Unleaded fuel

[Tun up]

One of the great things about this forum is the depth of knowlege of the members and their differing experiences and points of view.

I used to run my bike on original 4 star then moved onto avgas when 4 star became unavailable.

About three years ago I took the concious decision to use unleaded without any additives. I do use the bike but don't abuse it. It runs fine and the valve clearences have been ok. The tank has also remained sound without rust developing.

With some bikes this is not always the case.

What have other people found?

[Rex]

Never bothered with LRP (too hard to find) or additives (too expensive) nor replacement valve seats (not needed) or Broquets (leave that to the buyers of snake oil) and never had any discernible problems on any of them.
The ones with manual timing are the best though as you can find the sweet-spot as you ride..

[Revband]

I agree with Rex, never had any problem with unleaded on any of my bikes from 1946 to 1999

[johnnyboy-wonder57]

RE Fuels:
Apparently Shell "V-power" has no ethanol in it, so I was told?
Of course a lot of older bike stuff was probably designed round pool petrol 72  octane or thereabouts  with engines having 6.5:1 7.5:1  lower compression ratios, not quite sure how unleaded fits into the mix of machines using it? Typically thought the problem was around valve-guide wear & the absence of lead as a lubricant.

Cheers


JBW

[twolitre]

Putting aside the ethanol problems, which mostly seem to affect only the fuel system parts where early plastics took over from brass. The biggest problem is that tapered valve faces contacting tapered seats generate a lot of friction, as anyone familiar with decanters and tapered stopper vinegar bottles will remember. They often jammed so as to be almost immovable.
Simple maths say that @ 3000r.p.m. each poppet valve on a fourstroke engine hits its seat an unbelievable 25 times a second. The tetra ethyl lead in "old" petrol helped to reduce face friction and wear. Without that "lead" increased valve seat wear is likely on softer seats. Many people fit hardened seat inserts to overcome that.
In practice, even with cast iron seats, as long as they have age and work-hardened, serious wear takes many thousands of miles and having seat inserts fitted prematurely is largely a waste of money.
I have four vehicles all made in "leaded days" which have now covered many thousands of miles on unleaded fuel with no mods. or additives.
NONE show any signs of problems.

Note: Pool petrol was NOT available to ordinary motorists or bikers. Only to bona-fide  commercial users. Octane rating is of no significance as long as it is high enough to prevent detonation due to higher compression ratios.

[rosko]

with a "proper"  vintage bike, if it burns it'll run on it.

I once even had a Bantam running on Paraffin  ( I didnt mark the tin d'y'see)

[bikerbob]

Well I have 2bikes a BSA A65 Star Twin and a BSA Gold Flash and to be honest I do use an additive Castrol Valvoline but I have enough in the garage to last me about 4-5 years and when it is used up I will not buy any more as I reckon after reading numerous articles I do not think it is needed. I did run the Flash for a year without any additive and had no problems I took the head off to check. The general "expert" opinion seems to be that provided you do not run at motorway speeds for long periods then you should not have a problem. If you want to check for problems what they advise is that you should set your valve clearances as per manual then check them every 500 miles for 1500 miles and if the exhaust clearances have not closed up any then you do not need to take any action.

[johnnyboy-wonder57]

Hi,
RE WW2
From  3rd September1939 to  Summer 1942 petrol limited to 200 miles a month for cars, including those in private ownership, from Summer 1942, no private vehicles allowed petrol, unless licensed as essential through occupation.

Pool petrol is only all the various mixes put together, consequently it came out with a low octane value,  example a motorcycle like an AJS Model 18,  had a 5.9:1 compression ratio, postwar, because of poor  fuel quality after the war. Octane value just gives a  measure of the chemical energy contained in fuel, so that fuels can be compared to one another relatively speaking.   
Higher compression engines, give higher performance typically 10:1 and 11:1 compression ratios, need higher octane fuels to combust correctly, however, so much has changed in liquid engineering of  petroleum, its difficult to compare old & new fuels directly, except through burn quality ratings. Needless to say octane ratings give you an idea that the fuel you use is suitable for your respective venicle, like the old SAE oil formula classifications.

Obviously as technology advances, amendments can be made.

I would be careful running unleaded in any vehicle pre mid 1970s, or early 1980s in some cases, depending on manufacturer; a good safeguard is tin pellets in the "Fuel Cat" brand drop them in your tank & forget about the engine for 200,000 miles, they lubricate, stabilise unleaded fuel  further & optimise a possible premature wear situation of the valve gear & cylinder head inserts. Personally I think its worth it with old engines, obviously not everyone wants the extra expense, but then I am in the "better safe than sorry camp"!


Cheers

JBW

[johnnyboy-wonder57]

Hi,
Just read an article that has been published on the net, rendering the tin pellet steel cage "Fuelcat" situation as chemically dubious in effect in unleaded  combustion and engine wear situations
Having said that the engine I used them in ran amazingly well. So I do not know how to equate the effect & advantages I felt they had & the chemistry of the combustion process!


Cheers

JBW

[Rex]

The power of suggestion....?

[R]

Octane value just gives a  measure of the chemical energy contained in fuel, so that fuels can be compared to one another relatively speaking.   

This is not strictly true. (Although doesn't detract from most of the rest of this discussion). Calorific value gives a measure of the energy in fuels.

Octane rating is purely a measure of how resistant the fuel is to detonating, instead of burning when the flame is lit. It used to be calculated by comparing how a sample of fuel performed (detonation wise) v's a known sample of fuel with octane in it = the more octane required to match it, the higher the octane rating. (octane being 8 in the fuel series  hexane heptane octane nonane decane etc, fuel being a mix of this and others, many others...). 

Alcohol (ethanol) has an octane rating over 110, but a lower calorific value than most petroleum fuels, for example.

[rogerwilko]

This subject has been flogged to death on every make forum for 20 years! Give it up! If idiots want to waste money on new valve seats, let them! And i'll explode if any tosser goes on about oil!

[JFerg]

So there's a special oil to go with unleaded fuel??

Best I start worrying now.

JFerg

[johnnyboy-wonder57]

R
I stand corrected!
So is it right that Octane value denotes fuel burn stability, under compression & ignition?
You're right Calorific value is the Scientific  measurement of actual energy content.

Cheers

JBW

[twolitre]

I'm with Rogerwilco on this!!!
There are so many expert opinions about this.
I am the only person I know who has had YEARS of experience of running high mileage vehicles on unleaded fuel. Admittedly Propane and before the advent of lead free petrol. However we are not discussing the fuel, but the lack of tetra-ethyl lead in the combustion process.
The vehicles were Taxis and included Fords, Austin/Morris etc., Vauxhalls, Hillmans and others. Total mileage involved several million. Additives nil.
Although SOME BMC engines did suffer valve pocketing, it was only noticeable after considerable mileage (typically around 80 or 90 thousand miles) and then not because of performance deterioration. No engine ever received valve attention during its normal service life-span.
From my experience no one is qualified to pass an opinion about lack of lead or additives until they have run an engine for many tens of thousands of miles with and without lead or additives.
Sorry about this rant, but like Rogerwilco I am getting p***** off with the subject.
My own (Triumph) car has never run on propane but is now pushing 160,000 miles. About half on unleaded petrol. The cylinder head HAS NEVER BEEN OFF and the valve clearances do not change.
Jim.