Lean, mean, fightin' machine

In between chores tonight, I had about an hour or so in the shop. I took the opportunity to mess with the carbs a little.

Last year (has it been that long?) when I first started the engine, I was getting lots of popping and spitting back out the carbs at and just off idle. I had heard that this is usually indicative of a lean air/fuel mixture, so I decided to try swapping out my 0.55 idle jets to 0.60 size. This seemed to fix the problem, but I always thought it ran a little too rich, even with the mixture screws turned in pretty far. The exhaust smelled really rich at idle, and although I didn't keep track, it seemed my mileage was really bad.

Since I still had the engine cover off, it was the perfect time to make some changes. I decided to drop back down from the 0.60 jets to the 0.55 jets. Now that I'm much more familiar with 308 engine tuning, perhaps I can use the 55s and still get rid of the carbs spitting. Burning less fuel and getting better mileage won't hurt either.

Once the air cleaner housing is removed, it's really easy to change out the jets on the Weber DCNF. The idle jets are on each side and the main jets are in the center. It took me all of 15 minutes to swap out the jets. I started the engine, turned out the mixture screws a little to compensate for the smaller jets and balanced the carbs again. The result is not bad -- I let the engine get up to temperature and there is almost no popping or spitting. The next free moment I get, I'll put the engine cover back on and go for a little drive to test out the new jetting. Also, since I replaced the XR-700 ignition units, hopefully my misfire issue has been resolved.