How to find TDC on #1 piston

[ReelDrag]

I'm trying to set timing on 92 Johnson 115 crossflow and I need to find TDC on the #1 piston. I think there is a misprint in my Clymer manual because I just don't understand the procedure.

 

[Hooty]

Re: How to find TDC on #1 piston

It's not a misprint. That's the way it's done. To do it right, you'll need a piston stop tool. I got mine at a motorcycle shop.<br /><br />c/6<br />Hooty

 

[R.Johnson]

Re: How to find TDC on #1 piston

How does your manual say how to do it? Hooty said he got his piston stop tool at a motorcycle shop. Hooty! does this stop use a dial indicator? This could give you a false reading as it don't take into account crankshaft over-lap. I only use the OMC method, so I don't know how you guy's are doing it. Help me out here.

 

[G DANE]

Re: How to find TDC on #1 piston

The procedure is following:<br /><br />Remove sparkplugs. Turn motor by hand untill piston #1 has moved 1/2 " down past TDC. Insert piston stop tool, and adjust screw till it touches piston top. Lock Screw, and holding piston back against stop tool, make a pencil park on flywheel exactly at pionter. Turn motor clockwise till piston touches tool again, make another mark. Using a Flexible Scale, mark exact center between the two marks on flywheel. Turn motor to pionter is against the new center mark. Adjust pionter position to point against the original TDC mark in flywheel. Pionter now is correct.

 

[Hooty]

Re: How to find TDC on #1 piston

The Clymer method ReelDrag iz having a problem is just like the OMC method, like G Dane described. The piston stop I have doesn't have a dial indicator. I does have a adjustable plunger with a vernier scale though.<br /><br />c/6<br />Hooty

 

[rodbolt]

Re: How to find TDC on #1 piston

hello<br /> I use my dail indicator and .5" BTDC and ATDC then split the difference. its quik easy and fast. you can buy a decent Yuasa dail gauge and mag base for 30 dollars or so.<br /> if the water pump is not in and your a decent welder you can make a piston stop tool with an old spark plug and a piece of steel rod. then install it in the head. move the piston against it make a mark on the flywheel the rotate the engine until it hits the stop in the other direction and make another mark. split the difference and you have TDC. I think the easiest to understand method is in a chysler manual.<br /> good luck and keep posting

 

[G DANE]

Re: How to find TDC on #1 piston

You dont have to think about water pump. A lot of people think this procedure involves turning motor backwards. It doesnt. <br /><br />You just turn it clockwise till you are sure its a portion past TDC, Then screw tool down to contack with piston, then just hold it against tool while you mark, no turning back.

 

[ReelDrag]

Re: How to find TDC on #1 piston

Ok, I got it now. Turn it PAST TDC and then insert the tool. Didn't understand how you could turn the flywheel clockwise with the piston against the tool already, but I got it now. Thanks.