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Johnson 90 Fuel Feed Timing Major Stumper Help Me

M

Mike Kopf

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" Hello, My name is Mike I hav

" Hello, My name is Mike I have a 2001 Johnson 90 outboard; Mod# J90PLSIF.
The engine has been completely rebuilt. New #1 piston oversize 20 over (hole in top of old piston due to detonation I was told). I have followed the OMC service manual to a 't' and been meticulous in the rebuild. All new rings w compression about 120 in each cylinder give or take about a pound or two. All four carbs rebuilt and carefully cleaned. Link and sync done by Johnson service tech. Here is where I am frustrated to no end. The engine runs fine at med to higher speeds but idles very poorly even when out of gear. It is very difficult to keep running. If I press key in to use primer solenoid it will increase idle speed and run smoother for a few seconds and then go back to running poorly and usually runs slower and slower gradually until it quits. I have taken the carbs off so many times to go through them I lost count and each time it runs exactly the same with absolutely no change in performance. Floats are set to OMC manual and low speed needles also set at OMC recommended number of turns (5 3/4 out from seat). The three tiny holes near butterfly valve are all clear on all four carbs. Seems starved for fuel but I am stumped. Can you help? I am at wits end.
Thanks,
Mike "
 
" Hey Mike....Try this...
Wit

" Hey Mike....Try this...
With engine warmed up,run at the fastest warm-up the lever will allow...with the air cleaner off, hold you hand close the the carbs. one at a time and see if fuel is being blown back out..if so, that indicates a bent or broken reed plate finger and this will cause the engine to idle poorly if at all becouse of wrong fuel mixture...remove carbs,(one more time!)and look in at the reed plates and see if you see anything of suspect...this could be the problem....TommyG "
 
Thanks Tommy but when you pul

Thanks Tommy but when you pull the carbs the throttle bodies come right off and I have seen the reeds countless times and they are perfect.
 
" Mike,
Try using another fue

" Mike,
Try using another fuel tank and hose. Sounds like fuel supply pblm. "
 
" Sorry about the over done &#

" Sorry about the over done "!". First time on board, wasn't sure I would be noticed. "
 
Carburetors rarerely are a ca

Carburetors rarerely are a cause of the problem.Your symptoms are "classic" of poor crankcase compression.Did you inspect crankshaft sealing rings?? Did you take lots of time to clean the half joint?? What sealer did you use on the half joint?
 
Sealing rings looked good not

Sealing rings looked good not scored or messed up from what I could tell. How do check these? Used OMC gelseal 2 on halves and spent hours cleaning surfaces to spotless.
How can I check crankcase seal? Man I hope that is not it. I am a garage mechanic and have limited OMC tools. Thanks for your help.
 
" You haven't mentioned th

" You haven't mentioned that you tried to adjust the idle mixture needles, only that you set them to the recommended specs. Did you try to adjust the needles? "
 
" I spoke with the Johnson tec

" I spoke with the Johnson tech guy today and he said that I might need to open the needles as much as ten turns. In the OMC manual it talks about turns in 1/8th increments. I tried that and it did not seem to make a difference. It would take me all day to get there at that rate. Tomorrow, I am going to really open them up and see if that does it. Thanks, I'll get back to you. "
 
" If your getting top end perf

" If your getting top end performance than fuel supply is not your problem. If your a garage mechanic than don't forget your basics.Let the engine run at high speed to clean it out for a few minutes than bring it down to idle. LISTEN to the engine run, LOOK at whats going on,are you getting more and more smoke, do you hear any cylinders misfiring. Whats the engine temp Too cold? Let it stall out. Pull the plugs and inspect them are they soaked,dry even colored. Try and find a starting point instead of a crap shoot. You can have anything from a weak coil to a recirc problem to a stuck themostat to a improper sync and link. "
 
" Mike I was having same probl

" Mike I was having same problem with my Johnson 10hp. Runs great mid to top range but wouldnt idle well at all then die out. I found I was running too lean. You said when you used the primer solenoid it idles better. Maybe it needs more gas, running too lean. And the Johnson mechanic seems to think the same thing. Mine now can idle down very slow and stay solid. Happy adjusting. cxd "
 
Eureka! Sometimes it is the o

Eureka! Sometimes it is the obvious. Turns out that you were all right. The low speed needles were not out far enough. The book calls for 5 3/4 turns out from seat. It began running correctly about 8 or 9 turns out. That brings up another probelem; how do I balance the carbs so that one is not overly rich or lean from the rest? Thanks for everyone's help.
 
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