1975 850 belt timing

[jimmy57]

just overhauled my 850 and had the flywheel off now dont know if i have it timed corectly .i put no.1 at tdc with dial indicator and then aligned 0 degree mark on timing tape on fly wheel with the pointer and bolted it down .have the distributor aligned with the tab on pully and frame aligned . arrow on pully points to center ofcrank .is the fly wheel correct? i crank engine with timing light and marks are 180 degrees . off how do you get all this lined up thanks i got it all but this last little tid bit

 

[Gomer50]

Re: 1975 850 belt timing

I will try to help,I have a 72 80 hp merc and the timing on these are pretty close to the same.I also used a dial indicator on the top cylinder (number1) just as it hits TDC marked my flywheel to the timing decal on my cowl TDC.Then I rotated my distributor pully so that the arrow on the pully is pointing directly at the center of the crankshaft.Also making sure the rotor inside the distributor cap is pointing towards number 1 cylinder in the cap.If your motor shows TDC on the number 1 cylinder and your timing tape shows your right on,then are you sure your plug wires are correct.If your timing light tells you you are 180 degree's off would mean number 2 cylinder/plug wire would be firing.I to took off my flywheel and didnt pay attention and took me awhile to figure it out,but thanks to the guy's on here got me pointed in the right direction.I hope this helps there should a couple of the merc. guru's on here that might be able to explain this better than I.Good Luck..

 

[Chris1956]

Re: 1975 850 belt timing

Jimmy, Something is obviously wrong. Are the plug wires on the correct spark plugs? The distributor cap should have the cylinder numbers molded in. Do you have the timing light on the top cylinder?

 

[jimmy57]

Re: 1975 850 belt timing

yeah got timing light on top cylinder wire is no.1 will have to double check and make sure cap is correct did the top dead center thing with dial put fly wheel on 0 degrees on timing tape and set arrow to the center of crank tried to start tonight and not a wimper of a hit there is two heavey black lines on timing tape with 3 degrees in the center is this a belt timing mark
? got me totaly strumped why timing marks so far off again did i get fly wheel on correct ly sure would like to grt it going thanks all for everyones help

 

[Gomer50]

Re: 1975 850 belt timing

Here's is another thing I did.After I found TDC on Nr. 1 with the dial indicator I put a spark plug in the number 1 cylinder wire and turned the ignition on and rotated the distributor back and forth to see if a spark would jump on the Nr. 1 cylinder.If not either your spark plug wires are wrong or your rotor is not pointing towards your number 1 cylinder on the cap.I think I got this off of this forum but this is a little math on the flywheel concerning timing marks if you dont have any reference point after you find TDC.Your flywheel is the same as mine.

25.4 mm = 1 inch
208 mm flywheel cir.
208 x 3.142 divided by 360 = 1.81mm per degree.
21 x 1.81 = 38.12mm
Find TDC on number 1 cylinder make a mark on the flywheel and proceed from there

1.5 inches or 38.12mm equals 21 degree's BTDC make another mark on the flywheel
6 degree's BTDC = 0.42 inches make another mark on the flywheel.
21 degrees max timing advance and 6 degree for your carbs to slowly open (actually in my case 4 to 6 degrees works) when running right.

25.729 inches flywheel Circumference
Good Luck.

 

[Chris1956]

Re: 1975 850 belt timing

Is the cast arrow on the distributor pulley pointing to the punch mark (or marks) on the flywheel, when the motor is at TDC?

 

[jimmy57]

Re: 1975 850 belt timing

well got it fired up today and running seems it might have been a fuel issue had to open mixture screws 3 1/2 turns from closed and finnaly got it to start lety it warm up and fires right up thank goodness thanks for everyones help i did have the timing correct all along

 

[Gomer50]

Re: 1975 850 belt timing

Glad to see you got her up and going,3 1/2 half turns out is alot.Normal settings are around 1 1/2 to 1 3/4.I couldnt get mine to run either until I had mine way turned out and it smoked like the devil.In my case though I got the wrong carbs (my motor has got the devils curse anyway).Have fun and good luck.