timing question

[Thumpbass]

OK I bought a timing light and made a piston stop out of an old plug and am getting ready to do a link and sync. I am curious though about the idle timing versus the maximum spark advance. Does adjusting the throttle cam during the idle timing adjustment process change the maximum spark advance setting? I know I'll get to adjusting the maximum spark advance later in the link and sync process but I'm just curious as to if the 2 adjustments afect each other.

 

[Thumpbass]

Re: timing question

OK I bought a timing light and made a piston stop out of an old plug and am getting ready to do a link and sync. I am curious though about the idle timing versus the maximum spark advance. Does adjusting the throttle cam during the idle timing adjustment process change the maximum spark advance setting? I know I'll get to adjusting the maximum spark advance later in the link and sync process but I'm just curious as to if the 2 adjustments afect each other.

1979 100hp Johnson...sorry forgot to mention

 

[R.Johnson]

Re: timing question

Idle advance does not effect full throttle advance. When you get into full sync. & link, this will be easier to understand.

 

[Theoutdoorsman]

Re: timing question

Thumpbass........... I'll likely be following your thread closely, as I am in the middle of a timing issue myself, with my 79 Evinrude 140. My service manual also covers your motor as well........ I think. Just curious what your model number is? Maybe together, we can get both our problems resolved, with help from some others here of course. My probems, like yours, isn't with the syncronization of the chokes and throttle valves (that's the easy part), but lies in getting the correct adjustment of the throttle pick-up point. My manual states that, "With the top scribe mark on throttle cam aligned with contact point of cam follower roller, loosen carburetor cam follower screw. Allow throttle spring to close throttle valves. *(no problem)* Hold roller against cam at top scribe mark and tighten screw. Check that throttle shafts begins to rotate as the top scribe mark aligns with contact point of the roller." Now this is where my problem starts????......... If we hold the roller against the cam at the top scribe mark and tighten the screw, aren't we already contacting the cam at the top scribe mark with the cam follower roller? This sentence kind of contradicts itself doesn't it? It reads almost as if there is meant to be a little play in the throttle cams movement BEFORE it hits the cam follower roller. Am I reading this wrong? Or, is the cam follower roller supposed to be in constant contact with the cam itself, and aligned with the top scribe mark? I don't care to go any further until someone can answer this. There are actually three scribe marks on the cam. Top, middle (which has the word "Start" stamped on it), and of course the bottom mark. I am setting mine up using the very top scribe mark as per the manuals instruction and it's specific referrence to this particular mark. Constant contact or not? Hmmm............

 

[Thumpbass]

Re: timing question

Yes, our manuals cover the same models...my motor is a 100TLR79S. I know exactly what you're talking about, I actually ran accross that today and was kinda scratchin my head too. I basically did what it said to do and held the roller to the mark and tightened the screw. I kinda stopped there because I didn't have time to get into hooking up the timing light and adjusting the cam...I'm going to my folk's lake house this weekend and will be able to really get into it on the water...with a boat house and a garage full of my step dad's tools. I did however just play around pulling the throttle cable back to get the screw to contact the stop...I then cranked up the motor and raised the warm up lever to go from around 700 rpms to around 1400 (actually because I read where you had your 5* around 1400) just to see what the cam and roller did. I shut the motor off and walked back and looked and it really didn't look like the roller had moved enough to complete the next step which is adjusting the yoke to make contact with the "upper embossed" mark. That's when I decided that I didn't have time to get into all that...I wondered at that point if I messed up doing the pick up point....

 

[Theoutdoorsman]

Re: timing question

I shut the motor off and walked back and looked and it really didn't look like the roller had moved enough to complete the next step which is adjusting the yoke to make contact with the "upper embossed" mark. That's when I decided that I didn't have time to get into all that...I wondered at that point if I messed up doing the pick up point....

Which leads me to MY next question.......... Are they referring to the "Start" scribe mark here? Or the top scribe mark again? When referring to the "top" scribe mark everywhere else in the manual, it specifically states, "top scribe mark". Here, it says "upper embossed mark"? The manual is kind of vague when referring to the various scribe marks. Maybe I'm just not grasping the concept though. I don't know. If we can't get any replies here, maybe I can do it one way, and you the other. Then compare notes.

 

[Thumpbass]

Re: timing question

I was kinda thinking the same thing...we don't even really say "embossed" down here in Alabama...my guess would be that y'all don't say it in Kentucky very much either...may be the guys who live in Indiana but cross the bridge to go to work in Louisville say it.d

I'll report back after Saturday...hopefully I'll get something figured out before Bama and Florida kick off..if not the motor will have to wait!!

Hopefully we'll get some replies...times like these are where the "get a manual" response doesn't quite cut it....know what I mean?

