Needle Height Adjustment

[Dan Hodges]

Your Mileage May Vary

Maybe not to you, but it's a HUGE mystery here.

Just do a search for carb setting issues and you will see it's probably the number one problem we have here.

What we need is science, as you describe, so that our manuals can be rewritten into what should work today.

We have people changing float levels, needle positions, main and pilot sizes, and mostly by guess work.
It's understandable that the more work done to an engine, the more experimentation needs to be done to get it tuned, but the majority of us are running pretty much stock, or as close as we can get, yet driveability and economy are all over the place.

If you build 12 stock Elevens exactly alike (factory spec) they all will be within 2%-3% of each other. If you build 12 Elevens, some having OEM parts, some having a hodgepodge of aftermarket parts tuned by 2 or 3 previous owners by guess, it's anybody's guess how they will run. Add to this scenario the fact that some have large fairings, small fairings, small windshields, large windshields, no windshields and yada,yada ,yada and it's no wonder for the difference in gas mileage. A stock Eleven with stock exhaust will work fine with the stock main jets, needles and floats set at the factory recommended setting however the 80-81 can benefit from an air pilot jet change and idle screw adjustment as they suffered from a lean condition at off idle. The needles in the 80-81 are not adjustable with clips like the 78-79 however you can thin the plastic/nylon donuts beneath the needles or use small washers depending on the direction you want to go. The 78-79 because of the clips are more easily adjustable but the principle is the same. Mention is made that the needles in the 80-81 Specials are different from the needles in the 80-81 Standards and should not be interchanged. I have also seen guys use the adjustable needles from the 78-79 in the 80-81 however you will need a dyno with a sniffer to ever get the fuel curve right with this combination because all these needles vary in taper, tip diameter and length. The Four Forces Of Nature are no different today than they were in 1979 nor is the XS Eleven or the shop manual that covers it and consequently doesn't need to be rewritten just because the people of today think they are smarter than the Japanese engineers who designed it.

A "new" XS worked well in 79 and works well in 09 but can obviously be improved upon with sound engineering techniques but you better damn well know what your doing when you start making changes or you will wind up with something inferior to the original stock piece.

Someone asked me about their clutch and I told them what they should use after which they talked to a dozen people and wound up buying the cheapest damn stuff they could find, too bad.

This is a good example of why the performance of these old bikes vary all over the place but like the old saying, [B][U]you can lead a horse to water but you can't make him drink. Good luck and power to the people.

[Crazcnuk]

But, again your reading way too much into it.

No matter what windshield, load combination or what have you, ALL these bikes ran perfectly fine, from the factory, on stock settings.

The range of settings came about later because none of us know how to compensate for changes in the last 30 years.

I am not talking about making improvements, I am talking about standardizing the tuning process. As I mentioned, you do mods at your own peril, but for the majority of us, who have more or less stock bikes, a good clean and a few routing adjustments should be all that is needed.

We are not talking performance tuning or anything like that, or compensating for wierd pipes or air box combos.

These bikes should run very well with the stock set up and tune. What we need are small, well tried, adjustments to make up for the realtively minor things that have changed in the last 30 years, ie fuel density/octane changes, etc.

We chould be able to stay within the 2-3% variation, until actual mechanical damage or serious modifications take place.

What people do with the info is up to them.

[MindWebs]

Wear and tear.

The main reason i see such a variation in tunes between bike is simple wear factors.
take mine for example, before i installed the carb rebuild kits, my float levels
varied by 8MM of each other due to wear on the needle valve springs.
i had the fuel at the same level on each carb but it took a hugh difference to
accomplish it.

as soon as i installed the rebuild kit, i adjusted all of them to stock settings and they all were "perfect" level.

so, it mearly depends on what has been freshened up on each particular bike.

that's my 2 cents anyway.

[Dan Hodges]

Wear & Tear II

The main reason i see such a variation in tunes between bike is simple wear factors.
take mine for example, before i installed the carb rebuild kits, my float levels
varied by 8MM of each other due to wear on the needle valve springs.
i had the fuel at the same level on each carb but it took a hugh difference to
accomplish it.

as soon as i installed the rebuild kit, i adjusted all of them to stock settings and they all were "perfect" level.

so, it mearly depends on what has been freshened up on each particular bike.

that's my 2 cents anyway.

