Leaded fuel in 250f/450? (50/50 mix w/ pump)

It won’t hurt anything, but you’re not going to gain anything out of it. Have you tried looking for Sunoco 260 GTX? I can buy it here out of the pump for less than $10/gal, it’s a replacement for pump gas just like T4. I use it mixed 50/50 with no ethanol 90 octane. 

It’ll be an unpopular opinion, but I think 93 pump is just fine for a modern FI four stroke MX engine. I’ve yet to ever have ethanol problems in anything other than an engine that uses a carb and I let it sit too long. 

Yes, been doing it for years to make 93-95 octane to avoid any possible detonation and have never had an issue. 

That's what they are deigned to use off the showroom floor. Expensive fuel likely won't get you anywhere accept poorer with a stock bike.

the lead will leave deposits over time. It is Aviation fuel and 100 low lead has 4 grams of lead per gallon, Unleaded AV gas is starting to be available but I haven't tried it. I didnt notice any power increase on straight 100LL

Umm, lead helps the valves not wear as easily as well.....is probably the best thing you can do for valve wear in fact. Supposebry

I tried 100LL in a stock YZ450.  It ran fine but seemed to leave a bit of a deposit on the plug and the fuel pump started acting funny.  It was also during winter, so cold operating conditions.

I'm not 100% sure if the fuel pump failing was coincidental or caused by the lead, as the fuel pump had probably 400 hours on it.


The manual calls for 93+ E10 and states to not use leaded fuel.

With the new fuel pump:
I tried 93 E10 pump gas and the bike worked good. 
Then I tried 91 EF, it runs just a good, so that's what I've been using since it is locally available at the pump, Seeing what the E10 fuel does to my lawnmowers and generator, I didn't want to use it all the time.

Puregas.org is a database for EF fuel at the pump in the US and Canada. 

 

Notice that says protected in the past tense. Modern engines don't need it for the valves. The purpose of lead was/is for octane, not valve protection

‘23 KX450  I’m mixing 1 gal of 100LL with 4 gal of pump e10 93. 
It has made a very noticeable difference down low, runs more smoothly allowing me to shift less. 
I had not expected anything, I was just using up some of my 2 stroke fuel.

I think anything but 93 pump for a stock engine modern 4 stroke is just wasting money but that's your prerogative.

I usually choose 93 over 89 non ethanol as that's usually what's in my area I also pump at least a half gallon into my truck before the can. If you are only getting a couple gallons of gas I like to make sure its mostly 93 not any 87 left in the hoses.  

Why do you not want to run pump gas?

The following is from Shell regarding their 100LL "Av Gas", and will clear up at least some of the misunderstanding of what lead in gasoline does.

Shell Global
Business customers
Aviation
AeroShell Aviation Lubricants
Aeroshell Knowledge Centre
 

Technical talk - Lead Fouling

I have had a lot of questions about Lead Fouling of engines in the past and this is a good opportunity to explain how it happens and how to help avoid it.

As you will know, Avgas 100LL contains a compound known as Tetra Ethyl Lead (TEL) which acts as an octane booster for the fuel. This results in a fuel which is commonly known as a 100 Octane lean mixture and 130 rich mixture Performance Number fuel.

In practice it is even better than this, with ratings more like 106 lean mixture & 130 rich mixture which are far in excess of the comparable 85 - 87 octane of road fuels. To achieve this a lot of TEL is used - around 5 times the quantity that was used in the old Leaded automotive fuels.

This increase in octane allows aviation engines to produce more power through increased compression ratios or alternatively by increasing the inlet pressure by using a turbo or a supercharger. The problem with using Leaded fuels is that they will always burn with more deposits than unleaded fuels.

The Tetra Ethyl Lead used for octane boost in the fuel naturally degrades to form Lead Oxide when it is burned. In reality it is this oxide which gives the octane boost. The problem is that Lead Oxide is a solid up to about 900 deg C which is well within the wall temperatures inside a piston engine.

In order to prevent these deposits from forming, a Lead scavenging compound is added to Avgas 100LL - this compound is Ethylene Dibromide. This scavenger is designed to react with the Lead oxide to form Lead Bromide which is more volatile - becoming a gas at around 200 - 250 oC. This is a low enough temperature to ensure that the Lead is removed from the engine as a gas end it subsequently goes back to the solid phase as the exhaust gas cools in the atmosphere.

