link and sync... operation of carb butterfly

[NMShooter]

(edited initial questions)

Working on link and sync of carbs. Initially confused about butterfly operation, but I think I have that resolved.

Was unable to adjust roller to contact cam.

I have two means for adjusting idle.

One is to just lengthen the ball linkage.

The other is to adjust the idle position of the timing tree... advancing the the tree a bit throws the throttle linkage forward.

What should the timing be set at for idle? Please read my thread below with pictures, and let me know if I should not be moving that idle / timing tree out quite as much.

 

[Black as]

Re: link and sync... operation of carb butterfly

You need to post what carby you are working on and what you are trying to achieve

 

[NMShooter]

Re: link and sync... operation of carb butterfly

Oops... sorry. 1988 Force 85hp.

Recently disassembled and cleaned carbs, need to try and sync them as detailed in Frank's instructions.

Trying to understand the directions of the sync, as well as understand how the carbs work.

 

[Justinde]

Re: link and sync... operation of carb butterfly

The ball link sort of 'pops' off with a little force.

The carb butterflies would be closed at idle. If they were open to horozontal, your engine would be idleing somewhere in the region of 5500-6000 RPM.

The choke butterfly is the one that you can easily see, and when the choke is engages, it closes with the solenoid. Have you taken off the 'air filters' at the front of the carbs?

Take a look and get back- maybe with a pic??

 

[NMShooter]

Re: link and sync... operation of carb butterfly

Okay.. I went in, and took a look, attempted to work through Frank's sync post, and I think I have some (slightly) more intelligent questions.

With the ball link unhooked, and pointing the cam slot at the roller, this is what I started with :

After rotating the roller around, I was unable to make the roller come in contact with the cam. This was as close as I could get.

Attempting to make the cam still point to the roller required me to shorten the ball linkage substantially. When I did this, and checked WOT position, the butterflies in the carbs were barely opening. I attempted to start the engine and the motor would not start.

So I panicked, thought about this a bit, and removed the ball link again. I pulled the cam completely away from the roller, and after a few tries the motor started. I then placed the cam barely against the roller, and adjusted the link until it perfectly fit the ball joints, and tightened it down. When I did this, at idle, this is what the cam and roller look like :

However, after doing this, I noticed that my idle RPMs were down from about 1000 to 500.

In order to bring the idle RPM back up, I did not adjust the cam link... I adusted the timing tree idle position screw. Was this an incorrect thing to do? Am I advancing the timing too far for idle? I did notice that on subsequent starts, the engine "popped" one time on startup each time. Should I back the timing tree adjustment screw back out, and adjust for initial idle RPM using the ball link?

I made some short throttle blips to about 2500 rpms, and the engine seemed to be pretty snappy. I'll try to post a video of this later, but I suspect that the audio will be crappy.

 

[NMShooter]

Re: link and sync... operation of carb butterfly

Video of the engine starting and throttle blips.

 

[Frank Acampora]

Re: link and sync... operation of carb butterfly

When you reassembled the carbs did you put in the lower carb butterfly correct side out? They are beveled on the edges and if you slide them (or it) on backwards they or it will hold the roller away from the cam. Thus, you will not be able to make the roller touch the cam as it should when setting up. This will not matter on the top two carbs but will make a difference on the bottom one.

It looks correct in the photo but looks can be deceiving. Lacking that, is the nylon bushing hole on the cam pivot worn oversized?

 

[NMShooter]

Re: link and sync... operation of carb butterfly

I did not disassemble the butterfly off of the carb. But I don't know the history on these carbs. They were clearly removed before I bought the boat.

Is this something that I can observe with a mirror, or would I have to remove the carb again to check? Or maybe check by feel?

 

[NMShooter]

Re: link and sync... operation of carb butterfly

Oh... and when i loosend the screw for the roller, the hole did not seem to be hogged out at all. So I don't think that it is oversized.

I'm hoping I don't end up having to remove the carbs again. I need some good luck!

Thank you for the replies.

 

[NMShooter]

Re: link and sync... operation of carb butterfly

Well, I am getting really good at pulling a carb

I took off the bottom carb, and it appears to me that the butterfly is mounted correctly. Three holes on top, on on the bottom. I guess it could be "inside-out". Are the numbers on the butterfly supposed to be pointing in or out?

I looked at the butterfly, and was unable to see any sort of bevel on the edge, so I am still at a loss for why the roller is not capable of touching the cam.

Take a look at this... is the butterfly attached correctly?

