Just completed my first valve adjustment yesterday and though I followed the protocol to align each cylinder at TDC prior to adjusting, I wondered why that was necessary. I can understand that it is important in both reinstalling cam belts properly, and is helpful to keep valves from dropping into the cylinder. I did also read that it is important to align TDC to get accurate measurements and with the belts off, I just don't see how the piston position would have any effect on the valve clearances? Am I right, or could someone enlighten me?
So the valves don't fall into the cylinder when the closing shim is removed. ;)
If you've removed the belts it makes no difference in the clearance.
When the engine is at TDC on the compression stroke, it is a guaranteed position for both cams to be in a position where the rockers are on the base circle of the cam and not anywhere on the ramp that opens the valve. If either of the cam's are either beginning to open or finishing a close of a valve it will throw off the measurements. This holds true for adjusting any engine's valves not just the Desmo's. Hopefully I typed that so it makes sense..
[thumbsup]
Very clear thank you. I figured that was the reasoning.
Plus, I fugure, once you remove the belts to rotate cam to check for closer binding - you wanna get that sucker back where you had it
...to save yourself the 3+ hours it takes to fish an 8mm valve out of an M900i.e. through the valve stem hole.
Oh wait, nevermind...that's just me. ;D
File that under 'W' for whoops!
3 hours???? Why can't you just take a magnetic retrieval tool and get it out? Why does it take so long? Hopefully I'll never have to find out. I can't find W. I'll just put it under C for crap! [cheeky]
Hopefully, your magentic-retrieval tool is thinner than 8mm....and you still gotta snag it on the end.... [bang]
Quote from: uclabiker06 on August 14, 2010, 08:12:36 AM
3 hours???? Why can't you just take a magnetic retrieval tool and get it out? Why does it take so long? Hopefully I'll never have to find out. I can't find W. I'll just put it under C for crap! [cheeky]
It takes 3 hours because the 8mm valve stem has to go right up the 8.05mm valve stem guide. And you have to do it with a 7.8mm magnetic retrieval tool.
It was either that, or take the head off which would have been easier but taken longer.
Quote from: Ratfink749 on August 08, 2010, 11:21:13 AM
When the engine is at TDC on the compression stroke, it is a guaranteed position for both cams to be in a position where the rockers are on the base circle of the cam and not anywhere on the ramp that opens the valve.
So, if I'm reading this correctly at TDC all valves are in position for measurement correct?
I ask because I've heard/read twice that there are 2 TDCs and you need to use both (1 for horizontal, 1 for vertical cylinders). But that makes no sense to me and I'm trying to understand.
The cylinders reach their respective top dead centers at different times in the crankshafts rotation.
The only time the cam lobes are away from the rockers is at TDC for that cylinder.
If you remove the belts then you can manipulate the cams regardless of crank position, but you then run the risk of a valve falling into the cylinder
Quote from: INFIDEL on July 28, 2014, 02:28:17 PM
So, if I'm reading this correctly at TDC all valves are in position for measurement correct?
I ask because I've heard/read twice that there are 2 TDCs and you need to use both (1 for horizontal, 1 for vertical cylinders). But that makes no sense to me and I'm trying to understand.
There are 2 TDC for each cylinder. You want TDC on the compression stroke. You can see the valves open and close as you turn the engine through the spark plug hole to see whether it is on the the compression stroke or not.
By the way, I recently did the 15,000 valve adjustment on my bike and it runs so much better now. [thumbsup]
Quote from: Duck-Stew on August 14, 2010, 06:58:08 PM
It takes 3 hours because the 8mm valve stem has to go right up the 8.05mm valve stem guide. And you have to do it with a 7.8mm magnetic retrieval tool.
It was either that, or take the head off which would have been easier but taken longer.
How you didn't just give up after the first hour is beyond me. [bow_down]
Quote from: 1.21GW on August 02, 2014, 10:39:56 AM
How you didn't just give up after the first hour is beyond me. [bow_down]
Bike was due that day, didn't have base-gaskets should the barrel to case seal 'break', customer was already on his way... Got lucky, lucky, lucky...
On youtube (no idea where) I once saw a video of an animation showed a cutaway view of an operating desmo engine. I found it very explanatory.
Is this the link?
https://m.youtube.com/watch?v=Ak2rsfbVo60