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Just rebuilt a 93 SL650, and have an odd problem. It acts flooded when starting hot or cold. The motor is a fresh rebuild with 138-140-140psi compression, it held 15psi pressure in crankcase for 4hour, and held 26" of vacuum in case for 2hr. The engine was timed with Snap On timing light at factory inches BTDC. It has 3 new BR8EIX plugs in it, new plug caps with trimmed back wires, and spark registers 25-30kv on tester on all three cyl, which is about 3/4" gap.
With all this, I know three components of running are great, engine sealing, compression, and adequate spark at proper time. All that is left is proper fuel. I replaced the stock pump with new triple outlet pump, replaced all the fuel lines, eliminated vacuum petcock(was already missing), and installed new fuel filters between both pick-ups and petcock, and new filter between petcock and pump. The carburetors all have brand new kits, and diaphragms in them. I set the pop-off to 16psi (spec is 10-18), the lever is perfectly level with casting, and the needle&seats will hold 15psi all day. The mixture needles are all set to factory default settings, and the carbs have been syncronized both by feeler guage, and double-checked with vacuum syncing tool. The reeds are new, as are the stuffers. But after all this, the craft still floods when started hot or cold.
The problem presents as follows: When starting cold,you can't even think of choke because it will flood instantly , hold throttle half to full and it fires up raggedly with just a little choke pulling to keep running for first 15 sec. after initial start-up. To start hot even if only shut off 5 sec. you must hold throttle wide open and crank 2- 5 sec. then will fire up and go. Now for the weird parts. If I pull the air cleaner off and inpect carbs when sitting, the throats and the intake are dry. After unit is started it will idle beautiful for any length of time, and will accelerate away from standstill after idling with absolutely no rich flutter or lean bog telling me idle mixture must be **** close to perfect. It will run any rpm range flawlessly, and plug colours are all dark-tan/brown. One odd thing it does, is when it's cranked over the engine actually coughs and runs for about 1/2 sec. before it goes into its flooded start.
Does anybody have any ideas what could be causing this? I'm at a loss as to the reason. Could it be the pop-off to low? I know the spec is 10-18 and the carbs are Mikuni SBN's, but my 96 SL700 has the pop-off set to 24psi with Keihin's, and it starts normal with choke cold, and on first pop of exhaust when hot.
With all this, I know three components of running are great, engine sealing, compression, and adequate spark at proper time. All that is left is proper fuel. I replaced the stock pump with new triple outlet pump, replaced all the fuel lines, eliminated vacuum petcock(was already missing), and installed new fuel filters between both pick-ups and petcock, and new filter between petcock and pump. The carburetors all have brand new kits, and diaphragms in them. I set the pop-off to 16psi (spec is 10-18), the lever is perfectly level with casting, and the needle&seats will hold 15psi all day. The mixture needles are all set to factory default settings, and the carbs have been syncronized both by feeler guage, and double-checked with vacuum syncing tool. The reeds are new, as are the stuffers. But after all this, the craft still floods when started hot or cold.
The problem presents as follows: When starting cold,you can't even think of choke because it will flood instantly , hold throttle half to full and it fires up raggedly with just a little choke pulling to keep running for first 15 sec. after initial start-up. To start hot even if only shut off 5 sec. you must hold throttle wide open and crank 2- 5 sec. then will fire up and go. Now for the weird parts. If I pull the air cleaner off and inpect carbs when sitting, the throats and the intake are dry. After unit is started it will idle beautiful for any length of time, and will accelerate away from standstill after idling with absolutely no rich flutter or lean bog telling me idle mixture must be **** close to perfect. It will run any rpm range flawlessly, and plug colours are all dark-tan/brown. One odd thing it does, is when it's cranked over the engine actually coughs and runs for about 1/2 sec. before it goes into its flooded start.
Does anybody have any ideas what could be causing this? I'm at a loss as to the reason. Could it be the pop-off to low? I know the spec is 10-18 and the carbs are Mikuni SBN's, but my 96 SL700 has the pop-off set to 24psi with Keihin's, and it starts normal with choke cold, and on first pop of exhaust when hot.
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