Leaded Petrol For Bikes

[squirrel_hunter]

I was watching a TV program related to cars and the fixing of last night, whereby they converted a engine to run on Unleaded fuel and not the Leaded petrol that it was originally designed to use. And it got me thinking...

I've not heard of older bikes having to be converted to use Unleaded. Why?

[Dave-the-rave]

Lead additives do the trick. http://www.triumphshop.co.uk/Quiller/Unleaded/valvemaster.htm

Some old school types just chuck a lump of lead in the tank.

[rictus01]

yeah I had a metal mesh thing with lead balls in it for my old Norton tank, it dissolved over time, you could get the head reworked where they machined out the exhaust valve seats and put in a hardened insert (intake doesn't get as hot so doesn't need doing), but it was a couple of hundred quid.

Cheers Mark.

[joshwalker094]

I too was watching wheeler dealers the other night, nice car it was

[Sir Trev]

Trumpet Spitfire - I saw it as well.

Japan moved over to unleaded before us if I recall so they made their enginges to run on it from way back.

[yorkie_chris]

If it's got an ally head then it will have hard valve seats anyway. Lead was added for cast iron heads.

[squirrel_hunter]

I too was watching wheeler dealers the other night, nice car it was

Guilty.

yeah I had a metal mesh thing with lead balls in it for my old Norton tank, it dissolved over time, you could get the head reworked where they machined out the exhaust valve seats and put in a hardened insert (intake doesn't get as hot so doesn't need doing), but it was a couple of hundred quid.

Cheers Mark.

Now thats interesting, the first time I've heard someone with a bike who had needed to use Leaded petrol. So it is required for some bikes, you just don't really hear it.

If it's got an ally head then it will have hard valve seats anyway. Lead was added for cast iron heads.

Interesting, now how do I know if my head is iron or not? Or as Sir Trev indicated as a general rule if its Japanese its Unleaded, if old and British it might need some Lead?

[Specialone]

Wheeler dealers the other night was a triumph tr4 wasn't it?

A lot of decently restored classics already have the hardened valve seats done, it's an extra selling point.

[-Ralph-]

Leaded petrol is required for lots of classic bikes. What do you think all bikes used before the days of unleaded?

The reason bikes don't tend to get converted is because they are a bit easier to fill up from a gerry can, allowing you to mix your own leaded fuel at home.

With cars people want to fill at the pump, though a bottle of lead additive the size of a small orange juice will do 5 or 10 fill ups with a car so there's no reason why you can't, it's just like adding Redex. Lack of knowledge, nervousness, myth, causes car people to want the peace of mind of not worrying about it, whereas classic bike owners tend to know a bit about the bike.

[mep]

I'm a big fan of wheeler Dealers too. Ed China is the man. I believe it was a Triumph. There should be a bike version for us. Although I did see something along those lines on channel 5 possibly ? with some spanner presenting it who's style was really grating so I gave up pretty soon.

If I had an old motor than originally ran on leaded full I would be keen on having it converted. Just fill up & go.

[rictus01]

old brit iron was a constant battle, the bikes tried to lunch themselves at every turn or drop bits off when you weren't looking, my 15 minutes a week routine maintenance was about 4 hours to use is as a everyday bike; I kid you not, whilst I have a deep passion for them, I'd only ever have one as a "Show bike" now, it's the most effective way of showing just how good (and little care) modern bikes really are.

Cheers Mark.

[yorkie_chris]

Leaded petrol is required for lots of classic bikes. What do you think all bikes used before the days of unleaded?

True but remember all fuel used to be leaded.

A 77 CG125 specifies very clearly to use leaded fuel, think it may even say 3 star is OK.

The engine is the same to this day and runs perfectly well on unleaded, it had an ally head which needs valve seat inserts to run any fuel, you simply can't have an ally valve seat, it would mush back into the head an inch before it was run in!

[M65]

Trumpet Spitfire - I saw it as well.


Triumph TR6. Thank you please.

[Sir Trev]

Triumph TR6. Thank you please.

They are repeated on several channels all the time. I saw a Spitfire having it's head sent off by Mr China for rework but I dare say another programme broadcast on the same(ish) day had a TR6. So we're both right. You're welcome.

[Biker Biggles]

Derail alert
The Triumph TR6(the four wheel one)and the TR5 and 2.5 PI need a bit more than hard valve seats to run unleaded fuel.They also need their fuel injector metering units replaced and probably the fuel pumps as well.The mechanical fuel injection used the lead in the petrol to lube itself which becomes a problem when the fuel has no lead in it.

[M65]

TR6 got its Lucas fuel pump swapped for a Bosch one. It needed it though - the Lucas one was squealing like a little piggy!

[-Ralph-]

What do you think all bikes used before the days of unleaded?

Obvious answer = Leaded.

