Johnson 6hp problems

[heffkid]

Can anyone help, I have 1993 Johnson 6hp 2 stroke that will not run without choke, when it starts with full choke and you push it in it over revs and cuts out. I have removed the carb and cleaned out some crap but still the same, also tried new fuel, any ideas. Thanks J

[guernseylee]

Originally Posted by heffkid

Can anyone help, I have 1993 Johnson 6hp 2 stroke that will not run without choke, when it starts with full choke and you push it in it over revs and cuts out. I have removed the carb and cleaned out some crap but still the same, also tried new fuel, any ideas. Thanks J

air leak - needle valve - float has a hole - idle jet

[9D280]

Heffkid - Welcome to Ribnet!

I would maybe rearrange guernsey's thoughts:

Idle jet. What you describe sounds like it's set too lean. I don't have a manual for that machine, but someone will no doubt come along & tell you how many turns of the idle screw to start with, then its a caser of try it & see, turning the screw no more than about 1/8th turn at a time.

Air leak. If you can get it running on half cholke or by some other way, spray WD40 at all the gjoijts on the intake side. if it revvs you got a leak. While we're on the subject, you did use new gaskets when reassembling?

Needle valve - would be sticking to cause that, but you say you've cleaned it. Unless theengine has done millions of hours & it;s worn, but I still ereckon you are running lean.

Simialr thoughts on the float sinking - it would flood the engine as the fuel pump merrilyt filled the carbs. Also I guress you might have spotted it was full of fuel when disasembling.


Hopefully someone will be along soon with more detialed knowledge of that engine. If however you know which one the idle mix screw is, probably worth richening it up a bit.

[guernseylee]

Originally Posted by 9D280

Heffkid - Welcome to Ribnet!

I would maybe rearrange guernsey's thoughts:

Idle jet. What you describe sounds like it's set too lean. I don't have a manual for that machine, but someone will no doubt come along & tell you how many turns of the idle screw to start with, then its a caser of try it & see, turning the screw no more than about 1/8th turn at a time.

Air leak. If you can get it running on half cholke or by some other way, spray WD40 at all the gjoijts on the intake side. if it revvs you got a leak. While we're on the subject, you did use new gaskets when reassembling?

Needle valve - would be sticking to cause that, but you say you've cleaned it. Unless theengine has done millions of hours & it;s worn, but I still ereckon you are running lean.

Simialr thoughts on the float sinking - it would flood the engine as the fuel pump merrilyt filled the carbs. Also I guress you might have spotted it was full of fuel when disasembling.


Hopefully someone will be along soon with more detialed knowledge of that engine. If however you know which one the idle mix screw is, probably worth richening it up a bit.

cheers for that

[heffkid]

Hi Guys, thanks for that, since your response I bought a carb rebuild kit and started from scratch which has sorted one problem and now created another. Now it runs fine without choke and idles fine all day long however when you put it into gear and give it a small bit of trottle it just cuts out I am baffled!!

[9D280]

Open the idle screw by about 1/8 turn.

What happens is as you open the throttle, the carb goes from using the idle jet (down stream of the valve) to the main jet (upstream). problem is if you don't have enough fuel flowing though the idle port, that half second of changover as the throttle opens & lets more air in before the main jet "kicks in" means you get a brief spell of too lean a mix, and because it's not spinning fast enough for the flywheel to overcome it, it stalls.

One way to check that is as you open the throttle blip the choke - if it takes off & continues to run at open throtttle that's your problem. But don't open the idle adjuster more than about 1/8 turn at a time or you'll end up flooding it.

[joe_db]

Check the throttle and timing linkages!
If it is the same as my 6 HP Johnson, the throttle actually advances the timing and moves a linkage that presses on something that moves the throttle (think Wallace and Grommet invention). So if it breaks or comes apart, you can idle but any throttle and it stalls. I had a LONG trip home one day at .5 knots because of this