Re: Lightwin 3hp / firing on 1 cyl
- Engine runs well for ~2 minutes. I kill it, install silencer, restart, and it goes back to "running rough" w/in 30 seconds.
- is not receiving proper fuel/air?
Ibdavis, Look at this little bit of information. Now, I have only been messing around with outboard motors for a little more than a year, but have listen a lot and read a lot. This little acronym always gets me back on target to find most of the my engines running problems.
CSF
systematic approach (in this order)
C= compression ( if your compression is low are uneven between cylinders >10% then others checks don't matter until the that is resolved)
S= Spark (if your having problems with your ignition then you can have the cleanest carb and great fuel delivery but it will run bad or not at all)
F= Fuel (if your carbs are not clean and fast/slow idle needle are not set right then it will run but like crap. If you have it set too lean then you run the risk of poor fuel/oil delivery and damage your pistons and cylinders then you run into the problem of C (poor compression from damage).
*****
Now to the problems at hand*****
I went back and reviewed your other associated post. Lets review what you have done so far.
Compression= You stated that you have 67/67 each cylinder (OK)
Spark = You stated that you change the coil, points,condenser and new spark plugs. Points gapped at 0.20. You stated that you have a good blue spark on both cylinders and you performed the dropped cylinder test and the engine ran rough even with one plug firing either on the top or bottom cylinder.
So you have constant spark on both cylinders (OK)
Fuel = You stated that you rebuilt the carburetor.
- You stated "
- Engine runs well for ~2 minutes. I kill it, install silencer, restart, and it goes back to "running rough" w/in 30 seconds.
"
The above statement tells me you have fuel/air problem. The silencer that you connect to the carburetor slightly restricts the airflow,
so you will have to adjust your slow idle needle with the with air silence on not before This will allow proper fuel and air mixing. You have a fixed high jet vent so no adjustment there, it just needs to be clean.
Here is a link from distinguished Joe Reeves that explains carburetor adjustments.
Link: http://forums.iboats.com/showthread.php?t=167352
Here is the portion that pertains to your motor.
(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)
Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.
Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.
Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.
Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.
When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
When Joe states gentle seat the slow idle needle, he means turning the needle clockwise slow until it gentle seats and seals the passage way. (very careful not to damage the tip of the needle. (The needle controls the air/fuel mix)
When Joe states turning the needle adjustment in, he means turning the needle clockwise when facing the motor.
When Joe states turning the needle adjustment out, he means turning the needle counter clockwise when facing the motor.
Look at this link, it has the parts breakdown for your motor.
http://www.marineengine.com/parts/v...ntage-evinrude-johnson/278442/27844200001.htm
Things to think about your carburetor
- When you performed a carburetor rebuild, did you remove all the core plugs and spray carb cleaner in all the holes.
- Did you replace the float in the correct position. Here is a link given by Tasha's Daddy on how to do that.
Link:
http://forums.iboats.com/showthread.php?t=244013
The important thing is that float is even and parallel with the carb when the carb is upside down...you will see in the picture. Also, the carb kit comes with a little wire spring that attaches to the float needle and float arm so when the carburetor bowl is full it stops further fuel from entering the bowl. That wire like spring needs to be on both the float needle and float hinge.
Here is a link of a guy that a similar problem with his carb, air silencer and it carburetor adjustment.
http://forums.iboats.com/showthread.php?t=417648
Just a bit of advice (LOL)....like I have given you enough
Fuel to oil mix ratio should be 16:1 and absolutely definitely no less than 24:1 ratio. I spoke with experts on antique outboard motor club inc, forum and they highly stress using the 16:1 ratio of fuel to provide increase lubrication and longevity to your motor.
Fuel oil ratio 16:1 is 1 gallon of fuel to 8 ounce of TCW-3 marine 2cycle oil (personally I subscribe to this fuel ratio)
Fuel oil ratio 24:1 is 1 gallon of fuel to 5.3 ounce of TCW-3 marine 2cycle oil
24:1 is 3 gallon of fuel to 16 ounce of TCW-3 marine 2cycle oil
Oh, make sure the little screw on your vent cap on your tank is open, clean and clear when you are starting and running your motor. Don't forget to close it if your transporting or laying it down or you will have a mess on your hands
Hope this helps you out!
