Needle Height Adjustment

[WMarshy]

Hi guys,
Can the height of the needles be adjusted in these carbs? I took the bottom of my air box off to see if it ran better because it runs rich (starts, idles, and runs fine up to 3000 RPM, has no @SS above that), and I suspect it cant get enough air to carbs. It ran noticeably better above 3000 RPM with it off and was thinking needle adjustment to lean it out...? Any thought? All stock except for the pipe, I suspect jets are too, meaning I haven’t had them apart to look. I have read many different ways and opinions to achieve the "correct" tuning, and just would like to adjust before changing parts/jets. Thanks guys.

[psycoreefer]

To answer your question, yes, the needles are adjustable on 78's and 79's. If its all stock you shouldn't need to make any adjustments. You haven't had the carbs apart yet so I'd suggest starting with a good cleaning, synch, and idle mix adjustment and see where that gets you. Also when you had the box apart did you check that the snorkel wasn't plugged up and the air filter was clean?

[randy]

Yes, if you have the stock '79 carbs, the needles have three clip positions. Normally the factory setting is the middle position.

[WMarshy]

To answer your question, yes, the needles are adjustable on 78's and 79's. If its all stock you shouldn't need to make any adjustments. You haven't had the carbs apart yet so I'd suggest starting with a good cleaning, synch, and idle mix adjustment and see where that gets you. Also when you had the box apart did you check that the snorkel wasn't plugged up and the air filter was clean?

Filter was usable not too bad, didnt check the snorkel. Whats its deal, what purpose has it, saw it there and didnt know anything about it..? (I can already hear you repeating yourself before you finish reading this next line) I rode the bike for about 2000mi in its current state and ran 3 cans of seafoam in it (it had plenty of WOT too). I suspect the circuits are clean given that the low rpm circuit is usually the more “problematic" one and if it starts, idles, and runs fine up to 3000~3500 rpm that usually is a good indication that they are “clean”. I mean were talkin, I put half a can of seafoam in on reserve, drove 5 mi, then sat for 10 days or so... Anyways, a synch is in the works with a mix adjustment. Thanks psycoreefer

Im thinking if I need more air, the easiest/cheapest way to get more air would be K&N and maybe drilled air box, but dont really want to go drilling holes in it before I have a better understanding...

[Crazcnuk]

These bikes easily get enough air through the airbox, in stock configuration.

Unless , of course something is plugged!

A big thing is that you may not know what any POs did. It's a good idea to pull the carbs apart, do a good clean and double check that nothing wierd has been done internally, ie wrong jets, needles out of whack etc., while yourin there.

Seafoam is good, but it can only do so much.

[WMarshy]

These bikes easily get enough air through the airbox, in stock configuration.
Unless , of course something is plugged!
A big thing is that you may not know what any POs did. It's a good idea to pull the carbs apart, do a good clean and double check that nothing wierd has been done internally, ie wrong jets, needles out of whack etc., while yourin there.

I meant it needed more air as in mixture, takin the bottom off the airbox leaned it out and made it run somewhat better so I thought the cheapest easiest way to lean it out might be to add K&N + pods...

Anyways, no problem cuz... I just got a call from my mechanic with good news. He adjusted the needles to the leanest notch and did some cleaning in there. He said they were pretty clean, nothing in or around the jets to cause restrictions, and ditched the snokel. He said its a whole new animal.

I will report later on what I think of the job and specific run down of everything if anyones interested in exactly what he did and $ just FYI.
He did warn me it has a clutch slip now. Far as im concerned thats a good thing, it means its not running like a moped anymore. Maybe some clean oil will take care of it?? Thanks for the tips, time to read up on clutch slip.

[Crazcnuk]

You really shouldn't need to be going to the extremes on the needles. 80% of us are running in the stock needle position, with all kinds fo mods.

Our usual cure, for richness, is to drop the floats 2mm. It seems to compensate for the changes in modern gas, ie; less specific gravity, or what have you.

The clutch slip usually indicates the springs have weakened over the last 30 years. They can still be bought for a reasonable price.

[WMarshy]

Im not sure if they are at the very leanest position or not, will get specifics when I pick it up. Is there a difference between the two, do they do the same basic thing, lean/richen the mixture through the entire RPM? Is there an advantage to adjusting the float level vs needle, given easy start, good idle, and 0-3500 rpm runs good?

Is there an easy way to tell is the clutch plates are bad without taking them out? Would you advise shiming the spring first? Thanks.

[Dan Hodges]

Slipping Clutch

Im not sure if they are at the very leanest position or not, will get specifics when I pick it up. Is there a difference between the two, do they do the same basic thing, lean/richen the mixture through the entire RPM? Is there an advantage to adjusting the float level vs needle, given easy start, good idle, and 0-3500 rpm runs good?

Is there an easy way to tell is the clutch plates are bad without taking them out? Would you advise shiming the spring first? Thanks.

