Adjusting carb and timing on 1975 9.9

[newfiez]

Anyone have info on how to adjust the carb on a 1975 9.9 Johnson (model 10EL75C)? It only has the low speed adjustment.

Also, how do I check the timing on this? I can't figure out where the timing marks are.

 

[tashasdaddy]

Re: Adjusting carb and timing on 1975 9.9

if the flywheel key is intack there are no adjustments, you have a magneto ignition. all of it is covered here. http://forums.iboats.com/showthread.php?t=299680

 

[jay mendoza]

Re: Adjusting carb and timing on 1975 9.9

The 1975 has points, not CDI (I edited out unnecessary comments and PM'd Mendoza - QC)

Set the points to .020" at maximunm gap. The roller on the throttle arm of the carb should just touch the cam on the magneto stator as the arrow mark on the cam aligns with the throttle arm. Try rotating the throttle grip and watching where it begins to just move the carb throttle arm and note the position of the arrow on the cam, adjust the cam as needed. Check the timing with a lighted continuity checker, but you have to dissconnect the points from the condensor and primary coil to do this. See the manual on how this is done. You can also use a timing light with a seperate 12 volt battery to power it and look at the marks on the flywheel with the srobe timing light to see how close you are, and fudge the points to get it perfect. Opening the points more equates to advancing the timing. Good luck.

 

[newfiez]

Re: Adjusting carb and timing on 1975 9.9

I did all of the above already, except check the timing. I'm not quite sure which of the 4 separate markings on the flywheel (has ring gear for electric start) is the one to use for the pick up. Also, which reference on the engine do you use?


Playing with the SS adjustment, I would get the idle just about perfect, then the engine would "pop" like a misfire, then die. As I brought the RPM's up, I noticed a slight change in sound in the engine...the other cylinder would start to work. It only runs on the lower cylinder at idle...explains why I can't adjust the fuel properly!

 

[newfiez]

Re: Adjusting carb and timing on 1975 9.9

I'm still having issues with the "pop" at idle, and it won't stay idling at low rpm's. I don't know what's going on with the upper cylinder. I replaced the coil for troubleshooting, and it still does it. I put a spark tester with a large gap (3/8") and it jumps it no problem, but if I try to start it on that cylinder, it won't go. No issues with the lower cylinder. I double checked the gap on the points, and they're at .020". I'm thinking a weak condenser, or something's up with the coil in the mag?

 

[newfiez]

Re: Adjusting carb and timing on 1975 9.9

OK, doing some troubleshooting...I removed the whole mag assembly, and replaced it with one from a known running engine (without electric start), and now the motor runs fine. So which component caused the misfire?

 

[bktheking]

Re: Adjusting carb and timing on 1975 9.9

Get a "tune up" kit for it and replace the points and condensors, cheap and easy plus dirty points does exactly what you describe, gap is great to set but if they are even slightly dirty or corroded they will misfire.

 

[mikesea]

Re: Adjusting carb and timing on 1975 9.9

it could be coil,pts.or condenser,if the coil is orig.it could have broken down with age alone,pts.condenser are maint.parts anyway,so change them,and,based on age ,get a new set of coils,playing with the old stuff wil let you down that many times,start fresh

 

[bktheking]

Re: Adjusting carb and timing on 1975 9.9

Why would he replace the coils when he said in his previous post that he replaced the mag assembly and it ran fine? The coils are external on these engines and it ran fine without different coils. Points and condensors first, coil's aren't cheap. I'm not saying if you can afford it don't change them as well but I'm a believer that if it ain't broke don't fix it, I could spend thousands replacing parts on my car cause they wear out but i'm not going to.