JimL
11-10-2014, 11:39 PM
In the process of building my Street Tracker, I really wanted the look of a classic V-Twin and a little more power. These pics show the simple manifold that worked out well.
The manifold is a simple 2-bolt exhaust flange made for 1 3/4" pipe (available at muffler shops or industrial hardware stores). The plenum is a piece of 1 3/4" pipe welded to the flange. Leave about 1-2" extra length to allow the end to be sliced, folded, and welded as shown in the first pic.
The inlet adaptors are short pieces of 1" tube, welded into holes cut in the plenum. The trick is to simply cut off the original manifold tubes, bolt them to the heads with duct tape covering the intake ports, and then mark the plenum for drilling 1" holes to weld the short pieces into. I actually positioned the short tubes into the rubber runners, and then spot welded them to the plenum while the manifolds were bolted to the engine.
After the tubes were welded to the plenum, I used a Dremel tool to dress and smooth the openings inside the "back end" of the plenum. After removing the manifold from the engine, remove the rubber intake runners and set them aside.
The end of the plenum, left extended beyond the short tubes, is sliced to allow folding over and welding. Do not try to make all the welds perfect (without pinholes, for example). After the plenum is closed, reassemble and double check fit when bolted to the engine.
To finish the manifold, use JB Weld to glue the steel tubes into the original rubber manifold runners. Coat all the welds with JB Weld to eliminate air leaks. Put wax paper, rags, etc, under the intake port area and bolt the assembled manifold onto the engine for a 24 hour cure of the JB Weld.
The TM28 carb, carb mount, and throttle cable/drum assembly were purchased on Amazon. The carb return spring will need about 3/4"-1" of coil cut off (top end of spring inside the slide) for nicer feel. While you have the slide out, remove the needle and move the clip DOWN one notch on the needle. This will richen the part throttle response.
For jetting, use a 250-260 main jet (I simply drilled an old Short Hex Mikuni jet with a 1/16" drill bit). This runs very well at Sea Level.
You will need to set the idle using "lean drop" method. To accomplish this procedure, adjust idle speed down to comfortable level, adjust for smooth idle, and then lower the idle slightly by adjusting the mixture screw leaner (about 1/8 to 1/4 turn in from best idle). Idle speed can then adjusted up slightly with the knurled knob. This process is necessary to make the engine idle down quickly when the throttle is chopped.
The air filter (small K&N) is mounted to a piece of curved exhaust tubing, to make a little more knee room.
I STRONGLY RECOMMEND angling the plenum/carb mount flange slightly forward. Mine is just a little snug on my right knee for a 6' rider.
The exhaust is constructed of 1" steel tubing, heat painted, baked, wrapped, and clear ceramic painted. The front header is easy, and joins a 1 3/4" collector below the right footpeg. A pair of the 1 3/4" flanges allows the use of an old Toyota Corolla exhaust gasket between the front and rear exhaust systems. If you don't make it 2-piece, you can't mount it on the bike. Front header length is 29" (actually extends a little past the gasket in the collector.
The rear header is a series of curves, entering the side of the collector behind the gasket joint (through a long oval slot). It is also 29" tuned length and actually extends into the chamber of the Super Trapp muffler (also from Amazon).
Results:
Great throttle response, nice slow "loping" idle, quiet exhaust, and cruises "sitting up" at 75 MPH. I was really surprised to find 10 more MPH with just a carb and proper exhaust tuning. Additionally, the fuel pump system is gone and the carb can be disassembled and reassembled without removal from the bike!
Here are the pics.....I will make a "reply" for one more pic.
The manifold is a simple 2-bolt exhaust flange made for 1 3/4" pipe (available at muffler shops or industrial hardware stores). The plenum is a piece of 1 3/4" pipe welded to the flange. Leave about 1-2" extra length to allow the end to be sliced, folded, and welded as shown in the first pic.
The inlet adaptors are short pieces of 1" tube, welded into holes cut in the plenum. The trick is to simply cut off the original manifold tubes, bolt them to the heads with duct tape covering the intake ports, and then mark the plenum for drilling 1" holes to weld the short pieces into. I actually positioned the short tubes into the rubber runners, and then spot welded them to the plenum while the manifolds were bolted to the engine.
After the tubes were welded to the plenum, I used a Dremel tool to dress and smooth the openings inside the "back end" of the plenum. After removing the manifold from the engine, remove the rubber intake runners and set them aside.
The end of the plenum, left extended beyond the short tubes, is sliced to allow folding over and welding. Do not try to make all the welds perfect (without pinholes, for example). After the plenum is closed, reassemble and double check fit when bolted to the engine.
To finish the manifold, use JB Weld to glue the steel tubes into the original rubber manifold runners. Coat all the welds with JB Weld to eliminate air leaks. Put wax paper, rags, etc, under the intake port area and bolt the assembled manifold onto the engine for a 24 hour cure of the JB Weld.
The TM28 carb, carb mount, and throttle cable/drum assembly were purchased on Amazon. The carb return spring will need about 3/4"-1" of coil cut off (top end of spring inside the slide) for nicer feel. While you have the slide out, remove the needle and move the clip DOWN one notch on the needle. This will richen the part throttle response.
For jetting, use a 250-260 main jet (I simply drilled an old Short Hex Mikuni jet with a 1/16" drill bit). This runs very well at Sea Level.
You will need to set the idle using "lean drop" method. To accomplish this procedure, adjust idle speed down to comfortable level, adjust for smooth idle, and then lower the idle slightly by adjusting the mixture screw leaner (about 1/8 to 1/4 turn in from best idle). Idle speed can then adjusted up slightly with the knurled knob. This process is necessary to make the engine idle down quickly when the throttle is chopped.
The air filter (small K&N) is mounted to a piece of curved exhaust tubing, to make a little more knee room.
I STRONGLY RECOMMEND angling the plenum/carb mount flange slightly forward. Mine is just a little snug on my right knee for a 6' rider.
The exhaust is constructed of 1" steel tubing, heat painted, baked, wrapped, and clear ceramic painted. The front header is easy, and joins a 1 3/4" collector below the right footpeg. A pair of the 1 3/4" flanges allows the use of an old Toyota Corolla exhaust gasket between the front and rear exhaust systems. If you don't make it 2-piece, you can't mount it on the bike. Front header length is 29" (actually extends a little past the gasket in the collector.
The rear header is a series of curves, entering the side of the collector behind the gasket joint (through a long oval slot). It is also 29" tuned length and actually extends into the chamber of the Super Trapp muffler (also from Amazon).
Results:
Great throttle response, nice slow "loping" idle, quiet exhaust, and cruises "sitting up" at 75 MPH. I was really surprised to find 10 more MPH with just a carb and proper exhaust tuning. Additionally, the fuel pump system is gone and the carb can be disassembled and reassembled without removal from the bike!
Here are the pics.....I will make a "reply" for one more pic.