Rich?

[Chachiboy]

New to me 1978 XS650 running rich. Let me start by saying i'm not technically savy (YET!) but my beast is running rich. Black spark plugs, backfiring, lost of power etc. After almost every ride, i clean out the spark plugs. The air/fuel screws are about 2 or 2.5 turns out of the recommended 1.5. Any recommendations? My next thought is the air filters. My bike is stock, which ones should i buy?

 

[RustiePyles]

New to me 1978 XS650 running rich. Let me start by saying i'm not technically savy (YET!) but my beast is running rich. Black spark plugs, backfiring, lost of power etc. After almost every ride, i clean out the spark plugs. The air/fuel screws are about 2 or 2.5 turns out of the recommended 1.5. Any recommendations? My next thought is the air filters. My bike is stock, which ones should i buy?

What Kind of carbs, BS38's?

 

[5twins]

How many miles on the bike? If 30K+, your needle jets may be worn out. The plugs on my '78 have been getting progressively darker over the last few years and are now pretty black. Nothing has changed on the bike as far as tuning parts (jets) or mods (exhaust, pods) so I'm thinking the needle jets in the original carbs are worn. I recently swapped an eBay set of '78-'79 carbs onto my '83 and while it ran well, the plugs were black. The needle jets were rather beat up but I decided to try them anyway. I swapped in new ones and the plugs have lightened up nicely. I have new ones on order for the '78 and hope they will fix it as well.

The recommended mix screw setting for the '78-'79 carb set is 2.25 turns out, so your setting is probably good. Remember, these factory settings are just a recommended starting point. From there, you need to fine tune them for best running (smoothest and fastest idle). I think when my '78 was mostly stock, that worked out to be about 2 5/8 turns out.