Re: Changing Carb Jets!
You'll see better hole-shot with the 15, and fuel efficiency will be better.<br />Not a hit, seahorse, but we've dealt with 4000ft on these since the early 70's, and our central distributor at that time (until about 1989) is the people who taught us to set these up for 3000ft+. I've ran 2 sizes leaner in my '97 115 down to 700ft above sea-level with no ill affects. we advance timing at least 2 degrees above 3500, and lean 1 size on mains for every 1500ft. At 4000ft going 3 sizes leaner shows about a 300RPM gain, no plug fouling or any bad signs. we have a 1978 115 with 4 sizes lower with well over 3000hrs, and has had nothing but good PM and no issues.<br />Being at this elevation, and seeing the results of our down-sizing over the last 25 years on conventional carbed engines, I highly recommend he drop down 2 at the least, and he will still have a safety margin.<br />A carbed V4 at altitude doesn't run well at 5000RPM either...thin air, it's not developing anything near designed power, so stress isn't an issue, but 5000RPM would be lugging when running that (factory) rich on the mains. That kills'em quick here.<br />At Dillon in Colorado, at 9100ft, I run 7 sizes leaner and 5 degrees advanced from max, and drop from a 20P to a 15P to get the same R's...I wouldn't have went THAT far lean, but the JohnRude dealer there told me how they set up V4's at that lake...I trust these guys..they were selected to run a bunch of the E-Tec prototypes due to high altitude and cold weather.
