Johnson 20 hp 1972 severe lean sneeze type cough.

[thatone123]

20R72R - Has severe cough at idle. Got this last year and never tried to run it. Good condition for it's age. RE-set idle mixture needle to 1 1/2 turns out.... no effect. This is not the first of these I have seen with this problem. Compression is at around 100 psi.

 

[hardwater fisherman]

I have a 25E72R and I was told there was a idle problem around this time... And also on some motors the bleed valve hose coming off the bypass cover was moved from the top to the bottom...Mine was fitted with a nipple on the lower bypass cover and the bleed valve was plugged on the upper bypass cover.. I also moved the fuel pump to the upper cylinder like on the 18s from an earlier time.. And I kept the bleed vale hose on the bottom..Dont know if it helped but it seems to run better in a barrel..

 

[kbait]

If top or bottom crank seal is leaking, you will have a lean sneeze on that cylinder. Broken/blocked reed valve = same. Cylinder drop test will tell which cylinder, then investigate. Assuming clear passages in low speed circuit on carb and fresh fuel..

 

[racerone]

I am sure they did NOT sneeze when they left the factory.-----Simple repairs / adjustment are needed.

 

[thatone123]

All sounds good! Guess I will break down and do a carb clean first....see what happens then!