Johnson V4 driving me nuts!!

[derek4325]

Always loved OMC but this one is really testing my faith. 1976 johnson 135. So... compression. 105psi in all cylinders except for #2 which was 115psi. Just rebuilt the carburetors with all new gaskets needles and seats. I have spark on all 4. Hopefully the timing is right.. i have no clue at this point. I synced the carbs the best i could. Motor starts hard, idles poor, and has no acceleration. Once in a while i can get it over the "hump" and it will take right off and scoot my 18' starcraft supersport around 41mph. But most of the time its disappointment. So someone help me! Thanks in advance

 

[racerone]

Pull bypass covers and inspect pistons and rings.

 

[derek4325]

Pull bypass covers and inspect pistons and rings.

Sure i can do that but why? Is that compression not sufficient?

 

[racerone]

Oh well.----It is your motor do as you like.-----Trouble shooting is a " lost art " I think.

 

[derek4325]

Oh well.----It is your motor do as you like.-----Trouble shooting is a " lost art " I think.

I'm not questioning you i just dont understand the reasoning of pulling the bypass covers if the compression is sufficient. But if you think that i dont troubleshoot and not willing to take advice then you're sadly mistaking.....

 

[racerone]

I see no orderly trouble shooting mentioned in post # 1 ----Over and out.

 

[derek4325]

I see no orderly trouble shooting mentioned in post # 1 ----Over and out.

So checking for compression, spark, fuel, and so on isn't troubleshooting. Okay gotcha. Please keep the arrogant comments to yourself and leave this thread open for others including myself to learn from their input. All i did was ask a question as to what your reasoning is to do something in order to ... you know... learn. Thank you

 

[interalian]

105psi per hole is low for that motor - should be 125-135. If you're confident your compression tester is accurate, he's suggesting you take off the bypass covers to see if the rings are sticking or maybe broken. Try another gauge before taking anything apart IMO. Are you testing with all 4 plugs out? No need to open throttles for the test.

 

[ChrisO26]

First off, I am NOT an outboard expert/mechanic, but I do know a thing or two about 2-stroke and 4-stroke motors.

105 is pretty low, but I've seen engines with that compression run pretty well, and given the fact that it occasionally runs well, leads me to believe its not a compression issue.

I think the key here is the question, how'd it run before you pulled the carbs? I'm already leaning towards it being a carb jetting/mix issue, and if it ran better before and all you did was mess with the carbs, that'd pretty much confirm it. How were the floats and seats? Bogging down at high throttle is pretty indicative of a too-rich mixture, is there maybe a stuck float allowing too much fuel in? That'd also cause hard starting issues.

 

[flyingscott]

Did you soak the carbs or just put parts in it? Does pumping the primer ball help the situation? If it was my motor I would take the the transfer port covers off. The crossflow V4 motors are good for breaking rings.

 

[derek4325]

I'll pull the bypass covers and see what's what there. But no i am NOT confident in the accuracy of my compression gauge, its a cheapy and i dont have another one to compare it to. At least i can say it's consistent in all 4 so that's a plus. But I'll pull the covers and examine. It will only take a second. I did not remove all the plugs prior to the test. I probably should have. Anyways this is the second time i jave had rhe carburetors off. The first time was a cleaning and the second time was a cleaning/ rebuild. Didn't soak but used 2 fresh cans of carb and choke cleaner. One of the float arms has been messed with though i did make sure both floats were level when being held upside down. Pumping the primer bulb makes no difference. And Chris i agree 100% but the issue here is these carbs have fixed jets so I'm not sure where to go from here with that. Thank you for tbe replies everyone. I'll send an update when/ if i find something else

 

[interalian]

If you were doing the compression test without pulling all plugs, your motor wasn't cranking fast enough to give valid readings IMO. I'd try again before taking off the covers. Yes, that's easy and the gaskets are cheap, but there's a fair amount of ancillary components to remove for access. And scraping gaskets is a pain in the keester.

 

[derek4325]

Aside from the drain plugs, is there supposed to be any o rings or gaskets for the carb jets?

 

[interalian]

The main jets screw right into the bottom part. The 'drain plug' covers that jet and has a fibre washer. Same for the ones on the side. Do you have a jet wrench? Shouldn't use a screwdriver on them.

 

[jakedaawg]

Hopefully the timing is right.. i have no clue at this point. I synced the carbs the best i could.

If you removed and cleaned all 4 orifices on each carb then the "link and synch" is your issue...get a manual.

Is it really a 76? Post model # so we can advise which manual to get...76 was a weird year for Johnson's...

well, I'll butt out now. I dont do those old ones ifn I can avoid it...your in good hands.

 

[derek4325]

I took a cheap screw driver and ground it down to fit in the orifices. Seems to work okay. Im going to pull them once again and double check the floats

 

[derek4325]

Pulled them again and i found that one of the float pins were bad on the top carburetor. Put a new float and pin in, new plugs, double checked the link/sync and it ran beautiful! Thank you for the input everyone!

 

[SweetD]

Love a happy ending, especially a relatively "easy" fix. Good job!

 

[w2much]

Good on ya. What was wrong with the float pin ?

 

[racerone]

?---Post # 1 says carburetors were " all rebuilt with new needles and seats ?---