1977 50050 Carb sync

"Got this engine on the run now!!! Gettin close to be goin fishin. Thanks to Jeff, but got one last item to deal with, I hope anyway. Carb sync. Im pretty sure Ive got it close but I still think it is a little off. What is the proper procedure to sync them. Im sure its in the manual but I wont have that for a few days yet. Thanks for all the help you guys, dont know what Id to without ya....."

"Here's the theory behind

"Here's the theory behind carb syncing:

To get a 2 stroke motor to idle low enough to shift it (without...you know) the spark has to be retarded something awful! (A typical car engine has at least 8 degrees advance at idle--and that's without the vacuum advance adding 10 more.) A stroke may be 10 degrees RETARDED at idle, with the carbs closed, just to get that sucker to slow down!

So...when you throttle up, you have to take all of that retard out of there, and add some advance as well BEFORE opening the carbs. If not, the motor will blubber like crazy; it may may even stall.

So...the trick is to get LOTS of advance going on BEFORE the carbs start to open. I typically get virtually all of it (the advance) in before the carbs start to open--the more the better.

Some might claim that this could cause cause pinging, from having it advanced so far, but since the carbs are barely open that is hooey!

Jeff

PS: I ran my old KG-7 at full advance ALL the time, opening the carbs only with my hand throttle. That motor had no neutral, so it wasn't a problem shifting."

"Actually Jeff, what I was ask

"Actually Jeff, what I was asking about was the syncing of the two carbs to each other. Top carb is preset for the most part but the bottom carb throttle connection has the adjustment. I just cant tell when they are both in the same position before tightening the lock screw. I got the manual but it doesnt refer to that adjustment. This motor has 120 lbs compression even up. Should run like a new caddie...... I will be doin the timing adjustments in the next day or so but if the carbs arnt right the rest is going to be wrong also. Yes??"

"Oooohhh! Never heard that qu

"Oooohhh! Never heard that question come up before.

Far as I know there's no way to do it other than bending/ twisting the linkage. Frankly, since Merc didn't bother making them adjustable (even on sixes with 3 carbs) I suspect it's not an issue.

Jeff"

In that case I guess maybe som

In that case I guess maybe somebody elongated the attaching hole at the bottom carb. for who knows what reason/. Ill get a pic and look closer.
Thanks for the help again Jeff.....

I WAS WRONG! There is a small

I WAS WRONG! There is a small bolt that allows the bottom carb linkage to be moved. Doh! on me for forgetting that.

Jeff

"We used to use a piece of pla

"We used to use a piece of plastic tubing ,one end in the carbie venturi,or somewhere around there,other end in your ear,for adjusting carbies on car engines.cheap simple way of checking the throttle openings of each carbie.works on any multi-carb motor"

"Back the throttle linkage off

"Back the throttle linkage off and loosen the screw on the plastic connector and retighten, idle the idle screw up and adjust from there.

The old inline sixs were progressive throttle opening due to the plastic connector between carbies and they ran great"

Re: 77 50050 Carb sync

Its a valid question. It may be that the engine manufacture is more interested in the matching the throttle plate openings vs matching inlet air volume/intake manifold pressure drops. 4 strokes seem to be more susceptible to syncing as it helps the drivability like on a motorcycle and some marine engines but some 2 stroke engines have manifold test points as well. I'm looking for smoothness on a Mercury Classic 50 so I'm going to start with matching the plate openings (2 carbs) as it has no test points for carb sticks.