Valve timing

I don't know what facilities you have cam, but I did exactly what you want to do 15 years ago on my RGA.  As you have done I established what the timing was, then clocked each sprocket up on a rotary table and drilled a new set of holes at X-teeth plus the offset to get back to factory numbers.  Came out <0.5 crank degrees.  If you can't do it locally, I could do it for you, but not till after the Barry Sheene.  Should be easy enough to find someone nearby though.
Might want to do a set at factory 4C timing, and another set at Phil's suggested timing and do some experimentation.
No doubt you have it covered, but don't forget you only need to move the holes 1/2 of what the crank degree error is. :-)
Cheers
Steve B
 
Got it sorted now.

I discovered a handy rule of thumb along the way. Slotting the holes in the camshaft flange by 1mm gives 4o of timing change at the crankshaft.

I didn't want to drill any new holes in the sprockets because I don't have a 7mm tap and can't buy one on a weekend. I wanted to get it done today, so I stopped and had a think. The exhaust had to move 3o, which is only 0.75mm of filing to slot the camshaft holes. The inlet had to move 13o. Flipping the sprocket over gave me 16o which was 3o too far, but within slot filng range. Another 0.75 mm slot and bob's your uncle. Job done.  :D

Now I need to find my torque wrench. Workshop is a mess.

Cheers,
Cam
 
Well Done Cam - There's a lot of ways to make it complicated - filing and flipping is so good, and,as Rob said - once you've set it how you want- there's no reason to move it again unless you are developing a motor.  I do modify head and centre pillars  on my own Laverdas and use a nut and bolt assembly with substantial slots in the wheels so that it's easy to change timing or cams. - Regards - Phil
 
Well, that was interesting. Got it back together, tried to start it but it wouldn't fire - dead as a dodo. I had a bit of a panic thinking I may have done something stupid with the valve timing until I realised that there was no fuel in the carbies. Duh!
Put some petrol in and it fired up OK.

Doing the valve timing has lifted the compression from around 160 (I think - going from memory) to 180 psi. I suppose that's because the inlet valve is now closing earlier on the compression stroke. Hopefully that'll find some of the missing horses.

Haven't taken it for a ride yet. Got a couple of other jobs to finish. I'll see if I can book it on the dyno next week. I'll let you know if it's made any difference.

Thanks for all the input guys.

Cheers,
Cam

 
I expect you've done it already, but do put good new marks on the "flipped" wheel - I'm afraid i didn't do such good ones on some of the ones i did and the next owner has been a bit confused !! - Regards - Phil
 
Yes, I did think of that Phil. I put marks on the sprockets with a felt tip pen, just to keep track of where I was. I had intended to do a couple of centre punch marks once it was all together and I'd confirmed that the timing was correct - but I forgot.

I guess I'll find out how permanent the permanent marker pen is next time I open it up.

Cheers,
Cam
 
motoddrob said:
Anyone have the specs for the Axtel cam? Also any thing else I shoud be aware of.
Click to expand...

G'day Rob

Axtell specs:

Note that opening and closing angles are specified at .040" (1mm) valve lift
  Open   Close   Max Lift Lift
IN  18.5o BTDC 48.5o ABDC 75o ATDC   9.24 mm
EX 51.5o BBDC 15.5o ATDC 108o BTDC 9.24 mm

This info was taken from JLO's technical pages, here: http://www.laverdamania.net/cams.htm. Other cam timing info is there too.

I found it easiest to work with the max lift figure for valve timing. If your valve clearances are correct then the opening and closing figures should fall into place. It's hard to pick the exact angle where the lift peaks, but if you measure the angles where the lift is the same either side of max, and take the average, that gives it pretty accurately. It's the same logic as finding TDC with a piston stop, only you use a point on the dial gauge rather than a positive stop. I found it easy enough to measure to better than 1 degree at the crankshaft (0.5 deg at the camshaft).

Cheers
Cam
 
It is good you got it sorted.
It is not the bolts that hold the camwheel to the sprocket as such. It is the friction between the faces which tightening the bolts provides. Many cams have no positive locators and are the wheels are free to rotate without the bolts in place. If the bolts loosen they will snap pretty soon after, and if the faces are uneven no bolts will stop them loosening. Slotting camwheels has always been the method of choice for most tuners. Even on my twins I have slotted the flanges and cut the woodruff key so that it doesn't go through the camwheel so I have each side independent, run them like that for over a decade (no doubt famous last words now!!)
Also after I saw a photo of the Tainton brothers with the ASBK (Oz) winning superbike on their bench with a half meter diameter degree wheel on the crank I started thinking and made a bigger one for myself. A bit smaller than a vinyl LP.
Print out a 360  degree pic from the web and glue it to any disc you can make.
 
Thanks Cam. It'll be interesting to see how acruate my Cams are. I checked the phasing and that was spot on.
Being abit of a thick head, I not sure how to understand.... "Note that opening and closing angles are specified at .040" (1mm) valve lift"
So the given opening and closing angles are measured when the valve is open/bucket depressed .040" then?????
Correct me if I'm wrong

Cheers
 
Yes, Rob, that's what it means.

But the specified clearance also needs to be known, cam grinders often state a given clearance that differs from the service clearance specified by the engine manufacturers.

