Need help with finding top dead center.........?

[Theoutdoorsman]

Can someone explain, in detail, how I can make a piston stop so that I can be absolutely certain I'm not setting my timing wrong? Thanks a bunch.............ALAN

 

[RPJS]

Re: Need help with finding top dead center.........?

I don't know anything about your engine Alan, but TDC is normally marked on the flywheel which is a much more accurate way of setting than piston height, you will find that when you bring a piston to the top of it's stroke there are a few degrees of dwell as the crank rides over TDC.

 

[Barnacle_Bill]

Re: Need help with finding top dead center.........?

I use a dial indicator that I modified to screw into my #1 plug hole.

 

[Theoutdoorsman]

Re: Need help with finding top dead center.........?

RPJS......... The TDC is marked on the flywheel, but the indicator arrow is adjustable. Just want to be certain I'm not getting an incorrect reading. The motor will not run below 1000 rpms without coming to a sudden halt. Makes me think the timing is off a bit. My service manual states:

"Turn the flywheel 1 1/2" past TDC mark. Insert the stop and bring in contact with the piston. Lock the piston stop. With piston held firmly against stop mark flywheel directly under pointer. Then, turn the flywheel opposite pointer. Remove tool. Then measure the mid-point between the two lines. Mark the mid-point line on the rim of the flywheel. If the mid-point line on the cast-in TDC mark on the flywheel are in agreement, the timing pointer alignment is correct."

I just want to check this and be certain everything is as it should be. Thanks............................ ALAN



EDIT: I've also read on hear somewhere that it is a good idea to retard the timing 2 degrees for the breakin period. Is this a common practice, or should I stick with the service manual on this?

 

[JC1933]

Re: Need help with finding top dead center.........?

Alan you can make a stop using a spark plug ,

Remove the porcelin from the plug and insert a threaded rod with a nut secured in the plug, you now have a $75.00 tool ...d

 

[Paul Moir]

Re: Need help with finding top dead center.........?

In a pinch, you can just use a regular spark plug with a long threaded section.

 

[Theoutdoorsman]

Re: Need help with finding top dead center.........?

So............ I screw my home-made piston stop tool into the #1 hole (top starboard side) in the head, adjust the threaded rod until it makes positive contact with the head of the piston at the very top of it's stroke...........correct? Will this show me top dead center whereas I should move my indicator pointer to reflect this? The engine is trying to hiccup almost like it's running lean. However, I have rebuilt the carbs and I know they are clean. Also, I cannot let the engine idle on the muffs below 1000 rpms without it dying on me. When it dies, it stops right now and kicks back a little. No backfiring, just kicks back a little. This is what leads me to believe it is a timing issue.

 

[F_R]

Re: Need help with finding top dead center.........?

Huh? The way you copied the procedure doesn't make sense. Insert the tool and turn the flywheel till #1 piston comes up against the stop. Mark flywheel under the pointer. Now turn the flywheel backwards till the piston again comes up against the stop. Again, mark the flywheel under the pointer. Mark the flywheel half way between the two marks. This line should agree with the cast-in TDC mark on the flywheel. If it does not, turn flywheel to align the mid-point mark with the pointer. Then without moving the flywheel, move the pointer till it points to the TDC cast-in mark on the flywheel and tighten the screw. This is from the factory manual.

Yeah, yeah, I know, somebody will warn against turning the flywheel backwards because of the water pump. What do you think happens when the crankshaft rocks backwards on the last compression stroke when the motor is shut off?

 

[Theoutdoorsman]

Re: Need help with finding top dead center.........?

F_R................. Thanks for clearing that up. I've been working too hard I suppose. d It helps to take a break from it and then go back later on when all the mud clears. Have you guy's ever seen an instance where you had to actually move the indicator?

 

[ondarvr]

Re: Need help with finding top dead center.........?

Yes, mine was 2* off, the timing was correct, but the pointer had been move in some way. I used a long reach plug and then straightened the electrode so it was even longer, worked great.