I installed a YS140L on my 1/4 Cap 232 and got the cowl to fit nicely after creating clearance for the YS valve cover. However, there is interference with the twin exhaust pipes on the Slimline Pitts style muffler as they contact the bottom of the cowl within an inch of the cowl being in final position. I can cut two oblong slots in the bottom of the cowl to allow the exhaust to slide through, but I was hoping to create just two small holes big enough for the exhaust tubes to protrude through. Any ideas?

Joe

I was thinking the same thing when I put a pitts on my Cap. I ended up cutting two slots for the exhaust tubes. You have to look real close to see them in the air. The slots will help draw air from the cowl intakes and keep the exhaust tubes cool.
I laid a piece of thin card stock on the fuse such that it overlapped the exhaust tubes and taped it in place on the trailing edge. Cut slots in the card stock till it was parallel to the fuse. I then flipped the card stock up, took the pitts off, and mounted the cowl. I flipped the card back down, transferred the slots to the cowl via dry-erase markers, and dremelled them out-little by little.
Worked like a charm and hardly noticeable.

Someday I'll get that scanner/printer/fax machine so I can post pics!

Joe:

It looks neat when only the tips come thru the cowl, but is the
bottom of the firewall beveled enough to let the heat out. 4 s
engines don't like to be in an enclosed cowl without plenty of air
outlet. Exit opening should be about 3 times the inlet size.

jazzy...thanks...that is what I was thinking of doing

rreiss... there is already a good size cutout at the rear bottom of the cowl on the H9 Cap. A little more would not hurt..

Joe

I actually used a two-stroke with a pitts. The outcome is pretty much the same though.
It is important to cut a nice half-moon where the cowl meets the bottem of the firewall/fuse for air draw.

(I suppose 'sickle moon' would be a better term... You know what I mean! )