Unleaded valves

[Tony_Pattison]

is there any way from the outside to tell if the valaves have been "done" as far as making them okay to use with un-leaded fuel?  i.e. is there anything on the outside (markimgs etc.) that shows that it has been moded for use with unleade fuel.

thanks
Tony
1982 R65 in the UK.

[airhead]

If you are talking about Airhead heads, there is a date marking/code cast into the fins, unfortunately it faces the barrel when installed so is a bit hard to see. If this date says '86' or later, it will be unleaded.
The valve seats are the determining part in the process, not the valves, so simply eyeballing or looking for markings or signs is not an option. The only signs then are rapidly recessing valve seats if they aren't!!

Bill...................;-)

[thrang]

hey Tony,
if in doubt get a Broquet fuel catalyst from motorworks and toss it in the tank, they only cost forty odd quid and are designed to protect leaded seats from regressing.

http://www.bmwandguzzispares.co.uk/bmw/products/product.php?f=g&code=YZ&shnew=New&model=Accessories&shnewcode=15&part=Fuel+additives&modelcode=90&partcode=YZ

Cheers
Tony
Cumbria

[dewjantim]

I have had more bikes than I can remember and have NEVER had a problem with valve recession due to unleaded gas. My R80 has 138000 miles and is still running on stock heads with no problems. I really think this valve recession thing is an urban myth......Dew.

[Tony_Pattison]

Gents,
many thanks for your replies.

In case 'Dewjantim' is wrong, I'll pay my 40 quid to Motorworks and get a Broquet fuel catalyst, like 'Thrang' suggests.

I'd also like to say that I will try and follow Thrang's most sensible advice and not get hit by pheasants at  any speed, but if I do, I'll remember Dewjantim's advice and look positively on the pain.  

Again, thank you gents, for your replies.

ride safe

Tony

[airhead]

I have had more bikes than I can remember and have NEVER had a problem with valve recession due to unleaded gas. My R80 has 138000 miles and is still running on stock heads with no problems. I really think this valve recession thing is an urban myth......Dew.

In general running around town, very unlikely one would suffer the effects of major recession. However, I live in a country where long hot high speed runs are not uncommon, and I can tell you for sure, the seats do recess if running unleaded fuel with leaded heads in these situations, particularly the early '80's heads.
In fact, was just last week talking on the phone to someone who had ridden from Albany in our South West of the state, all the way to Newman in our far North West, about 2500km, in his sidecar equipped '81 R100. He wanted us to send him new valves and seats as he was stuck there unable to even start his bike due to recession. Hopefully he can get a machinist up there to do a decent job for him.
I have unleaded heads in my '86 Mono and I still run an UCL, as I will do with my 90/6 when it's on the road as I've kept the standard seats in it as the material is superior to the later leaded heads, though not quite as good as the unleaded. I will be monitoring any valve adjustments closely though just the same!!

Bill......................;-)

[Justin B.]

From personal experience I can guarantee that exhaust valve issues are NOT an urban myth, at least on my my '81 R100...

[trolle]

Not on my '84 r65 either! A recession from .20 mm to .05 in less than 300 miles at an average speed of 65 mph!

greetings from a rainy north

trolle

[nhmaf]

I think that about the only things that one can do to try to avoid or postpone the
valve issue as long as possible include:

1.  Running your valve clearances toward the upper end of the adjustment range,
    such as 0,2mm to 0,25mm (.008 to .010 inch) which leaves them a bit more time
    to be in contact with the seat, and thus longer time for heat transfer/cooling
2. Don't run your mixture of fuel/air any leaner than necessary
3. Don't run a hotter grade spark plug than necessary.

Still, I think that with enough time or high speed running at warm temperatures, it
is probably going to need new valve seats eventually if it was made prior to 1984/85.

My $.02, anyhow !

[airhead]

The grade of spark plug doesn't affect the running temperature of the combustion chamber. It simply means the spark plug itself runs hotter (it has a longer path from the tip to the head contact part) so as to burn off combustion and oil contaminants. Usually used in slow running, stop start conditions.
A cold plug runs cooler for when running continuous high speed. It has a short path for the heat to travel from the tip to the head.

Bill...................;-)

[Semper Gumby]

OK here is the rub.  I started to notice the dreaded valve recession at 70,000 miles.  So I called up Nathan at Boxerworks and dutifully had my heads worked on.  Nathan and Dean replaced the valves the guides the springs but not, to my surprise, the seats.  They were aparently just fine and were cut to fit the new valves.  The exhaust valves were aparently "sharp enough to shave by"  Now since 29,000 miles this bike has been spending much of its time in the 4000-5000 rpm range out on the highway which is really hard on BMW valves.  Airhead exhaust valves just can't take the beating.

Nathan said the heads are good for another 200,000 miles as is and I'm counting on that.

So I guess that is why they call it "Valve" recession and not "seat" recession.  Now I'm not saying that you can't burn a seat.  In fact I suspect with the latter airhead leaner carburation and emission controls may make this more likely.  But if you are one with your tuning (timing, valves, Carbs) then I think you can avoid damaging your seats.  Something like the Colortune will help keep you in the center of the normal range away from the lean end.  Prophalatics like Marvel Mystery Oil (I use 2oz per 5 gals at every re-fill) and the fuel catalist from England (?) will help but nothing will protect your seats if you are running too lean for an extended period of time.

My R65 now runs purrrfectly.  And athough I have not replaced the crankcase breather (yet) I did put an extra washer on top of the reed disk rather than use the secondary clip position (which looks too far down) and the motor is not puking as much oil on my left foot.  

Or perhaps the rings are finally getting seated?  

(I'm using .006" intake and .008" exhaust - .008" and .010 is for the BSA's - too many numbers.......)

[Bob_Roller]

Just for a clarification on valve recession on the '81 to maybe '85 model year bikes, the valve seat material was changed in '81 to some new material for BMW, it was quite wear resistant, but the new material acted like an insulator, and prevented the valve from transfering heat to the seat and then to the aluminum cylinder head. The official term for this was called " valve face plastic deformation ", I think in simpler terms, the valve overheated and was 'soft' enough to be reshaped. My valves were replaced at about 45,000 miles, material had 'moved ' down the valve face toward the valve stem, and only the upper third of the valve was makng contact with the valve seat. I wished I had saved those valves to post a picture of, they were quite unbelievable.

[nhmaf]

That is also my understanding of the situation, Bob.  One generally wants to replace the valve
seats not so much due to the possibility that they are wearing - they generally aren't - it is to get
new seat material in there that will get the heat out of the exhaust valves and into the aluminum heatsink
better/more quickly, so that the metal in the exhaust valves does not start to melt/deform/weaken
from the high temps.

This also relates to my theory of running a cooler plug - anything that can improve the transfer of
 heat energy from the combustion chamber to the aluminum head/heatsink as quickly as possible is
to be desired.  The hotter plugs do have higher thermal resistance by design, and the worst case
temperature situations are usually at the high speed/high RPM conditions, where one doesn't
generally need a hotter plug.