Valve timing...
Posted: 09 Dec 2022 12:03
Hi All
SIMPLE VERSION OF MESSAGE BELOW= QUESTION: Should my LOWER drive gear for the cam belt be easy to remove? (it is) and how do I know where it should be positioned on it's shaft? (The belt is off and I've turned crank and cam...ooops..).
PPREAMBLE>>>>>I have had my pickup and magnet checked by a well known Morini mechanic who tested them on their bike and all fine....so I put them back on my 350 Electric start 1979 bike.
I also decided to replace my cam belt and new one is tighter and less floppy consistency which I understand is a good thing...
...HOWEVER...stupidly I have moved the bloody crank and cam and lost cam timing I think... I have not removed the top camshaft gear from it's shaft and it has a clear timing mark to align with the mark between cylinders on casing at 12 O'clock...so that is reliable I think..
...What I have a problem with is the lower drive gear which the belt also goes on. On my bike this gear is easily removed and with the half moon key in the crank slot it can be placed back on at least two various positions with key in place. This is a bloody nuisance as I therefore can't rely on the timing marks- it has one yellow dot on outer edge of the drive gear and a punch mark on inner casing around 2 o'clock. I believe the yellow dot on it's outer edge is supposed to line up with the punch mark on the casing when the mark on the upper drive gear is at 12 o'clock as in diagram in Blue Manual page 4, top left image.
QUESTION 1>>>>If the lower drive gear can go on the crank shaft in different positions how do I know which position it should go on?
In an attempt to answer this Q1 - The crank should be positioned so the front cylinder is on TDC compression stroke at this point?
QUESTION 2: How do I know when I have TDC on compression stroke? (WITH CAM BELT OFF) The Workshop Manual says "with engine at TDC on compression stroke" but no advice as to how this is achieved. People write on internet to "put finger in plug hole and you will feel the compression rise"...ALSO presumably both valves must be closed... but the belt isn't on so they don't move unless I turn the cam manually with socket spanner.
SO...
QUESTION 3...Should I put the valves in closed position (visible with lid off) by turning cam (top drive gear) then find Compression TDC on front cylinder by turning the crank? Then put lower drive gear on aligning the marks? ....I have tried this but the mark on the upper drive gear (cam) is NOT at 12 o'clock. To have the calves closed it has to be at 3 o'clock ish.
HELP !!!!
SIMPLE VERSION OF MESSAGE BELOW= QUESTION: Should my LOWER drive gear for the cam belt be easy to remove? (it is) and how do I know where it should be positioned on it's shaft? (The belt is off and I've turned crank and cam...ooops..).
PPREAMBLE>>>>>I have had my pickup and magnet checked by a well known Morini mechanic who tested them on their bike and all fine....so I put them back on my 350 Electric start 1979 bike.
I also decided to replace my cam belt and new one is tighter and less floppy consistency which I understand is a good thing...
...HOWEVER...stupidly I have moved the bloody crank and cam and lost cam timing I think... I have not removed the top camshaft gear from it's shaft and it has a clear timing mark to align with the mark between cylinders on casing at 12 O'clock...so that is reliable I think..
...What I have a problem with is the lower drive gear which the belt also goes on. On my bike this gear is easily removed and with the half moon key in the crank slot it can be placed back on at least two various positions with key in place. This is a bloody nuisance as I therefore can't rely on the timing marks- it has one yellow dot on outer edge of the drive gear and a punch mark on inner casing around 2 o'clock. I believe the yellow dot on it's outer edge is supposed to line up with the punch mark on the casing when the mark on the upper drive gear is at 12 o'clock as in diagram in Blue Manual page 4, top left image.
QUESTION 1>>>>If the lower drive gear can go on the crank shaft in different positions how do I know which position it should go on?
In an attempt to answer this Q1 - The crank should be positioned so the front cylinder is on TDC compression stroke at this point?
QUESTION 2: How do I know when I have TDC on compression stroke? (WITH CAM BELT OFF) The Workshop Manual says "with engine at TDC on compression stroke" but no advice as to how this is achieved. People write on internet to "put finger in plug hole and you will feel the compression rise"...ALSO presumably both valves must be closed... but the belt isn't on so they don't move unless I turn the cam manually with socket spanner.
SO...
QUESTION 3...Should I put the valves in closed position (visible with lid off) by turning cam (top drive gear) then find Compression TDC on front cylinder by turning the crank? Then put lower drive gear on aligning the marks? ....I have tried this but the mark on the upper drive gear (cam) is NOT at 12 o'clock. To have the calves closed it has to be at 3 o'clock ish.
HELP !!!!