1987 Johnson 70 Carb Rebuild Questions

[BOAH]

I've got an '87 Johnson 70 that has been sitting for quite a while. The only way to keep it running is by choking it before it dies. So first thing I'm going to to is rebuild the carbs. I've got the carb kits and I'm ready to start but I have a few questions.

First at the top of the body running perpindicular to the body is an opening on both sides that has a screen placed on each end. I haven't seen any mention of servicing / replacing these two screens. What are these for? Air flow?

Second, on a rebuild like this, is it necessary to replace the core plugs? I haven't seen much mention of replacing these. the manual says don't do it unless you see them leaking? Not sure about that.

Third, apparently there are two different possible low speed types of jets and needles. One is the long needle and the other looks like a shorter screw. Are both of these types adjustable and if so what is the procedure?

Thanks for your help!

 

[Bosunsmate]

Re: 1987 Johnson 70 Carb Rebuild Questions

I think those are all orifices on those carbs, just get a smaller screw driver and undo them clean them, check nothings blocking them and blow some carb cleaner or wd40 or something down the holes where they came out of and make sure the cleaner comes out another end somewhere indicating the little passages behind and inside the carb that you cant see arent blocked. Thats where I normally i find any blockage.

So no adjustment is done when you have fixed orifices.
I would take the manuals advise to not remove the plugs too unless by spraying down one of the little holes you think there is a blockage in there.
Not sure what the screen is you mention, a photo would help

 

[BOAH]

Re: 1987 Johnson 70 Carb Rebuild Questions

Here's a picture of those screens.

 

[Bosunsmate]

Re: 1987 Johnson 70 Carb Rebuild Questions

I dont know what those are, in my opinion any opening should of being closed with a plug.
Has this motor ever run well?

 

[boobie]

Re: 1987 Johnson 70 Carb Rebuild Questions

They were installed from the factory as vent screens. Leave them right where they are.

 

[Bosunsmate]

Re: 1987 Johnson 70 Carb Rebuild Questions

Your carbs dont seem to match what comes up under that model as there are no screens on the schematic of them

 

[boobie]

Re: 1987 Johnson 70 Carb Rebuild Questions

Most likely part of the carb body and non-serviceable.

 

[BOAH]

Re: 1987 Johnson 70 Carb Rebuild Questions

Sounds good to me. I'll leave the screens where they are.

Another question, what is the proper measurement of the float drop for this carb? According to the diagram in the carb kit, they measure from the carb body to the first edge of the float and say that it should be 3/4 of an inch. According to the manual, they measure it from the carb body to the far edge of the float and say 1 1/8 to 1 5/8. Which one should I use?

Thanks!

 

[175se]

Re: 1987 Johnson 70 Carb Rebuild Questions

measure float drop from body to bottom edge or the 1 1/8 to 1 5/8