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Old 18-12-2007, 14:16   #1
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TDC on a Bukh 20 ME

Anyone know how I find TDC on a Bukh 20? I want to adjust the valves, but can't find a reference for TDC - my service manuals give the clearances, but don't indicate where I can find the markings for TDC.


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Old 18-12-2007, 14:56   #2
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Don't know specifically for that engine, but in general with any engine we use a dial gauge on a magnetic base with the feeler end extended into the cylinder. Turn it over by hand and find TDC that way. Used the spark plug hole on gas engines, probably an injector hole would work on a diesel unless it has a pre-chamber or something else that obstructs access to the top of the piston.

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Old 18-12-2007, 16:19   #3
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Bill, I have a Bukh 36 and had read that the flywheel (a real old flywheel, eh, must weigh 30kg on the 3-cyl) had a mark that could be aligned with a protruding metal pointer on the engine block.

In my case though, the flywheel showed no mark, so, as per Jdoe71, I used a dial indicator through an injector hole (the Bukh does not have any pre-chambers or obstructions) to find TDC. And then made my own mark.

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Old 18-12-2007, 18:09   #4
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Oooh finally a question I can help with...

Cams are wonderful things, they have what is called a base circle. They hit a point where if you turn in either direction the push rod or rocker doesn't move.

When you are adjusting the valves on an engine so long as the push rod or rocker isn't moving, your on the base circle. The lash is not changing during this period, it is as loose as it will get... exactly where you want it. When is top dead center? The intake valve was the last thing to close, this is top dead center on the compression stroke.

The most marvelous thing ever invented for adjusting valves is the remote starter, hit the button for a split second and bump bump bump. Intake valve is closed, now no movement... wiggle wiggle theres the slack.. its not changing. Set the lash and repeat.

(This is not specific to your engine, and the specs and whether its done hot or cold depend on your engine. This adjustment method works best on flat tappet, solid lifter engines... but it works to find TDC on the compression stroke of any engine.)

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