Adjust valves - confused.

[Bob_Roller]

When I had the heads reworked around 40,000 miles ago, San Jose BMW installed I think, stainless steel valves, they recommended a larger valve clearance, I think it was .008 in. for intake and .010 in. for exhaust, I'll have to find the paperwork that came with the heads to be sure  I'm right .

So my settings aren't valid for other valve types .

[azcycle]

Mike: No harm done... in fact I'm learning a lot, so ya'll just keep chatting.

Oh, and whether by accident or on purpose the guy at Iron Horse BMW only charged me for one valve cover gasket.

[Barry]

Mike,  just to be awkward I set mine at .005" and .009" and notice no increase in noise level.  Snowbum advises slightly larger clearances for R45/R65 models compared to other airheads but doesn't say why which is a shame because I'd like to understand his reasoning.


BTW I added the service bulletin PDF on valve clearances to my earlier post.

[Semper Gumby]

Thanks for the Service Bulletin.  Probably should go in the Tech section - eh wot Justin?

Barry - Why don't you send The Snowbum an e-mail.  He might answer!

[Barry]

The tighter the valve lash the more advance the valve opening.What effect this has on engine tune is beyond my pay grade -- but there will be an effect.
 

You got me thinking Bill.

The most important aspect of cam timing is when the intake valve closes which determines how much valve overlap there is with the exhaust valve. Larger clearances close the intake valve early and the cylinder builds more pressure because there is less valve overlap. This improves power at low revs.  If you close it later you have more valve overlap but the engine will breath better higher up in the rev range.  The amount of valve overlap is said to determine at what revs the engine "comes on song".  How much difference a few thou makes I don't know probably not much but in principle larger clearances - more tractable and efficiency at low revs and tighter clearances better performance at high revs.

As an aside the R60\series airhead is notorious for pinging because it has modest low overlap valve timing compared to other models. This results in a higher effective compression ratio at low revs hence it's more prone to pinging on modern fuel even compared to other engines of the same nominal compression ratio

[Mike V]

Barry, awesome. I just realized your attachment after your reminder. Thank you.  That's another link I have in my favorites I always forget to refer to; the SB's.

I think I'll open the exhaust to 0.010" for break-in then run them at .004" intake and .008" exhaust after a few hundred miles checking them often.

Good info here guys, thanks.

[Barry]

Barry - Why don't you send The Snowbum an e-mail.He might answer!  

I might just pluck up the courage to ask about this on the airheads list one day. Perhaps I should come up with a plausable theory first.

I also have 3 other service bulletins I can post if wanted :-

Clutch adjustment

The front wheel recall (not applicable to us)

pre-delivery inspection

[darrylri]

Wow.  I don't have the owners manual for my bike, I'm just going by what I found in the Haynes book, which I've also been using for my R90S.  Haynes just says .004 and .008 for all Airheads.  

[Mike V]

I'm with you Darryl, that sounds like a healthy and safe combination.  Even though I've experimented with my /7 I've been tempted to decrease rocker gap to get rid of noise but as soon as I adjusted the rocker axial play the noise went away completely.  Not so much an issue with the 81 R65.

Been riding that R52? Gawd what a beauty!

[montmil]

OK, I was just gonna leave it alone but what the heck...

Overly loose valve valve lash settings can hammer the crap outta the valve stems. And obviously, yes, larger lash settings do alter performance at different rev ranges. The bigger gap also permits the valve to remain on the seat for just a nano second longer thereby transferring additional heat from the valve to the head and away.

I do believe the 0.004" and 0.008" settings to be a good all-around choice for the R65.

As for Mike V's engine break-in period, I'd suggest not opening up the gap but instead check the valve lash frequently until the engines is 'settled'.

Monte

[Mike V]

As for Mike V's engine break-in period, I'd suggest not opening up the gap but instead check the valve lash frequently until the engines is 'settled'.

Jump on in Monte! Interesting suggestion. I mean we're talking about ±.002". I may just leave it as is for 50 or so miles as you suggest and check often.

Ok az...back to the original scheduled program thread.

[nhmaf]

I have been running mine at .005 and .009, I think that it might be slightly noisier but have not observed any issues with power or pinging - engine seems pretty happy and pulls well.  My primary reason was to increase the time for heat transfer from valves-to-seat as I'm still running the original valves &seats.  With newer replacement seats&valves I'd go back to stock settings.  I might still consider going back to .004/.008 if the tap-tapping gets any louder, thouch I definitely did improve things in that area by snugging up the axial play in the rocker support blocks.

[darrylri]

I'm with you Darryl, that sounds like a healthy and safe combination.  Even though I've experimented with my /7 I've been tempted to decrease rocker gap to get rid of noise but as soon as I adjusted the rocker axial play the noise went away completely.  Not so much an issue with the 81 R65.

Been riding that R52? Gawd what a beauty!

Actually, I took the R52 out for a ride last week, with a friend riding the R51/3 along with.  Did about a 60 mile loop out to the Corralitos Smokehouse to buy some sausage, and then back along the Monterey Bay.  That's a lot of work on a hand shift, no twist grip machine with 3 thumb levers to manipulate.  We also had the R60/2 out for a putt.  

But I've put a couple hundred on the Free Bike (the R65) since rebuilding the forks, again -- had to helicoil the drain plug on the left side and put new caps and felts on.  When I got it apart, I had rubber chunks with goop on the damper feet, so I needed new rubber donuts.  Then I did an oil change and valve adjust, which leads me to this thread.

[Mike V]

Not to divert attention from this thread again but...you have one of the most impressive stables I've seen, dripping with envy and wondering if you charge admission for visitation rights. Your collection is a brilliant display of time and beauty. Searching for my next restoration project...

[Semper Gumby]

Hey Barry,

I suspect Valve lash has to do with the camshaft installed on the bike.  On Map Cycles catalog they list a bunch of different camshafts from stock to racing for Triumphs and BSA's that list different lash for each cam.

Did the camshaft change from the 1980 and earlier to the 1981 and later bikes?