Adjusting advance 57 35hp Lark

[55'Fleetwin7.5]

Hello

I am in the middle of repairing a mess I created when my flywheel got loose.
While I am there... I am making other adjustments as well.

Is this correct? When the roller is in line with this notch (see pic) I should begin to see the lever move (see pic)... correct?

 

[tmcalavy]

Re: Adjusting advance 57 35hp Lark

You are correct. Look in the carb throat, when the roller contacts the cam plate the back butterfly should be cracked a little...it should smoothly open all the way as the throttle is advanced, bringing the roller forward.

 

[55'Fleetwin7.5]

Re: Adjusting advance 57 35hp Lark

You are correct. Look in the carb throat, when the roller contacts the cam plate the back butterfly should be cracked a little...it should smoothly open all the way as the throttle is advanced, bringing the roller forward.

Ok... is it when it makes contact at all? or when it reaches that notch. If it is when it makes first contact, then what is that little notch for?

 

[tmcalavy]

Re: Adjusting advance 57 35hp Lark

The notch is a reference mark. When the butterfly is just cracked open, the roller should be in contact with the advance plate...that should be pretty close to Start on your throttle grip/control, but they get a little sloppy over the years.

 

[F_R]

Re: Adjusting advance 57 35hp Lark

I believe this is all incorrect. Look to the left of where the roller attaches to the intake manifold. Do you see a pointy upward projection cast as part of the intake manifold?

All the slop and looseness in the linkage should be taken up and the carb shaft just barely start to open when the notch on the brass cam alignes with the pointer, not the roller!!!

 

[55'Fleetwin7.5]

Re: Adjusting advance 57 35hp Lark

I believe this is all incorrect. Look to the left of where the roller attaches to the intake manifold. Do you see a pointy upward projection cast as part of the intake manifold?

All the slop and looseness in the linkage should be taken up and the carb shaft just barely start to open when the notch on the brass cam alignes with the pointer, not the roller!!!

Perfect description! I found the pointer and made an adjustment... Here is a wrinkle. I can't actually see the butterfly because the silencer is on... i could remove it but, i see the lever (where the linkage attaches) just begin to move... is that ok? I hear "just begin to crack" I am more than willing to do that but I am juggling a lot now for my comfort .

 

[F_R]

Re: Adjusting advance 57 35hp Lark

Nobody actually peers down into the throat to see anything move. If you see the lever move, you know the butterfly is moving too. It should be just ready to move when notch is aligned with pointer.

 

[Xcusme]

Re: Adjusting advance 57 35hp Lark

In service manuals, they mention using a small alligator clip (with a short piece of wire attached) to amplify the rotation of the throttle shaft. You would clip the alligator clip to the exposed end of the throttle shaft. Any rotation of the shaft will be easy to see when it moves, or 'starts to crack' the butterfly open. I have found it easier to use a very small tie-wrap on the throttle shaft. You can trim the tag end of the wrap to length if needed.

 

[55'Fleetwin7.5]

Re: Adjusting advance 57 35hp Lark

Outstanding tip! Thank you for sharing it. Every little bit helps. I have resurface the crank shaft... removing the flywheel material that was transfered over with the vibration. i did this using polishing compound and a bit of emery clth on only the most stubborn spot. it looks very clean now. I attached a lead to one of my coils to help with the kill switch... the was another existing on the other coil providing for a different function... I will tap into it rather than introducing yet another connection on the points.

Soon it will be re-assembled... then we will see.

 

[Sea18Horse]

Re: Adjusting advance 57 35hp Lark

F_R wrote;

"I believe this is all incorrect. Look to the left of where the roller attaches to the intake manifold. Do you see a pointy upward projection cast as part of the intake manifold?

All the slop and looseness in the linkage should be taken up and the carb shaft just barely start to open when the notch on the brass cam aligns with the pointer, not the roller!!!"

I take it this is something unique to the big twins? I read this at work this afternoon and wondered about it. I didn't remember seeing any pointers on the intake manifold or near the cam on my 10 or 18. I checked them both when I got home and neither have any pointers of any kind. If no pointer are they set to the roller then? Sorry, I don't have a manual yet.

Can't afford to spend $90.00 on a manual just now. I do have parts manuals now but not a service manual.

Cheers.................Todd

 

[Joe Reeves]

Re: Adjusting advance 57 35hp Lark

Sea18..... Set the roller so that the throttle butterflies just start to open when the scribe mark is dead center with the roller.

 

[F_R]

Re: Adjusting advance 57 35hp Lark

Sea 18, yes the pointer is unique to the Big Twin series of motors. The exception to the rule, if you will.

 

[Sea18Horse]

Re: Adjusting advance 57 35hp Lark

Thanks guys for clarifying that for me. That's how I had them set.

Cheers.................Todd

 

[55'Fleetwin7.5]

Re: Adjusting advance 57 35hp Lark

I made the adjustment... bolted everything back on... now the butterfly opens a bit too early. the notch is about 3/16th from the pointer. What is the result of this going to be... I need to know how important this is before I start ripping things off again. It is nearly impossible to reach the adjustment bolts unless you remove the armature plate... Any tips?

 

[tmcalavy]

Re: Adjusting advance 57 35hp Lark

That's why you look in the carb throat to watch the butterfly...factory marks/pointers are all well and good, but mechanical things develop slop over the years and previous owners may have done who knows what to your outboard. Can't beat watching the butterfly by eye and adjusting from there, whether you have factory reference marks or not. I adjusted my 57 Big Twin 35 hp by eye, just like my FD-11 Johnson 18 hp, and it runs better than when it's set by the marks...go figure.

 

[F_R]

Re: Adjusting advance 57 35hp Lark

I made the adjustment... bolted everything back on... now the butterfly opens a bit too early. the notch is about 3/16th from the pointer. What is the result of this going to be... I need to know how important this is before I start ripping things off again. It is nearly impossible to reach the adjustment bolts unless you remove the armature plate... Any tips?

3/16" translates to 3 1/2 degrees in timing. Putting it into perspective, the timing marks are 1/4" apart, so if you use the special tool to set the points there is a 1/4" timing tolerance allowed even when you get it "perfect".

To answer your question, opening too soon has the effect of making it run lean. Too late same as running too rich. This effects apply only at mid throttle range. Again, to put it into reality, if it is too soon you may have a bit of hesitation as you slowly open the throttle. Too late and it may blubber and "four cycle". But these are symptoms of being way, way off. Other things built into the system are able to take care of such minor misadjustments.

My advice to you is don't worry about it. You've gotten it as good as you can and that is good enough. Move on to something else.