What Gasoline should I use?

[roloscot]

Hi,

I know that this must be one of the most stupid questions of all time but what grade of gasoline should my 1977 xs400D use? The manual says regular, light leaded fuel. Does this mean that an additive needs to be added to regular unleaded gas?

After many months of rebuilding my xs400D, it started for the first time yesterday. I just put in regular gas to get it going. I will post some photos use I have the bike fully completed.

Many thanks,

Mark.

 

[Travis]

I think most guys run premium. In a lot of states, the premium fuel doesn't have ethanol which can cause problems with fiberglass tanks (cafe bikes) and certain rubber parts like aftermarket carb holders.

 

[roloscot]

Thanks for the tip. Premium it shall be. No need for any additives to replace the lead?

 

[Travis]

I don't think you need to run the lead additive, but I'm no expert. I've done some reading on the issue and there is a lot of conflicting information out there on the topic. Sorry I can't be of more help.

 

[Shawngilr1]

Premium is the way to go!

 

[bcware]

Lead was just used to boost octane. Currently ethanol is used to boost octane instead; some states mandate this by law and others are not required to label the pumps indicating it has been added. I cannot imagine an older bike needing more than regular fuel. Octane is just a resistance to (premature) detonation; higher compression engines require higher octane fuels. A 30 year-old bike does not have a "high" (relatively speaking) compression engine.

Ethanol probably does destroy fiberglass from what I have read, but I am not sure about rubber. I work in a lab that contains specimens kept in glass vials full of ethanol with rubber stoppers; some of them are over 50 years old and all they do is swell up over time.

 

[xschris]

91 octane or more. I was told that lead was used in the older engines to help with valve sealing. Older valves where not made as well as new ones and would tend to wear fast. Also lead not good for the air we breath. As for the ethanol in the gas yamaha make a additive that takes care of that and it seems to work very well. I used it last summer and my bikes started and ran better.

 

[roloscot]

Hi,

Thank you very much for the advice and guidance. I am not sure where we should add this to the website but I think we should add a FAQ or How to section especially for new owners of xs400s. For example, my question related to fuel would be a great FAQ for newbies like me!!!!

Any just an idea!!!!

Mark.

 

[OliverB]

Lead was used as a lubricant for valve seats to prevent recision, or excess wear, of the seats and to reduce "ping" or early detonation of the fuel. Amoco used nickel in their "white gas" for the same effect. Recision of valve seats was mostly a problem with stationary engines running at a constant rpm for extended periods of time. Don't worry about the use of lead free gas in your XS400. The engine will be fine! No need to use valve lubrication additives, either.

I run 89 or mid grade in my bike w/o any sign of ping. The compression ratio of our XS400s, from '77 through '82, is 9.2:1. Many folks feel that an engine with a compression ratio in that neighborhood will do fine with lower octane gas. Of course, if you run with advanced timing, use premium gas.

Alcohol is used in gas today to make the fuel burn more completely and reduce pollution. It has replaced MTBE, which was widely used for the same purpose, because it was found that MTBE is very dangerous to the environment. No need to worry about rubber parts if you are using gas with 10% or less alcohol. Above that percentage, problems could occur unless the materials are designed for higher alcohol percentages. There is a move by some to mandate all gas be at least 15% alcohol (E15) in the future and that is generating some concern for older vehicles.

 

[xschris]

compression ratios (us models) xs400D 9.2:1 xs4002 E 9.4:1 all other models 9.3:1

 

[drewpy]

all yamahas were designed to run on unleaded since 1973/4

 

[totalgearhead]

Just a heads up to all, I just finished dealing with some bad gas. I have had toys stored over 3-4 month winters for the last 20 years and never had gas go bad. This year, I blame Ethanol!!!!!

Anyways, to the web! I found out that Ethanol can start seperating in just 2 weeks!!! I would highly recomend sourcing non-Ethanol in your part time rides. In Canada we have Shell V-Power 91, that has zero Ethanol. I also picked up some Seafoam as a fuel stabilizer when I don't make a Shell fillup this season!

 

[HoughMade]

I use 87 octane and have never had a problem.

Also, I just woke up my bike after the the winter. I had the tank full and treated with Seafoam, but the petcock was off and the carbs were drained. Out of an abundance of caution, I drained the tank and filled it with fresh gas (87) before starting it and it started and ran perfectly having sat since early November.

 

[hardtailed77]

I used to run 91 octane in mine, but switched last year to 87. I haven't had a single problem with the switch yet, and with the gasoline prices these days, that's a good thing!

 

[OliverB]

I have used Shell gasolines exclusively for many years. For the past couple of years pumps in this area now carry a sticker indicating ALL grades of Shell gas may contain UP TO 10% alcohol so we really don't know how much alcohol is being added. All grades of Shell gas contain the additives to clean the combustion chamber and it really works - I know because I have scoped some chambers before and after.

Gas usually does not deteriorate when stored over the Winter but it is always better to be safe than sorry.

In our area, NO STATION sells gas w/o alcohol!! Not an option here. I have vehicles ranging in age from 1977, 1980, 1990, 1999, 2004 and 2006. None have problems with E10 from regular to premium grades.

A few rare areas in the U.S. sell gas that is E15 by local Gov't mandate and some areas have regular that is only 85 octane and premium of 91 octane. Ours are 87, 89 & 93.