As a point of interest the pale brown / ash coloured staining that is often seen leading from the exhausts of high powered engines, such as those found on the warbirds, is in fact Lead Bromide.

To enable this reaction between the Lead Oxide and the scavenger to work, there needs to be a relatively high combustion temperature.

What a lot of people do is conduct the warm up with the engine power lever on the idle stop, and this is inappropriate. The technique for the common Teledyne Continental Motors and Textron Lycoming General Aviation engines is as follows.

After start up, the engine should be operated at 1000 - 1200 rpm for the initial warm up period and not at the 600 -650 rpm idle speed. This serves a number of purposes.

The higher cylinder pressure encourages the rings to seal properly, not only limiting oil egress into the combustion chamber, but also reducing the amount of corrosive combustion by-products going the other way into the sump oil. This technique thus also helps reduce the risk of corrosion problems in the long term by reducing the amount of acids and Lead being pumped into the oil.

Meanwhile in the combustion chamber, Lead Oxides tend to form deposits because of the low combustion temperatures. The temperature for Lead deposits to form tend to be favourable around the spark plugs (as the whole mixture is quite cool before the flame starts to propagate) and on the exhaust valve stem (as the mixture cools after combustion).

The problem is that the deposits are electrically conductive, which shorts out the spark plug - and corrosive, which can start to attack the metal of the valve stems.

Temperature is a key factor in preventing Lead fouling and it is not just at start up, but also the correct shut down procedure should be carried out.

Engines that have been involved with long, low power descents, or have taxied for some distance, can have quite low cylinder temperatures and this - as we now know - can lead to lead fouling. Again the advice from Textron Lycoming and Teledyne Continental Motors to remedy this is: once on the aircraft is on the stand, the engine speed should be kept between 1000 and 1200 rpm until the engine temperatures have stabilised.

Once the temperatures are stable, the engine speed should be increased to 1800 rpm for a period of 15 to 20 seconds, which should generate enough temperature to burn off any deposits. Once this period is past, the engine speed should be reduced to 1000 - 1200 rpm once again and then immediately shut down using the mixture control.
Spark Plugs

If problems persist, then another question to ask is are the plugs of the correct type? Check the charts for your engine, but generally a hotter plug should be used in a lower powered engine. Higher powered engines tend to generate enough combustion temperature to keep the spark plug nose hot, and therefore deposits down, even with cold plugs.

A hot plug does not transfer heat rapidly away from its firing end into the cooling system and is therefore better at avoiding fouling where combustion chamber or cylinder head temperatures are relatively low. In order to achieve this, hot plugs have a relatively long insulator nose with a long heat transfer path.

With the Champion plugs, the higher the number, the hotter the plug, for example the REM-40-E is hotter than the REM-38-E.

Some of the spark plug manufacturers have some other solutions too. If we look at the example of a Champion REM-37-BY plug which is recommended for the most of the Lycoming O-320 and O-360 engines, this plug does not prevent the accumulation of Lead deposits, but its design is supposed to make it capable of firing even with severe Lead deposit build up.

This problem can also be an issue with Microlight engines such as Rotax 912's. These engines are designed to run on unleaded fuels, but they will run on Avgas 100LL - indeed Public Cat aircraft, such as the Rotax engined Diamond DA-20's used for flight training, must run leaded Avgas 100LL. A similar trick can be employed with this engine too when using Avgas 100LL.

If you are running a Rotax 912, using the recommended NGK DCPR8E plug and you find it is fouling then try using a hotter plug like the DCPR7E (also allowed by Rotax). This should help as the plug tip will run hotter and discourage the Lead Oxide deposits from forming.

There is a limit on how hot a plug should be used, the plug tip can become so hot that the plug itself becomes a source for fuel pre-ignition, which can cause engine damage.

One final question to consider is, are the plugs rotated regularly? It is common knowledge that the lower plugs in an engine will run dirtier than the top plugs even in normal operation, and rotating plugs every 25 to 50 hours is recommended by the engine manufacturers. This results in a self cleaning action, but the plugs should always be swapped in magneto sets as the plugs themselves can herald clues about the magneto condition. Swapping the plugs randomly loses this information.

