Another post on this 18 horsepower

[Thompy_04]

I think I'mma make a new record on posting about the same motor... I've been posting on this motor forever but still can't get things right. Took it out today to fish, and got to a good spot farely well, even though the motor surged at WOT some. Stopped fished a little, and began to leave to find another, motor wouldn't start. Finally started but sputtered real bad at idle, as soon as I got it in gear it died. Checked for spark and the bottom cylinder didn't have any. I've had problems with this before and it turned out to the plug wire came loose from the coil, so I think thats the problem. Another thing, the motor seems to be running warm, the head is quite hot after WOT, or prolonged idling. I'm running a plug hotter than usually but tend to use more WOT then idle, could this make my motor run hotter than usuall? I changed the water impeller last year and only ran it two times before putting it up for the winter, and have only ran the motor twice this summer with the same impeller. I think this is the last thing. It won't idle for anything. I can get it to idle fine, w/o dying but it won't idle very high, you have to set the mixture setting very rich to get a good idle. I believe the upper crank seal is bad, there is some oil and fuel under the armature plate, could this be the problem for the rough idle? Wait there's one more thing. I can't get the midrange correct. It misses REAL bad in the midrange, and I don't know why. I think it could be because the carb needs to be synced but I can't be for certain. Thanks for any help.... I'm about to throw the thing to the curb if nothing gets working correctly here.

 

[Thompy_04]

Re: Another post on this 18 horsepower

*bump*

 

[Thompy_04]

Re: Another post on this 18 horsepower

^

 

[Paul Moir]

Re: Another post on this 18 horsepower

I think you've got it about the bottom cylinder. There isn't much that will prevent spark on these motors. If you have the aftermarket coils in there you really have to screw in the spark plug wire as the post in them is threaded. I coat the wire insulation with silicone (dielectric) grease to make it easier. You can check to see if the wire is seated properly by measuring the resistance between the boot and the block with a multimeter. You should read 3.5-7k ohms. A bad (open) connection will cause mid-range problems.<br /><br />Sync is critical to a happy mid-range. Adjust the linkage so that the throttle shaft on the carburetor just begins to move when the mark on the throttle cam (on the armature plate where the coils live) is at the centre of the cam follower. Use a peice of stiff wire to amplify the movement of the throttle shaft.<br />To adjust it, loosen the bolts that hold the cam to the armature plate and move it in or out.<br /><br />With a leaking seal, the engine will never idle properly and it'll have a very rough early mid-range. It's been my experience that a leaking crank seal will drive you mad until you find it. You should be seeing no oil up under the flywheel. OBJ told you how to replace it. If your dealer can't find you a crank seal (he should, that basic block was sold up into the '70s), take the old one to your local bearing house and they can match up a new one for you. It would be helpful if you could measure the crankshaft.

 

[the rebel]

Re: Another post on this 18 horsepower

Let me throw some more stuff into the equasion. Oil under the flywheel means one or more things, worn seal, worn bearings and seal. That creates a lot of possible problems. Oil on the breaker points will cause a miss. Worn crank bearings can cause crankcase pressure leakage resulting in loss of mixture in the combustion chamber causing uneven cylinder pressures. Air leaks cause that too. Sounds like you have a loose engine needing some attention other than your average tune up. Check the crank for lateral(side to side) play after you take the flywheel off, if it is tight, just replace the seal and set your points right and you should be on the right track. Make sure the breaker cam isn't cracked, I had that problem on one of my 18s before. Missed like he)). BWJ

 

[Thompy_04]

Re: Another post on this 18 horsepower

There isn't a mass amount of oil under the armature plate, just enough to be noticed, which is why I think there is a little leaky seal in there. The points are as clean as a whisle, so I'm not real worried about that. The cam is good, but I believe a new wick is in store for it. The crank is tight, I did get around to that, right now just waiting for my seal and to get into replacing it. In the mean time I'm working on getting this thing in sync, replacing the thermostat (went bad), and getting the high tension wires in a good position on the coil posts. Thanks for all the help guys, I don't mean to be a burden on all these questions!