Unleaded Fuel

[Nice_One_Son]

On another thread, there is a 80 R65 for sale. One of the comments the seller made was that the bike has not been modified for running on unleaded petrol, he maintains that this has a basis for building a concours bike.

Is this true?

My 81' has also not been modified to take unleaded petrol, anyone have any experience of running on additives?

Cheers

[drewboid]

I don't think the judges take the bike apart to check if the valve seats are original!
None of mine have had the upgrade although it is probally just a matter of time until they need it. I'm not running any additives. YMMV

[nhmaf]

I don't know if I agree with that statement - but I am not a concours competition judge either.  begining in the 1981 model year, BMW's valve seats become notorious for not transmitting heat well, which could eventually end up with causing valve plastic deformation and if not corrected, valve head separation and severe engine damage.   Lead additives were believed to facilitate the conduction of heat between the valve and the  valve seat through microscopic 'welds' of lead, but this is somewhat of a false security blanket, at least for 1981-85 airheads, as the issue is really getting the heat from the valve seats into the head alloy, and this is where the thermal conductivity of the "unleaded" valve seat material, which was too low in those years, causes the problem.      Valve seats on pre-1980 bikes were of a different material, and to my knowledge, didn't suffer as much from poor heat transfer as from just wear.   In any case, factory BMW OEM valves and seats are available to fix up all these airheads.   As they are indeed real BMW parts and not aftermarket items, I don't think this violates the concours judging rules even though they are not necessarily manufactured and fitted at the same year as the machine's production - but what do I know?

I haven't been to many concours judging events, but the few that I've seen they haven't gone in to pull a cylinder head to see if the valve seats on the bike were original factory vintage.

My  [smiley=2cents.gif]

[Nice_One_Son]

Thanks for the feedback.

I am suggesting that I want to build a concours machine, just wanted to know if this could cause a problem in the long run.

Thanks again

[Barry]

That's excellent info on the topic Nhmaf.

I run unleaded  with no additives. I've monitored valve clearances very carefully and so far I can't detect any sign at all of valve seat recession.

[Lucky_Lou]

I had alot of greif with carbs and diaphragms when i completed my rebuild check out my old posts in reverse order
page 21 Is this a diaphragm problem
page 19 Throttle lag
page 17 Still lacking power
page 14 Can you believe this
page 13 Revs not shutting down
page 12 Fuel additive test
page 11 Blown another diaphragm
all the above problems i attribute to wrong diaphragm choice and use of additives i now run on standard unleaded , not had a problem since
Lou

[Bengt_Phorqs]

To my knowledge, unless you buy aircraft fuel or racing gasoline, leaded fuel is not available to the unwashed masses so we're condemned to use unleaded/ethanol fuel.  My concern is modifying the valves.  The R65 is an '83 so it may be OK for unleaded use, but my '75 R90/6 is factory stock.  (Come to think of it it's all original and a prime candidate for shampoo, set and curl to concours condition, but I'd rather ride it.)  

Is there a risk to not modifying an engine designed for leaded fuels?  I intend to add either STP or NAPA zinc oil additive at the next oil change to bring the crankcase oil up to SG standards.  Does that achieve the same results as modifying the valves?

[Lucky_Lou]

From the bit ive learned about the difference leaded v un the key issue is the octane rating and therefore the operating temperature of the valves.When they first introduced unleaded it required higher octanes to get the same power output, modern versions are a bit more clever and dont, so as far as i can tell and discussing it with some vintage sports car drivers i know the consensus is its a none issue and none of them are using additives (old jags and mg,s) so ive stopped worrying about it and no longer use additives or super unleaded just plain old unleaded its a bit like the pepsi coke challenge.....whatever floats your boat.
Lou

[Bob_Roller]

I think that most motor vehicles built since the late '70's are designed to use unleaded fuels .

The 'active' ingredient tetra-ethyl lead, was an octane booster, and provided some level of 'lubrication' to the valve face/valve seat interface .

I have an '81 model year R65 (from some accounts, the worst year for valve recession), and I had my valves and seats replaced at 45,000 miles due to 'valve face plastic deformation' .

The valve head in the face area, was worn down to where the shop that did the work said I had at best 5,000 miles until the valve probably would have 'collapsed' into the port area .

[Barry]

I don't worry about valve recession but I can't run unleaded on the stock ignition timing without pinging at 2500 - 3000 rpm under load.  I have to retard by approx. 2 Deg.  I'm not aware of any significant power loss from retarding the ignition.  I  think unleaded burns faster and so can't tolerate so much advance.  

[montmil]

To a certain degree, the change in recommended valve lash settings -to 0.004/intake and 0.008/exhaust- permits the valve to remain on the valve seat for a nanosecond longer, thereby transferring additional heat to the valve seat. Supposed to extend valve life. Hence, our lovely BMW music with loose valve settings.

Next time you visit your local municipal airport, if you can get to the ramp past the idiotic Homeland Security and FAA security traps, ask what the going rate is for a gallon of 100LL avgas. Yikes!

Monte

[nhmaf]

The R50/5 was also pretty well known for pinging under various conditions unless the highest octance fuel was used and/or ignition timing was tweaked.      Retarding the timing can help as you already know, but it may also be helpful to intentionally run your R45 a little bit more rich.  Trying to achieve a balance between no pinging and no backfire is always a joy, isn't it !  

[Nice_One_Son]

Great advice fellas

Thanks

Off with the carbs amd more engine cleaning tonight and my son Conor is going to remove the rivets from the seat cover.

The previous owner is coming over to have a look see tonight as well, so hope to get some more history.

[invincibleone]

Just a side note...........
 My home town is home to VP Racing Fuels North East Distribution Center. This is very convenient as they welcome cash customers.

 While I don't think it makes much difference to my 82 R65LS, my Gilera Sei Giorni 5V absolutely must have leaded fuel as it has über soft seats and fairly high compression. Thankfully I don't ride it often (perhaps 500 miles annually) but when it needs fuel I buy a 5 gallon pail of VP-110 and whatever is leftover goes in the R65. To be honest the bike doesn't seem to run any different whatsoever, but perhaps it will get a few extra miles out of my stock heads & valve seats.

-Fissel the Missile

[Bengt_Phorqs]

Missile, you really need to post a picture of your Gilera.  That's like having a bottle of rare single malt scotch whisky that you only pull out about once ever five years to take a sip.