 

[R.Johnson]

Re: timing question

Starting from the beginng, these adjustment's can be made easier if you disconnect the throttle cable to get it out of the way. Move in the idle stop screw until the throttle cam is out of contact with the rubber roller, loosen the throttle link screw so that both carb's snap fully closed, then tighten screw. Advance throttle cam until it contact's rubber roller, it should contact top mark, or embossed mark, "same thing" so that it is centered on the roller, loosen screw on roller, and adjust if it is not. This will make the adjustment close enough. Start the engine with the trottle cable still disconnected. With a timing light on #1 cylinder, screw in idle stop screw, and adjust until you are at 4-6 degree's B.T.D.C. Now remove the cotter pin, and washer from the throttle cam yoke, this is the white threaded yoke on the bottom of the cam, remove it from it's pin, and screw it in, or out until top mark, or embossed mark just touch's rubber roller, and replace washer, and cotter pin. Now adjust idle speed to 700, to 800 if running on muff's. Replace throttle cable, and adjust trunnion until the throttle linkage is just back to.the stop screw with slight tension. Shut the engine off, and see if the throttle goes completely open, and back to full idle. This should complete the set-up

 

[Theoutdoorsman]

Re: timing question

Sounds easy enough Mr. Johnson. Let's give it a go. Thanks a million for your input on this!!! It is much appreciated............. ALAN

 

[Thumpbass]

Re: timing question

same here!

 

[Theoutdoorsman]

Re: timing question

Hey thumpbass.......... Refer to this link on setting your WOT timing. It will get you really really close if not dead on.

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=28;gtid=1167985

Also, check out my posting mid-way down on that page. There is another link in that thread that will be of considerable use to you in building a spark tester. This will insure you are getting good fire, on all cylinders at the same time, while checking the WOT timing. Works absolutely great!!! And takes about an hour to make it with some old lumber you might have laying around the house or shop. Good luck and let me know your outcome. I'll let you know how things work out on my end.................... ALAN

 

[Theoutdoorsman]

Re: timing question

I just ran through the procedure. This went very very very smoothly, and quick, I might add. It was definitely as easy as reading the walk-through. I have one problem though. I cannot get my idle down to Mr. Johnsons recommended rpm's for the muffs. Mine will go no lower than 1400 as apposed to his recommending 700-800 rpms. I am certain this will drop once it is dunked in the lake, which I plan to do first thing in the morning. The manual suggests idling no more than 650 rpm's in gear with the prop installed. However, I recall having mine set a wee bit higher to avoid stalling out while trailering the boat. I'm curious to see what you come up with, as far as your rpm's on the muffs are concerned. Let us know..................... ALAN

 

[Thumpbass]

Re: timing question

Before I did all my maintenance work (carbs, fuel hoses, fuel pump etc...) My motor was running around 1400-1500 on the muffs and was in the 700 range in the water...I was getting the low idle miss then, that's why I did all the work. I had leaking fule hoses so I was certain that I had a lean condition at idle because I was getting 5000+ at WOT (I know that's arguably lugging, I'll deal with that next). So...I haven't done anything since Mr. Johnson's post but I am flip flopping bewteen cautiosly optimistic and unencouraged (due to my lack of mechanical skills).

I was encouraged when you said you were idling on the muffs at 1400 because that's how my motor was when I got it (before the cough)...but I still could not get the idle screw against the stop with out it idling lower than 700...I know that's close to what Mr Johnson said it should be on the muffs but like you said...If my motor was idling rough (dying getting on the trailer too) at 700 rpms in the water...i know 700-800 in the water is going to be a stretch...who knows though maybe the proper link and sync fixes that...I guess I won't know until saturday when I dunk. It would be nice to get an idle under 650-700 but If my cough problem hasn't cleared up, I still have to address that...I have already replaced 3 coils one power pack (that tested bad on the meter) all the plugs in addition to all the fuel system maintenance.

We'll see...any thoughts?

Thanks

 

[Theoutdoorsman]

Re: timing question

Have you done a compression test to rule out any internal problems? I think mine is definitely a fuel related issue. My compression is 110 psi all the way around. I have done a spark test at WOT and everything looked good. My spark jumps a 7/16 gap easily on all four leads. I just couldn't fully grasp the concept on the link and sync. For some reason I'm a little sceptical about things now being right with mine. I plan to replace all the plugs, before the launch this morning, in order to rule that out of the equation. I'm thinking with over an hour on this rebuild, at an idle running double oil, they very well could be fouled. If this doesn't work, off with the carbs again. Maybe I missed something while I was in there before. I don't know? Too, I'm going to try running her with the cowling off, just in case that #4 plug boot isn't arcing to the cowling lock down latch. Another poster had this problem and said that he found this out by accident. I have also bought a 6 gallon external fuel cell to perform my testing to rule out the onboard fuel cell having a clogged pickup. I don't know, but in a few short hours, I hope to narrow down and isolate my problem source(s)................ Cross your fingers for me and wish me luck.................... ALAN


UPDATE: My test run was a flop. I am pretty certain the link and sync was definitely good to go, however, as it did run a little better. My idle, on the lake, dropped to around 800 rpm's too. I was really tickled with that. It sounded good with the exception of the ever so annoying cough that still persists. Soooo........ Off comes my carbs again, as I found that my lower one was leaking fuel from the front side and it smelled like it was flooding out. I'll get that fixed this weekend and try again sometime Sunday. If you do the link and sync, and that's all the problems you have, it should do the trick for you!!!! Good luck................. ALAN