You nailed the the problem my friend because the main culprits to float level changes is, rough riding, worn needle valves and or bent/improperly adjusted float tangs. As I said in a previous post, the specific gravity of pump gas will range from .724 to .800 and a slight variation in the specific gravity will not alter the float level. All XS models were designed to operate on unleaded regular gas with a minimum research octane number of 91. Mention is made that the shelf life of gas is limited and it will go bad even in a sealed container and so it's a good idea to buy "good" gas from a station that sells lot's of gas and even that's no gaurantee the stuff you are buying is fresh and the brand it's purported to be. If you buy gas at Git & Go or Stop & Rob who knows what kind of gas you are getting.

The Yamaha V-Max came out in 85 and I have a Yamaha shop manual that covers all models from 85 to 2005. There were no major carb changes like with the XS but there were slight variations in jetting depending on where it was sold however the float settings are the same for all models.

It's true that the fuel level in the float bowls is critical to proper performance as the fuel flow rate from the bowl up to the carburetor bore depends not only upon the vacuum in the throttle bore and size of the jets, but also on the fuel level in the float bowl however a slight variation in the spec gravity of the gas will not change the level. An 81 model XS has fuel bowls that are designed so that you can use a clear plastic hose "sight gage" to check the fuel level with the bike leveled out on the centerstand which is easier and more accurate than the method used with the old style bowls.

If an XS has carburetors that are in perfect condition and the bike is bone stock, it will work fine with the stock setting with maybe just minor tweaking of the pilot jets and idle screws however if it's operated at high altitude this stock setting might be a little rich.

If you are using aftermarket coils which generate more juice, the fuel curve will be leaner, if your coils, wires and caps are junk it will be richer.

If you have one of these old bikes and you are not positive as to the conditition of a specific part you have to check it and if you don't it's strictly a guessing game as to why it does what it does.

As for me, I'm finished on this subject.

Dan

[Crazcnuk]

Well, it's pretty easy to rhow out an opinion, and then say your not going to defend it.

However, since a LOT of people are finding they have to drop thier floats 2mm (or more) to get their bikes to run properly, whether modified or stock, lots of miles or not, it doesn't take a genius to know something has changed over the years.

Now it may or not be changes in density, or flow rates of gas, or maybe the floats are getting lighter with age, or maybe the gravitational constant of the planet is changing, or what have you.

But the fact is many people are now running with thier floats or needles adjusted to lean out engines that were actually very lean to start with, 30 years ago, and you can't contribute the change to wear, as all these carbs are in various stages of rebuild, some have new parts some old, some have no miles others have lots of miles.

I just thought that, since we KNOW the chemistry of gas has changed, that was the easiest solution to our issue.

[Dan Hodges]

C/8h/17

Well, it's pretty easy to rhow out an opinion, and then say your not going to defend it.

However, since a LOT of people are finding they have to drop thier floats 2mm (or more) to get their bikes to run properly, whether modified or stock, lots of miles or not, it doesn't take a genius to know something has changed over the years.

Now it may or not be changes in density, or flow rates of gas, or maybe the floats are getting lighter with age, or maybe the gravitational constant of the planet is changing, or what have you.

But the fact is many people are now running with thier floats or needles adjusted to lean out engines that were actually very lean to start with, 30 years ago, and you can't contribute the change to wear, as all these carbs are in various stages of rebuild, some have new parts some old, some have no miles others have lots of miles.

I just thought that, since we KNOW the chemistry of gas has changed, that was the easiest solution to our issue.

I don't deal in opinions and my information on gasoline was obtained from VP Hydrocarbons and the works of MIT engineer Charles Fayette Taylor called, " The Internal-Combustion Engine In Theory and Practice" volume II: combustion, fuels, materials and design. You can find the chemical properties of gasoline in table 4 on page 120.

If your XS is running lean and you want to change the float level to richen the mixture be my guest.

[Crazcnuk]

"If your XS is running lean and you want to change the float level to richen the mixture be my guest. "

But if you can't even follow this thread...

[Dan Hodges]

Following A Thread

"If your XS is running lean and you want to change the float level to richen the mixture be my guest. "

But if you can't even follow this thread...

Okay, if it's running rich adjust your floats to lean it out, how's that?

Let me repeat this for the final time. I have an 81 Special and the fuel level is set by a sight gauge at 3 mm below the top surface of the float bowl. I have always maintained this setting since I bought the bike new in 1981. Last year I put a Dyno-Jet kit in it and per their instructions the float level remained stock. Over the years, I have replaced the floats once and the float needles twice. I always used the stock Yamaha OEM parts and didn't have to bend the float tang to achieve my prefered 3 mm setting. I had it on the dyno with this combination and my fuel curve was in the 13 range but a little lean on top with the DJ recommended main jet. I put in a one step richer main jet and it's between 13 and 14 from 7,000 rpm up, good enough. I've did all of this the best that it's humanly possible to do but I admit I don't know what others are doing nor do I care because it's the end results that counts for me.