 

[jason32038]

Re: link and sync... operation of carb butterfly

The first thing you'd want to do is make sure all throttle butterflies are closed with the ball link removed. All carbs closed adjust ball linkage to where it just touches the roller and there are no gaps between the roller and the cam. Next move throttle to WOT position and make sure the throttle butterflies are horizontal. Timing should be near zero or the right mark on the flywheel in neutral. I believe that when you go full fast idle the trigger advances completely..you would then need to adjust to the mark on the left. Triple check timing on the water at full throttle. One thing I forgot to mention...in my experience working on my '86 85hp...the line on the cam NEVER lines up with the roller you will just need to adjust the ball link to make contact with the roller no matter where the line ends up.

 

[NMShooter]

Re: link and sync... operation of carb butterfly

Ahhh.......

OK, I can come out of panic mode now. I was concerned, as the sync instructions said to point the line at the roller, and adjust the roller to touch the line.

So... that brings me to my other question.

There are two ways to adjust initial idle speed. One is to only adjust the length of the throttle link. The second is to adust the idle speed screw.

Adjusting the idle speed screw also shifts the timing just a little bit. When you increase the idle using the idle screw, it also advances the timing.

How is this best set up? There does not seem to be a timing spec for idle. I'm trying to figure out where to set the idle screw on the timing tree. I don't want to have my idle set at the proper RPMs, but have my timing messed up. Seems like that could cause a melted piston.

Thanks....

 

[jason32038]

Re: link and sync... operation of carb butterfly

The idle screw on the towershaft is for idle speed adjustment only. Make sure your throttle butterflies are horizontal at WOT. Then drain the carb bowls of fuel and while you have a helper crank the engine check the maximum timing advance. You will need to tape the button on the neutral safety switch so you can crank the engine at WOT. The timing mark on the carb should line up with the line on the left of the flywheel or a sixteenth after (slightly to the right of the line). You can then adjust your idle with the idle screw on the towershaft. The carbs and the trigger need to be synched properly to the towershaft so that when you adjust your idle screw they move in sync. Timing is adjusted with a link on the trigger above carbs. The ball link going to the cam should only be adjusted if your butterflies arent completely open or are open too far.

 

[NMShooter]

Re: link and sync... operation of carb butterfly

Yes... throttle butterflies are fully open at WOT. At this point I am not concerned with the timing advance at WOT. I am concerned with the timing setup at idle.

Adjusting the idle screw also rotates the timing tree, which advances the timing at idle.

There appears to be no guidance on how to set the initial length of the ball linkage, or where to set the idle speed screw.

I can screw the idle speed screw all the way out until the minimum point is reached for the idle adjust screw, then lengthen the ball joint link to get the idle speed to the 700rpm spec. But I bet this is not the right way to do this. There must be an initial setup procedure for initial placement of idle screw and initial length of ball joint linkage.

Idle speed is dependent on two things... the length of ball joint link, and the position of the idle speed adjust screw. I am worried that if I have the ball link length incorrect, that the timing at idle will be screwed up.

 

[jason32038]

Re: link and sync... operation of carb butterfly

If your carb butterflies are horizontal at WOT then your ball link doesnt need anymore adjusting. The purpose of the ball link adjuster is to operate the throttle butterflies. The only way to get that thing timed properly is by checking timing at WOT. I suppose you can get timing at idle close for land testing. At idle in neutral the timing should be around zero degrees (The line on the right of the flywheel).

 

[NMShooter]

Re: link and sync... operation of carb butterfly

Okay... I think I got this......

Advance the throttle to the WOT position, and adjust the ball linkage such that the butterflies are perfectly horizontal. (Step 5 on the sticky)

Then adjust the idle using the idle adjust screw. Timing at idle is not as important.

Thank you for being patient as I fumble my way throught this.

 

[Frank Acampora]

Re: link and sync... operation of carb butterfly

There is NO specification for timing at idle. The only importand spec it total advance at WOT. Usually, if the engine is set correctly, timing at idle will fall about + or - 2 degrees from TDC. Similarly, the only importand setting of the ball link is at WOT. Carb butterflies must be horizontal or nearly so. THEN, you set idle speed and carb opening with the idle stop screw.

The roller set to the line on the cam only gives you a baseline from which to work. When set correctly, it lets the carb butterflies open slightly as the throttle is opened and timing increased. In fact, when the engine idle is set, the line will almost always be below the center of the roller.

If it is not touching the cam when the line is pointing to it, the butterflies will not be "cracked" open at idle. No major problem, the engine will run and idle, but not quite correctly.

Your butterfly does seem to be in correctly with the numbers facing out and the three holes facing up. It is difficult to see, but trust me: there is a bevel on the plate. Because it is tilted in the carb bore when closed, the bevel allows it to seat flush against the wall at the top and bottom.