Rough O-200

[Tom Downey]

Gentlemen.
Here's what I have done so far. Visual check of induction system. Different spark plugs. Tried another O-200 carburetor. Removed both ignition leads from one cylinder at a time and ran engine below 1000 RPM to see if miss would disappear with the dead cylinder. Tried setting the idle mix very lean (1/4 turn). Tried very rich mix (3 turns). The miss is still present below 1200 RPM.

Riddle me this. If the crank and cam gears were off by 1 tooth, would this create this problem ???? There were no index marks on my gears. I set them by feel of the #1 cylinder valve overlap per the OH manual.

First of all, set the idle mixture by allowing the engine to run 3 minutes, then pull the mixture to idle cut off (full lean) and watch the tach, you should get a 10-to-50 RPM rise as the engine dies, above 50 lean it, below 10 enrichen it. after that leave it alone.

Next, when you have no timing marks. you must inspect for them prior to teardown, If you don't have any place #1 cylinder at TDC by the crank flange and mark the gears.

So that has not been done, we are now guessing where the gear goes.
To dial in the cam gear, you need two dial indicators, set them up on the two rocker arms to both valves in #1 cylinder turn the crank and watch the opening and closing of each valve, When #1 cylinder is at TDC on the compression stroke, the two valves should be midway between touching there respective cams. Both should be fully closed.
To change the gear mesh, remove the crank gear, and rotate the cam, then replace the crank gear.

Now that we've been thru that, answer this, is this engine making full power, as in does it make rated RPM static. If it does the gears are correct.

If you wish to send me the cam gear I will place the correct timing mark on it.

PM me for the address if interested.