The friction plates/disk of the stock XS clutch are made of a cork material and have been submerged in oil for 30 years and won't hold the torque of a strong XS. The friction plates and steel disk are the same for the XS and the FJ-1100 & 1200. I bought new disk and steels for mine and when I miked the thickness of the original disk and steels they both were within spec but would not hold my motor. I also bought new clutch springs from Vesrah, EBC and Yamaha and checked the spring tension on them all and found that the springs from EBC were the stiffest/strongest of them all and they are the ones I used. New clutch springs are cheap and might solve your problem but working on the clutch is a pain and if you replace the original friction disk with new OEM disk and the stiff springs you won't have any further clutch problems to worry about. You can also add an additional steel disk for increased pressure as others have done using the original parts which in some cases will cure the slippage however if you use new frictions and new springs you are good for another several years of clutch free problems.

Mention is made that if you do much running with the clutch slipping you will also ruin the steels but if you fix it when it first starts to slip the original steels will probably be okay. If you fix it right the first time you only have to do it once.

You also need to get yourself a shop manual or a copy which I believe T.C. the moderator has for sale and study it thourghly before you go about making tuning changes. When you are completely lost on your tune up, you go back to stock and tune from there. If you don't know what size the pilot jets, pilot air jets, needle jet part numbers and main jets are in your carburetors no amount of fiddling with the idle screws, floats and needles will get you where you need to be. You can obtain the the correct numbers for these pieces either from the shop manual or from Yamaha's web site and you need to do this before you screw up your carburetors. The needles primarily control the midrange fuel curve and have little effect on the top end. The float level/float setting will change over time due to viberation and so forth and should be checked per the shop manual.

If you remove the air box snorkel and don't radius/fish mouth the new air box entry, it will not flow as well as it did with the snorkel but will only make more noise. A better method for increasing air box flow is to drill holes in the air box bottom/plate in the interior area of the air filter but be advised, any modification to the air box including a less restrictive air filter like the K&N stock replacement type will effect the operation of the carb slides and this is doubly so if you use pod filters.

The stock valve seals in an XS are of the Viton type with the spring like retention band and deteriorate with age primarily from heat. Once they lose their seal on the valve stem, oil can and will enter the combustion chamber due primarily from vacume on the intake stroke. The degree to which this will occur depends on the valve guide to valve clearence and how well the motor is sealing up (ring seal). Any XS with the original valve stem seals needs a new set of the stock seals as they are the best. The valve springs in these old motors are junk also particually in the ones that have been sitting for ages because some of the springs have been fully open/compressed during that time. When you change the seals you can check the tension of the valve springs on your mechanics valve spring checker and make sure of their condition.
Of course I'm sure your ace mechanic has already told you all this stuff.
Happy tuning.
Dan

[Crazcnuk]

Yes lowering (or raising) the floats changes the mixture ratio throughout the rpm range.

We have had some discussion on why this seems to affect almost everyone, given that these bikes all ran perfectly on the stock settings when they were made.

And while there are some theories, pertaining to minor wear and tear, etc, my pet theory is that gasoline is different now, than in the late 70's and the floats sit lower in the fuel making the mixture rich. (lower specific gravity?). A minor float adjustment, usually 2mm lower, and most bikes seem to respond well.

Moving the needle can do the same thing, but it will only affect the mid range from just off idle to about 3/4 throttle, where lowering the floats affects all ranges.

[Dan Hodges]

Specific Gravity

Yes lowering (or raising) the floats changes the mixture ratio throughout the rpm range.

We have had some discussion on why this seems to affect almost everyone, given that these bikes all ran perfectly on the stock settings when they were made.

And while there are some theories, pertaining to minor wear and tear, etc, my pet theory is that gasoline is different now, than in the late 70's and the floats sit lower in the fuel making the mixture rich. (lower specific gravity?). A minor float adjustment, usually 2mm lower, and most bikes seem to respond well.

Moving the needle can do the same thing, but it will only affect the mid range from just off idle to about 3/4 throttle, where lowering the floats affects all ranges.

