Model 49 Tail Muffler

[usabulto]

Hello,

New here,

I am rebuilding a 1969 Sammy Miller M49. I say rebuilding, rather than restoring, because I am not trying to keep it "exactly like when new". Just want a good solid bike. I am about to complete the frame, tank, side covers, and muffler. I started with two bikes, one the Sammy Miller and the other a 1970 M49 that I am using as a parts bike. The parts bike had a SuperTrapp T-99 Spark Arrestor in place of the triangle box end muffler that comes stock. It was mounted with a piece of rubber hose connecting it to the main muffler. The stock one from the SM bike simply isn't usable.

The SupperTrapp spark arrestsor has 9 baffle plates and a half inch pipe thread. It has very little restriction to flow. See pic.

http://s916.photobuc...zps1237362d.jpg

I decided to try to make use of the SuperTrapp arrestor, but I really didn't like the way it had been mounted. In cleaning up the stock main muffler, I discovered that it is made out of copper....yeah...all copper; so it's something that can be soldered. I visited the local hardware store and got a few brass plumbing fittings and made up what I think will be a suitable configuration. See pic

http://s916.photobuc...zpsa0c427f3.jpg

The fittings consist of a two inch piece of striaght pipe, a coupling and a 45 degree nipple, all silver soldered together to the main muffler. See Pic.

http://s916.photobuc...zpsf316f16a.jpg

When mounted, it points down at about a 45 degree angle and away from the rear tire. I will have to fabricate a support from the top shock bolt just ahead of the spart arrestor. As to how this setup will affect engine performance, I don't know, yet. I hope it knocks down the exhaust bark some. The stock box tail end muffler seems more restrictive than the spark arrestor, but I will just have to get the rest of the bike together and try it out. Just thought I would pass along this bit of my rebuilding experience. Any and all comments welcome.

Edited September 24, 2012 by usabulto

[usabulto]

Well, after trying very diligently to make it work, I had to remake the fittings for the muffler. The end of the pipe and muffler were just too close to the rear tire. Don't know why I didn't think of it the first time around, but realized I only needed to use a female/female elbow fitting and didn't need the coupling. This time went with a 5 inch nipple and an F/F 45 degree elbow. Think this one will work.

http://s916.photobuc...nt=IMG_1606.jpg

Bt the way, can anyone tell me how to post pics without posting your entire photobucket album? Thanks.

[usabulto]

Hello,

Here is a pic of the complete exhaust system for my Model 49. I had the header pipe re-chromed and installed a new rubber coupling. Need to get a couple of stainless steel hose clamps and another can of black engine paint to finish up. I am waiting on the fellow to get back to me with the crankshaft. Once I get the crank back, I can begin to assemble the engine. The rest should be just a matter of putting parts back together....I hope.

I see that quite a number of people have viewed this thread. Does anyone on this forum reply, or comment......or are new members just boycotted until they say some sort of magic words?

[feetupfun]

I have a lovely 1968 M49 so am always interested in other peoples M49s. I was pretty shocked and speechless initially with you making a tailpipe using plumbing parts, but accept that everyone has their reasons for why they do things. You did ask for feedback though so here is my 5c worth:

The main section of the exhaust is probably not made of copper. Maybe it has been repaired using bronze welding which made it look like copper. Those mufflers are usually made of pressed steel. I can even see the weld along the seam on yours so it's probably just a normal Bultaco item made of steel.

By using such a long tailpipe of such small internal diameter, combined with the 45 degree elbow and the steps in internal diameter that accompany the use of BSP plumbing fittings, you have probably created a design with more resistance to flow than the original triangle muffler.

The piece of 1/2 steel pipe and the gal elbow with the super trapp on the end will put a lot of load on the end of the Bultaco muffler when you ride the bike on rough ground so probably need to be supported from the frame somehow.

That is a pretty cool idea to use that super trapp muffler and I'm wondering what it came off. I haven't seen one with a 1/2 BSP thread on it before and was thinking maybe it came off a Briggs and Stratton stationary engine because they have a threaded exhaust port. One thing about the Super Trapp is that because the gas comes out all the way around it is hard to avoid the exhaust gas overheating things in line with the louvres. I managed to melt the edges of a few rear plastic guards when I had a super trapp on my 4 stroke enduro bike in the 1980s. I figure that might have been why you relocated it from where the previous owner had it mounted. Another way around the heat problem is to fit a heat shield part way around the outlet of the louvres. That did work for the heat problem, but after the super trapp fell apart for the fifth time despite reinforcing all the bits that failed previously, I put a normal muffler on.

A super trapp on a M49 will have a much easier life than on a 400cc hotrodded 4 stroke enduro bike so it probably won't self-destruct for years.

An alternative way to fit a low resistance tailpipe and muffler is to use smooth bore steel tubing of approx 22mm ID leading to an absorption muffler supported from the rear frame loop. If you need it to also be a spark arrestor, then something like a TY175 or TY250 muffler would do the trick. That size tubing should fit inside the shockie, and additional clearance for the tyre if necessary could be gained by making the tubing flat-sided where required.

Regards

David

[usabulto]

Feetupfun,

Thank you for your reply and helpful information. When I first looked at the main muffler before I started to clean it up, it appeared as if there were abrasions through the paint that sure looked like copper. If you will go back and look at the all of the muffler photos, you will see that the last small tip of the main muffler definitely is copper. I would have to agree, now, that the rest of the muffler is probably steel. As for the diameter of the tail pipe I am using, I measured it and though it is a nominal half inch, it measures a little over 0.6" (15 + mm) ID. Your 22mm is nearly an full inch. The stock diameter is not that large and the parts book shows a connector that must be 4-5 inches long that turns 90 degrees before it connects to the stock triangle muffler. That bend must also slow down the exhaust gases quite a bit.

I am not taking issues, I am just clearifying. I do appreciate your comments. One of the bikes I started out with came with the SuperTrapp and it was fitted with a 4-5" section of rubber hose. I didn't much like that set up. The other had the stock triangle muffler, but it was really beat up and really not usable. In concert with your comment, I have already started making a support for the tail end. See pic below. I will use some sort of padding around the tail pipe where it fits through the support and tighten up the cross bolt "just enough". I used the 45 degree elbow to get the SuperTrapp away from the rear tire. Even now, it will only have about a couple of inches clearance from the tire. I hadn't even thought of how the exhaust would blow out all around the SuperTrapp. Thanks, good information to know.

I had to chuckle when I read your comment on the plumbing hardware. Back over 40 years ago when I worked in a dealership, the shop foreman, who was a british bike fan, used to say that Bultaco frames where made out of water pipe. I am sure he was kidding, but then I do remember reading more recently that the choice of frame materials was the reason that Bultaco broke off from the Rickman brothers. That kind of made me think........regardless, the strength of the design and low weight of the Bultaco frames always impressed me.

Getting back to your introductory remarks, I believe that my M49 will be quite nice when finished. It has been a ground up rebuild. Below is a pic of where I am at now. The engine is getting all new bearings and seals. The rod bearing looks and feels good, but I am having a machinist check it out. I have a 28mm flat slide Mikuni and leonelli electronic ignition for it, which I hope are not hard to figure out and tune.

I first had the idea for this project about 5-6 years ago and am just now getting on with it. I chose orange because that is the color I painted my MK4 Pursang that I raced scrambles and flat track from back in the early 1970's. Working on this project has definitely brought back a lot of long lost memories.....most of them good. Cheers and thanks for your 5c worth.

Regards, John

Edited September 29, 2012 by usabulto