Proper way to measure valve clearances?

[skydoc_17]

I have posted a pic of the cam timing wheel I use to position the crankshaft for valve adjustments. I am sure this is overkill, but being a Machinist, I try to do things the best I can. I have had this timing wheel for a number of years now and it is a great size for motorcycles. (smaller than pic size)

BradT, to answer your question about the change in the point of tangency between the Lobe Ellipse and the static diameter, a change in the static diameter by -.005 only changes the tangent point of the Lobe ellipse .00003 (thirty millionths of an inch)

I am not trying to insult anyone here, and I would also like to point out that if the static diameter of the cam on YOUR VR is only -.001, and you used your method of setting the cam timing, then your valve adjustment would only be .001 tight. Surely not enough to cause major damage. The reason I brought up the method in which cams are ground is because it has changed with the introduction of more modern equipment. I know for a fact that Honda, Kawasaki and Bombier have been using the newer equipment and 2 step grinding method for a number of years as well as many of the major aftermarket cam makers.

I use the method in the service manual in conjunction with the timing wheel, and was trying to show you why it is better, nothing more. I have seen more than one tight valve adjustment, but very few cams or valves damaged as a result of a tight adjustment on the ventures. I can see where it would need to be set correctly on the VMAX seeing how those bikes are run a lot harder.

My intension was to share knowledge and tools I use to make a job that is not any fun to do easier and more accurate. Not to make anyone mad, or say that my way is better or your way is bad.

Earl

[skydoc_17]

I was wondering if the point that is missing here is the fact that the piston needs to be on TDC of the compression stroke not the exhaust stroke to position the lobe of the cam off of the valve shim bucket for all of the cylinders.

Just a thought,

Earl

[Squidley]

Earl,

No offense taken here by me or anyone, I understand where your coming from and appreciate your taking the time to get right down to the basic bolts of how it's done. Perhaps it's just me in the fact that if I go verbatum by the book the valve is already starting to load up. I'll play around with it a bit more and see if the timing mark is just a "in the area" reference.

Thanks again everyone, this is a very informative thread and I appreciate all the input

[Squeeze]

Brad, you should ever regard those Timing Marks as a Area and not as a Spot. When you look at the H-styled Mark, only this Size of the Mark covers more or less two Degrees Angle.

 

Even though i found the Marks fairly accurate on the V4, a Lot of others are not so accurate at all. Suzuki's are somewhat prone for being "somewhere" near. The only real Reference Point you gotta seek and relate is TDC an the Cylinder who is in checking at the Moment.

 

When you're working on a bored, high compression Motor with really hot Cams, you need to ensure this or you may need to change a Valve or two, because they're bend.

 

Using a Timing Wheel is a smart Move because it makes Life easier, but IMHO, it doesn't spare you to check for actual TDC. The Wheel is a really nice Tool when you're playing with slotted Cam Wheels and setting the Cams on different Overlap.

 

Brad, the Answer to your Question/Problem is as easy as it can be.

 

You got the Piston in TDC in the Compression Stroke and the Cam is somewhat engaging on the Shim already ? The Feeler isn't going through the Passage ?

 

Answer: The Shim is way too thick.

 

You gotta keep in Mind, the Clearance will always get too tight over Time. In other Words, the Shims is getting thicker and thicker in Regard to accomplish proper Clearance. You always will have to go to a thinner Shim to achieve the proper Clearance. If you find a too big Clearance, you have Oil Cole sitting on the Valve Seat or the Valve/Bucket is stuck somehow.

 

 

As a Sidenote, it just came to my Mind ... what if Yammi did 2-Step Production Method and used this also as a "Safe Harbour".

 

Basically, the lower Clearance will start to make up a real Problem when there's no Clearance left at all. The Valves, especially the EX-Valves won't be be able to distribute the Heat during Combustion to the Valve Seat and cool down by doing so. They finally burn down on due the hot Gas flowing by. If the static Profile Diameter is lower than the supposed Clearance Point, it adds up some Safety Margin.

[Venturous Randy]

I have not taken the time to go find my manual and read it, but just from what I am reading here, I am seeing things that do not make sense. First of all, if you are reading valve clearance at Top Dead Center TDC between the compression stroke and power stroke, you are going to be on the back side of the cam on those lifters.

The reduction of the valve clearance is not caused by the shim getting thicker due to sludge or anything, but from the valve face hammering into the valve seat and wear in that area. The more it wears at the valve seat, the less clearance you have at the shim.

Now what is the reason for clearance in the first place? There needs to be enough clearance to allow the valve to close completely when "off" the lobe and there should not be excessive clearance to allow the shim to rattle. If too much clearance, you will hear the valve "ticking".

The specified clearance takes these two things into consideration along with the various heat ranges that everything will be operating in. Therefore, if you set your valve clearance to be checked in any of the area where that valve is completely off the lobe, you should be just fine. And, when you check the clearances with the engine cold, that specification takes into consideration any heat changes.

I have checked a few valve clearance in my day, from several different bikes to soild lifter high performance cams in small block Chevys and the off lobe clearance is what is always used. The only time any loading was used was when duration and cam timing was taken into consideration and that is usually at the .050 lift point at the beginning and ending of the lift area.