But if angles are specified at 1mm lift only, you can assume clearance should be adjusted to service dimensions.  You'll find out soon enough if your measured angles are way off spec..... :D

piet
 
Cheers Piet, just need to get my head back now. I'm looking forward to checking to see how inacruate the timing is. When I fitted the Axtells I did notice a big difference from the A11s in the mid range so maybe they're not that far out if not spot on.
 
one way around the different timing values different grinder use or factory listings is to figure the lobe center from the published values

using the axtell figures posted

inlet 18.5 + 180 + 48.5 = 247 /2 = 123.5 - 18.5 = 105 lobe center
exhaust 51.5 + 180 + 15.5 = 247 /2 = 123.5 - 15.5 = 108 lobe center

using published (green book) figures for 4C

inlet 50 + 180 + 74 = 304 /2 = 152 - 50 = 102 lobe center
exhaust 70 + 180 + 38 = 288 /2 = 144 - 38 = 106 lobe center

i recall phil saying he altered the 4C lobe centers with good results
with inlet between 104 and 106 and exhaust between 110 and 113

i find the larger diameter you can make a timing disc the more accurate your readings will be
 
Not so sure about the fresh camchain ,most racers perfer a chain that has done at least a 1000 miles before setting any thing up :-\ :-\ :-\ :-\ :-\
 
I didn't change the cam chain before dialling in the valve timing. If/when I install a new chain, I'll re-check and adjust if necessary. Although I don't reckon it would make a lot of difference.

BTW, I took the bike for a ride today. First time since dialling in the cams. I didn't get much of an opportunity to stoke up the fire, but managed a couple of short full throttle squirts up through the revs. It seemed to rev more willingly than before and I think the mid-range has improved too. So the initial seat of the pants dyno results are encouraging.

I won't get a chance to run it on the proper dyno before heading off to Sydney later this month for the Laverda Rally (dyno time is heavily booked). It'll have to wait until the bike is back after Easter.

Back brake works a lot better too. That was one of the other jobs I did. It feels like I've doubled its effectiveness just by re-engineering the linkages between brake pedal and master cylinder. Well worth the effort. I should have done it ages ago.

Cheers,
Cam
 
Rufustbear said:
Not so sure about the fresh camchain ,most racers perfer a chain that has done at least a 1000 miles before setting any thing up :-\ :-\ :-\ :-\ :-\
Click to expand...

Most classic racers don't even have a cam chain!  :D :D :D
 
Depends what class, Bob.
A stretched camchain can retard the timing so much that the bike will barely run. I have seen it.
An example, bike engine was diagnosed totally worn out. Sounded like everything inside was about to be destroyed, not just camchain rattle, almost no compression, blew smoke like the marlboro man etc. Broke owner asked for just new camchain while he saved for the big job. Result, full compression, no smoke, went like a charm. An extreme case admittedly. 
I cannot remember any new camchain of mine moving much on the adjuster at its next service and they never get worn like that one. If I degree it in I won?t do it on an old stretched chain or keep doing it as the chain wears out. Cam I can?t imagine you have an old worn out chain in your bike either so I doubt you?ll have to do it again. It sounds like it was well worth the effort too.
 
we recently had a  racer blow up due to a worn cam chain,it was a hyvo and has an automatic (engine oil pressure) tensioning device, the chain had reached its limit, and so had the tesioner,(unbeknown to us) with the plunger at full stroke of the tensioner, to the point where it popped out of its bore, then a few of the 4 valves per cylinder touched, and it started to rattle, then the piston broke up and jammed itself against the head, next the rod broke on the tension stroke, and the flailing big end of the rod, then wiped a nice slot in the crankcase.And all of that because of a knackered chain, which to all the world looked in tension and OK,that was a 1990 ZXR400, now it has a ZZR600 in the same chassis, and no it wasnt easy since 3 of the four mounts on the alloy frame are very different, and there is  no room to manouver the motor left and right in the cradled chassis, to get the  drive chain line right, lots of machineing of wheel and gearbox out put etc,Double the power and torque of the 400 though, so worth it.We have geared for 155MPH instead of 120MPH
CLEM
 
Tippie, I agree,I change my cam chain every season and I can't see the point in stretching a chain before setting up the valve timing, most automotive cam chains are pre-stretched anyway.
I was trying to think which typical classic bikes have cam chains and apart from the obvious Italian GP exotica most of OHC bikes are post classic Japs.  No cam chains in yer average Manx, Commando :D, Bonneville, Ducati, Velo, Matchless :D TZ, RD, TR, TD etc etc
 
bob said:
Tippie, I agree,I change my cam chain every season and I can't see the point in stretching a chain before setting up the valve timing, most automotive cam chains are pre-stretched anyway.
I was trying to think which typical classic bikes have cam chains and apart from the obvious Italian GP exotica most of OHC bikes are post classic Japs.  No cam chains in yer average Manx, Commando, Bonneville, Ducati, Velo, Matchless TZ, RD, TR, TD etc etc
Click to expand...

Bob,

Surely that's an oversight on your part......

Matchless/AJS/AMC pioneered the spring-loaded cam chain blade tensioner, first in the R7, then 7R Boyracer and later the mighty G50.

And Commandos, all 500 and up Norton twins for that matter, also have chain driven cams.

piet
 
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