Somethings thats always bugged me about setting cams

I've done the valves on my CBR600f4i a few times now. According to the book you turn the crank sprocket to line up a mark on the sprocket with a mark on the clutch cover for setting the cams at TDC. I know its not the most exact method, but I stick a plastic straw down the spark plug hole to verify TDC. As I turn the motor over, piston gets there, hangs for a second, and then actually drops the slightest amount when I line up the mark on the sprocket and cover. That means I'm past TDC, so I etched my own mark on the clutch cover and set the cams there. Am I right doing it this way? Is it just manufacturing tolerances that make it not line up right? Ran it about 50,000 miles this way so I can't be totally wrong haha.

 

might have been bored and stroked.

 

Also intrested have to do mine soon..

 

Production Tolerance.

 

2mm fo sho. It corners real low.

 

Bored and stroked will not change TDC. I've timed many V8s cams but never DOHC. So not sure if all the tools transfer but a degree wheel and a piston stop will give you exact TDC. Getting perfect cam timing often relies on the adjustability of the cam gears.

 

So, here's the question: Are the reference marks on the cam sprockets based on true TDC or marks on the cases? Secondly, if you're not playing with adjustable sprockets and can only swing things a tooth at a time, does this tiny difference actually make any difference or do you end up on the same teeth anyways?

 

If it were gears it might stay close to perfect, but with a chain or belt you always have that element of wear to consider. We set some Subaru timing belts a tooth off because in the first 1000 miles the belt stretches and wears. The timing marks end up being about half tooth off initially, no matter how you set it, so we set it on the correct side and let it wear into a better alignment.

 

Nobody has ever thought of it that way before. Bravo for F'ing with my head sir. haha.

Yes, it actually is a one tooth off difference. All OEM stuff.

 

My question would be are you doing this in the bike or out.
If in, good luck I did mine last time that way. NEVER AGAIN.
Seeing the marks properly in the bike is next to impossible. Spent twice as much time confirming I had it correct than if I pull then engine.

 

Prolly not the place to put this but.. how do you guys rotate the cams after there reinstalled and the chain is still off?

I only need to rotate them a few mm becouse after i reinstalled them the marks are just a little off and i cant move them by hand is there a tool for this?

 

I do not know of a way to move the cam's once the chain is on.
For my bike the exhaust side chain is tight, cam correct position, then Intake.
Helps to have extra hands to HOLD the cams while tightening the carrier down as it will cause a cam to rotate.
Make sure tensioner is on before moving the crank. Rotate engine back to a check cylinder 1 again.
If it all doesn't line up, repeat until it does.

 

Thanks for the reply. Sounds like you just have a friend hold the cam when you reinstall the camshafter holders.

Heres a link to my exact issue. Not my vid just one off utube. Anyone know of a tool if you dont have a friend?

 

chain on cams in the right spot (counting the links is a good practice to get into, especially the middle links), 2 zip ties on each cam gear holding the chain to the gear. tighten 1 cam at a time and then pop the tensioner. it's always a good rule of thumb to just do 1 cam at a time, it's a little bit more of an arduous process but you generally wont mess up cam timing that way. always zip tie the chain to the gear.

 

I was not amused to find the Yamaha service manual doesn't specify the link count between cams for 2nd gen R6 machines... half a day fighting those f$@%@%!

 

Nope and I'm pretty sure they still don't list it. I count and write down on the top of the paper I'm doing my valve clearance checks on. Its a habit now. Saved my ass more than a couple times.

 

I use a paint marker and mark the 3 sprockets and chain

 

wow......you guys make me feel absurdly better about cams and valve clearances on the o'l F4i......seems like a cake walk. _indy- seeing the cam sprocket marks on an F4i is extremely easy, the frame is not in the way at all.

 

This. Piece of cake putting everything back together. I use the "white out" stuff for correcting typing errors, which also stays on the chain and sprockets for years.