Valve Timing Fun

Golgother

Golgother

Hero member
Hey All

I have dug out my DTI,magnetic stand, Degree disc, small round file and read all relevant posts on Laverdapedia & MSN so I'm ready to go in.........Cam timing here I come !

I now have a set of 120 F1 cams in addition to the 4C's currently in the bike so I'm looking forward to experimenting. Must have the Swiss cheese look cam sprockets too  :D

Any advice is welcome.

                    Cheese
                          Matt
 
  Take your time, check, check again then check again as you go. I find it helpful to put a bit of tape on the degree wheel indicating max lift for the valves.

  Have fun, if it stops don't force it !  ;)


  Keith.
 
Being thick, I go one step further than Keith's piece of tape and draw all over my degree wheel in big fat marker pen.

I draw 2 separate arcs in separate colours. 1 being inlet open-peak-closed and the other exhaust open-peak-closed.

Much easier to follow a graphical representation than numbers.

I found the 'when the dial stops/starts moving, you are at peak' method inaccurate and found that measuring a full 1mm of bucket travel either side of peak (divided by 2) better for determining true peak. Recording peak is only really an overcheck,  measure 0.5mm bucket movement from closed position (opening and closing) as the true indication of what the valves are doing, this is important because your valve grind might not have the axis of the heel of the cam perfectly coincident with the rotation axis of the cam which makes peak-only measurements inaccurate.

Although the 30/50 50/30 timing of the F1 grind looks symmetrical, the maths can be a right bastard if your degree wheel is not similarly marked, with BTDC, ATDC, BBDC and ABDC for example, so do all the maths away from the bike and get the marker pens out!

HTH, Paul H
 
the cam bolt to sprocket tooth relationship is different from the 4C and A11
the F1 sprocket shares the relationship with the A11 (but not the hash mark for setting up stock cams)
based on the core used to make the F1 you can select the correct holes if you have a 4 hole cam gear

the "advertised" valve timing values are worthless
if you want to set the F1 up to factory spec you need to use the lobe centers

lobe centers for the F1 are 100 and 100 (degrees)
here's how to find them using paul's figures:

inlet opening + 180 + inlet closing = duration
divide by 2 then subtract the inlet opening to find lobe center
30+180+50=260 /2=130 -30 =100

for the exhaust you will subtract exhaust closing
50+180+30=260 /2 -30 = 100

doesn't really matter what measuring lift you use
it still works

cam blocks must be torqued and chain installed along with tensioner

make certain you have some valve clearance

make an arbitrary decision at what lift you want to make your measurements
for example .040" and stick to it

repeat your measurements until satisfied they are repeatable

mind the dial indicator stem isn't sliding across tappet or fouling camshaft
mind, also, the stand isn't moving about

a larger diameter degree wheel will give greater accuracy
as will a point on the pointer  ;)

cam, the dellortoman, did a nice chart for drilling the 4C/7C sprockets
so one may have 2 degree increments of valve timing change
and you have 14 holes for the swiss cheese effect
(can't drill all with the 4 hole sprockets)

cheers,
scott
 
Hey All

Thanks for all the advice it's greatly appreciated.

This will be the first time I have measured valve timing and I'm really looking forward to discovering whats what on my bike.......

                                            Cheers
                                                    Matt
 
Hi Matt,
I'll be doing the same with my Axtell cams over the next couple of months so I'll be interested how you get on. Likewise, never done it before and currently I don't have a clue!!
Good luck
Rob
 
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