Maximum Valve Clearance Timing (SOLVED)

[GnarlyBus]

A few more questions while I'm learning to adjust the valves. It's the stuff they don't say in the book that makes me wonder.

How do I know when a cylinder is ready to have the valve clearance adjusted? Is there some way of knowing EXACTLY when the rockers are at maximum clearance?

It's hard to tell the answers to these questions when I turn the engine over by myself and crawl back in the right side of the engine bay. I think I'm gonna have a friend turn it over while I watch the rockers move. But I appreciate any help before I can do that!

[eagle19952]

2 stroke

when the injector is fully depressed..the valves are fully closed...

[Templar52]

Yes,it is whent the center (injector) rocker is fully compressed. You should do all the valves in only one rotation of the engine.

[GnarlyBus]

Yep, but how do I know when the injector is "fully depressed" as opposed to 3/4 depressed? Ha! I can't be helped!

I guess I'll have to have someone else turn the engine over while I watch them move. Then I'll know. I've been trying to do it by myself and I can't tell what's what from behind the engine.

[eagle19952]

depressesd at all is fine,as in the inj. rocker arm is lower than the valve rocker...pull the fuel at the govenor and get a bumper button...
or bungee the racks...
or drain the fuel filters and plug the air intakes
PS. For sure you're setting the injectors...
and your doing this on a hot motor, right ?

[GnarlyBus]

No, I'm adjusting the valve clearances. Injector timing will be next. I'm following the manual instructions for setting cold valves then I'll check them hot. Thx.

[GnarlyBus]

Ok I think I get it now.

In the cycle of valves and injectors, there is a very short momentary pause when the valves move from open to fully closed before the injectors are pushed down. Then the injector is completely "undepressed" right before the valve bridges are pushed down.

So as long as the injector is depressed, the valves are closed and can be adjusted for clearance. Yah?

And when the valve bridges do not wiggle they are open and the injectors can be timed with the cocktail stick tool, yah?

I'll do all the valves in order in one rotation. Then go through again and do the injectors.

[eagle19952]

i just do them as i see them...
one bank then the other.
inj or valves which ever is there.
on injectors.. a drop or two of oil on the plunger surface is your friend...
when you twist your timing tool it gives you another reference comparing the "wipe"...

the cocktail stick doesn't hold olives well...the holes are too big, go with onions for Martini's.

ps. the mechanics I know drink Rye whiskey.
ok

[bevans6]

In tech-speak, a cam has a lobe with a base circle.  A full rotation is 360 degrees, and around 200 - 220 degrees of that is base circle.  There is a short transition from the base circle called the ramp which takes up clearance smoothly, and then comes the flank.  The flank lifts the valve (or closes the injector) until it reaches the nose - the point of maximum lift.  Then you get another flank, another ramp, and back onto the base circle.  The base circles are ground with an extreme degree of accuracy, so you can set valve clearance or time the injector at any point where the cam follower is on the base circle.  There is no special need to find the center point of the base circle, any point 10 or 15 degrees past valve closing is fine.  Similarly any point 10 or 15 degrees past the injector finding it's tallest point is fine, but the injectors never have any clearance - they are always under tension from the cam/follower/pushrod.  You set the timing by adjusting the height of the injector with the cam lobe on it's base circle.  Since you are rotating the engine anyway, it's just as easy to find a good center point on the base circle by setting the valves when the injector is all the way down, and setting the injectors when the valves are fully open, but there is no need to be anal about it - "around" fully down or open is perfectly fine.  Remember to lock the engine stop lever in "no-fuel", engine speed lever in idle, and if you use a wrench on the front pulley bolt always turn the engine clockwise as if you were tightening that bolt.  Never turn the engine backwards, or you stand a chance of losing torque on that bolt.

Brian

[Geoff]

Hint:. Since you have Jakes, you are going to have to bend the injector height tool handle at a 45 degree angle so you can get under the Jake body.

[Utahclaimjumper]

 As an aviation mechanic/inspector for 33 years its interesting to note that the FAA requires  that a mechanic whom hase'nt performed a task, cannot do so unless he/she performs that task in the presence and under the supervision of one whom has.. It would prevent a lot of goofups by newbe's trying to to technical work for the first time that can have very expensive results.>>>Dan

[luvrbus]

Hint:. Since you have Jakes, you are going to have to bend the injector height tool handle at a 45 degree angle so you can get under the Jake body.

Or buy a set made for setting the injectors with Jakes

[GnarlyBus]

In tech-speak, a cam has a lobe with a base circle.  A full rotation is 360 degrees, and around 200 - 220 degrees of that is base circle.  There is a short transition from the base circle called the ramp which takes up clearance smoothly, and then comes the flank.  The flank lifts the valve (or closes the injector) until it reaches the nose - the point of maximum lift.  Then you get another flank, another ramp, and back onto the base circle.  The base circles are ground with an extreme degree of accuracy, so you can set valve clearance or time the injector at any point where the cam follower is on the base circle.  There is no special need to find the center point of the base circle, any point 10 or 15 degrees past valve closing is fine.  Similarly any point 10 or 15 degrees past the injector finding it's tallest point is fine, but the injectors never have any clearance - they are always under tension from the cam/follower/pushrod.  You set the timing by adjusting the height of the injector with the cam lobe on it's base circle.  Since you are rotating the engine anyway, it's just as easy to find a good center point on the base circle by setting the valves when the injector is all the way down, and setting the injectors when the valves are fully open, but there is no need to be anal about it - "around" fully down or open is perfectly fine.  Remember to lock the engine stop lever in "no-fuel", engine speed lever in idle, and if you use a wrench on the front pulley bolt always turn the engine clockwise as if you were tightening that bolt.  Never turn the engine backwards, or you stand a chance of losing torque on that bolt.

Brian

Thank you for taking the time to share this. You filled in some of the knowledge I was lacking. I appreciate it!

[GnarlyBus]

As an aviation mechanic/inspector for 33 years its interesting to note that the FAA requires  that a mechanic whom hase'nt performed a task, cannot do so unless he/she performs that task in the presence and under the supervision of one whom has.. It would prevent a lot of goofups by newbe's trying to to technical work for the first time that can have very expensive results.>>>Dan

I hear that. It isn't easy to learn from a  manual that assumes you're generally trained on diesel engines. A lot of basic information is left out. That's why I come here.

Some day I'll have to get to one of these rallies and spend some time learning from you guys in person, but for now, these threads are what I've got. I've resisted the urge to not post threads because eventually someone's gonna tell me if I don't already know the answer then I shouldn't even be doing this. But I figure some newb somewhere might appreciate reading these someday.

Maybe when I come to a rally we can shoot some videos on how to do this kind of maintenance stuff for the bus community. Then people do it the right way and preserve these engines.

[Scott & Heather]

I for one applaud your bravery...cool stuff. Keep posting


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