Air intake grills.
I think this is my favorite modification to this bike. I really dislike stuck–on non-functional “performance” parts that are purely cosmetic. Like a hood scoop on a car that not only doesn’t feed the engine but doesn’t even let air in (or out) to cool the engine bay. Stock RD’s have this very thing; little plastic louvers on the side cover and oil tank that are just non-functional trims. I suppose they don’t look bad, but the poser aspect has always bothered me. I have seen a fair number of bikes where the builder removed them and filled the recesses in, and you can immediately tell why Yamaha added them; the covers look just too plain without them. I doubt opening them up is actually a performance improvement, but it can’t hurt! So easy enough on the right side cover – just open the fake duct with a die grinder and job done. The left side is another matter, and takes a LOT of determination to match the right side because the left side is the oil tank, and cutting out the duct there cuts straight into the tank rendering it useless. Well on this bike I decided to go ahead and see just how much trouble it would be to make the ducts functional.
Basically I cut the back half of the front of the tank off and welded in a “wall” back up to the front of the tank to seal off the open section. It was then a simple matter to carve out the false duct opening to make it functional. I did a number of other mods to this tank as well: The factory filler pipe that led under the seat was removed and patched over, and the dip stick and vent tubes likewise eliminated. There is also a sight glass in the lower front corner to visually inspect for low oil. Since I feel this is too hard to see making it fairly useless I eliminated it as well. I silver soldered on a steel bung with a vented alloy cap as you can see and while I was at it I flooded my welded up bits with silver solder because I was paranoid it might leak – not the easiest welding work on the very thin sheet Yamaha stamped the tanks out of.
I wanted to make some screens for the openings but decided they looked cheesy with just a flat piece of screen so I made up some 3 dimensional dies out of aluminum plate and pressed up the screens you see here in my bench vise. The first set looked like crap because the wires in the screen intersect at 90 degrees, so I made a jig to clamp a piece of screen in to skew the wires to the correct angle. A lot of work for a simple part and I had to make two sets of dies as there is a right and left side. I simply epoxied them in from the back side after I finished the paint work. Like I said, it was a lot of work, but I still have the dies if I ever want to do this again!
Actually both the side cover and the oil tank are not in their original locations, though it is nearly impossible to tell without having a stock bike to compare to. The reason is that the stock bike is quite asymmetric - the oil tank bulges way out compared to the very much flatter side cover, so I moved the side cover out as far as possible without it conflicting the kick lever and moved the tank in as far as I could and still get to that cap. Also moved them both up a bit to tighten up the gaps. A fairly negligible change but I think it's the small things add up to making an overall nicer finish.
Here is a pic of an original tank for reference.