Unleaded Fuel

2.  Vintage bikes (pre, say 1980ish) were designed to run on leaded fuel, and the hardness of the valve seats varied from model and make to model and make. Later bikes (say, post 1980ish) were designed for unleaded fuel, and have hardened valve seats as a result.
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Nope, not true for Laverdas. The material used for valve seats only differs with all alloy heads and skull heads. Material in skull heads appears to be the same for early (pre 1980) and late (post 1980) ones.

see.....I told you...
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So, if no-one disagrees, you are right. If someone does disagree, you are still right. Ugh!  >:(

By the way, "vintage" generally means 1919 - 1930, so you are roughly half a millenium wrong.

 
Lead was originally added to boost octane ratings, the valve protection properties were a welcome side effect.   So much so, that engine manufacturers could save a penny or 2 per engine by installing "second-rate" valve seat inserts.  The de-coking Rusty refers to, was necessary because of the generous clearances present in the engines of the day causing high oil consumption, as well as the available oil qualities and the low compression ratios.  Very inefficient, often poorly maintained and neglected engines eventually choked on their oil residues that had built up in the combustion chambers and ports.

Diesel engines require hardened valve seats as a matter of course, same with LPG or similar fuelled engines, so it wasn't a matter of "we can't do it yet 'cos we don't know how", it was simply a cost cutting exercise not fitting hard seats where they weren't absolutely necessary.  With the introduction of lead-free, manufacturers were forced to install suitable valve seats to avoid premature warranty claims.

While Japan and the US introduced lead-free technology (catalytic converters) in the 1970s, it took till the 1990s for Europe to catch on.  Europe was also very late (and slow) with its lead ban, in Italy and France e.g., leaded fuels were available long after they had disappeared elswhere.

piet
 
Aluminium bronze valve seats worked very well in old alloy heads until TE lead was added.

The lead attacked the exhaust seats.

I had a MKI Ariel Square 4 with bronze seats. They work hardened pretty good and gave long life.

Cheers,

Rob
 
I asked a long term Sei owner about unleaded fuel and possible valve recession/clearance issues and he told me that he hasn't had any problems sofar.

HTH
Gerald
 
Well,

My knowledge of Benellis is limited to early 70's 2 strokes with Harley Davidson written on the tank....

But - when I brought my Laverda 750 (a loose SFC replica using a '69S engine with '74 large valve head & 5C cams), back from Europe in the early 90's, I quickly began to have valve recession issues.

Had the head flowed and new valve seats installed by a very reputable Triumph specialist in Cali who was recommended to me by Tim Parker (who for whatever reason was living in Minnisota...lucky for me anyhow)

Once that was done, have had no further issues.......oh, until the crank snapped.....but I dont think that had anything to do with unleaded fuel...
 
I have had good results in preventing exhaust valve recession in a tuned MG Midget motor.
With so little power, full throttle was was very common and valve recession could be measured in weekly valve adjustments.
Using a mix of 200-1 fuel to syntetic 2 stroke oil stopped it completely, in fact it seemed to put a thin layer of about .001" on the valve and seat as clearance increased a tiny bit after a few tanks.

I am now using this recipe in my Mirage even if full throttle is nowhere near as common.

Frank.
 
Frank from Quebec said:
I have had good results in preventing exhaust valve recession in a tuned MG Midget motor.
With so little power, full throttle was was very common and valve recession could be measured in weekly valve adjustments.
Using a mix of 200-1 fuel to syntetic 2 stroke oil stopped it completely, in fact it seemed to put a thin layer of about .001" on the valve and seat as clearance increased a tiny bit after a few tanks.

I am now using this recipe in my Mirage even if full throttle is nowhere near as common.

Frank.
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Surprise surprise another oil thread :D

                                    Dave
 
Must be time for a beer. Yay now it's a beer thread..... Still got a truck load of Corona pigs swill the Lav Klub yobbos brought over on Saturday, oh well it'll have to do I guess....
 
As the point that the original owner was doing a mix of avgas and regular fuel to run with, did he mention what avgas he was using (80/87 or 100LL) or any problems with the lead fouling the plugs, or excessive lead buildup in and around the valves? As the lead was added into aviation gas as the anti-knock agent the amount of lead added was far greater than the automotive side when 100LL (Low Lead) was brought into use. One thing that 100LL does, if used, is foul the plugs and build up deposits of lead inside the head. A lot of older aircraft engines were never designed around the need for the such high compressions that we find in todays high performance engines so we have had to use additives to keep form getting the lead fouling of the plugs, and valves (TCP). The solution was to get an STC (FAA permission slip, so to speak) and start burning MOGAS (car gas). The lower compression engines loved it and only reported issues at higher altitudes. I worked for a FBO when I first got started in aviation that had a flight school (how I got there in the first place) that would have the problem of lead fouling at lower RPM since there was not enough heat to burn it out. The trick (a bad one) was to run the engine at high RPM (above 2000) for a minute or so and then start leaning the engine back until the CHT got high enough to literally burn the lead out. Sometimes it worked, sometimes it didn't, but it sure put a lot of strain on the heads and valves, but then most of our valves that are used today are sodium filled so it is not as bad as what I did running the SF with a 50/50 mix of 100LL and BP 93. When I pulled the heads for the overhaul ('88) years before ethanol was around the only issue I had was the lead buildup using the fuel mix. Switched to a 75/25 mix and Scott Potter did not mention any issues with lead during the most recent overhaul (still completing the complete restoration on the SF) but the engine was never run on any gas that has ethanol in it so I can't say what it will do to the valves. As for the aviation side the issues started with unleaded fuel being the only MOGAS you could find east of Texas. The issue's that started there were higher operating temps, and burned valves when the operators tried to run it like they did before. The one really bad thing that unleaded and now the ethanol has done is corrosion and fuel seal leaks. The materials used originally were designed around fuels without additives, but the crap that is put into car gas eats up the valves and causes the seals to leak (swells like a tick on a hog). If it were pure unleaded it would probably be just like the old days with very little issues, but putting ethanol into an already toxic mixture of cleaners just means that we have to monitor clearances more often, and for me I have a cheap borescope that I can look into the cylinders and see what's going on.

Now, I wish I could have a beer but won't happen till October so ya'll have one for me.

Clay
 
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