Join Date: Feb 2002
Location: OKLAHOMA CITY OKLAHOMA
NPN I don't know what magic Numbers will work for you, but I can answer a few of your questions.
There are three ways I know of to check piston to valve clearance.
You can use clay on top of the piston. With this method you pull the head off, coat the combustion chamber and piston top with a light coat of oil (so the clay won't stick) and then re assemble the head and cams, then spin the motor over two full revolutions, then remove the head again and measure the impression made in the clay by the valves.
I personally don't love this method, though it is widely used. I find it more difficult to get accurate numbers from the very flexibly clay. Also i like to degree the cams before i check to v and this may well give you a false impression in the clay as you will have to rotate the motor over several times just to get the cams degreed.
Another method is to use a screwdriver and depress the shim bucket. With this method you set up a dial indicator that reads the actual valve bucket movement. once you do that you will rotate the piston just past TDC on the intake stroke and you will use a screwdriver or similar wedge to depress the valve bucket until you get an idea where the tight spot is. Once you find the tight spot, or spot with the tightest p to v clearance you zero you're dial indicator and take a reading while depressing the valve far enough o contact the piston. You then will take readings in 1 degree crank rotation increments until you find the tightest spot. You will be re zeroing the dial indicator for each reading.
The tight spot on the intake will be just past TDC on the intake stroke (maybe between 10 and 20 degrees past TDC) and the tight spot on the exhaust will be just before TDC on the exhaust stroke as the piston is chasing the valve closed.
this is also not my ideal method as it worries me to no end that I may scratch the cam lobe or the valve bucket with the prying instrument. Also the valve springs are very hard to depress making you exert allot of force while trying to take a precise reading.
The last way I know to do it, and the one I prefer is to use "checker springs". They are just light springs that you can easily compress with two fingers that are installed in the place of the normal valve springs. You just need 4 or 5 of them and they can be had pretty cheap at any hardware store.
With this method you remove the head, install the weaker springs in place of the regular valve springs, reinstall the head, degree the cams, set up a dial indicator to read directly off the valve bucket, and just as before rotate the piston just past TDC on the intake stroke and start finding the tight spot and measure it.
this method I like allot, it's super easy and less chance for me to scratch anything.
I just install the valves for one cylinder, degree the cams, and then take my readings. It's super easy to find the tight spot as you can hold the valve bucket down with your finger and follow the piston to feel the tightest clearance. Then just zero your indicator and start taking readings till you find the tightest spot.
Any of the methods will work, and have all been used a zillion times by people way smarter than me.
Important things to remember are : You need to be using the head gasket that will be used on assembly with the head torqued to proper specs, the cams MUST be DEGREED first!! Everything has to be exactly as it will be on final assembly.
I have not done any R1 motors myself, but it is my understanding that they do not have allot of room (P to V clearance) for a broad range of cam timing adjustments. Small cam timing changes can have a huge effect on P to V, so you must check it any time cam timing is changed.
Yamaha valve springs are pretty cheap (price wise not quality wise) so it would be a great investment for anyone building one of the R1 or R6 motors to buy new OEM springs at the least on a rebuild.
As far as the valve timing measuring points it's pretty simple. To measure the timing they use a set lift to take timing measurements. That means that they start measuring when the valve lifts a set amount, and stop measuring when the valve reaches that same amount right before it closes. When you degree a cam you will be doing the same thing. You will set up your dial indicator and degree wheel, and you will rotate the motor while watching the dial indicator, once it moves a set amount you take a reading off the wheel then record it, then continue rotating the motor until you reach that same measurement right before the valve closes. I use .050 when i do cams, but it actually makes no difference what lift you use.
Cam manufacturers are in business to sell cams, and the buying public like big numbers, so some companies start measuring a a smaller lift to make the overall numbers look bigger. If you use .040 as your set lift then your duration (how long the valve is held open) will look bigger on paper than if you used .050 to measure at.
I know some of this probably makes no sense to you at the moment, but I promise once you do it you will understand. it's not really all that hard to do, just takes allot of time and patience.
My only other suggestion would be to use a good quality assembly lube, as you will be rotating the motor over plenty before it gets oil in it.
I Pray I am strong enough to never give up.
Worry about doing what is right, and let someone else worry about everything else.