Engine runs rough for a while, then smooth for a while, repeat

   / Engine runs rough for a while, then smooth for a while, repeat
  • Thread Starter
#11  
My guess is that perhaps I've got the throttle linkage hooked up wrong (throttle is the vertical rod in the back, with the little spring next to it / on it; the vertical rod in the front is for the choke, I'm pretty sure - the front rod actuates a butterfly in the front of the carb closest to the air intake and the back rod actuates a butterfly at the rear of the carb where the mixture exits to the engine intake manifold), or that one adjustment screw way off.
 
   / Engine runs rough for a while, then smooth for a while, repeat
  • Thread Starter
#12  
I pulled it all apart, and put it back together. Noticed that the fuel shut-off solenoid was stuck in fully-retracted position (shouldn't matter to the normal running of the engine) and managed to pull it apart and clean it up so it operates.
All together, it ran, smoky at first but then cleaned up... I went out and mowed about a half of an acre; it seems to work reasonably well now - I'll swap the plugs tomorrow anyways, but I'm pretty sure that my original problem was simply that the connector to one of the points was becoming intermittent as it was only partially seated... could've saved a ton of effort by noticing that in the first place :/

So hopefully this is the last posting in this thread!
 
   / Engine runs rough for a while, then smooth for a while, repeat #13  
From what I have read here, I would suspect that it has to do with your fuel. I assume you are running "premium fuel". How old is the fuel? If in doubt, drain the fuel from the tank and start with fresh premium grade fuel and add to the tank fuel some Sea Foam. Let it run for a bit and see if the problem improves at all. I have found that over a number of years that most situations are caused by poor fuel. The Sea Foam will clean out a lot of the problems. Good luck!
 
   / Engine runs rough for a while, then smooth for a while, repeat
  • Thread Starter
#14  
So hopefully this is the last posting in this thread!

I was wrong.

It's still doing its thing.

Now I'm suspecting something which is common to both points, here's why: When it's running rough, I pulled the connector off of one spark plug.
The engine didn't bat an eye, kept running at the same RPM. Well, that points to either that spark plug, or its wire, or that point, right? You'd think so, except... when I put the spark plug wire back on (again, no change to the engine speed), and pulled the wire off the other spark plug - the engine didn't care, again. If both spark plugs were bad, or both wires were bad, the engine wouldn't run at all.

This is telling me that the two points aren't getting enough juice to drive both plugs? - so only one ever firing? But that doesn't make sense either, because they're not firing together (this isn't a dual-fire v-twin!).

Any ideas of what to look for? Getting desperate here :(
 
   / Engine runs rough for a while, then smooth for a while, repeat #15  
Bad battery/condenser? If your problem is not being able to get a spark in quick succession could be a problem with getting enough juice from battery to spark plugs. I'd also see if maybe you have a short from battery to points/etc.
 
   / Engine runs rough for a while, then smooth for a while, repeat #16  
No need to get desperate here. First off here is your engine info: SV735-0017 Kohler. Second , the ignition system that came on this is krap and has been replaced. The instructions come in the box. 25-707-03-S is the part number. Thirdly, there are no points. Breakers haven't been used since the early eighties.
 
   / Engine runs rough for a while, then smooth for a while, repeat
  • Thread Starter
#17  
No need to get desperate here. First off here is your engine info: SV735-0017 Kohler. Second , the ignition system that came on this is krap and has been replaced. The instructions come in the box. 25-707-03-S is the part number. Thirdly, there are no points. Breakers haven't been used since the early eighties.

I understand the spark modules may be crap, but you're suggesting that they've both gone bad at the same time? This is a very new issue.
Regardless, it doesn't sound like a loss to replace them so I'll do it and hope that's it.
 
   / Engine runs rough for a while, then smooth for a while, repeat #18  
What you have now is a module that controls the coil packs. SAM= Spark advance module. They do get wacked and intermittently will decide to drop a cylinder. Many of them. I have had twice before with a no start that was caused by a partially backed out bullet connector where the engine harness meets the chassis harness. I suppose that could create an intermittent condition too and would be easily checked. BTW, the number I pulled off the Sears site searspartsdirect should you need further service parts for your rider.
 
   / Engine runs rough for a while, then smooth for a while, repeat
  • Thread Starter
#19  
What you have now is a module that controls the coil packs. SAM= Spark advance module. They do get wacked and intermittently will decide to drop a cylinder. Many of them. I have had twice before with a no start that was caused by a partially backed out bullet connector where the engine harness meets the chassis harness. I suppose that could create an intermittent condition too and would be easily checked. BTW, the number I pulled off the Sears site searspartsdirect should you need further service parts for your rider.
I've got the replacements on order. Even if they're not the current problem, it's obvious that they'll be a problem and I'm totally ok with fixing things before they break.

I'm curious about the current things - are they not driven by the magnets on the flywheel? The reason I ask is, there's a huge gap and they don't seem to be adjustable. IMG_20180512_092148.jpeg
 
   / Engine runs rough for a while, then smooth for a while, repeat #20  
Should be .012" on a SAM system. Can you rock your flywheel back and forth like the upper bushing in the case is badly worn? Otherwise they are slotted to make the adjustment.
 

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