Valve timing marks

[j2maria]

I inherited a 3 1/2 with no timing belt! I, being a newbie looking at the manual, assume that at TDC on the front piston, the mark on the camshaft pulley aligns with the notch on the crankcase, and that the mark on the crankshaft pulley aligns aligns with the punch mark on the bearing boss? Do I have to also make sure when bringing the camshaft pulley/case marks into alignment that the inlet valve has closed and, if the belt was hooked up, the piston would be at TDC on the compression stroke? Seems a pretty basic question but I don't want to force the valves into the head when testing....

[George 350]

Hi,
No belt? Don't worry - you can't bend the valves unless you are REALLY brutal as they are vertical to the piston. Set cam to the correct position (align dot and notch), then slowly turn crank to TDC - denoted by either aligning dot on belt sprocket with dot on cases (about "2 o'clock" position when viewed from the right. Personally I always check it is at TDC by slipping the rotor/flywheel back on and checking that "PMS1" is in line with its mark as being bigger, any error is magnified.
When the marks are in alignment, slide the belt on and reassemble everything..
Martin Gelder and others did an article for Real Classic regarding a belt change. See here. http://www.realclassic.co.uk/techfiles/ ... video.html

All the best,

George.

[j2maria]

Hi George

Many thanks for the response. I aligned the top and bottom pulley marks with the notch (top) and the punch mark (bottom) with the crankshaft keyway, dot on the lower pulley, and the punch mark at 2 o'clock as you suggested and fitted the belt. However, when I now bring the front piston up to TDC (PMS1 on the rotor aligned with the notch on the case) at the end of the compression stroke, the dot on the camshaft pulley which originally was aligned with this notch (12 o'clock) is now 180deg. opposite (6 o'clock). So, do the dots align the way suggested at TDC on the compression stroke or at TDC on the intake stroke?

Joe

[George 350]

Hi Joe,
It's a 4 stroke, so the cam rotates at half the speed of the crank. If you turn the crank another full turn the marks will line up! As to whether the 'dot at the top' on the cam wheel = TDC firing or at the end of the exhaust stroke, I don't know without taking the nut off the cam wheel to see where the keyway is. What I do know is (from a spare cam I have) is that with the keyway on the camshaft at the bottom, the engine is on the firing stroke.
Hope it all works for you,
George.

[j2maria]

Hi George

Many apologies for taking so much of your time! I followed the instructions in the manual for setting valve timing: I first brought the front piston to TDC and also set valve clearance to 1.0mm. I then turned the camshaft pulley clockwise until the 1.0mm clearance on the inlet valve was taken up (I could not twist the inlet pushrod anymore). With the inlet cam/rocker now just about to open the inlet valve, I turned the crank clockwise (not to the left as incorrectly translated in the manual) until the inlet open mark I had scribed on the rotor (28deg for my Sport or approx. 8mm to the left of the ANT1 mark) aligned with the notch. Now, the camshaft is about to open the inlet valve and the crankshaft is 28deg BTDC just finishing the exhaust stroke. When I then turn the crank the 28deg needed to get the crank/piston to TDC, the mark on the bottom crankshaft pulley and the punch mark on the bearing boss and the keyway on the mainshaft all align at 2 o'clock. The dot on the camshaft pulley now also aligns on top with the notch on the case. The camshaft pulley keyway is now at the bottom 180deg opposite the notch. This is TDC on the intake stroke and all the the dots/keyways align as shown in the various videos and in the manual. My only question is rather than it being the start of the firing stroke, it looks like this is the start of the intake stroke. Is this right? The manual keeps talking about setting the front piston to TDC on the compression stroke which does not seem correct. This is a link to my Morini restoration project - the last three photos show what I am talking about.

https://picasaweb.google.com/1169829683 ... MotoMorini

Joe

ps: I am updating my post above after having set it the way I describe above and found that the engine runs fine.The manual is incorrect when it states that it should be at TDC of the compression stroke - the only time the cam pulley and case notch align and the crank pulley, crankshaft keyway and punch mark on the bottom bearing boss ALL align is when the piston is at TDC on the intake and NOT compression stroke. End of saga!

[MarkB]

Hi Joe, not sure if you made a typo, but the valve clearances should be 0.1mm, not 1.0mm.

Cheers, Mark.

[MickeyMoto]

Hi Mark,

I think the book says set the valve clearances to 1.0mm when setting the valve timing?

I have a couple of belts to change this winter so have been watching the posts with interest.

[MarkB]

Hi Mike

Ah, maybe when setting timing it's different? I'll be quiet now and wait until EVGuru turns up with a definitive answer!

Cheers, Mark.

[j2maria]

Hi Mark

The manual says to use a valve clearance of 1.0mm when setting valve timing, hopefully a rare occurrence. However, when setting normal running clearance you use 0.10mm for all valves.

Joe

[EVguru]

You only need to set the cam timing if a new cam or crankshaft pulley has been fitted (that's what the crankshaft pulley has seven keyways for).