73 Johnson 9.5 rough low speed

[cr9c1]

I posted about this earlier but wanted to update as some things have changed.

It has new coils, points, and condensers. New spark plugs. I've had the carb apart 3 separate times and done a complete rebuild on it. No ports are plugged, float is adjusted properly, all new seals + gaskets in the carb including the core plugs. It also has brand new spark plug wires.

It runs rough at low speed. It sounds like its dropping out on a cylinder or maybe misfiring. I checked the points again and they are gapped at .020, and the coils are adjusted properly. The flywheel is in pristine condition. It'll go right up to WOT no problem but it idles real rough.

Anyone have any ideas as to where I should go next? It does it w/ or w/out the cowling on so I know it isn't exhaust smoke choking the engine out. It runs real good like I said at WOT but rough at an idle. Its starting to get to me now, because I know the carb is in perfect shape, all the ports are clean and I have blown it out with compressed air 3 times.

 

[tashasdaddy]

Re: 73 Johnson 9.5 rough low speed

whats your compression nubmers, also go to engine faq forum, Joe Reeves carb setting.

 

[cr9c1]

Re: 73 Johnson 9.5 rough low speed

Cyl#1 118
Cyl#2 116

Compression is fine. Have already tried Joe Reeve's carb adjustment. Problem still persists. I know the carb is clean but Im starting to think its ignition related.

 

[iwombat]

Re: 73 Johnson 9.5 rough low speed

Might want to double check the position of the coils. Are they set right with respect to the bosses? Too far back and you'll miss. Sure sounds like everything else is on track though. Might want to try cleaning all the grounds up and dressing with a file, just to eliminate that possibility.

 

[cr9c1]

Re: 73 Johnson 9.5 rough low speed

I thought about that iwombat, but, it doesn't miss any other time. Midrange-to WOT is perfect. I've heard that some new coils right out of the box are messed up and I'm thinking this might be the case, that one is dropping out low speeds for whatever reason. I think that the dealer put the wrong points in too, because they dont seem to operate correctly, like, the parts that touch aren't touching squarely at all. I modified them as best I could but it didn't seem to make any difference.

I'll try swapping coils out and see what I can get accomplished that way.
If it fixes itself I'll try the new ones again and if the problem reoccurs, I know whats messed up.

 

[iwombat]

Re: 73 Johnson 9.5 rough low speed

If they're not set right you'll see it worse at idle. The magnets are moving at enough speed at mid->WOT to generate a bigger field change and create more current. The slower the magnets are moving, the more important the placement of the coils is.

 

[cr9c1]

Re: 73 Johnson 9.5 rough low speed

Coil placement seemed perfect, right on the money. No change in the rough idle. Im not sure how to link n sync on this but i've tried some different adjustments with no success at all. Currently open to suggestions. Also tried known good carb, no difference.

 

[iwombat]

Re: 73 Johnson 9.5 rough low speed

Well, hrm worth a shot . . .


Clogged recirc system?

Leaky fuel pump diaphragm?

 

[cr9c1]

Re: 73 Johnson 9.5 rough low speed

What do you mean by recirc system?

As far as the fuel pump diaphragm goes I suppose its possible. My Sportster 25 HP uses the same identical fuel pump. I may swap pumps and see what happens. It does run noticably rougher with the cover on (Which I encountered with the last 9.5 I was working on) but this one doesn't stall out. It continues to run. I have realigned the coils somewhat so I will have to take it to the lake and try it out. The fuel mixture in both mine and my fathers tank may be more like 24:1 too, I can't really tell. I also noticed that my saw horse isn't sitting right either and the float bowl may be over filling with fuel.

All possible problems. I tried my other carb and it ran the same, actually somewhat lousier so I'm going to take it to the lake, run all the "unknown" fuel out of it, and get some XD-30 and 89 octane fuel and try that out and see how it runs. Its got excellent spark and it appears to be running better since I adjusted the coils so I'll try some things and see what happens.

 

[iwombat]

Re: 73 Johnson 9.5 rough low speed

On that '73 the plate that has the reeds (different from the rest of the 9.5s) has a couple (or is it just one) of bronze jet-looking dealies for recirculation of excess fuel. Never seen 'em clogged, and don't really know the effect if they were. But maybe - just maybe they'd dump excess fuel into the lower cylinder at idle speeds if they weren't working properly.

An odd theory, yes. But, sort of maybe plausible.


(I'm going for long-shots here)

 

[iwombat]

Re: 73 Johnson 9.5 rough low speed

Before we go chasing rabbits though. Take a hard look at your spark plugs. Is the top different from the bottom?

 

[cr9c1]

Re: 73 Johnson 9.5 rough low speed

Neither plug looks different. I've tried a complete different set of coils, points, and condensers with no effect. So I put the new coils in. I suppose it could be something with carb'ing but I've had it apart 3 times and everything looks right. Not only that, I have another 9.5 that runs well, and the carb on that did the same thing on this so I'm leaning towards reeds. Or something else, fuel pump maybe as suggested?

 

[iwombat]

Re: 73 Johnson 9.5 rough low speed

The reason I ask about the plugs, is if it's either a leaky fuel pump or a bad recirc valve, you'll be running a richer #2 cylinder. I'd expect to see a darker plug on #2.

Worn reeds will cause the symptoms you describe. Reeds on the '73 are easy to change, but are unique to that year.

 

[HighTrim]

Re: 73 Johnson 9.5 rough low speed

New fuel pump diaphragm is cheap id try that, but id imagine the plug 2 would be darker if it was leaking, worth a look into though.

oops type too slow

 

[cr9c1]

Re: 73 Johnson 9.5 rough low speed

It looks like I have to take the entire intake manifold off to remove the reeds, my 72 only has (Or what appears to be) like 6 screws holding the reed plate in.

 

[iwombat]

Re: 73 Johnson 9.5 rough low speed

That's right. The '73 was a redesign of the reeds. They're behind the intake manifold.

 

[cr9c1]

Re: 73 Johnson 9.5 rough low speed

Im starting to lean more towards a leaking fuel pump diaphram than anything. I'm going to run it again tonight and take the plugs out and examine them. I'll know then if its the problem. Or I may just swap my fuel pump from my 25 and try it to see if it changes the running of it or not. Im having a hard time thinking my reeds are dead, the motor has very little run time whatsoever. I would go for something keeping the reeds stuck open or something though, judging the varnish that was in side the carb when i took it off.

 

[iwombat]

Re: 73 Johnson 9.5 rough low speed

It wouldn't hurt to inspect and clean them up. I doubt they're dead, the redesigned reeds are much better than the older ones. They might have some crud on them not letting them close.

Have you checked for manifold leaks at all? Spray some wd-40, deep creep, or premix around the intake seams while running and see if anything perks up.

 

[cr9c1]

Re: 73 Johnson 9.5 rough low speed

Yeah I'll try that.

Just out of curiosity, can I get the intake manifold off without having to split the two halves of the case?

 

[iwombat]

Re: 73 Johnson 9.5 rough low speed

Oh, yes. Um I'll post the old tried and true . . .

The dark blue part is the intake manifold. The reeds are right under that.