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Folks often complain of poor mileage. I found I get good mileage even with a heavy wrist.
But I have a fairly open exhaust.

I followed the example of the previous owner and drilled the holes under the right side cover (the big black one IIRC). Figuring that was on the opposite side of the main air intake. Then played with duct tape until the air/fuel ratio was about right (not lean).

With the D&Ds I got a very reliable 47-50. Unless I was in the mountains with out a passenger. Then it was all fun!

With the Yoshimura, which is a bit quieter (presumably 3 into 1 and slightly more restriction) I get 45-50. So just a bit less mpg. All on regular (I can't find any advantage in performance or mileage using anything else, but altitude calls for less octane anyhow).
 

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Cyclepath,

When you cut the extra hole, is it in the "front" half of the air box? (The piece that connects directly to the carbs...) Or did you cut the "back" half? (The piece that does NOT connect directly to the carbs...)

I kept thinking you cut the back half, but now that I have it apart (with new jets installed) I'm thinking you meant the front half.

Aaaand... once I got it apart, I noticed my air filter was dry-rotted... CRAAAAAP!!! So, I'm going to "old-school" it and make a custom filter to put in the box instead of waiting for a new filter from Triumph, which would likely take 3 or 4 months. Off to Cycle Gear tomorrow to get some air filter material!!
CajunRider,

Sorry for the late response. I recently picked up a '67 Trophy and I've been spending some time on the Vintage page.

It looks like you've got it figured out. The large hole I placed was in the front air box which effectively bypasses the rear box for a large part. You mentioned a few 1/4 inch holes, I'd do more. The place to do it is on the back of the right side of the front air box, in the same spot where the air comes in from the rear air box on the left side. Those 1/4 inch holes are still somewhat restrictive at high air speeds (high rpms open throttle) so you may not be completely unleashing the beast.

Also, I run my pilot screws out three full turns. Your low speed fueling and popping on decel should both get better with that change.
 
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