True but remember all fuel used to be leaded

Errm, yep, that's what I was inferring.

[Sid Squid]

True but remember all fuel used to be leaded.
And even before that it was - unleaded!

Lead started to be used as an additive before the materials that would make hardened valves and other bits were developed, but very early fuels had none added.

With very few exceptions, and all of those that I know of are specific competition stuff, all Japanese bikes from '74 onwards can use unleaded - despite some bike's handbooks saying otherwise - that's all they've had in Japan for a long time apparently.

[yorkie_chris]

Obvious answer = Leaded.



Errm, yep, that's what I was inferring.

I can't help but think you're being overly pedantic here.

The reason I state the case above of the CG, and as Sid confirms above, they used to use leaded because that's what you got at the petrol station, NOT because they needed the lead content to run reliably.

[Biker Biggles]

I can't help but think you're being overly pedantic here.

The reason I state the case above of the CG, and as Sid confirms above, they used to use leaded because that's what you got at the petrol station, NOT because they needed the lead content to run reliably.

Being even more pedantic,Was he really inferring it or was he implying it:D

[squirrel_hunter]

Leaded petrol is required for lots of classic bikes. What do you think all bikes used before the days of unleaded?

Thats sort of the reason for the question... As I haven't really heard of motorbikes being converted I was wondering if Lead/ Unleaded affected bikes. And if I were looking at getting something older then me its good to do your research, which might just mean asking a few questions.

And even before that it was - unleaded!

Now thats interesting. Which prompted me to do a little more research, it would appear if I go for something pre 1920's then its unleaded, but between the 1920's and 1970's it likely to be Leaded unless its Japanese. All good things to know when it gets late, I've had a couple of beverages, and I find myself on eBay.

And to end the speculation it was the TR6 episode that prompted me to ask, but yes they've done Unleaded conversions with others before.

[embee]

A few slight misunderstandings going on.

Lead (tetra-ethyl) was used to increase fuel octane number. The fact that lead compounds got deposited onto the hottest surfaces, in particular exhaust valve seat faces, was something of a side effect. It was realised that this provided some solid lubrication when engine speeds began to increase.

Valve seat wear (recession) rates are very highly speed dependant.

The lead content of fuel was progressively increased to gain octane rating allowing higher compression ratios and hence more power and economy, (thermal efficiency), and also supercharging especially in aero engines. Unfortunately these very high lead content fuels result in lead compound being deposited at alarming rates, clogging things up and fouling spark plugs.

In order to control the deposit rates, "scavengers" were also added (usually chlorine/bromine bearing compounds) which formed lead chloride/bromide which gets carried out in the exhaust gas. This however also made the exhaust gas and condensates (during short trips) very acidic so rotted out mild steel exhaust systems very quickly. It also ate spark plugs.

Some engines designed for high lead fuels (typically military use) even had valve rotators fitted below the springs to encourage rotation which scrubbed lead off the seats to keep them clean.

Getting rid of lead in fuel was good news all round.

Valve seat inserts come in numerous different materials, as usual in engineering the choice is a compromise of cost, machinability, wear rates etc.
Exhaust valves can have hard material faces (e.g. stellite) weld deposited in extreme cases in order to achieve acceptable wear rates. Most production engines don't use hard faced exhaust valves due to cost. Also modern valve gear is usually better controlled and seating velocities are kept to moderate levels (OHC designs vs. pushrod), minimising wear rates.

Typical 50/60's cars with cast iron heads had parent metal soft seat faces and generally need inserts to live for long with unleaded fuel. The modest engine performance means they are run at pretty high load most of the time (if you've ever driven an early Morris 1000 or A35 etc you'll know the throttle tends to be open or closed) so do suffer.

Slightly later cast iron heads had induction hardened seat faces, but still parent metal. These will often live fine with unleaded fuel. American engines were typically like this late 60's onwards.

As YC says all alloy heads have inserts, very often these will be adequate if rpm is kept modest. I've run my Triumph Tiger Cub, early Trident (T150V), and 1975 BMW on unleaded fuel ever since it was available with no significant valve seat wear. It's only if you're going to run them at high load/rpm a lot of the time that you'll get problems.

........and no, a few lumps of lead dropped into the fuel tank won't help.

[squirrel_hunter]

Very interesting stuff

And that is why I like the org.

[-Ralph-]

I can't help but think you're being overly pedantic here.

The reason I state the case above of the CG, and as Sid confirms above, they used to use leaded because that's what you got at the petrol station, NOT because they needed the lead content to run reliably.

I can only be pedantic if I'm disputing something, but I don't think there's any dispute.

Understand what your saying about the CG, but I don't think there's any dispute about that either.

All bikes used to run on leaded = agreed.

Not all bikes had to run on leaded, but lots of bikes do = agreed

Confused.Com

Sent from my Galaxy S3 using Tapatalk