How I set my valves « Thread Started on Mar 4, 2011, 3:24pm »
I don't like adjusting the valves using top dead center (TDC), especially on these GY6 engines.
There is a far better way of doing this.
Here is how I do it:
Cold Engine.. like overnight cold. Remove the plug
Turn the engine in a clockwise direction if you are using the fan. (Counterclockwise on the variator)
When the EXHAUST valve is fully open stop turning. If you missed it exactly you can turn the engine back a bit, until the exhaust valve is open as far is it can go. It is really easy to see the exact spot.
Use some oil on the feeler gauges.
Gap the INTAKE valve to .004".
Now turn the engine again until the INTAKE valve is fully open.
Gap the EXHAUST valve to .005"
Turn the engine again and check the gaps on both valves. Use some oil on the feeler gauges.
Put the valve cover back on ...you are done.
Why is this better?????
1. It is very difficult to get the engine at exactly TDC. Even with the cam chain sprocket aligned and a good mirror you get some parallax. A better alternative is a feeler in the cylinder chamber (through the spark plug hole) but it takes an experienced mechanic with a fine touch to get exactly TDC.
2. The cam lobes on these engines are often not ground exactly. They may be within tolerance but who knows what that is. The method I use accounts for this fact also accounts for any cam lobe wear.
By the way, there is no way to set the engine to TDC using the flywheel.
Joined: Jan 2011 Gender: Male Posts: 146 Location: West Central Illinois
Re: How I set my valves « Reply #2 on Mar 4, 2011, 10:44pm »
I've used your method when hand checking the valve lash on hot 4 stroke dirt bikes, but I always set the lash cold using the timing marks......they were always good on the Jap bikes I had.
When using good timing marks, never roll the engine backwards....if you pass it, roll it forward to TDC on the next compression stroke; this is because of the slack in the timing chain and the nature of the cam chain tensioner relative to the camshaft and oil pump.
Next time I adjust the valves on my scoot, I use your method to check them.
I'm not exactly mechanically inclined. I understand the timing mark procedure. But with you method, how do you know if the valves are exactly opened?
Hi Squeekie Because, you can see when top of the cam lobe is fully opening the intake valve .. Meaning the exhaust is fully closed. And ready for adjustment. As he said this method accounts for slight imperfections.
His method is sound, I use it myself.
I've also done it the other way, making sure the top of the intake cam lobe is pointing straight down at the piston then adjusting the intake valve, then doing the same for the exhaust.
The idea is still the same, to adjust the valves so they are exactly and any point in the rotation of the cam at what you set them to and account for wear and other imperfections.
« Last Edit: Mar 5, 2011, 10:58am by larry001964 »
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Re: How I set my valves « Reply #5 on Mar 5, 2011, 2:58pm »
larry001964 is right on!
It is really very easy to watch the rocker arms too. When one arm is fully down on the valve you adjust the other valve and visa versa.
This is the only way we used to gap the 4 stroke racing engines
This method is the most accurate by far and you don't need to spend 15 minutes trying to get the piston at top dead center.
Just different strokes... this one is old and proven on small engines.
Timing marks are fine for setting the cam chain, but useless for valves. At least this applies to GY6 engines. The flywheel marks vary considerably and it is hard to see accurately...
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Joined: Sept 2007 Gender: Male Posts: 464 Location: East Tennessee
Re: How I set my valves « Reply #6 on Mar 6, 2011, 8:40am »
Great tip Sprocket, I've only done mine once, but I do it also. I use the kick starter lever to advance the engine. Another thing I do is to check again when both valves are closed by feeling the compression stroke with the kick starter and stopping kinda in the middle. The valves are both closed then and you can check again before placing the cover back on.
Re: How I set my valves « Reply #7 on Mar 6, 2011, 12:07pm »
Why do you guys make it so difficult? Just line up the two small holes on the cam sprocket to be parallel with the top of the head when the large hole on the sprocket is furthest from the engine. With the spark plug removed the kick starter is fine for rotating the engine close enough and then a screwdriver can be used to carefully push on a fan blade thru the opening. The direction of rotation and the flywheel timing mark are unimportant when it's set in this manner.
Re: How I set my valves « Reply #8 on Mar 6, 2011, 12:30pm »
>>Why do you guys make it so difficult?
>>Just line up the two small holes on the cam sprocket to be parallel with the top of the head
It is not difficult at all and doesn't use TDC...in fact is faster , more accurate and easier.
The cam sprocket method is inaccurate due to parallax when viewing the small holes and the edge of the head and doesn't allow for cam/valve stem wear...
Give my method a try and you will see there is a difference in the gap between the two methods.
Joined: Jan 2011 Gender: Male Posts: 146 Location: West Central Illinois
Re: How I set my valves « Reply #9 on Mar 9, 2011, 12:09am »
I must remove the fan cover then the top of the plastic cooling jacket so as to gain access to the valve cover. So I use the timing marks on the flywheel.
After adjusting the valves, I can't tell any difference in the measured clearance 6 degrees or so either side of TDC.....that would be 3 degrees on the camshaft. Could be no difference at 20 degrees, but I never checked that far off.
But next time I will check the diff doing it with opposite valve fully opened.
Based upon the way-back-machine, I remember we set the valves on our cars (hot and running). What we actually measured and set with a feeler guage was the maximum valve clearance around each cam lobe....all you have is feel...no way to tell the position of the lifter on the cam lobe at anytime.
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