1990 28 hp spl johnson idles rough

[buttonhook]

I think I may have a weak spark in the top cyl. I get spark but I don't know how strong it is.<br />I got my tiny tach yesterday and I was trying to tune the engine To the correct rmps at idle. I got 700 but at that point it was jumping and shaking real bad the manual calls for 5-600 rmp and idle. so I pulled the top plug and the engine changed a little(rougher) but did not die. I put it back on and pull the bottom plug. It died almost instantly. Does this sould right? I know the top plug has spark as it didn't take me long to look at it if you know what I mean!!<br />I'm trying to get everything up to snuff on this motor. Carb has been dis. and cleaned there are good to go. I got plenty of water. I have decarbed, new plugs etc.etc....<br />BTW,<br />I was testing in a tank so backpressure should have been ok to.

 

[JB]

Re: 1990 28 hp spl johnson idles rough

Howdy, Buttonhook.<br /><br />Sounds like your top cyl. is making very little or no power.<br /><br />I wouldn't suspect the carb, as it feeds the same mix to both reedplates.<br /><br />The trouble has to be unique to the one cylinder.<br /><br />I would first do a compression check. <br /><br />If that is okay (less than 10% difference between 1&2) I would try swapping plugs, coils and plug wires between 1 & 2. If the trouble follows one of those components you have your culprit. If not, I suspect the powerpack.<br /><br />But before getting a new powerpack I would pull the carb again and inspect the reed valves and the gaskets on reed plate and bypass plate.<br /><br />Good luck, and let us know what you find.

 

[buttonhook]

Re: 1990 28 hp spl johnson idles rough

thanks jb,<br /> I need to check compression. I runs real good other than at idle. I was think power pack as well. There is no change between warm engine and cold engine. with a power pack isn't there nomarly a differance when they change temp???

 

[buttonhook]

Re: 1990 28 hp spl johnson idles rough

the NAPA doen't carry the s.p. wires here is there someplace else that carries them??

 

[buttonhook]

Re: 1990 28 hp spl johnson idles rough

ok I went home and checked the spark I've got a nice blue spark on both plugs. NOW what?????<br />It runs ok, just at idle it shakes like an epileptic in and earthquake. ans sounds like it is missing.

 

[buttonhook]

Re: 1990 28 hp spl johnson idles rough

ok I checked the compression 115 psi top 115 psi botttom on a stone cold engine.<br />Any more ideas??????<br />btw,<br />I swapped coils and plugs, wires every thing still the same.