Help with carb and synch - 1959 35hp Lark

[deserttoad]

I was given a boat and motor from my grandfather about 5 years ago. He claimed it had just been gone through at the boat shop and was ready to go. I brought it home and put it in a bucket to fire it up. After a bit of work it ran with lots of smoke but settled down and seemed okay. Took it out to the lake and it ran fine for 30 minutes or so, then quit and wouldn't start. Pulled the plugs and they were fouled bad (TOP cylinder worse than the bottom). Rebuilt the carb - same prob.<br /><br />So I'm reading in my repair manual (Seloc), about how to synch inginition to the carb. It was way off, best I can do is within 1/8 inch of the mark.<br /><br />So now the question: would the synch cause this, or did I do a bad rebuild job?<br /><br />Also, the book claims a bad fuel pump will foul the top worse than the bottom plug, but it tested okay.<br /><br />thanks for the time,<br /><br />DT

 

[Paul Moir]

Re: Help with carb and synch - 1959 35hp Lark

The Seloc manual is a bit unclear about what you need to line up with scribed line on the cam. Have a look at this post to make sure:<br /> http://forums.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=28;t=033290#000006 <br /><br />On your 35hp, is the fuel pump connected to the top cylinder or bottom? A good test for the pump is to detach the pressure hose, pump up the primer bulb and see if any fuel leaks out.<br /><br />Other than that, it would be worth checking ignition (just in case). If you can get both sparks to jump a 3/8" gap you can safely assume it's just fine.<br /><br />If none of that turns up a problem next, I would check compression. After that I would be hunting for a crankcase leak. You've got the J4C plugs in there right?

 

[Joe Reeves]

Re: Help with carb and synch - 1959 35hp Lark

(Synchronization Of Older 2 Cyl Engines)<br />(Such As The 28, 33, 40hp Etc models )<br /> <br />On the linkage that runs from the armature plate (the plate the coils & points set on) to the carburetor throttle roller, loosen the set screw on the brass collar that you see there and temporarily move it away from the armature plate/vertical throttle arm clevis (clevis is that thing the linkage rod slides through). We'll refer to that vertical throttle arm/armature plate clevis simply as the "clevis" from this point on.<br /> <br />Look at the cam that's attached to the front of the armature plate.... the cam that slides up against the carburetor throttle roller. You'll notice that there's a scribe mark on it. The carburetor roller should contact the cam and just start to open the throttle butterfly when that scribe mark is dead <br /> with the roller.<br /><br />With the engine in gear (not running of course) have the armature plate advanced all the way (by hand) so that it is up against its stop. Now adjust the brass collar (set screw) on that associated linkage rod so that it is up against the clevis. It should be adjusted so that there is either no play, or just a hairs play between the collar and the clevis.<br /><br />At this point, the armature plate movement is not advancing the throttle butterfly via the rod movement, but further movement of the throttle control, although the armature plate cannot move any farther, causes the tension spring at the armature plate to allow the vertical throttle arm to move farther which now advances the carburetor throttle butterfly via the rod.<br /><br />If all else with your engine is as it should be, that should do it.

 

[deserttoad]

Re: Help with carb and synch - 1959 35hp Lark

Thanks for the info. My pump is attached to the upper cylinder, and I checked like you said, no leaks at all. When I adjusted that eccentric, I couldn' get it just perfect, but I didn't have the motor in gear - will this matter? I got the scribe mark about 1/8 inch to the left of where is should be. I didn't adjust the brass collar, I'll look at this real close as well.<br /><br />Checked compression, top cylinder 80lbs, bottom about 78lbs. So that seems good. <br /><br />Book says to use J4J plugs, that different than J4C?<br /><br />Thanks for the info!<br /><br />DT<br /><br />PS Found a guy who has a 35hp Evinrude that runs great, he'll sell it for $300. So that option looks good as well.

 

[Paul Moir]

Re: Help with carb and synch - 1959 35hp Lark

It does not matter if the engine is in gear for the carb/timing sync, since the armature plate hits the neutral stop well after the pointer & mark line up. At least that's the case on my engine. You will need to put it in gear to do the brass collar adjustment though. To put the outboard in gear without running it usually you have to turn the propeller a little bit.<br /><br />Getting the timing perfect is important because it greatly affects the engine's mid throttle performance and efficiency. If it's really far off it can cause engine damage. 1/8" doesn't seem very far to me, but I usually aim to get it closer than that. Rather than fiddle with the throttle, try just turning the armature plate itself by hand. Also snap the carb's butterfly closed so it's fully closed. No sense haveing precision on one and not the other.<br /><br />Champion no longer makes the J4J plug. But they do make the J4C. The only difference is the J4C plug's ground electrode is a little longer so it completely covers the centre electrode. That matters very little so the J4C is the recommended replacement plug, as per BRP's latest chart. Champion's current chart erroneously suggests the J8C plug, which is far too hot and can cause serious engine damage. <br /><br />When you pump the primer bulb, is there any hint of fuel leaking out of the carb? It sure sounds like you're running rich and there can only be a few causes of that. Was there anything funny when you adjusted the mix screws? I usually end up somewhere around 3/8 of a turn out on the high speed and about 1 turn out on the low speed.

 

[deserttoad]

Re: Help with carb and synch - 1959 35hp Lark

Okay, just noticed that my motor cover calls for a J6J plug, a bit hotter than the J4J. Also, with the J4J plugs the spark looked good, but didn't jump from the plug.<br /><br />And since this will be a family boat, I'm thinking of buying that $300 motor, and use it this year. That way I'll have a spare once I get mine going.<br /><br />The carb isn't leaking fuel, but tonight it would fire for just a half second and quit. So perhaps I should check or replace the points and condenser to get a better spark, and clean out the carb again - it's been sitting with fuel in it for about 4 years I think.<br /><br /><br />Thanks again for the info!<br /><br />DT