Does changing idle speed change WOT timing?

[Cady8special]

Hey guys,

1988 Johnson 90HP-- running petty well right now. Idles at 650 in gear, tops out around 5100 at WOT. Starts well, no issues.

I set the idle by closing butterflies all the way, and adjusting the timing advance screw until the idle was 650 in gear. My question is this-- does that "idle screw" change the WOT timing? I know it advances/retards timing at idle, but does that change my WOT timing at all?

Also, I don't have a timing light, and never changed timing before, but was thinking about buying the light and checking the timing myself. If my motor is running as I say it is, would it be wise to leave it alone, or would you guys recommend that I buy the light and check timing? I bought it used last season, and don't really know what the previous owner has done.

Thanks for any advice guys.

 

[Lyle29464]

Re: Does changing idle speed change WOT timing?

I think you need to call in someone. You really should not mess with the settings on the advance.

 

[Cady8special]

Re: Does changing idle speed change WOT timing?

The book says that's how I'm supposed to set the idle-- butterflies closed, advance timing until idle is correct. Is this not right? The screw I'm talking about is about 2 inches long, and when screwed in, advances the timing the same way it would when reving the engine, but doesn't open the butterflies at all.

If this is incorrect, how should the idle be set?

 

[Cady8special]

Re: Does changing idle speed change WOT timing?

Also, if the motor is running pretty well-- 650 at idle, 5100 wot, and starts with a crank or two-- should I leave timing alone, or could timing still need to be adjusted?

 

[fishfeatures]

Re: Does changing idle speed change WOT timing?

timing is set using the timing screw underneath the flywheel at the back of the top carb. Are you confusing something else for the timing screw? I think what you speaking of is the idle setting screw.

Your manual will have detailed pics and instuctions on this area in the lync and sync section. have a look at that, is my suggestion.

 

[Cady8special]

Re: Does changing idle speed change WOT timing?

timing is set using the timing screw underneath the flywheel at the back of the top carb. Are you confusing something else for the timing screw? I think what you speaking of is the idle setting screw.

Your manual will have detailed pics and instuctions on this area in the lync and sync section. have a look at that, is my suggestion.

The "idle" screw I'm talking about is a 2 inch, flathead screw, about 3/8th of an inch thick located on the starboard side. With butterflies closed, I adjust idle speed with that screw as it advances/pulls back the timer base. My question was this-- by adjusting this idle screw, am I changing the top end timing or not? The other question I had, was if my motor is running well at low, mid and high speeds, should I leave the timing alone or would it be a good idea to get a timing light, and really try to fine tune it so that it's running perfectly.

Thanks guys.

 

[wired247]

Re: Does changing idle speed change WOT timing?

The idle speed adjustment only changes the idle timing. It does not affect the total timing. To change the total timing you would adjust the long screw with the rubber stop that is attached to the manifold located above the carburetors on the starboard side That will limit the travel of the timing base in the WOT position.


#75 adjusts the idle timing/speed. It is not supposed to adjust the throttle plates as there is an internal idle circuit that feeds fuel and air for idle.

 

[Cady8special]

Re: Does changing idle speed change WOT timing?

That's perfect- thanks man. I didn't think it affected the total timing, but wasn't 100%. I really appreciate the help.