Thread: Intermittant missing Force 9.9

Ok, I revived this motor. 87 US Marine /Force 9.9 hp. I have taken apart and cleaned the carb. It had what looked like fine grit or powder floating around in the carb bowl. But no rust of any kind. Float valve looked clean also. New spark plugs, and compression at 115, 110. It starts great on first or 2nd pull. Have taken points off and apart and polished the points contacts. Best I can determine, the condensers are functioning. I did a continuity test on both, and shows good. Did a resistance test with my analog VOM and the needle jumped a little and settled back to below the zero line towards the infinity mark.

Problem: When running 1 of the cyl is cutting out. I can't determine which. I get only one spot on the throttle that I get smooth running which is just below start mark, but otherwise, its hitting and missing, even at idle, and especially above the start mark to full throttle. It has been worked on before, I suspect, because the spark wires have been moved from the holder on the ignition plate. As if the thing was doing this before. It also has had the kill switch wiring replaced with what looks like brown lamp cord. I think (but can't find) there is a wire leaking. I'm going to look at the lamp wire first and try to fish it out from under the front coil and replace it with a better quality wire set. I'm also ordering a new set of condensers for it to see if that solves the problem. Any other suggestions anybody has would be appreciated.

Check all your electrical connections for any corrosion or loosness. Sounds like you have but just making sure.

When you pulled the carb did you clean the jets?? Sounds like you have a clogged jet.

Could also be a timing issue. Look at the linkage from the the handle. Make sure everything is moving and is free. As the throttle ramps up so should the timing. Should be a linkage going up to under the flywheel. Could also be out if someone has messed with it. It may not be advancing as it should.

Did you do a spark test?? You should have a nice BLUE not orange or yellow spark...should be able to jump close to 3/8".

Just some thoughts. Also anytime you do a carb job. Let it soak overnight in carb cleaner. Unless its plastic. Need to make sure you blow air through every orifice in it. Do this after it has soaked. Lots of spots deposits can hide in there.

Run a can of seafoam with a gallon of mixed gas. Use the full can. Will help loosen things and you probably have some carbon built up on the cylinder tops and on the rings.

Thanks Scrapper - one of the points set had some corrosion on the wire connectors from condenser, the coil and the kill wire (remember lamp cord) so I did clean off the corrosion, but in the back of my head I'm thinking maybe some corrosion in the wire where I can't see it. I'm seeing good linkage movements and smooth, too. No hanging up as it advances. I'll take a picture of it tomorrow. I have to pull the flywheel off again to put in the new condensers I ordered. I am not saying the carb cleaning I gave it, was perfect, but it really wasn't gummed up at all. I've seen way worse. And I did blow it out good with my air compressor. But when I change out the kill switch wires, and if it still doesn't run smoothly, I'll redo the carb and let it soak overnite. The spark was excellent, and bright blue with a good 3/8" streak on my spark tester. It has really good compression, too. It wants to get going! It cranks up after only one or two pulls. Its gonna be a sweet little motor when I get through the missing issues.

I finished replacing the kill switch wiring, and re positioned the spark plug wires where they exited the the ignition points/coil area just to put them in less stress as they exited out towards the plugs. I got the new condensers today and also replaced them as well. Replaced the flywheel, and it was 10pm, so packed up the tools, and I'll check it out tomorrow and see if I solved the missing problem. I feel better knowing the "lamp cord wiring" is gone, and replaced with wiring compatible with 12vdc. That might not have been needed to be done, but I feel better knowing when I pull the rope, a lamp won't light up instead. I will report back tomorrow evening, and let you know how it went. I may be soaking the carb if that isnt the fix.

Changing kill switch wire and changing condenser, didn't help. Still have a miss.
Guess I should have ordered the points sets as well. Or maybe its the coil on back/bottom cylinder - it was showing lots of raw gas.

Hmmm-did a continuity check - took off one side of kill wire at switch then connected probe of VOM to wire end of kill wire (connecting other end to the post with the condenser and coil wire attach) and connected the other VOM probe to ground. What I got was continuity whether the points were open or closed. Shouldn't it have had continuity when points closed but not when they opened? I think points must be bad? That post should be isolated from ground except when points close, correct? I only replaced condensers. I was thinking coil, but could it be this simple?! Or am I the simple one here - what am I missing?

I found the problem !!!! It wasn't the coil or the points, and probably the condensers, but they were replaced so they are there. It was one of the spark plug wires at the plug wire boot. The connector contact (the part that clips onto the spark plug tip)that was pushed through the insulation to make contact with the spark wire only the wire had broken. Oddly every time I was checking for spark, there was spark --- except when it was running. I nearly bought another coil, and at $66.00 (cheapest I found) to as much as $111.00 it was gonna be hard on the wallet. With the price I paid for the motor $40.00, and condensers were $25, and spark plugs were about $5, I've got a nice 9.9 hp for $70.00. And it runs great!!!

DANG!! My bad on that...should've mentioned that before. Had that happen to me on a 78 140 johnnyrude I was trying to running. Had a plug wire messed up. After replacing lots of parts...hahaha. I was SOOO glad to figure it out...but SOOO mad and embarrassed I didn't find the easy thing. Remember KISS...keep it simple stupid....lol. I forget that too much!! :D Glad to hear it worked out!! Now go catch some slabs!!