If you or others alter the float setting and achieve the desired results that's a good thing and you won't get an argument out of me because it's the end results that count for your combination.

My original intent regarding this post was to share some of the information I have come by over the years with you and others, nothing more.

Your statement, " but if you can't even follow this thread" is condescending and completely unnecessary as this stuff is about information, not one upmanship Good luck with your endeavors.

Dan

[Crazcnuk]

Perhaps, but it was you that came off condescending using your reading of one article to trump all the work that has been done by dozens of people in this forum. I am much more impressed with the actual work you've done and the end result.

I agree, it's the end result that counts, which has been MY point for the entire thread. The discussion was about WHY the modifications that many of us have been doing works.

Perhaps gas is the same, but maybe the companies that are making our float/needle assys are slightly off.

What you have to remember is that VP Racing fuels are just that, racing fuels. They have been making specialty gasolines for carburated engines for decades. (I don't think FI cares about such things as fuel density, since it can comensate on the fly, and doesn't rely on tacky things like floats.) So VP can make thier gas exactly the same for ever, but I don't think it equates to what we buy at the corner gas station every day.

Second we KNOW that gas has changed. They took out lead, a heavy dense metal, and put in MTBE, which is now outlawed in most states. Not sure what they are using as a lead substitute these days. And to top it off they are now cutting gasoline with up to 10% alcohol (Ethanol, Methanol, or whatever). This HAS to change the density of the fuel.

Some would say that they can't do this as it would affect ALL carburated engines. I agree, and I say it did. I believe this is why older engines all of a sudden started running rich enough to wear out in under 100,000 miles. Many of the 4 cylinder engines built in the mid to late 70's were worn out by 70,000 miles, in the 80's. Those same engines now go 150,000+ miles regularly.

The auto industry didn't care, more sales for them, and it only caught people who didn't tune thier cars regularly.

Not trying to start a fight. I think this is a very interesting topic. If anyone else has any theories as to why all of the old vehicles decided to start running excessively rich by all means throw it out.

[Dan Hodges]

Perhaps, but it was you that came off condescending using your reading of one article to trump all the work that has been done by dozens of people in this forum. I am much more impressed with the actual work you've done and the end result.

I agree, it's the end result that counts, which has been MY point for the entire thread. The discussion was about WHY the modifications that many of us have been doing works.

Perhaps gas is the same, but maybe the companies that are making our float/needle assys are slightly off.

What you have to remember is that VP Racing fuels are just that, racing fuels. They have been making specialty gasolines for carburated engines for decades. (I don't think FI cares about such things as fuel density, since it can comensate on the fly, and doesn't rely on tacky things like floats.) So VP can make thier gas exactly the same for ever, but I don't think it equates to what we buy at the corner gas station every day.

Second we KNOW that gas has changed. They took out lead, a heavy dense metal, and put in MTBE, which is now outlawed in most states. Not sure what they are using as a lead substitute these days. And to top it off they are now cutting gasoline with up to 10% alcohol (Ethanol, Methanol, or whatever). This HAS to change the density of the fuel.

Some would say that they can't do this as it would affect ALL carburated engines. I agree, and I say it did. I believe this is why older engines all of a sudden started running rich enough to wear out in under 100,000 miles. Many of the 4 cylinder engines built in the mid to late 70's were worn out by 70,000 miles, in the 80's. Those same engines now go 150,000+ miles regularly.

The auto industry didn't care, more sales for them, and it only caught people who didn't tune thier cars regularly.

Not trying to start a fight. I think this is a very interesting topic. If anyone else has any theories as to why all of the old vehicles decided to start running excessively rich by all means throw it out.

If I was condesending, you have my apology. The book I mentioned by MIT engineer C.F. Taylor contains all the information you ever wanted to know about combustion and motor fuels and is a good read for any motor head and that's not being condesending.

