Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

[kippstakes]

The mixture screws on my Lark's carbs won't stay in place after adjusted- threads are not snug enough. As the engine runs and vibrates, they work their way all the way out til they hit the carb cover. They each have a seal/o-ring that might have kept them in place at one time, but they don't seem to be doing much now (if that is their purpose).
I'm thinking about installing springs over the threads to keep them in place (similar to my motorcycle's idle jet carb engineering). I think it will work, but it seems strange that they are engineered this way. I'm pretty sure they don't come with springs stock, so how do they stay in place normally? Maybe the o-rings, I guess.

Sound like a decent idea? Anyone else had this problem?

Thanks

 

[kippstakes]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

Update:
Just did a bit of research and found out that the o-rings are actually valve retainers (I think). SO, in the light of this discovery, do you think a spring will work in the retainer's place to keep the screws in?
Thanks

 

[kippstakes]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

Wow, actually it seems that the 'needles' in my carb are actually just basic flat-tipped screws. It looks like they should be tapered needle screws- is this normal, or did the last guy tamper with these things?

 

[racerone]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

Sounds to me like your carburetors are from a newer model.------------The adjusting needle was brass on a 1972 model.---------The screw you have is an inch or so long and steel ?-------Carburetors on newer motors had a fixed idle jet.---------Pictures always help clear up the confusion on these matters !!!!

 

[midcarolina]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

The retainer valves are wore out........they are cheap to replace, or once you have them set correctly just dab a little blue thread locker on exterior to lock needle in position.

 

[kippstakes]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

Correct, screws are about an inch and steel.
I'll grab some new retainers, maybe some thread lock also just to be sure.
Thanks for the info.
Also, since they seem to be from a newer model, does anyone know what the standard/baseline setting is for them? (ie how many turns out from snug?)

 

[racerone]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

Sorry , but they are NOT an adjustment screw at all. -----They are a plug and are to be installed tight !!!!!!!!!!

 

[midcarolina]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

kippstakes.....for clarification are you referring to the slow speed needle valve?

 

[racerone]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

I am not sure why this subject is confusing folks !!

 

[midcarolina]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

I am not sure why this subject is confusing folks !!

In this case it makes no ( zero ) difference if it is adjustable or not......... it is still NOT supposed to back out while under way...

 

[racerone]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

I believe the owner says that he thought they were adjustable so he had these screws turned out 2 turns or whatever.------They are a plug and should be tight !!!!!!!

 

[midcarolina]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

The op said his have retainer valves........ wanna guess what something with the word " retainer " in it's description does....

 

[F_R]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

A 1972 Evinrude Lark 50 has adjustable needles, linked together, with plastic retainers to keep them from vibrating around. Another link connects them to the knob on the lower pan.

If that is not what you have, somebody has changed the carburetors, dinked around with the carburetors, or whatever. Are you sure it is a 1972? Later models had screw plugs with gaskets under the heads.

 

[racerone]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

Thank for that comment Frank.

 

[kippstakes]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

Thanks for weighing in, everyone, this has been very informative.
According to the powerhead serial# it is a 72 (50273C). Now the liklihood of tampering is high considering that there is evidence of other part swaps (new head and a few other things), and according to your posts I am dealing with carbs that are newer than the powerhead. The screw I'm concerned with is, I believe, the slow jet. It is definitely not a needle (in shape), and scews into the same spot the needle would on earlier models, just above the intake on the carb body, #30 on the diagram:

http://www.**********/parts/search/BRP/EVINRUDE/1972/50273C/CARBURETOR/parts.html

Now #29 on the diagram is also there, and it appears to act as a retainer and not (just?) a seal since the openning for the screw has a groove on its bottom side to keep the retainer from spinning as the screw is turned, which leads me to believe that the screws are not meant to be seated (though it would certainly be much easier if they WERE meant to be snugged and left alone). If they are meant to be seated, how is the slow mixture adjusted? There are no other adjustment screws on the carbs.

Behind the screw there is a small hole, which leads into a circuit that makes its way back to an open-air hole next the the slow jet screw's openning, which also leads me to believe that the screw plays a role in mixture/air flow.

What's the story? Snugged up or adjusted out to mix?

Thanks

 

[racerone]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

When you take the screw out and look inside you will see a brass orifice.----That brass orifice is a calibrated hole !------It controls the mixture !----No adjustment provided.----The screw is a plug as it is called such in the parts manual.----The red gasket seals it.----This screw is to be tight !----Likely somebody installed a set of newer 55 / 60 hp carburetors on your motor hoping for a magic power increase.----Any numbers printed / stamped on the carburetors ???-------Look up the carburetor parts for a 1982 60 HP model if you like.

 

[kippstakes]

Re: Mix adjustment screws won't stay in place, considering fix- Evinrude 50hp 72

Excellent. That makes sense, thank you. The carbs are stamped with part numbers, which I don't have access to at the moment- I'll check them when I get home and get their corresponding years. I will also have a peek at my manual, see what she has to say. Your advice sounds correct tho, thanks again. It wouldn't really make sense to use non-tapered screws to adjust the mix.