Topic: Valve clearances different from tuning spec

[Achmed]

I read the below post from Hondaman regarding valve clearance adjustments (reply #32) and I am about to adjust my valves on a 750F1. My interpretation is that exhaust valve clearance should be adjusted to .004 in instead of the published .003 in. And is this to prevent wear on the valve guides? I thought I also read another Hondaman post about increasing the intake valve clearances to .003 instead of the .002 published but now I can't find that post. I would be inclined to use book values but Hondaman does seem to know what he's talking about.

I know it was the F2 and F3 heads that had valve guide wear issues, but the below post says all F's benefit from this change.

http://forums.sohc4.net/index.php?topic=7401.30

Is anybody running the larger clearances? By the way, I have to admit this is the first time I've adjusted valves (on anything) so take it easy on me.

Thanks,
Nate

[scunny]

the extra clearance is to aid in cooling the valves(longer contact time with the head to dissipate heat) I am running the larger clearance, no issues here

[Achmed]

Intake valves, too, or was that a figment of my imagination?

[754]

It wont hurt anything.

 I run an eyebrowraising .012, with a hotter cam, and it is not  as loud as you may expect, in fact.. not really noticeable..

[WFO]

Iam running .005 on the exhaust on my 82 per hondaman ( which suffers the same valve guide condition) and she run alot cooler, you just have to get used to a little more tappet noise even more when starting up cold.

[NitroHunter]

Live with the (minimal) extra noise. An extra .002" lash is a lot safer than being ANY too tight!

[Achmed]

Thanks, guys, for all your input. It sounds like just about any setting wider than the spec setting will work? And the only difference is noise? I guess it has something to do with the cam duration but I don't really understand it. Does it affect reliability in any other way than what Hondaman described? How about fuel economy or power output? I suspect it doesn't but I don't know the theory behind it.

Why does it make the engine run cooler?

[ludo410]

it runs cooler because the valve is contacting a larger piece of metal for a longer duration.

the extra clearance is to aid in cooling the valves(longer contact time with the head to dissipate heat) I am running the larger clearance, no issues here

i do the same in some of my other bikes... well the ones that don't take shims. also takes longer for then to tighten down on ya..

[WFO]

Thanks, guys, for all your input. It sounds like just about any setting wider than the spec setting will work? And the only difference is noise? I guess it has something to do with the cam duration but I don't really understand it. Does it affect reliability in any other way than what Hondaman described? How about fuel economy or power output? I suspect it doesn't but I don't know the theory behind it.

Why does it make the engine run cooler?

http://forums.sohc4.net/index.php?topic=10540.0

[Achmed]

OK. So I set the exhaust valves to .004 or .005 and check them for lateral play within the guides. The intake valves should stay at the spec .002 because the cam duration requires them there. Thanks for educating me about the link in my original post! I guess it's never too late to learn how an engine works.

Does the valve train make a louder noise when actuating the valve because the rocker arm and valve are in contact longer? It's the same noise it would make with the spec clearance, right, just louder? Sorry for my infernal questions.

[WFO]

OK. So I set the exhaust valves to .004 or .005 and check them for lateral play within the guides. The intake valves should stay at the spec .002 because the cam duration requires them there. Thanks for educating me about the link in my original post! I guess it's never too late to learn how an engine works.

Does the valve train make a louder noise when actuating the valve because the rocker arm and valve are in contact longer? It's the same noise it would make with the spec clearance, right, just louder? Sorry for my infernal questions.

Opps i missed that   sorry and the tappet slaps on the cam you really only notice when it's idling or at cold start up you will get used to it.