I agree that the pump gas in St. Louis is different than what might be available in California but the specific gravity is essentially the same. Lead added to gasoline will increase the octane rating but so will other additives but lead was removed from pump gas in the very early seventies before the XS came out. Most pump gas today (not all) contains 10% ethenol however an alky motor requires larger jetting not smaller as every drag racer that uses alcohol knows however 10% will not change the jetting requirement. Alcohol has a specific gravity of .790-.800, heavy stuff. Oxygenated fuels will have a lower spec gravity than non oxygenated fuels and most race fuels are oxygenated however the spec gravity of gas isn't the only reason one blend of gasoline might require different jetting than another. I have been a member of the NHRA for over 30 years and the NHRA publishes a rule book every year and I have kept them all. Up untill the 90's they used spec gravity to check the legality of gas and in the 73 rule book it states, "service station pump gasoline as sold to the general public must be used and have a spec gravity between .700 and .750". By 79 racers began cheating by using aviation gas, nitrogen, oxygen, lead and octane boosters and consequently the NHRA began using the dielectric method and the average DC for service station pump gas was and still is 2.026. Today only certain classes of stock class cars are required to use pump gas by the NHRA and all others are allowed to use the various blends of race gas. I use VP C-14 in my drag race Camaro and as I stated in another post I used some of that in my XS just to see what it would do and naturally it ran like crap and real fat but the float level didn't change. I also tried some of their U4.2 which was designed for applications like my XS and I gained 4% more power on the dyno over pump gas but had to richen the mains but again, the float level didn't change. At the moment, VP Hydrocarbons markets over 28 blends of racing gas and each blend is designed for specific applications which are based primarily off cylinder head and intake air flow, compression, blown/unblown, use of nitrous and RPM range and in naturally aspirated applications it makes no difference whether the motor is carburated or has either mechanical or electronic fuel injection in as far as the fuel blend goes.

I have wore out a lot of passenger cars since 1970 but all of them saw at least 100,000 miles before they gave it up including a 73 4 cylinder Ford Pinto. It's generally true that the quality of American cars went south in the 70's but that's not now the case. Of course there are exceptions to every rule and a case in point is my nice old 77 Chevy 3/4 ton 454 pickup that I tow my Camaro with. While it's true that it doesn't get driven in bad weather and is used only as a tow truck, it runs as good now on 89 octane as it ever did and gets the same mileage.......it gulps it and I don't care.

The V-Maxes have been around since 85 and I have a low mileage 96 and I know lots of folks who have some old ones since they were new and nobody I know has noticed their bikes going fat since they bought them and an 85 Max is close to being as old as my 81 XS.

The one thing I have noticed in recent years is that if you let a bike sit for over a couple of months with gas in the carbs you will probably have to pull the carbs and blow out the pilot jets because today's gas seems to go bad much quicker than it once did, at least in my case anyway.

I haven't experienced the same problem with the rich mixture that you guys are having but obviously there has to be a reason. When you replaced your floats and needles did you use Yamaha OEM stuff or something else?

One of the members here did the 1196 deal on his 81. He put a stage I DJ kit in it, set the floats to spec and it ran killer with the A/F ratio in the 13's and 14's on a dyno in Stillwater Oklahoma.

At the end of the day, if you are happy with your combination that's all that counts in this world.

Maybe somebody else would like to share some information with this thread as I've said enough.

[Crazcnuk]

Exactly. There may be no simple answer, although it would be nice.

Specific gravity may not be the issue, it was just a thought. Maybe viscosity, atomability, who knows.

It just seemed odd, to me, that we are all doing the same sort of variance from what the manual says.

I know our gas, up here in Canada, seems to be much different than that in the US. I've left gas in bikes for years, and had no issues starting them up. I've never used any kind of stabilizers as they seemed unneeded.

I have seen carbs that were gummed all to heck, too, but they had to have sat, not once, but several times, ie started once every couple of years, but not really driven. That or they came from the US.

The wearing out of 70s cars occured mostly with people who don't maintain their cars. People like you and me, who pay attention to such things, didn't have a problem.

[WMarshy]

Hi guys,
You both make valid points on both sides and do a really great job of describing them in an intellectual manner. I have read every single word you guys have said about the matter and I have learned A LOT. Do I think one way is more correct than the other? No not really, as you both have said, the end result is what matters. I see now that it’s all pretty much guess work unless you’re tuning on a dyno. Don’t get me wrong, I’m sure a guy with an extensive background and wealth of knowledge like so many here could tune a bike probably just as good as another using a dyno, but you don’t have any documentation that goes with it besides your ¼ time. (Not that it matters to most.) As an engineering student we are taught to make assumption, estimate, approximate, correlate, compensate, generalize, and guess. Does the density of gas change from location to location, how about the octane quality, acidity, viscosity, water, ethanol content and age ect…? I have no doubt it does. The question of “How does this affect out bikes?” will always be open to great interpretation. The next question we should be asking is “Is it worth it to have an answer to all these questions?” Answer: Maybe. Some are more important than others but I still wouldn’t care too much if my bike still pulls my arms off. What I’m getting at here is you both have already provided way more information than most of us will probably put into practice. I must admit its very interesting reading though and wouldn’t mind hearing more about A/F mixture and combustion in general. Thanks for sharing guys.