cylinder bolts and Valve adjustment?

[montmil]

Just to muddy the waters a bit... It would appear that if you were to error on the valve lash setting, looser is better than too tighty. Of course, the BMW shop manuals are never incorrect on their specs? Now, let's talk tires!     Monte

This from Snowbum's site http://bmwmotorcycletech.info/setvalves.htm

"I set the clearances to .0045" intake, .0085" exhaust, with pressure on adjustor end to take up oil film slack. That is equivalent to an easy smooth fit for the .10 mm and .20 mm metric feelers, same for .004" and .008" feelers.   The R65/R45 models probably should have the valves set a wee bit looser, .006" intake and .010" exhaust is fine.  There is nothing wrong with using .006 and .010 on all the various models, actually, and a case can be made for some slight benefits, at the expense of a VERY SMALL amount of noise and potential wear." - Snowbum

New shooter coming out...

[weasel01]

It looks like there is a bit of wiggle room here probable be ok as long as they are in the range of .004 to .006 on the intake and .006 to .010 on the exhaust and just make it equal on both sides?
Sound reasonable?

[Barry]

To add to the range of valve clearances that can be found in print my original Riders Handbook says .002" inlet and .008" Ex

I use .004" and .008" but would love to know what the theory is behind Snowbum saying R45/R65 clearances should be bigger than other airheads.

[weasel01]

I'm going to stick with .004 in .008 out...
I've seen that referenced more than the others...geez I hate that I'm not experienced enough at this to make decisions

[montmil]

You'll be fine. It's so easy a caveman could do it. 8-)

[Justin B.]

BMW actually changed the spec over the years and what you read differs depending on when your particular manual was printed.  I think I quoted specs from a '79-'80 manual as the wiring diagram is labeled R45/65-78 and pictures inside show a round master cylinder.

[weasel01]

Well, I ended up with evenly torqued cylinders and .004 in .008 out
Put all back together fired it up and sounds way better than before the
valve noise is down 50% and the exhaust sounds throatier and cooler.
There seems like more power and smoother but I only took a 20 minute ride.

[montmil]

Yea [smiley=clap.gif]

[nhmaf]

.004" intake and .008" exhaust is the original factory spec - I tend to run mine closer to .006 and .010 - they are  slightly more "tappy", but they spend more time in contact with the valve seats, so in my mind that may extend their operating life a bit longer (still on original valve seats which do not transfer heat well, problem solved in 1985/86, but all airheads in the 1980-1984 range have the potential for developing valve deformation due to inadequate heat transfer because of metallurgy issue with the original factory seats).   The key thing is to get used to the sound they make, and check the clearance every few thousand miles to make sure the clearance isn't rapidly closing up on you - a sign of valve deformation and impending failure.   A new set of BMW factory seats and valves, properly cut and fitted with new valve guides and keepers will have her set for another 100,000 miles.

[weasel01]

Thanks Monte!
You, Bob_Roller and Justin B. have been absolutely great in helping me out with polishing this ole' turd back into a cool bike and I really appreciate it!

[weasel01]

Nhmaf, I am a total greenhorn at this mechanics related stuff so bear with me.

My question is how does setting the valve adjustment looser give more contact time with the valve seats?

The way I'm understanding this the tighter they are set the longer each valve is open therefore more contact time? or am I way off?

Setting them looser uses part of the rotational cycle in travel time before contact and then again after the release?

[weasel01]

I found this and thought it sounded interesting I realize the r65 is not listed in the applicable models but it cant be too different cant it? :



BMW motorcycle valve adjustment procedures

by Duane Ausherman


This page applies to the BMW motorcycle models R50/5, R60/5, R75/5, R60/6, R75/6, R90/6, R90S and some later models.
Why adjust BMW motorcycle valves?

Valve adjustment is one of the most misunderstood maintenance items on the BMW.  You are really performing a diagnostic function.  For example, the engine will run very well with a setting of exactly zero clearance up to double the spec.  With zero clearance, the valves will open a bit more and allow more fuel into the combustion chamber and that will make more hp, but you may not be able to measure it with a dyno.  Really wide spacing will make more noise and not allow as much fuel into the combustion chamber, but again, you probably can't measure it.  The wider clearance will make more noise.

The main reason to do the valve adjustment is to check for a change in settings from the previous time.  If one or more valves are more than .001" off of where they were last set, you better make a notation in your log book.  If a dozen people set your valves, they would each do it slightly differently.  Which method is right? All are probably right.  The important thing is to do it exactly the same from one adjustment to the next one.  Then, any change shows you that something must be diagnosed to look for more serious problems.

If you find that the valves all still have a correct setting, this means that the heads are stable.  If that is the case, then there is no reason to check the torque on the head nuts.  All you will have done is remove the valve covers, check settings and replace the covers.  And be happy.

If you found some change in the settings, then ask why? Reset them and check them again soon to see if it still changes.  Find out why it is changing.

[montmil]

My question is how does setting the valve adjustment looser give more contact time with the valve seats?

The cam has acceleration ramps designed into the component. Looser valve settings postpone lifter -to cam -to rocker arm -to valve tip contact; thereby allowing the valve to remain in contact with the valve seat a nano second longer, thus dissipating more heat... particularly important with the exhaust valve, hence the wider clearance gap setting/s.

Hope my lame explanation helps a bit.  Monte

[Justin B.]

He pretty much got "out of the business" before R65s came out.  You'll notice that R80 and R100 are not mentioned either.  The underlying logic in what he says still holds true.  If the gap is appreciably changing then something is moving/wearing.  Most R65 riders will notice the exhaust valve clearance getting smaller over time unless they have had a valve job and the exhaust valves and seats replaced.

[weasel01]

I think I was thinking about it backwards...it's not how long the valve is held open but how long the valve is allowed to stay in the closed position.
Staying closed longer keeps it in contact with the head or "heatsink" longer thus allowing it to run cooler. right?