Merc '65 500 50ph pulley re-install - timing

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cotterj

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Hello All,

I recently took my engine apart to find the reason for my poor WOT. I didn't mark the flywheel before taking it off and now i'm a bit confused on how to reinstall it. I see the two marks to line up the flywheel and the pulley gear on the distributor. My manual says to set it 38 degrees BTDC. Without a timing tool, is there a way to do this accurately? Should I start the motor at TDC and adjust one of the set screws? The 3 screws I have are (Spark advance screw, throttle adjustment screw, and idle adjustment screw).
 
achris

achris

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Re: Merc '65 500 50ph pulley re-install - timing

You can achieve the same thing with judicious use of a vernier calliper with a depth rod on it. Just turn the engine until #1 cylinder is close to TDC. Put a screwdriver in the hole and feel until the piston is right at the top. Remove the screwdriver and measure the depth with the vernier. Remove the vernier and set it at 1/5" (0.20") more, and lock it off right there. So if the TDC depth was, for example, 1.15", then set the calliper at 1.35". Now turn the engine in the right direction about 3/4 of a revolution. Insert the vernier and continue to turn the engine slowly until the piston JUST touches the end of the vernier calliper rod. That is your set position....

Chris.......
 
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cotterj

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Re: Merc '65 500 50ph pulley re-install - timing

I tried this and when I tried to start the engine it just popped while rolling over. Does this likely mean I have timing off?

I should get the piston at top dead center. Then measure back .20 since it is supposed to be .200 before top dead center?
 
achris

achris

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Re: Merc '65 500 50ph pulley re-install - timing

cotterj said:
I should get the piston at top dead center. Then measure back .20 since it is supposed to be .200 before top dead center?
Click to expand...

That's exactly what that procedure does.

You have the firing order right? You set it BEFORE TDC, not after?

Chris.......
 
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cotterj

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Re: Merc '65 500 50ph pulley re-install - timing

I numbered the plug wire before taking off. So I must have the timing after tdc. Would you agree?
 
achris

achris

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Re: Merc '65 500 50ph pulley re-install - timing

cotterj said:
I numbered the plug wire before taking off. So I must have the timing after tdc. Would you agree?
Click to expand...

It's a possibility. Very difficult for me to say when I can't hear, see or touch the engine. I can only offer advise based on the feedback I get from you....

Chris.......
 
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cotterj

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Re: Merc '65 500 50ph pulley re-install - timing

I appreciate all the advice. It was back firing a bit while trying to start. I'll redo your procedure and see what happens.
 
achris

achris

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Re: Merc '65 500 50ph pulley re-install - timing

I do the best I can for you. ;)

Good luck with it.
 
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cotterj

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Re: Merc '65 500 50ph pulley re-install - timing

So. I get it to TDC then measure it. Measure .20" more. Then I turn it so the piston goes back before TDC about 3/4 of a turn. I put the depth guage back in and tun the piston towards TDC again so it touches the depth guage? Is that right?

Once I find this spot, is that when I line up the flywheel marker and distributor gear marker so the point at each other? Or does that not matter?
 
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achris

achris

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Re: Merc '65 500 50ph pulley re-install - timing

The flywheel and the dissy have there own marks. You need to line them up and set the dissy belt on the dissy, with the washers, plate and screw.

The process we have with the 0.20" from TDC is for the maximum spark advance. I have some pages I'll scan and post up... Stand-by...

Chris.......
 
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achris

achris

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Re: Merc '65 500 50ph pulley re-install - timing

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cotterj

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Re: Merc '65 500 50ph pulley re-install - timing

Ok. Thanks again. When you say turn the engine the right way, which way is that? If I were to pull start my engine I would turn the flywheel clockwise.
 
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cotterj

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Re: Merc '65 500 50ph pulley re-install - timing

I think I messed up my firing order. How can I fix this without take the distributor off again? I'm think I can just try it if it doesn't fire, I'll take the belt off the distributor gear, then spin it one revolution. Would this work?
 
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cotterj

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Re: Merc '65 500 50ph pulley re-install - timing

Update: I got it to start. However it not idling well and it shuts off. How can i make sure my magneto is lined up properly in regards to the idle screw, spark adv, and throttle screw? Or maybe I tighten the idle screws too tight on the carb?
 
achris

achris

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Re: Merc '65 500 50ph pulley re-install - timing

The idle speed is controlled by advancing the timing with the linkages. The idle stop screw just stops you retarding the timing too far. The idle mixture screws on the carbs should be turned fully CW until LIGHTLY seated, then turned back (CCW) about 1 full turn.. That should be enough to get the engine running. Make final adjustment from there.

Chris.....
 
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cotterj

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Re: Merc '65 500 50ph pulley re-install - timing

What are you referring to as linkages?
 
achris

achris

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Re: Merc '65 500 50ph pulley re-install - timing

Basically the engine at idle has the carbs closed up. There is a bypass, either a notch or a hole in the throttle plates so a control air volume can come through. Then the idle speed is controlled by advancing or retarding the timing. All the timing and carb movements are linked together, so the timing and the carb opening are synchronised. That's how the engine will run the best.

So when the idle speed is too high or too low, the carbs are NOT adjusted, the timing is adjusted to achieve the right idle speed. And that's done with the levers and linkages all working together. If you have a look at the throttle cable, then follow the lever it attaches to and have a look at it. Somewhere there will be a screw-stop, or it will rest against a screw-stop on a fixture. That will be the idle speed stop screw....

Chris.........
 
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cotterj

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Re: Merc '65 500 50ph pulley re-install - timing

I really appreciate all your help. I got it running good this morning. I did make a small adjustment on the idle stop screw to get it to idle with the idle advance lever down. Is it normal that the bottle idle adjustment screw on the carbs had no positive or negative effect on idle? The top did however.

I believe it's ready for a water test this week and a little fishing before the snow comes! Thank you again.
 
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