Resetting valve clearances after lifting head?

[mckutzy]

Hey guys, on my other bike, I have another 6.5 champion motor.
It had some water ingress in the intake and exhaust especially(broken off muffler)(the bike was given to me and I know nothing more).
I broke it down to examine more of what the extent was. Over all alright..

I didn't think when I attempted to remove the head, and remembered potentially that I'd have to reset the lash.
I didn't undo the rocker nuts, but did relieve the exhaust spring to see the valve.

At this point I went to my local equipment/lawnwnmower repare guy, The valve and seat can be cleaned and relaped apparently.
He said though, since I had removed the head, I had to reset the lash.
Is this true, Or can I just bolt the head back up?

 

[Russ2251]

He said though, since I had removed the head, I had to reset the lash.
Is this true...?

Yes, I certainly would take his advice.
Such a simple thing to rectify...why would you not want to?

 

[mckutzy]

I'm not exactly sure on the whole process. It seams that it wouldn't change if the head was torqued to right spec again.
I have reviewed a number of vids off of the tube.
Main question off hand, is the piston supposed to be in the tdc position.

 

[Russ2251]

is the piston supposed to be in the tdc position.

Yes. This act ensures that valves are completely closed and off the cam lobes.

 

[mckutzy]

I'm having a little difficulty finding the head torque value?
Something like 125in/lbs?

 

[Russ2251]

Something like 125in/lbs?

Isn't something to guess at. Someone here must know.

 

[mckutzy]

Anyone know, I'm not really finding anything?
I've been having problems with all sorts of tech today..

 

[itsid]

head bolt torques (M8 x 1.25)

are 24Nm for Honda GX200 as well as lifan 168F2 (gx200 clone)
(taken from the respective manuals)

I don't know about other clones though.

'sid

PS according to 'thetoolhut.com' 24Nm equals 212.42 in/lbs

 

[mckutzy]

So why would the lash to be reset, if head bolts are torqued to correct value?

 

[itsid]

well,
to be sure!

if you can make sure that you haven't touched the pushrods,
you haven't opened the crankcase (pushers, cam and such)
you haven't touched the rockers (nor loosened any related nut or bolt ...)

there is no actual NEED to reset the valve lash.. other than to be perfectly sure it's set correctly.

What I'd do is: torque down the head and CHECK the valve lash on three to four consecutive TDCs to make sure it's still within tolerances and get an average (well cancel out human erros )
then reset the lash only if it's off.

'sid

 

[Russ2251]

So why would the lash to be reset, if head bolts are torqued to correct value?

Clearly you do not want to do this, even though it would ensure that engine operates as it should and according to spec, correct?
Remember that efficiency equals horsepower.
If valves are not in spec, efficiency suffers...hence, horsepower suffers.

 

[KartFab]

At this point I went to my local equipment/lawnwnmower repare guy, The valve and seat can be cleaned and relaped apparently.

So are you going to do that part? Does it need to be done? Just need some valve grinding compound and a little suction cup on a rod. after that you for sure would need to redo the lash.

Also, another reason to reset valve lash is that it is one of those things that is part of preventive maintenance, just like changing oil, only rarely needs to be reset.

If it were me, I wouldn't do it just because I'm a little lazy, but literally takes maybe 5 minutes tops to do.

 

[Connell]

I have taken the heads off two engines, not done this and they both have ran fine since.

 

[Russ2251]

I have taken the heads off two engines, not done this and they both have ran fine since.

You're right. So why bother.
I'm on the other side of the spectrum.
I've done thousands of repairs related to cylinder head removal and checked for valve lash each and every time. But that's me.
Comes with age and experience I guess.

 

[mckutzy]

Ahh good point on the reset after lapping.. Didn't think of that.
I will go ahead and do the check and reset if necessary.
I haven't done any real engine work on stuff like this.

 

[Desertduler]

You're right. So why bother.
I'm on the other side of the spectrum.
I've done thousands of repairs related to cylinder head removal and checked for valve lash each and every time. But that's me.
Comes with age and experience I guess.

Russ is exactly right, I have been building engines for 40 plus years and some of them cost as much as a house, whenever you remove and replace a cylinder head it is the correct procedure to re set the valve lash,don't count on the new head gasket crushing the same as it was before and if you understand rocker arm ratios the difference WILL be magnified between the valve stem tip and the rocker arm.If you do not reset the valve lash then you are flat out cutting corners and don't care about your work and the end results.

 

[Poboy kartman]

I have taken the heads off two engines, not done this and they both have ran fine since.

Yeah....you and about a million other people....doesn't make it right!!!!

Let's take your average lawnmower owner: they buy a lawnmower....fill it with oil and then run it until it quits......

Just because this takes a half dozen years to happen...doesn't change the fact it's just plain idiotic....and has shortened the engine life by half.....

NOW....you wanna make that "no problem" statement again?????

And reimburse any members who suffer from shortened enginge life due to your extremely bad advice???,

It's like saying: "I drive home drunk all the time...and I've never had a problem ".......

 

[itsid]

..don't count on the new head gasket crushing the same as it was before ....

Oh see... haven't thought about that!

makes perfect sense!

'sid

 

[Desertduler]

Oh see... haven't thought about that!

makes perfect sense!

'sid

But bear in mind, this would only apply to push rod activated valve train with the camshaft below the cylinder head deck, not overhead camshaft or flat head engines of course.

 

[mckutzy]

Ahhh yes.... life. Got to like it(well really have no choice)...

So I go get valve grind compound(a many lifetimes amount of course)the tool(I didn't care as it was $2), Bottle of oil, dig out the feeler gauges and clean the carb.

Get all the head put together and about to tighten it down..... Look up this thread for torque value(I also looked for the conversion)... Get torque wrench and set for 17.7ft/lbs.... Oh that would be the easy part or so I thought...
The brand new torque wrench I got, cause it was on sale at the princess last year... Minimal value is 20ft/lbs.... W..T...F. (Yes that was my reply)

So a minute of head hanging and figurative tool throwing, begin to check the princess (again, yes I'm an addict) for another torque wrench with a lower setting. Cool the have one...

So after a good 20min bus wait, then another 10, finally get to the princess auto to find they have F-all for torque wrenches. The fancy digital ones didnt go that low..

So more figurative tool throwing and I have almost good to go motor, but no **** torque wrench that's good enough...