1978 Johnson 140hp running rough. Need advice

[Bman2895]

They certainly not my Favorite Item either, but many times I have removed them on Carbs that the Owner insisted were spotless, and found a pile of Gum/Varnish/Dirt hiding behind them with no way to get out.
On the Carbs with fixed Idle Jets, Settings like the Float become Critical, as well as proper Gasket Fitment, as you mentioned above. Wear on the Throttle Shafts can become an issue over time, as that can allow excessive Air to enter, which is undesirable as the Throttle Plates are Fully Closed at Idle, actually quite higher than Idle Speed, and an Lean Condition can occur.

Well I have noticed there throttle shafts do have some play. I'm gonna source some good rebuild kits. Get it all back together and then I heard someone say to try some axle grease around the shafts to help determine if they are causing an issue.

 

[Bman2895]

On the topic of float height. I read the idea is just to get the end of the float opposite the needle just above level with the body of the carb correct?

And what was the sealer recommended for the welch plugs? Recall reading about it but can't seem to find that post again

 

[tphoyt]

I have always set floats level with no trouble but others may have better info.
Some people use nail polish on the plugs.
I have used form a gasket on a few that I was suspicious of and had no problems with it.

 

[airshot]

A good rebuild kit will give you specs for setting the float along with other adjustments. As far as sealing the plugs, if installed properly, no sealant is needed. With low compression, everything needs to be set just right to run correctly.

 

[Bman2895]

A good rebuild kit will give you specs for setting the float along with other adjustments. As far as sealing the plugs, if installed properly, no sealant is needed. With low compression, everything needs to be set just right to run correctly.

Well I've found some OEM kits local. And yeah I can tell it's picky. For a moment yesterday it was just about right. The off idle was decent and the idle was steady.

Maybe the plugs were crappy and undersized or maybe I'm just not knocking them in hard enough to expand them fully.

 

[tphoyt]

It’s doesn’t take much to tap them in and you can go to far and they will become lose again.
I have killed a few over the years by saying I’ll give it one more tap.

 

[Open Water]

It’s doesn’t take much to tap them in and you can go to far and they will become lose again.
I have killed a few over the years by saying I’ll give it one more tap.

Berryman carb cleaner. Gallon can, remove carb soak according to label. Replace/rebuild kit. Might just help you out.

 

[Bman2895]

Little update. Had time this week to get the carbs back on. Fired it up on water horns and its back to idling good on all 4 again. Will take it to the lake this weekend to test in the water as again.

 

[ct1762@gmail.com]

I would be planning on a rebuild as Racer said... 100-110psi is too low. those 78' 140's had very tight heads unless someone replaced them for crappy fuel. im sure it will run for quite a while so if thats all your after no worries, but it would be a different motor once properly bored and finish honed to the next size. id be worried about carbon sticking the rings over all these years. after a rebuild i advise premium fuel and full synthetic oil (after walmart dino-juice break in oil) and an engine tuner decarb every season without fail.

 

[airshot]

I would never use premium fuel if the mfgr recommends regular grade. Doing so can make your engine less powerful as premium fuel burns slower. Numerous studies have shown this, if your engine actually runs better, then you have issues besides fuel.