To lean on idle

[mlaajanen]

Hi

My Johnson 55 1980 sneezes due to it runs to lean at idle.

If changing the idle orifici should it be bigger or smaller in order to make it run less lean?

Now I have simply removed the idle orifici on one cylinder in order to bring the RPM down for the gearbox safety so it runs very fat now.

Michael

 

[flyingscott]

Did you clean the carbs those orifices have been in there a long time to suddenly start having problems. Clean the carbs

 

[ondarvr]

And I think that year has an adjustable low speed screw.

 

[mlaajanen]

And I think that year has an adjustable low speed screw.

Sadly not, everything is fixed.

 

[mlaajanen]

Did you clean the carbs those orifices have been in there a long time to suddenly start having problems. Clean the carbs

The carbs has been clean even before I started to work on this, everything is now very clean atleast as clean as I can do it.
But the problem can have developed over the years due to airleakage in the throttle shaft and/ or the sealing the crankshaft which is not uncommon on old 2-strokes.

So my idea is to "compensate" for this atleast until I will lift the powerhead in the coming winter if needed.

So which orifici should I change and should be bigger or smaller?

 

[oldboat1]

Another vote here to go back to carb cleaning/rebuilding.

think that's the odd duck carb. Think should be a screw plug up on the shoulder and another up on the top. I think the one on the should is probably access to the idle orifice, and up on top for intermediate running. The plug on the bottom would cover the high speed jet. I wouldn't remove the actual orifice/jet, but soak them (disassemble the carb and soak parts and housings -- everything metal.) Follow with some careful picking with a tiny piece of soft wire or some monofilament -- followed by some carb spray. Don't pick at the jets -- just soaking and spray. You need to remove the domed cover to get at the passages under there, and clean them out. Remove the covers/plugs and soak the housing.

As you have taken out one or more of the jets, check them for damage and replace when both the carb housing and jet is clean. Be very careful not to bugger up a jet. There is probably no need to rejet unless they are damaged -- likely the carb just needs a thorough cleaning.

 

[ondarvr]

Check the compression.

 

[flyingscott]

You cannot compensate for a leaking crankshaft seal with a richer orifice. That is because the leak is after the carb which means you lose vacuum through the carb body so less fuel regardless. That is an air orifice for the idle no fuel goes through it so to make it richer you need to go smaller which restricts the air flow even more. For the carb to be leaking through the throttle shafts is pretty rare and for that to happen you should see a lot of play in the throttle shaft. Which will lead to the carb butterflies usually bind up. By taking out the orifice you leaned that cylinder out.

 

[mlaajanen]

Another vote here to go back to carb cleaning/rebuilding.

think that's the odd duck carb. Think should be a screw plug up on the shoulder and another up on the top. I think the one on the should is probably access to the idle orifice, and up on top for intermediate running. The plug on the bottom would cover the high speed jet. I wouldn't remove the actual orifice/jet, but soak them (disassemble the carb and soak parts and housings -- everything metal.) Follow with some careful picking with a tiny piece of soft wire or some monofilament -- followed by some carb spray. Don't pick at the jets -- just soaking and spray. You need to remove the domed cover to get at the passages under there, and clean them out. Remove the covers/plugs and soak the housing.

As you have taken out one or more of the jets, check them for damage and replace when both the carb housing and jet is clean. Be very careful not to bugger up a jet. There is probably no need to rejet unless they are damaged -- likely the carb just needs a thorough cleaning.

I have already rebuilt them, the cover plugs removed and cleaned cleaned and cleaned

Like I said, I think that the engine sucks air via the throttle shaft since there is no bearing and no seal on them like on a high performance carb but it could also be the main shaft sealing which leaks air. Now I have the boat far away in the summer house and will get back in two weeks time so I was thinking of ordering some new jets to solve the issue.

Since I am i Sweden, shipping jets takes 2 weeks and costs $$ so I need to be a bit ahead.

If I was there right now I could use startergas to spray around the engine to search for leakage.

They engine runs perfect at middle and high speed, just did a 400 Nm trip with the boat

 

[mlaajanen]

Check the compression.