So I say checking the clearance anywhere on the off lobe will be fine.

RandyA

[jcdas]

I'll add my 2cents worth.

 

I found that the timing marks and instructions didn't make any sense for some of the cylinders. So I disregarded the instructions. I think something got lost in the translation from Japanese to English.

 

Manually crank the engine in the normal rotation. I make sure that the cam points 180 degrees away from the shim. Check for clearance.

 

When the gap is between two settings, I'd rather go loose than tight. You can barely hear the difference.

 

If it's too tight, the exhaust valve doesn't have enough time to fully seat and transfer the heat to the cylinder head, and the exhaust valves can burn up as a result. If the intake is too tight, it might have a habit of poping through the carbs.

 

Regards.

[Squidley]

Lutz,

I do understand where your coming from as I have used a cam wheel (albiet many years ago) I will play with it a bit more, there wasn't really any issue with the bike. I believe it was more carbs than anything. Thank you all again for pounding into my thick head, I'm somewhat a hard sell on things some times. It's always good to get these things out in the open here on the site so many of us can learn new things, I appreciate all you folks help

[Bob K.]

Here are pictures that I took of the camshaft and lobe positions while following Yamaha's method of indexing off of T1 and T2 on the crank.

 

This picture shows the position of Cylinder #1 camshafts with the crank at T1. The lobes are pointed inward and upward.

 

This pictures shows the position of Cylinder #1 camshafts with the crank at T1 when the crank is 360 degrees out and the cylinder is not at TDC at the start the combustion cycle. Notice that the lobes are pointed downward. The exhaust valves are almost closed and the intake valves have started to open. This is not the correct position to start at T1 and begin alignment for Cylinder #1 .

 

O.k. Assume we're back at the correct crank rotation. This picture shows the position of Cylinder #3 camshafts after the crank has been rotated 180 degrees from T1. This is the position to measure Cylinder #3 valves. Notice the lobes are pointed inward and upward much like Cylinder #1 .

 

This picture shows the position of Cylinder #2 camshafts after rotating the crank 180 degrees plus an additional 70 degrees from the measuring position for Cylinder #3 , and aligning with T2 on the crank. Notice the lobes are almost horizontal and are pointed outward from the center.

 

This pictures shows the position of Cylinder #2 camshafts with the crank at T2 when the crank is 360 degrees out and the cylinder is not at TDC at the start the combustion cycle. Notice that the lobes are pointed downward and inward. The exhaust valves are almost closed and the intake valves have started to open. This is not the correct position to start at T2 and begin alignment for Cylinder #2.

 

O.k. Assume we were back at the correct measuring position for Cylinder #2. This picture shows the position of Cylinder #4 camshafts with the crank rotated an additional 180 degrees from the measuring position for Cylinder #2. Notice the lobes are almost horizontal and pointed outward, much like the lobes for Cylinder #2.

 

The correct rotation steps, then, are:

1. Align to the correct T1 position for Cylinder #1. Measure Cylinder #1.

2. Turn the crank 180 degrees. Measure Cylinder #3.

3. Turn the crank to T2, which ends up being 180 degrees plus an additional 70 degrees. Measure Cylinder #2.

4. Turn the crank 180 degrees. Measure Cylinder #4.

 

I note that the lobes are in different positions for Cylinders #1 & #3 (pointed upward and inward) than they are for Cylinders #2 & #4 (almost horizontal and pointed outward). If the official Yamaha instructions have us measuring at different points on the base radius of the lobes--Cylinders #1 & #3 more on the bottom of the lobe and Cylinders #2 & #4 more on the side of the lobe--that would seem to indicate that it's acceptable to measure anywhere on the base radius of the lobes. That includes skipping the official measuring method and just turning the crank on each cylinder until the lobes are pointed straight up (as others have suggested).

Edited August 11, 2018 by Bob K.

[Vickersguy]

As am addendum to Bob K's ( Squidly ) observations, here's my thoughts for those without Metric feeler gauges. Given that wear results in tighter clearances, one will almost always be going to a thinner shim. The intake minimum clearance is .11mm or .00433* inch. If you have a good set of feeler gauges it will have a .0015 and a .0025 "leaf" in the stack. The .002 and the .0025 add up to .0045. If the .0045 will not go under the cam, it is at a minimum clearance and you need the next thinner shim. The exhaust minimum clearance is .15mm. This is .0063 inch. Use the .004 and the .0025 together for .0065 inch. If this combination will not go under the cam, then it is too tight and you need the next thinner shim. The .0045 and the .0065 become a simple go/no go measuring point for deciding if you need to change a shim. One shim step is .0024 inch. In my opinion, if the feeler gauge is tight, but goes under with some wiggling, you probably can go to the next thinner shim. Being 1/4 step too loose is way preferable to skipping the change and quickly wearing to the minimum clearance. I, for one, do not wish to go back in again any time soon. I haven't done the math, but if .0025 inch leaf won't pass under the cam, you need to go two steps on the shim, rather than one.

Edited December 26, 2018 by Vickersguy