Logo
FULL SITE MENU

1970 9.5 Sportwin Missfire

S

sheepdogreno

New member
So here is what ive got. Bought this motor and took it out one time and it ran great but spuddered a bit. tried to take it out again and would fire. Replaced tank and line (bulb) and still nothing. Replaced fuel pump and then discovered it would only run with gas poured directly in top of carb. So i buy rebuild kit and rebuild the carb and clean it up looking new.

after carb rebuild she fired right up in the barrell and would idle for ages. take it on river. under load the motor would spudder and missfire. at first i thought it was a fuel issue so would prim bulb while running. Well bulb ended up doin its job and im gettng plenty of fuel. now its hard to start and while idle up like its ready to go and then i give it throttle and it spudders and dies.

i was thinking coils until i looked at plugs and realized they both look same...

HELPHELP please
 
Hello sheepdogreno

My newfound knowledge (thanks to this forum) is that these motors will run on one cylinder.
My '64 Sportwin had a similar problem where it would misfire under load.
Turned out that one coil was weak, and not able to fire a 1/4 inch air gap on a spark tester.
If you go to the trouble to change the coil (requires removing the armature plate from the motor), you may as well toss new points and condensers in there while you're at it.
Check the coils with a spark tester, and let us know what you come up with.
 
about the most i know about checking for spark is putting plug on case and pulling and checking for spark. ive changed a coil on a smaller motor but i dont know much about on this...do you have any pics from when you did yours?
 
anybody else have any ideas? i thought maybe i messed soemthing up cleaning the carb or the lean rich was wrong but i know carb is clean and together and ive adjusted the lean rich with no results
 
Way in back of that 7/16" threaded slotted drain plug at the bottom of the float chamber is the brass high speed jet. This jet if even slightly fouled, clogged, gummed, will cause the engine to act as you described.

Also, if pumping the fuel primer bulb results in the engine improving somewhat, taking into consideration that you have installed a new fuel pump... that indicates that the float isn't set properly.

Clean that high speed jet and reset the float as follows.

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.
 
sheepdogreno said:
about the most i know about checking for spark is putting plug on case and pulling and checking for spark. ive changed a coil on a smaller motor but i dont know much about on this...do you have any pics from when you did yours?
Click to expand...

Firing a spark plug in the open air only requires a few thousand volts, so it is not conclusive.
The only way to know if the coil is putting out proper voltage is to connect a spark tester to the spark plug wire, with the alligator clip connected to engine ground. Or, you could make a tester by hammering two nails into a piece of wood spaced 1/4 inch apart, and have your test leads connected to the nails. One lead to spark plug wire, and the other lead to engine ground.
Or you can do it the old fashioned way by shoving a phillips screwdriver into the spark plug boot, then hold the screwdriver blade 1/4 inch from the engine block. It's a bit of a PITA to hold the screwdriver and turn over the motor at the same time though.
Once you know your electrical is up to snuff, you can then move on to fuel.
Hope this helps.
 
joereeves said:
Way in back of that 7/16" threaded slotted drain plug at the bottom of the float chamber is the brass high speed jet. This jet if even slightly fouled, clogged, gummed, will cause the engine to act as you described.

Also, if pumping the fuel primer bulb results in the engine improving somewhat, taking into consideration that you have installed a new fuel pump... that indicates that the float isn't set properly.

Clean that high speed jet and reset the float as follows.

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.
Click to expand...

Hey Joe,
I remember reading your post about setting up the float in the carb but couldn't find it.
Here it is!
Right now I seem to be experiencing carburetion problems. I pulled mine to take a look, and the float was saturated (NFG). LOL. That's what I get for not draining the fuel bowl in the off-season (didn't know you had to). It's great to have newfound knowledge, learning is half the fun.
Pulled the carb off my '72 parts motor because it literally looks BRAND NEW, and the float appears to be ok, it's dry and no sign of saturation.
I'm going to check the float in the way that you have described. Thanks! :)
 
well thanks for all the help guys but i just got her figured out i think....i took carb apart again today and realized when i rebuilt it i put the main jet/float needle in upside down. put it in the correct way and its running like a dream now. dunno how i managed to put it in upside down but i did. must have worked enough just to let it idle but not run at higher rpms...no it will run wide open and back down to idle with no spudder or hesitation...gonna hit the river with the wife this afternoon hopefully she will run well...the boat that is! lol
 
Yeh.... If you managed to install the float needle valve upside down, I'm pretty sure that none of us would have come up with a suggestion to check that. :cool:
 
joereeves said:
Yeh.... If you managed to install the float needle valve upside down, I'm pretty sure that none of us would have come up with a suggestion to check that. :cool:
Click to expand...

haha i cant believe i caught it...only reason i did was i thought i would double check my cleaning of carb after i rebuilt it...once i started taking it apart i was like OMG i have the needle in upside down! glad thats all it was!
 
Back
Top