Hitchcocks Forum

Now I know this won't apply to many people here but just in case you are still running the stock exhaust and air filter do not hesitate to upgrade it. I fitted our hosts british made exhaust system, fitted a cone filter and rejetted the carb. I have just completed a 1hr run back from watching the olympic road race in surrey to my home. I could not believe the difference it made, the bike runs so much better and the extra grunt up hills is well worth it. I kept mine stock for 5 years (350 iron barrel) - i wish i had changed it sooner, if it is left stock you are not getting the best out of these wonderful bikes.

Yep, did the same when I had my Sixty 5 a few years ago. Put a cone filter, changed throttle slide and jetting. Already had the short silencer fitted when I bought it. Made a significant difference to the stock set up.
As Rustygman says - highly recommended!

Rusty, an even better mod, especialy for the 350, is a close ratio conversion. It gets rid of the huge gap between 3rd and top. Makes the bike so much more flexible. You'll know how hills tend to make a 350 pant? Well with a higher 3rd gear you can drop down without revving it's nuts off.

Yup, best mod I ever made to my 500 iron barrel Classic