16 oz. draft and they have the good stuff! A group of cycle guys meet every Monday evening to shoot the bull. Everything from tatooed 20 year old artists to concealed carry retired conservatives (and then there is me!) The guys got together through VinMoto, a loose email group with vintage motorcycles as the glue. Google and click on the Col. Ohio button.

About mufflers. I am all about sound and have strong opinions about what sounds best. One of the nicest sounds is the stock mufflers with the blocking plate punched off the inside of the outlet tube. The exit tube is 8 to 10 inches long with a plate lightly welded to the end that is inside the muffler. There are ~1/4" holes in the tube to strain the sound though and restrict the flow. By punching off the end plate, the exhaust can flow out the exit tube. The exhaust flow is increased enough that going one up on the main and pilot jet is recommended. I also lifted the needle one groove and use K&N pods. The sound isn't loud but is very low and powerful sounding. Riding, I heard a low purr at light cruise, a distinct deep blump, blump at idle and a muted low roar at full throttle. It's hard to beat that sound.

Along with the mufflers griz suggested is the Emgo Dunstall copies. These are period correct, 27" long tapered cones with a wide O opening. These are repackable with fiberglass or stainless wool. The removable 'baffle' is a long tapered 1 3/4" perforated tube with a perforated plated welded in the middle. The plate can be knocked off if you want the mufflers a pure straight through. Good looking, very good sound, free flowing and traditional 60's/70's British cafe mod. I put real Dunstall's on my Norton in the spring of 1972, have them on my old Triumph currently.

You might want to get in touch with the guys at Venturi Moto. It's a bike shop specializing in old bikes, Japanese, British and European. They are getting together that old time bike shop vibe with stuff to look at, a library and coffee. I go to hang out and tell them old man bike stories. (over and over probably) Matt and Keith can get parts for you and do the tough work an owner can't do. Keith's go to bike is a '72 XS650 so he is very well versed.

www.venturimoto.com

Tom

[mitchp]

Thanks for the info Tom. I will keep you posted on the muffler install. I should be able to ride to the tavern this spring as Monday is one of my days off. Look forward to hanging out with a bit of bench racing. Mitch.

[650leo]

I had the stock mufflers punched out. They did sound good.
I replaced them with Emgo #80-84052, they sound very close to the same as the punched out stockers, but weigh much less and are shorter.
I like them becuase they end just infront of the rear axle. This makes getting the rear wheel off much easier.
One more thing, The clamps that come with the mufflers are crap, won't seal the muffler to the pipe. Go to your nearest Harley dealer and get the 1 3/4 inch clamps. Cost a bit but worth it.
Leo

[orion61]

There are two other things that can cause backfire while slowing or going down a hill, first is an engine running too lean of fuel, (it also runs hotter)

also retarded timing can cause backfire too, just as too much advance can cause carb pop.

Cousin Larry