How to set and adjust valves on all 4-stroke engines

[shadetree 5,877]

First let me say, this is not by the book ?, It is how I set and adjust my engine valves on my builds. some parts of this ''How To'' will work just fine, while other parts of this you may want to use the correct tools ?, I will point out which tools you need when I get to that point.

 

Ok, lets start off with having the rocker box off, or valve adjusting cap off. Depending on which type of motor your working on ?, this next step will not be the same, with that in mind, it does not matter too much, as you still need to access the crank. if its the newer engine ?, your 17mm access bolt will be behind the rear pull starter ( if your engine has one ?, some trx420's do not have a factory pull starter on them ). Remove the pull starter, now you can see the 17mm head bolt holding the cage on the end of the crank. next, remove spark plug ( this makes it a lot easier to turn the motor over ). Older engines have the 17mm crank bolt on left side of engine cover, where the flywheel is located. with a 10mm box wrench, loosen the tappet lock-nuts on both the intake and exhaust valve ( valves ).

 

Remove the sight hole ( inspection cap ) from the right rear of motor ( front left side on old style engines ), so you can see the flywheel. Your looking for the letter T on the very edge of the flywheel, this stands for TDC= top dead center for those that are new to engines. Keep in mind, there is 2 TDC's !!!, one Is for exhaust stroke , other is for compression stroke, YOU WANT TOP DEAD CENTER ON COMPRESSION STROKE !!!. Now your asking me..'' how the heck do I know which stroke I am on '' ?. Its very simple to find out, least for me anyway :-).

 

With spark plug out, 17mm socket on 17mm bolt, turn the crank until you see the letter T line up with the index in the sight hole, your piston should be on top dead center , but the question is, now how do I know which stroke...right ?. here's how I do it !. once I have the letter T lined up in the sight hole with my index, I then rotate the crank backwards , SLOWLY !!!, as I am doing this, I watch my intake valve too see if it starts to move ?, if it does ?, then I did indeed have my piston on top dead center on the compression stroke. now all I need to do is rotate the flywheel/crank back to where I started, line my T back up where I had it to begin with in the sight hole, then go up to valves, and adjust them. now comes the tool part !, the book say's on most valves they call for 0.006 with feeler gauges ?, I do not use them, never have, never will !. Please don't tell me I am doing it wrong ?!, I have been doing it this way for 28 years, I GO BY FEEL !, its a skill you must learn over time, its not something your home mech can do on every valve adjustment ?..BUT ITS SOMETHING I AM GOOD AT !.

 

Now if for some reason when you started moving the flywheel/crank off the letter T from the start, and your watching the intake valve, and it never began to move ?, then you had your piston on top dead center on the exhaust stroke !. To solve this, turn the crank back to where you started, get the letter T back in the sight hole, once there, turn the flywheel around one full turn, until the letter T is lined back up again in the sight hole, you should now have your piston on top dead center on the COMPRESSION STROKE, WHICH IS WHAT YOU WANT !. To make sure your correct ? ( or me at this time ), I then turn the crank backwards ( SLOWLY ! ), As I am doing this, I watch the intake valve, it SHOULD start to move as I am going backwards, which in most cases..it does !. Ok, now I stop, turn the crank back the other way to line my letter T back up in the sight hole, I leave it there, go to the valve ( valves ), and set them. for you green horns, you now will use your feeler gauges to set the valves, me ?, I go by feel.

 

NOTE: if your cam chain is stretched ?, you will have a hard time getting the valves set no matter how many times you use this How To ?, you must have a good cam chain at all times to get the valves set correctly !.

 

Final words : again, this process is not by the book !!!!, this is how I do it ?, EVERYONE WILL HAVE DIFFERENT RESULTS !!!.

Edited January 20, 2020 by retro
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[jeepwm69 7,599]

Just saw this process posted on the old HL forum.

 

Curious as to what yall think about it.  Makes sense, but on the other hand I'd rather them be a little loose than too tight.

 

What I've learned on these bikes is that after 20+ years the rocker arms tend to wear some. So the way I set the valve is not by setting the motor to TDC. I rotate the motor over until I see the exhaust valve starting to open. This should indicate the intake valve is closed all the way. Set the intake valve at this time. Then do the same thing to set the exhaust vale. Watch for the intake valve to start opening. Even after adjusting at TDC several times my motors would always tick. I did it this way and much quieter

[retro 4,048]

That method is more correct than Honda and every other engine maker recommends. You want the cam lobe to be 180 degrees away from the lifter so the lifter is resting on/at the middle of the base circle radius of the cam lobe. Honda's recommended method works in other words, but it is not the ideal valve adjusting method.

 

You can add two valve adjusting marks onto the flywheel using a center punch as you are assembling your motor to provide quick reference marks for all valve adjustments that you'll perform in the future. When I was building racing SBC V8s back in the day I used a number punch set to mark the harmonic balancer with valve adjustment reference points, but on single cylinder motors a couple center punch dots will cover your needs for quick, precise, repeatable results.

 

EDIT: That guy does not understand the subject, he gave false info for his excuse, but his method is closer to being ideal than going by the book.