1978 Johnson 140hp running rough. Need advice

[Bman2895]

Ive had people say you just beed to smooth out the high spots and run it? And they are abundant, but if i can reuse this set of heads id rather.

 

[jimmbo]

Those pits will also likely fill with Carbon, creating Hot Spots leading to Detonation, which I suspect had something to do with the last Ring Failing. I suspect that this engine has had this Dance before

 

[Bman2895]

So no saving that head?

 

[saltchuckmatt]

In my opinion, not enough picture to really tell but others may disagree...but if it is savable, besides saving some "clams" a figure 8 pattern on a dead flat surface with some very large 120 grit sandpaper will make it pretty damn flat.

Mix that with new gaskets, and torquing them correctly gradually 2 or three times and you may be in business.

Are you retired or young and out of control....possible broke or rich...

Question goes down the rabbit hole.

 

[jimmbo]

I would Not reuse that Head. However, it is your Motor and your Money, so you can do whatever you want.

 

[Bman2895]

Definitely doing things on a bit of a budget. I can try and find another head, but it seems a bit hard to get a starboard head

 

[Mc Tool]

Id give it a go , pien down as much of the high bits so to push them down ....not fold them over , bit of a wizz with a wire wheel ( to remove any loose bits ) and Bobs yer auntie .
Tell ya what .....most of the peeps telling you not to use it .....would if it was theirs and another replacement was proving hard to find .
I have seen worse

 

[jimmbo]

There Tens of Thousands of those 99 inch 135s and140s out there. Shouldn't be too hard to find a Head

 

[saltchuckmatt]

Definitely doing things on a bit of a budget. I can try and find another head, but it seems a bit hard to get a starboard head

Send us a better picture from farther away perhaps.

 

[Bman2895]

So I've been away a bit. But I decided to swap the later 140 carbs on. Smaller bore carbs but from a 82or 83 140. Fixed ALOT of the issue's idles good. Runs strong. No bogs off idle etc. They do have some float issues. One of them was going from hanging shut and me having to hold the primer down to keep iy from bogging to hanging open and flooding it. Then it goes right back to running perfectly for a bit.

 

[jimmbo]

Smaller Bore? That will cost top end Hp, but will help Hole Shot

 

[Bman2895]

Smaller Bore? That will cost top end Hp, but will help aacur

Actually helped both. But helped the hole shot tremendously. Idle was smooth and it no longer has a lean sneeze.

 

[jimmbo]

Actually helped both. But helped the hole shot tremendously. Idle was smooth and it no longer has a lean sneeze.

Shows there was something wrong with old Carbs, but if they had been functioning properly, they would have delivered even better top end performance

 

[Bman2895]

Well I'll say it seemed smoother on the top end. But these like i say have some float issues? Sometimes you'll hear the rpm bog and hitting the key for the primer it picks right back up. It'll also do the same if you swing a turn to hard. But both sets wide open ran out about 39-40mph.

 

[Crosbyman]

kind of curious what can go wrong with a carb other than expendable parts the rest is just holes to clean out and mecanical links.

 

[Bman2895]

kind of curious what can go wrong with a carb other than expendable parts the rest is just holes to clean out and mecanical links.

No idea. I went through those carbs several times. Honestly? Those carbs weren't supplying enough fuel on the idle/transition. Drilling the jets on the top carb did improve it, but wasn't happy with it. Something was wrong on those idle circuits.

 

[saltchuckmatt]

Well I'll say it seemed smoother on the top end. But these like i say have some float issues? Sometimes you'll hear the rpm bog and hitting the key for the primer it picks right back up. It'll also do the same if you swing a turn to hard. But both sets wide open ran out about 39-40mph.

If what you describe is happening you will soon have a ship anchor if you keep running it.

 

[Bman2895]

If what you describe is happening you will soon have a ship anchor if you keep running it.

I pulled plugs after that run and it didn't appear to be running lean. Atleast not for long enough periods for the plugs to show.

Not sure what to look for though on the floats. One did kinda "catch" when I popped the bowls and made sure all was clean. But it was okay once I shot some cleaner through it.

 

[saltchuckmatt]

I pulled plugs after that run and it didn't appear to be running lean. Atleast not for long enough periods for the plugs to show.

Not sure what to look for though on the floats. One did kinda "catch" when I popped the bowls and made sure all was clean. But it was okay once I shot some cleaner through it.

Kind of a tough one, but your kind of doing the big "experiment" anyways.

 

[jimmbo]

kind of curious what can go wrong with a carb other than expendable parts the rest is just holes to clean out and mecanical links.

Bowls can Warp, Throttle Shafts and Holes can wear leading to a Lean Mix, Mixture Needles being less than gently seated.
Gasoline with Alcohol in it can wreck havoc on the Carb