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78 Johnson v4 air screw adjustment

J

jagrbomb11

New member
Hey guys
I got my 1978 115 v4 Johnson out on the lake the other day and it seems to be running rich.(Idles bad, seems to want to always flood, always smells like lot's of gas in the air) I haven't done any work to it yet, but i was wondering if anyone knows what the air screw should be set at on this kind of engine.
Thanks in advance for the any help.
 
There may not be any mixture adjustments on those carburetors.--------Humble advice on my part is to do a compression test.-----------If primer bulb does not go hard you may have leaks.-------Could be the fuel pump diaphragm or a float valve stuck.
 
Nope----Find the reason why the motor appears to run " rich " to you.--------And how long have you owned it ?---------A new aquasition perhaps ?
 
Of course it is possible that somebody has messed with the jets. Jamming wires or drills through them to "clean" them is a killer. How long have you had it and has it ever run correctly for you? Link & sync is just as important as jetting. Maybe even more so. I guess we are saying there is no one-thing-fits-all answer to the problem (if there really is a problem)
 
I haven't owned it long. Bought it last year. I'll have to open up the carbs and see what's going on i guess. If that doesn't work maybe take it to a shop and see what they think.
 
Ok so just did a compression test and all cylinders looked uniform. They ranged from 100 to 110 PSI. However the bottom two cylinder spark plugs did look like they'd been running rich. The top two looked normal. So would the best bet be to get a jet kit for both carburetors?
 
A 10psi difference is a caution sign!!!! The 78 model came with high ring pistons and the top rings roll off and break due to carbon build up from crappy fuel/oil and improper cooling. I would pull the head and inspect first....
 
Did you do proper break-in/heat cycles? Still running double oil? Carbs should have been done during repair, was it bored???
 
I did the top end myself with the help of a mechanic buddy. And Yupp proper break in, give it lots of time to warm up and cool down, backed it off a bit on the oil at this point. Running 1.25 the normal mix ratio now. Wasn't bored, just honed. Carbs weren't adjusted due to the fact it was just honed.
 
A crossflow V-4 should run really , really nice when in " new condition " like that.-------------Where the cylinder bores measured after the honing ??----Checked fuel pump diaphragm ?---Does spark jump a gap of 7/16" on all leads ?---Any chance plug leads are shorting out on cowling pieces ?
 
You state in post #20... "Running 1.25 the normal mix ratio now".

For some reason, I have a problem grasping onto that..... the normal mixture is 50/1... 1pt of 50/1 oil to 6 gal gas. What does 1.25 compute to?
 
joereeves So i started with double the recommended the oil (50:1). I would find the oil mixture then multiply it by 2.00. After a bit, i backed it off to only multiplying it by 1.5. Now I'm multiplying by 1.25 to add just about bit more lubrication.
racerone they were measured after the hone, within tolerances. Fuel pump looks good as far as i can tell according to manuals I'm running the correct plugs. When i touch the plugs while its running i don't get a shock.
I just took the plugs out yesterday. Bottom cylinder plugs looked wet and oily. However the top 2 looked normal. So I'm thinking bottom carb might be pooched/ dirty/plugged.
 
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