These engine kits come with a cheap looking, ugly thing that they call a "chain tensioner". All it is, is 2 pieces of steel, with a plastic wheel mounted to it with a nut and bolt. There is a bearing in the center of the plastic wheel, but the wheel itself is just cheap plastic. The whole assembly is ugly and cheap looking. You are supposed to bolt this thing around the lower bike frame tube and run the chain over the wheel. When I see these on motorized bikes I cringe because they are so ugly, and so cheaply made. about 85% of the people who build these bikes, use this tensioner wheel...I threw mine in the garbage.
Here's what it looks like.
There was no way that I was using that tensioner wheel on my bike because it looks like a turd, and they do not work well at all. I made my own "chain tensioner." it's more of a chain guide than a tensioner. The sprockets with these kits tend to not be machined 100% precise and a lot of times the sprocket centering hole will be off center, causing the chain to go "loose, tight, loose" as the wheel spins. My chain guide allows the chain to slide across it's surface adding downward pressure when the chain gets to it's loose stage in it's rotation and letting the chain just skim it when it's in it's tight stage during rotation. It just keeps tension on the chain when it goes loose during the rotation and it does exactly what it's supposed to do. I made it out of very hard delrin /nylon, and I cut a wedge shape on the bottom face of it to match the angle of the chain. It's hidden on the inner top frame rail and is screwed to the frame through a small hole that I drilled.
Here's what it looks like...much better than the one that comes with the kit. It looks a lot better, is stronger and does a better job than that plastic wheel thing will do.
Now that I figured all of that out, on to the exhaust.
The engine kits come with a short pipe that bolts to the cylinder with a 90 degree bend, and then right into a "muffler". The muffler ends up hanging straight down at the ground and they look cheesy. the mufflers have an internal baffle that literally chokes the flow of exhaust in an attempt to make the exhaust as quiet as possible. Any gear head knows that a free flowing exhaust makes more power.
Here's what a stock pipe and muffler looks like.
The stock pipe and muffler will not fit an o.c.c. frame and the muffler ends up hitting the cranks. Besides that, I do not like the way the pipe and muffler look. they do not flow freely enough, and almost every motorized bike that you see has this same pipe and muffler on it. I am going for a more custom look here, so I made my own exhaust by cutting up 3 pipes and mufflers.
I bought this long pipe off e-bay for $30.00, but I needed it to make the pipe that I wanted to make. I used the short pipe and muffler that came with my engine kit, this long pipe, and a few pieces from a pipe and muffler I had from another bike.
Here's what the long pipe and muffler looks like, unmodified.
This long pipe is ok, but the end of the pipe with the flange on it that mounts to the engine is too short and the pipe would hit the cranks before I was able to even get it bolted to the engine. I cut the flange end of the pipe off and added about a 4 inch section with a flange on it, and welded it back together. Here's the pipes all cut up while I was trying to figure out how much I needed to add to the long pipe.
After getting the pipes cut and welded back together to make the pipe clear the cranks and the frame, I needed to do something about where the 2 pieces of pipe were welded together. I decided to add 3 chrome steel rings around the weld to give the pipe a rippled look like old style lake pipes.
I just tack welded the rings to the back side of the pipe and I think it gives the pipe a custom look and the rings look better than just a bare weld on the pipe.
For the muffler, I modified the stock muffler by pulling the baffle and end cap out and drilling 2 small holes in the baffle plate for better flow. Then I cut the end of the muffler housing at a 45 degree angle and pushed the baffle and end cap back up into the muffler housing to hide it. The baffle and end cap are secured to the muffler housing with 3 pop rivets hidden on the top, bottom and side of the muffler housing under the muffler support bracket. Then I painted the inside of the pipe gloss black to further hide the baffle that's up inside it. At first glance, it looks like a big open straight pipe.