Many people find the timing process for the Standard 23C Engine difficult to follow and understand. We wrote a brief article on fitting the timing chain recently.
The process is shown in full on the MF35 Engine Rebuild DVD, however, we also wanted to provide a written description to help people understand the process. So here goes…
Turn the camshaft clockwise until number 8 valve rises to its highest position. Then turn the camshaft a further half turn clockwise until the valve is in its lowest position.
Next set the valve gap on number 8 valve to 23 thou of an inch. Then do the same thing for valve number 7, but to 25 thou (again you need to turn the camshaft clockwise until no. 7 rises to its highest point, then turn another half turn clockwise until it is at its lowest point). This is done solely with the purpose of keeping things tight for the timing process.
To complete the positioning of the camshaft for timing purposes you need to keep rotating the shaft clockwise until number 8 (exhaust) valve has opened and then closed again and then just before number 7 inlet valve starts to open. As the valve clearances have been set as we have done them, this will now hold the camshaft in exactly the correct position for us to fit the timing chain.
The next paragraph should be done without the timing chain fitted.
Next, pistons 1 and 4 should be set to Top Dead Centre, this is indicated by the keyway in the crankshaft been in the 6 O’Clock position. If the engine is disconnected from the rest of the tractor then you can check this with the two arrows lining up on the flywheel.
Temporarily fit the camshaft sprocket and then slide on the crankshaft sprocket and check for alignment (using a straight edge), adding or subtracting shims from/to behind the crankshaft sprocket accordingly. When you have got that correct you can fit/key the sprocket to the crankshaft.
Now remove the studs from the crankshaft sprocket that you were using to temporarily hold it in place (for alignment using the straight edge)
You can now fit the timing chain over the two sprockets.
Next you need to fit the camshaft sprocket in its correct position. When trialing the fitment of this sprocket you need to place some weight with your fingers to the upper/left part of the chain (between the sprockets) so that the lower/right hand part of the chain is taught.
Don’t move the crankshaft or the chain, but move the camshaft sprocket over a link at a time until you get the sprocket aligned so that the small stud (one of them is smaller than the others) is aligned in the correct place. You can then fit all the studs.
Make sure your chain tensioner mechanism is in good condition before fitting it.
That’s it. The crankshaft and the camshaft are now timed!