Valve timing problem

[Sundie]

the cams are definitely different for the pre-447 models. And if you have a cam that doesn't have a "447" stamp on it, then you may or may not have a 447 cam.

Let's see if i can make a chart:
pre447 447 mike's performance
47BTDC 36BTDC 26BTDC inlet opens
67ABDC 68ABDC 66ABDC inlet closes
60BBDC 68BBDC 60BBDC exhaust opens
41ATDC 36ATDC 32ATDC exhaust closes

So, for pre447, the valves are open longer, with 9 more degrees of overlap. And the Mike's one is obviously a high revving one - lookit how short that intake opening is. But it probably has a higher and more drastic lift. Actually, looking at it, i bet it doesn't idle well, and you'd have to get big ass carbs for it. Meh. If i had a choice, i'd probably run the pre447 if it was otherwise identical to a 447.

As for adjustment - no, it's not something the general person would think about, nor can you adjust it. But it's an easy way to tell without your engine apart if it's time to replace your cam chain. If you can't get close on the degreeing without excessive lifter adjustment, it's time.

John, how do you "move the cams"?

 

[Sundie]

oh - and the other reason i made the degree wheel was so that i was absolutely *sure* i got the cam in right. I now am. The notch did not look "90 degrees up" to me - it just looked more like 90 degrees than the other two choices. OCD is a bitch sometimes.

 

[angus67]

so... to adjust the cam, we just adjust the valves to the specific year of our cam?
Unless a seasoned veteran like john has a tried and true method? like adjusting the valves?

 

[xsjohn]

A bit of retard in the cam from a stretched cam chain probably isn't noticable.......but if you lower the deck according to Grisld1 you will notice a lag at 3000 and the cam should be moved back to the stock position I would think....lowering the head rotates the cam back (retard) raising the head rotates the cam forward (advancing)....now I know what happens if the cam is too advanced.....even a couple of degrees.........it's called artificial leanness from an incomplete cylinder fill due to the intake valve closing to early and the engine runs like a crappy 2 stroke and gets very hot..........found that out when I raised the head .040 to get to 8-1 and had to move the cam back to the stock position........now I know how far to go for changes....and have done it successfully to quite a few...the chain wheel has to be pressed off and repositioned and pressed back on......the amount of movement is critical and it took me some serious practice to get the hang of it.........

The last one I did was a Mikes 750 kit......447 cam.........barrels raised .060 thou with a base spacer..............going from 9-1 to 8-1..........would be my dream engine........he is going to gear it up taller and retard the timing a bit for a super cruiser.....

..xsjohn

 

[inxs]

- john, im sure ive suggested this before, you should put all this together in a dedicated thread so that the info isnt all spread out...youre going to cop some flak from the nay-sayers, but hey, thats going to happen anyway

 

[650Skull]

Here is a link to.....XSjohn's 8.1 compression Mod

 

[grizld1]

Angus, you asked about adjustment. Valve timing is adjusted by pressing the sprocket off the camshaft and moving it. My advice is, if you have to ask, don't try it. Calculate the distance, mark the sprocket using a corner of the timing slot as a reference, and take the job to a machine shop.

 

[Sundie]

Angus, you asked about adjustment. Valve timing is adjusted by pressing the sprocket off the camshaft and moving it.

Yeah, i thought that would be the only way to do it, but figured i'd ask.

My advice is, if you have to ask, don't try it. Calculate the distance, mark the sprocket using a corner of the timing slot as a reference, and take the job to a machine shop.

Hey, it's not that difficult - if you've got a 20 ton press and lots of patience.

That being said, i don't think i'd bother unless i'm changing the geometry by raising or decking the head.

 

[grizld1]

Right, it's not that difficult--if you know what you're doing. I've seen a few camshafts with chunks broken out of the sprocket bosses by guys who didn't. 'Nuff said.

 

[Sundie]

Pre heating is your friend.

 

[angus67]

Yeah, sounds alittle too involved for a first timmer, like me. My engine dimesionaly is stock, The head has only been shaved to flatten it, the deck isnt raised or lowered, the crank is in stock formation, the only difference is oversized pistons.
So..Am I to assume that when the notch is up on the left side, the punch lines up with the cover seam on the rite, and the pistons are at tdc, that the magnets on the rotoe and the cdi will take care of the rest? I have a 1980.

 

[xsjohn]

If it was mine I would just run it and see what you have.....as for cam timing I would be willing to bet you don't have a problem al all...........if by chance the cam is too advanced you will never be able to tune it.......it will always be lean from incomplete fill and if it's too retarded it will not preform well at lower rpms........

and as for ignition timing my 80 was to advanced even for stock gears and would not cruise along smoothly.....I tell people from my experience and many others that I have delt with that if it won't pull down to 2000 around a easy corner with very little load without getting too cranky I would retard it a bit....most will barely get to 2500 ...and i'm not saying you should drive it around at 2000 all the time......I'll show what I did to mine so I could set the timing the way I wanted it one more time........The break off screws that hold the pickup coil on can be ground off and replaced with screws.....the stator is thredded and with pliers you can grab the bit of break off screw and turn it out and replace with wcrews ........notching the case makes it so you can change the ignition timing without taking off the case......mark it first to the case before you do anything.....It's kind of a ride it and see what you have thing untill you get it where you want it....and isa must for tall gears for sure...and if it likes to kick you when kick starting that is a good indication for the need of a bit of retard on these TCI's.....it's my contention these were advanced for EPA compliance on emisions...but who really knows..........

Now I set my ignition at .168 thousands retard......that I found for mine from all the miles I have ridden it with the tall gears......surely everybody's is not the same...........

xsjohn

 

[Fernando]

Digging this up rather than posting another thread on the same subject.

79xs that I had to change the front cam chain, did that successfully and put it all back together with the timing slash on the came in the 12oclock and the punch mark facing the back with the "t" on the stator and the mark on the rotor lining up, put it in and something was wrong, pulled it back out and it wasnt lined up. REDID everything to the same procedure and it still wont fire?? When I look at the advancer unit the mark is no longer in the 12 oclock position as it should be when the "t" mark is lined up.

Im so lost as to how this could get out of time twice. How can I insure that this wont happen again when I for the third time pull the motor? The camshaft is placed with the points to the left side (shifter side) and the advance unit is on the right side (kickstarter side) Now that I have been staring at this I am loosing my mind on how things were set up.

Any help is greatly appreciated, I think Im loosing hair over this

 

[Fernando]

front cam chain guide***