As you may remember, I decided to design and make spacing tubes for carburetors to place pod air filters behind the frame central tube of Honda CB750 Seven Fifty cafe-racer.
I decided to model these tubes from PVC pipe because it looked like 50mm PVC pipe should fit quite easy. Then I cut them off and formed dents on internal pipes to round the central frame tube.
I had some thoughts about using PVC pipes not only as models but as parts themselves. I tested these pipes for durability and found more than satisfying their strength to mechanical loads. I even designed special aluminum washers and bracket to join all pipes together (to avoid unintentional tube slipping from carburetor). The only question I didn’t solve theoretically was how I can coat PVC pipes into black colour.
But I set a level of my projects high and I couldn’t lower it even on a dime. Even if PVC pipes look good, work good and someone may install them like real, there surely should be someone another who’ll poke a finger on them and be shouting about inadmissibility of using plastic water pipes in custom builds.
So using of PVC pipes was not my way. Yet one friend of mine helped me to find exhaust workshop which specialized on making stainless steel exhaust components. This workshop is on some 500km from Kiev, but I easily explained by phone that I need four custom exhaust pipe reducers, they took my order, we checked out dimensions and in a few days after prepayment my parts where ready.
Still there was a lot of work to do: to align lengths and cut tubes off, to treat the carburetor side ends, to make quite accurate dents on inner tubes so they could round the frame tube (this part of work was quite tricky, I also had to avoid both superfluous tube deformation and lose of roundness). That’s not to mention new mounting system designing, making, aligning and welding, tubes polishing and farther rubbers modifying .
I even had no time to shoot any photos in progress, so that’s how parts looked after I finished my work:
Now about filters. This time I wished to use some special pod filters and found such items on Webike: Kijima pod filters with foam filtering element and very interesting design: