kbait
Commander
- Joined
- Nov 13, 2007
- Messages
- 2,471
J25RLCOS. Spark tested great (5/16"), new QL77JC4 plugs gapped to .030", good compression.
Customer motor hadn't been run in 6 yrs, and started ok, but low speed would run lean. I cleaned the carb spotless (removed welch plug for low speed ports), new needle retainer (low speed needle 'seal'). No change. This one has the primer instead of choke, so I disconnected that to remove the primer as a possible issue by plugged it's feed from front of bowl, plugged primer port at carb base, and plugged tube from crankcase to essentially remove the primer. No change (link/sync is perfect). I can put my hand over carb throat (manually 'choking') and it'll speed up, but will not retain idle unless I do so. Also, doesn't really 'lean sneeze' (maybe just a bit, but not like when low speed circuit is clogged).. just not enough fuel at idle. Throttle needs to be at 'start' and cam must be opening the throttle plate slightly for it to stay running. I can adjust the low speed needle 'in' to make it starve out, and I can open it past 3 turns and it's still too lean.. seems like the needle is working and metering fuel fine, just not enough (Yes, I cleaned the carb again to be sure, and re-replaced the needle retainer to be sure it wasn't leaking air around the low speed needle).
Question: Where is the air getting in? I figure it must be getting raw air in somewhere. I sprayed some carb cleaner around the carb base and intake plate, but no change. Could it be a leaky crank seal? I've heard that the upper seal can let air in and cause this problem. Any advice or possible further tests are certainly welcome. Thanks, and Happy Easter!!
Customer motor hadn't been run in 6 yrs, and started ok, but low speed would run lean. I cleaned the carb spotless (removed welch plug for low speed ports), new needle retainer (low speed needle 'seal'). No change. This one has the primer instead of choke, so I disconnected that to remove the primer as a possible issue by plugged it's feed from front of bowl, plugged primer port at carb base, and plugged tube from crankcase to essentially remove the primer. No change (link/sync is perfect). I can put my hand over carb throat (manually 'choking') and it'll speed up, but will not retain idle unless I do so. Also, doesn't really 'lean sneeze' (maybe just a bit, but not like when low speed circuit is clogged).. just not enough fuel at idle. Throttle needs to be at 'start' and cam must be opening the throttle plate slightly for it to stay running. I can adjust the low speed needle 'in' to make it starve out, and I can open it past 3 turns and it's still too lean.. seems like the needle is working and metering fuel fine, just not enough (Yes, I cleaned the carb again to be sure, and re-replaced the needle retainer to be sure it wasn't leaking air around the low speed needle).
Question: Where is the air getting in? I figure it must be getting raw air in somewhere. I sprayed some carb cleaner around the carb base and intake plate, but no change. Could it be a leaky crank seal? I've heard that the upper seal can let air in and cause this problem. Any advice or possible further tests are certainly welcome. Thanks, and Happy Easter!!