Done that, fine on both cyls 140 if I remember right in i different thread

 

[mlaajanen]

You cannot compensate for a leaking crankshaft seal with a richer orifice. That is because the leak is after the carb which means you lose vacuum through the carb body so less fuel regardless. That is an air orifice for the idle no fuel goes through it so to make it richer you need to go smaller which restricts the air flow even more. For the carb to be leaking through the throttle shafts is pretty rare and for that to happen you should see a lot of play in the throttle shaft. Which will lead to the carb butterflies usually bind up. By taking out the orifice you leaned that cylinder out.

For sure I loose vacum but still there is alot of vacum at idle that can suck fuel since the throttle is closed!

Aha, but how come the engine gets to fat mix without the top cylinder idle orifici and why does the RPM at Idle go up very very high thats usually what a lean mix gives?

I have play in the trottle shaft, but if it's to much or not I can't tell.
If I compare tyhe jets that I have with the ones here, they differ.
I have 37 in the intermediate jet, 48 in idle and 57D as main jet which if I understand mean that my engine is set to leaner that the spec below!

http://www.iboats.com/Carburetor/dm/...iew_id.1533025

 

[flyingscott]

For sure I loose vacum but still there is alot of vacum at idle that can suck fuel since the throttle is closed!

Aha, but how come the engine gets to fat mix without the top cylinder idle orifici and why does the RPM at Idle go up very very high thats usually what a lean mix gives?

I have play in the trottle shaft, but if it's to much or not I can't tell.

There is no AHA about it that's how they work the bigger the orifice the leaner the mix the smaller the orifice the richer the idle mix.. You obviously know more about your motor than I do so good luck with it.

 

[mlaajanen]

There is no AHA about it that's how they work the bigger the orifice the leaner the mix the smaller the orifice the richer the idle mix.. You obviously know more about your motor than I do so good luck with it.

So what do you think about the jets I have which does not correspond to the one on iboats spec, should I order a set of the one specified here?
My engine is assembled in belgium, mark 1980 and its a short shaft, but it seams like in the US there is no short shaft 1980, so I used the 1979 spec at iboats.

I have 47 in idel jet but iboat says 44, intermediate is just dirfferent on one carb, iboats say that the upper and lower should be different.

 

[flyingscott]

Need the model# there is a short shaft built then what I found is a #35 or 36 for a 1980 55 hp

 

[mlaajanen]

Need the model# there is a short shaft built then what I found is a #35 or 36 for a 1980 55 hp

Sadly, I don't have it here bit it stated 80 and some character for Belgium assembly.

Do you mean that the jet should #35 for Idle or intermedia idle?

And can you find a 1980 short shaft?

It's a electric starter on the engine which seams to affect the jets

 

[flyingscott]

Where are you pulling these jets from late production electric start model Has a #45 high speed jet. MODEL # is going to be critical for your motor because they distinguish between rope start and electric start and because of the short shaft. Very seldom does Evinrude have a idle orifice in the 40s we really need a model # because we are just guessing and need to narrow your motor down. The 1979 and 1980 are very different blocks not the same. Lot of OMC Belgium built motors nothing special about that.

 

[oldboat1]

Hmmm. e.g., Electric start model J55RLCSA.

For what it's worth, I saw one reference to the following jets: idle 48 early and 45 late, intermed. 35 or 36, main/h.s. 55D upper, 56D lower.

BRP shows 36 for idle, 36, 45 or 48 for intermediate (depending on carb), main/h.s. 55D upper and 56D lower.

That's if I read it right.

Try the BRP site: http://epc.brp.com/Index.aspx?lang=E&s1=b2f77940-97df-4ba6-9b86-52e1e2700186

 

[mlaajanen]

Thanks both of you. I will let you know once back to the summer house how it goes. Have ordered a set of jets for the 1979 55 so I have something to do once back with the boat

If interested in the our Vator 15GL boat it can be see it on Facebook, the picture was taken just after we arrived after a ~400Nm trip on the east coast of Sweden for a week ago, https://www.facebook.com/Vator-Boats-407578942758901/?ref=ts&fref=ts

The boat makes 30 knots with me and two kids and during the trip we had 5 OMC tanks with us due to some long offshore legs .

Michael