XS360 jetting

[cosworth]

I live at sea level. Bike is bone stock except for pamco ignition, and a Mac single wall exhaust. 2 into 2. Carbs are stock. Mixture screw is 4 full turns out. If I set them to the stock 1.5 turns out, it pops a lot on decel.

Plugs are iridium and look great. I love how it hot idles so perfectly with the pamco and these plugs. Zero hiccoughs.

On choke when cold it doesn’t rev up, just idles and I have to rev it. It might be getting too much fuel on choke, but the plugs don’t show it. When it’s warmed off choke, it runs quite nicely. My thoughts are to go back to maybe 2 turns out, and move the needle up a notch. Or just reset the carbs to stock and change the pilot jet up on increment. I don’t really know if the sorta sleepy cold start is just the bike or the jetting. Carbs are ridiculously clean. Trust me. Ultrasonic. Welder tip cleaner. Sea foam often. I re-filter my own fuel at home even.

I’m not tuning for power. I’m tuning for rideability. And I ask because experimenting is a pain because the 360 intake tube is very fragile at this age and I’d rather ask than mess around. Hoping to save taking the carbs off 10 times.

 

[xschris]

Have you checked float height? That can effect rich/lean conditions. Syned carbs with manometer? That could cause popping.

 

[cosworth]

Yep to both. I have a really nice manometer too.

 

[xschris]

With aftermarket mufflers you would have to expect some "other than stock" adjustments for the carbs to work its best.

 

[NewHavenMike]

You shouldn't have to change any jets with that setup. My 360 doesn't rev high when I use the choke either. If I rev it with the choke, it may stay around 2500 for a bit. I usually will adjust the cable to idle a bit higher before turning it back in when I take the choke off. My bike doesn't like the cold weather either. It is hard to start when its cold. Even harder when I had the Pamco installed. I keep my stock 17.5 idle jets between 2.5 and 3 turns out. Needle jet is dropped one notch and main jets are 132.5. Stock airbox, points ignition, and stock headers with tapered slip on exhausts.

It seems as if I get some exhaust popping when the valves are out of spec and the timing is off.