Atomic 4, when starting kick back causes black smoke to come from flame arrester on the carburetor [sometimes] Engine will start and run on second or third try. Spark plugs have been changed along with new gas seperator filter. Can anyone shed light on this?
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Atomic 4 starting
I'd look at two things: Your carb may be flodding causing too much fuel and thus the explosions when it starts. Check the choke opperation also. It also sounds like the timing is incorrect and could have jumped a notch. Has it been running rough in the past?
I'd look at two things: Your carb may be flodding causing too much fuel and thus the explosions when it starts. Check the choke opperation also. It also sounds like the timing is incorrect and could have jumped a notch. Has it been running rough in the past?
Kick Back
I second the notion that your timing has jumped a notch. Could be a carb problem too, but the kick back is almost always a sign of timing too advanced.
I second the notion that your timing has jumped a notch. Could be a carb problem too, but the kick back is almost always a sign of timing too advanced.
Probably a 'sticking' intake valve
Atomic-4s are prone to 'sticking valves'; the valve stems get a teeny bit rusted and the friction doesnt let the valve close all the way - the engine fires when the valve is not fully closed; hence, the 'backfire'. Usually the exhaust valves stick when water siphons back into the combustion chamber when there is a pinhole leak in the exhaust system/exhaust manifold. If the problem continues, add some Marvel Mystery Oil to the fuel .... or any "top-oil". this will help coat the valve stems with oil and lessen the valves from sticking. If that 'treatment' doesnt work, remove the spark plugs (and coil wire), spin the engine with the starter and with your thumb in the open spark plug holes determine which cylinder has the 'lowest' compression, then when you shut down the engine for the week, add a few tablespoonsfull of Marvel mystery oil to the suspect cylinder... replace the plugs and with the coil wire off turn the starter to 'spin' the engine without starting. You'll probably have to do this several times until the offending valve stem re-polishes and 'frees up'. To avoid sticky valve stems .... run the hell out of the engine ... and when putting the boat away next winter BE SURE to FOG the engine internals with fogging oil AND put/seal a plastic baggy over the spark arrestor so that wet/damp air cant get into the engine when the boat is stored for long periods !!!!!!!!!!!!! To 'fog' an engine, simply spray the fogging oil into the flame arrestor while the engine is hot and idling until you see heavy smoke coming out the exhaust or the engint stalls .... then seal the flame arrestor with plastic to keep the damp air out during the winter. BTW ... get a copy of Don Moyers "Maintenance and Rebuild Manual for the Atomic-4" www.moyermarine.com expensive but will save you many $$$$$$$$$ in the long run. Hope this helps.
Atomic-4s are prone to 'sticking valves'; the valve stems get a teeny bit rusted and the friction doesnt let the valve close all the way - the engine fires when the valve is not fully closed; hence, the 'backfire'. Usually the exhaust valves stick when water siphons back into the combustion chamber when there is a pinhole leak in the exhaust system/exhaust manifold. If the problem continues, add some Marvel Mystery Oil to the fuel .... or any "top-oil". this will help coat the valve stems with oil and lessen the valves from sticking. If that 'treatment' doesnt work, remove the spark plugs (and coil wire), spin the engine with the starter and with your thumb in the open spark plug holes determine which cylinder has the 'lowest' compression, then when you shut down the engine for the week, add a few tablespoonsfull of Marvel mystery oil to the suspect cylinder... replace the plugs and with the coil wire off turn the starter to 'spin' the engine without starting. You'll probably have to do this several times until the offending valve stem re-polishes and 'frees up'. To avoid sticky valve stems .... run the hell out of the engine ... and when putting the boat away next winter BE SURE to FOG the engine internals with fogging oil AND put/seal a plastic baggy over the spark arrestor so that wet/damp air cant get into the engine when the boat is stored for long periods !!!!!!!!!!!!! To 'fog' an engine, simply spray the fogging oil into the flame arrestor while the engine is hot and idling until you see heavy smoke coming out the exhaust or the engint stalls .... then seal the flame arrestor with plastic to keep the damp air out during the winter. BTW ... get a copy of Don Moyers "Maintenance and Rebuild Manual for the Atomic-4" www.moyermarine.com expensive but will save you many $$$$$$$$$ in the long run. Hope this helps.
Manual always helps
Rich in Worton said, "your thumb in the open spark plug holes determine which cylinder has the 'lowest' compression," A compression tester is a better solution. Available at any auto store for not much. Other than that I agree. Any good manual will have troubleshooting guides.
Rich in Worton said, "your thumb in the open spark plug holes determine which cylinder has the 'lowest' compression," A compression tester is a better solution. Available at any auto store for not much. Other than that I agree. Any good manual will have troubleshooting guides.
If a valve is sticking open .......
there will be very little compression in the cylinder. An atomic 4 has such low compression, that I find that a thumb-in-the-hole is good enough to tell the pressure difference between cylinders.
there will be very little compression in the cylinder. An atomic 4 has such low compression, that I find that a thumb-in-the-hole is good enough to tell the pressure difference between cylinders.
Thanks to all
To Rich H, I put Marvel mystery in all spark plug holes. I do this each fall when winterizing the boat. I figured it couldn't hurt. To nice n easy and Karl , Don Moyer also believes it it a problem with the timing being too advanced. Thanks to Rodger for his suggestion. I ordered a manual from Moyer. It is more detailed than the one I had. Thanks to each of you who responded.
To Rich H, I put Marvel mystery in all spark plug holes. I do this each fall when winterizing the boat. I figured it couldn't hurt. To nice n easy and Karl , Don Moyer also believes it it a problem with the timing being too advanced. Thanks to Rodger for his suggestion. I ordered a manual from Moyer. It is more detailed than the one I had. Thanks to each of you who responded.
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