degreeing cams 750

I am at present trying to check the cam degrees on my z650 hybrid
make up-
gpz750 bottom end
zepher zr750 head and barrels
810 pistons
gpz750r1 82 ex cams
gpz750r1 82 or zepher in cam (not shaw, may have got them mixed up but both have the same lobe size 63.3

I'm using the Doug Meyer method of calcuating the lobe centre at 1mm lift. So standard is 60+30+180/2-30=105, and have found @1mm lift the inlet cam at 4* open, 42* close. So 4+42+180/2=113-4*=109 and -4* for chain slack =105
The exhaust measures 31* open, 11* closed. so 31+11+180/2=111-11=100
firstly, are my calcs wright? and if so shouldnt the ex be 105 and could it be 5* out because of zepher head ( I recall a member stating that the zepher head has been allready decked by kawsaki. Is this right? cheers

why are you subtrackting 4 for chain slack?I am also learning about this,so I am by no means an expert, but the formula dosnt say -4 for chain slack.The chain should not be slack if adjusted properly.This may be .004" for valve clearance(or what ever your valve clearance actualy is) but it is subtracted from the dial indicator reading.If you are taking readings from your degree wheel when your dial indicator says .040"of valve lift, and you have .004" valve clearance you would actualy read the degree wheel at .036" to compensate for the valve clearance(.040-.004"for valve clearance) Isnt this cool stuff:side:

If the timing chain stretched the cams will retard. Lobe center # for intake will increase. I degreed my stock cams over and over. To learn what were the effects of changing tension on the chain, lobe center changes, relationship of op and cl numbers compared to lobe center, lash. My stock #'s were right on. It was easy to see that things were exactly what kawasaki said, and that they used zero lash as reference to 30 and 70 as op. and cl. numbers. Cause that's where they are. Did you know that with the stock cams: using .ool5 clearance at the shim, intake will open at 35deg vs stock 30deg. It will close at 75deg vs 70. Youv'e increased duration. But the difference in compression is 150psi at .oo15 clearance and 180psi at .oo5 clearance. So if you have .008 and some at .003 you can expect Op. and cl. to be off 4 to 5 deg. and compression to vary an easy 10 to 30 psi. I prefer to run the motor using less lash and get the slight increase in top end, since the compression picks back up at higher rpm anyway. Anything more than that and your just bleeding off compression that you need for power.

mark1122 wrote:

why are you subtrackting 4 for chain slack?I am also learning about this,so I am by no means an expert, but the formula dosnt say -4 for chain slack.The chain should not be slack if adjusted properly.

Theres loop in the cam chain from exhaust cam to inlet cam through a guide set into the rocker cover when the rocker cover is on. So when degreeing the cam the rocker cover is off and the chain is taught which apparently makes 4* differance

all measurments are done when the engine has been turned in the running direction, never turned back

jimmybon wrote:

I am at present trying to check the cam degrees on my z650 hybrid
make up-
gpz750 bottom end
zepher zr750 head and barrels
810 pistons
gpz750r1 82 ex cams
gpz750r1 82 or zepher in cam (not shaw, may have got them mixed up but both have the same lobe size 63.3

I'm using the Doug Meyer method of calcuating the lobe centre at 1mm lift. So standard is 60+30+180/2-30=105, and have found @1mm lift the inlet cam at 4* open, 42* close. So 4+42+180/2=113-4*=109 and -4* for chain slack =105
The exhaust measures 31* open, 11* closed. so 31+11+180/2=111-11=100
firstly, are my calcs wright? and if so shouldnt the ex be 105 and could it be 5* out because of zepher head ( I recall a member stating that the zepher head has been allready decked by kawsaki. Is this right? cheers

any one?

even with pritty pic, can any one help?

1

Thats interesting to know.I didnt realize the 750 was dif than the 900.If you cant find the answer your looking for you could try cyclemadness, or drag bike .com. Sorry if I hurt any feelings guys.:blink: :ohmy:

Maybe try using the factory checking height of near zero, and zero lash also. The numbers should compare to stock. How is the valve lash? It sounds like the cam is out. Guess if was me i'd start with the checking height of zero and avoid using the dial to see if the lobe center is still off and take in account that tower set up being loose. You should be able to see something going on.
'

Post edited by: nads.com, at: 2007/01/30 03:40

i'v been stufin around with this model bike since new and still find it cool stuff as well, i've always had cam degreeing done by a mate.
the engine runs pretty good but i may have found some more horses
I appreciate your imput
cheers

nads.com wrote:

advance the cam 5deg and I get 5+44+180/2=114.5-5=109.5-4deg=105.5 ??????

mmm, are you suggesting that i advance the IN cam for more midrange power? if so i'll look at that. But, the EX cam I think is the problem @100 lobe centre.
5* out seems a lot so I thought it may have some thing to do with the zepher head
do I advance or retart the cam to get std 105?

You're right about the 4* difference in timing on the inlet cam due to the cover. The inlet timing figures look great so you can leave that alone.
The exhaust needs advancing to 105*.

If you don't have adjustable sprockets, I assume you are running a HiVo chain, then there is a trick you can employ. The sprocket teeth effectively have a 15.5* difference between each one, so thats too big a change, but the different cam mounting holes are offset to each other in relation to the teeth. So for instance if you mount the sprocket using the Z6EX holes instead of the Z7EX ones then you will end up with a different lobe center

Try it and see what figures you come up with.