Hopefully this helps in expanding on some of the myths of Lead fouling and helps you avoid being its victim in future.

Haven't been able to get leaded fuel in Australia since approx 2002. While it definitely helps with lubrication and isn't as harsh on valves, it not like we are using reduced service intervals or seeing premature valve seat wear compared with the US. We can get 91, 95 and 98 octane unleaded at most servos.

I think if you switch to using just pump 91-98 unleaded (if you are able to get it) the only thing you will notice is the time and hassle you saved from not mixing in the leaded.

Your airports do not have 100LL?

His desire is to use gasoline without corn whiskey in it, and not have to pay $20.00 a gallon for it, which is why he is asking about mixing 112 with non race gas, but all our pump gas in the US has Alcohol except for the mysterious "Pure Gas", which appears to be very hard to find. .

Also, if you want valve protection, it is perfectly acceptable to run some 927 at 100:1 or so to get the protection and otherworldly smell. :-) 

When I was at Bel-Ray nearly 20 years ago, we were experimenting with a 4-stroke fuel lubricant. It didn't catch on, but castor was the leading base oil after some research. 

As a motorcycle mechanic, the vast majority of jobs I get have to with rebuilding fuel systems related to bad gas.  Texas has some of the worst pump gas in the nation, because they are allowed to put all kinds of extra additives in pump gas, not just ethanol.  My thought, pump gas is OK as long as you are using it, but if it sits in your tank it can go bad after just a couple weeks.  

I agree id like to be able to get 93 non ethanol reliably, even 91 I've found a few times which would work as well but its not super common. 

I have a Sunoco station that sells 260GT on the pump about 30 minutes from me id like to do 50/50 with non ethanol but its 30 minutes in a direction I never go so haven't gave it a shot yet. 

Yes for aviation you can still get 100LL/Avgas however it is difficult to buy as you have to demonstrate that it is for aviation. 

My point was, if you can get ethanol free unleaded fuel at decent octane it will be fine for most Motocross applications (unless you are running high comp). I didn't realise how hard it is to get ethanol free fuel in the USA, but didn't rule it out (see "if you are able to get it" comment on previous post).

I use a mix of 90 octane ethanol free gas mixed with 110 octane race gas which is sold out of the pump at a local station. 1 gallon race to 3 gallons pump works out to around 95 octane which is plenty for a stock engine. 

I run 90 octane Non-ethanol fuel in all my four stroke MX bikes. Never had an issue. I don't see any reason to mix it with 110 for a stock engine and stock ECU mapping. I put about 40 hours on my MC350F with just 90 Non-ethanol and that's what I've run in my '24 KX 450 so far. 

I add lead and castor oil at around 100:1 to my four stroke fuel. Lead cushions the valves. Is it needed? No. Do valves last long enough on a modern four stroke? Also no. The added protection is welcome for me. Is a lubricant in your fuel beneficial? Most definitely. 

My manual calls for 95 octane is why I mix mine with 110, but you do you.

VP110* (Leaded) at the pump

What bike is that for and do you know which octane rating method they're referencing?

I glanced at one of my Yamaha manuals and it calls for a RON of 95 or higher and a pump octane [(R+M)/2] of 91 or higher. The pump octane is the one typically displayed and referenced in the states.

Lead is great for valve protection, especially the titanium valves in our motors. It was suggested to me years ago to run some leaded fuel (mixed with a quality pump fuel) by an experienced engine builder. In the early years of the 250Fs it literally doubled the time between valve clearances for me. I was shocked how much of a difference it made. 

It was a KTM and it does say ROZ 95. 95 octane is just a safe number to prevent pre-ignition even in deep sand or mud without needing any additional tuning. My Yamaha is like yours and says 91 pump would be fine, but I just don't want to go lower than that. We used to be able to get 93 non-ethanol, but don't have that anymore or I would run that.  

Same here - 93 E0 disappeared around here a number of years ago so I started mixing race gas with whatever E0 was available to bump the octane a little, as we had a few that would rattle noticeably with the 90 octane.