How Cold is Cold (for valve adjust)

[Guest]

I'd be very interested in learning the difference between hot and cold clearances too.

Do it for SCIENCE!

I agree as well, as someone on here has said before , "to measure is to know..." right Ed??

[JEEPRUSTY]

My little pea brain is working OT here.

I think that the requirement for a cold engine is to assure things are as loose ans they can get. There is more involved than just the clearance of the lobes to tappets. There is the cumulative space in the cam bearings and any of the other mated surface between them.

So its better to go a bit loose and know its loose than to guess that it may or may not be too tight at operating temps?

[waterman]

I'd be very interested in learning the difference between hot and cold clearances too.

Do it for SCIENCE!

You are tempting me to give it a go. Brings up many questions, such as is this engine specific or model specific or will it vary with 2V vs 4V engines. Likewise, how hot is hot? How quickly will clearance change with engine cooling off?

[JEEPRUSTY]

You are tempting me to give it a go. Brings up many questions, such as is this engine specific or model specific or will it vary with 2V vs 4V engines. Likewise, how hot is hot? How quickly will clearance change with engine cooling off?

With a cast engine it mat difffer form bikes of the same engine.
I read a nice article by the motorcyclist dud form the 80s.
In it he delved into the intricacies of the stresses on engine components going form fully contracted to fully expanded.

Said it takes engines a long time to reach the temp at which all stresses are relieved.
I think it was more than an hour but that seems crazy.

[rapidray]

Ed, if the guy is riding it to your house to do the valves, dump the oil & put a fan in front of the engine. It will take no longer than 2 hours to cool it off this way. If you leave the oil in it, it WILL take longer to cool off. The oil holds the heat is the issue & if you drain it you will be good to go in a couple of hours. Make the guy bring enough beer for the wait time!!! Ray.

[hampshirehog]

You guys are right - overnight. However, we didn't wait that long in the dealers on a service. If you leave the valve checks till last and do an oil / filter change and everything else on a full service, have a cup of tea and a biscuit, tinker with something else for a few minutes and then you'll get away with it. Did loads like that back in the day and never had any problems. Around 2 hours start to finish (though some bikes obviously sat for longer).

[posplayr]

You guys are right - overnight. However, we didn't wait that long in the dealers on a service. If you leave the valve checks till last and do an oil / filter change and everything else on a full service, have a cup of tea and a biscuit, tinker with something else for a few minutes and then you'll get away with it. Did loads like that back in the day and never had any problems. Around 2 hours start to finish (though some bikes obviously sat for longer).

So I'm guessing engine case/head temperature below 90 degrees is sufficent

[Nessism]

Ed, if the guy is riding it to your house to do the valves, dump the oil & put a fan in front of the engine. It will take no longer than 2 hours to cool it off this way. If you leave the oil in it, it WILL take longer to cool off. The oil holds the heat is the issue & if you drain it you will be good to go in a couple of hours. Make the guy bring enough beer for the wait time!!! Ray.

I was thinking this exact same thing. Great minds think alike.

Going to propose we do a valve adjustment after a cool down period and then perform a follow up check when the bike is cold.

I'll let you guys know how it plays out.

[Dogma]

Okay, so the rule is DRAIN the bike of oil, FILL mechanic with beer. Check.

Have him bring a new filter, oring and oil, perhaps ignitor cover gasket, breather gasket, valve cover gasket, right?

- JC

Breather gasket is optional, depending on the specific model.

I'm curious to see if any measurable difference can be found between overnight cold and just sorta cool. I doubt it's detectable with ordinary feelers.

[Nessism]

So 45 min. with a fan blowing on the engine (after dropping the oil) did the trick. Engine was cool to the touch and the clearances were as expected.

Stupid me, I broke my nice dial type Snap-On torque wrench trying to torque the head nuts (too much stiction in the threads resulted in a shock feeding into the wrench) - should have broke the nuts loose with a breaker bar first. Yet one more "lesson learned" - should have know better.

[Guest]

Sorry about your wrench Ed, that sucks...

I have a question though - when you are going to re-torque the head bolts when doing a valve adjust, do you typically loosen them all at one time, then tighten them in the manual recommened criss-cross method?

Or should you loosen/tighten them one-at-a-time?

[Nessism]

Sorry about your wrench Ed, that sucks...

I have a question though - when you are going to re-torque the head bolts when doing a valve adjust, do you typically loosen them all at one time, then tighten them in the manual recommened criss-cross method?

Or should you loosen/tighten them one-at-a-time?

Going to crack open that wrench and see if I can fix it. A small screw/nut sheared off. Fingers crossed...

I do the nuts one at a time. Crack it loose just a little then make it up again. Best to use the OE tightening pattern.