You are correct in that altering the float level will alter the fuel curve throughout the entire range. At the end of the day the only way you know for sure where you are going on the fuel curve is to sniff it on the dyno, otherwise you are just guessing. Todays pump gas will have a specific gravity in the neighborhood of .750 to .800 and generally a smaller number will require a bigger jet, ie richer setting. Oxygenation is the main reason for large variations in the specific gravity of gas and this is easy to check for yourself. Most pump gas and all pump gas here is 10% alcohol by volume and no pump gas that I know of is oxygenated nor does it contain lead. In some parts of the country there is what is called summer and winter blends however the specific gravity is little changed from the summer blends. Oxygenated and leaded gas were gone by the early seventies and by 1980 it was similiar to what we have today except the fact that today the octane numbers are 2 numbers higher than they were in 1980. VP racing fuels sells several blends of race gas and most all is leaded and oxygenated however their VP C-11 blend is the blend used on motors with up to 11:1 compression and is similiar to the old Sunoco 260 pump gas stuff that was available up to 1969 with a motor octane number of 104 containing 4.33 grams of lead per gallon. I bought 5 gallons of this gas in the winter of 08 for testing and with this gas in my 81 Special I checked the float level via the manual recommended clear tube method and the float level was the same as it was with the BP pump gas stuff. I bought another 5 gallons of their U4.2 blend which is oxygenated with a motor octane number of 102 and a specific gravity of .784 @60* F and the float level didn't change on this either but I had to go up 2 steps on the mains to get the AF ratio in the 13 range from 5500 rpm up. With the stock needles and pilot air jets I never did get the bottom and midrange right and finally put in DynoJet needles with their #190 pilot air jet and nailed the fuel curve perfectly with the float level at the recommended setting of DynoJet which happens to be the stock setting. My motorcycle is I would say highly modified with a Nigel Patrick ported head, MegaCycle cams, K/W valve springs, Wiseco 1179 kit Super Trapp 4 into 1 header with a 2.5 inch muffler core and it was a pain to get it right with the stock CV carbs but I finally did. I bought my bike new in 1981 and in stock form it ran pefectly with the carbs only modification being the idle screws turned out two turns, a 180 pilot air jet vs the stock #185 to clean up it's lean condition on the bottom end which all 80-81's had to some degree. Worn needles, emulsion tubes and restricted air bleeds in the carb bell will certainly cause it to run fat and on an old bike this is a good possibility but can be fixed. It's whatever works for you that counts however the carb float level in a 1981 XS Special remains the same for the Amoco Supreme of 1981 as it does for the 93 octane BP of 2009 as I've checked them all since the day I bought my bike and I keep the records of all my test on all my motorcycles which number several. You can put the thing on a dyno for 50 bucks or maybe less and in one pull you will know what your AF ratio is and if it's off you can go back to the house and change the jetting or the float setting if you wish and then try it again. It took me 4 tries to get it right and actually I wasn't too far off on the 2nd. and third attempt but was on the first. Theories are fine when talking about the origin of the species but with the XS Eleven the theoretical stage has long since past and what works for it is no longer a mystery.

[Crazcnuk]

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.

[WMarshy]

Hey Guys,
Well I picked the bike up yesterday and man, what a different bike it is. Its not an oversized moped anymore! I got some info to share…
Compression: #1-140, #2-140, #3-134, #4-140
Needles: 5G26
Main: 137.5
Pilot: 42.5
Main Nozzle: 266
Labor:
A) Test for state of tune.
B) Checked compression
C) Changed plugs
D) Cleaned carbs, lowered needled 2 clip positions to leanest setting
E) Adjusted low speed mix & idle speed
F) Cleaned/assembled filter/box, removed snorkel

Total: 3.7 hours @ $48 = 177.60 Labor fee + $20 in parts/hardware/gas

Comments: Clutch now slips. Could benefit from a steering damper.

The clutch slip isn’t too bad unless you’re getting on it fairly good. As far as state of tune, it runs well now, to say the least. It definitely has the midrange power I have read about on here, and sounds great doing it! (I may still have bugs in my teeth from smiling for the 100 mi ride I took after I picked it up)

“You also need to get yourself a shop manual or a copy…”

I have Yamaha’s service manual but it didn’t seem as in depth as the ones I found for free at; http://www.ringler.us/family/mybike.html
Are these the same that TC offers?

“The stock valve seals in an XS are of the Viton type with the spring like retention band and deteriorate with age primarily from heat. Once they lose their seal on the valve stem, oil can and will enter the combustion chamber due primarily from vacume on the intake stroke. The degree to which this will occur depends on the valve guide to valve clearance and how well the motor is sealing up (ring seal)….

Of course I'm sure your ace mechanic has already told you all this stuff.”

How would you check the how well the valves are sealing. He mentioned soemthing about a leak down test but Im unfamilar with it. Do you just do the compression test then let it sit with valves closed?
Would my seals benefit from adding some Marvels Mystery Oil or some other product to the oil? Should I be concerned about the clutch while using these products? I have read all about using the seafoam in the oil but I don’t recall is it helps out the seals or not… I don’t expect seafoam or another product to fix my clutch problems but might consider adding something to the oil to see if it helps out till I get it fixed.

My mechanic is very helpful and willing to share his knowledge but we never talked too much about the clutch. He didn’t think it was unreasonable to use the amount of oil it is, for its age. Thanks for your advice Dan, if I ever get to changing valve seals, springs may be added to the list. I have a 78’ in the bar that might turn into an “XSperiment” with a 1179 kit and the optimal heads you were talking about in your profile….

Crazcnuk I agree with you, it does seem there are a fair share of posts about carbs. There is not doubt I would still be working on mine if I had to do them myself. To me, it was money well spent to have someone knowledgeable do my carbs, and be able to riding the next day. If I get ambitious down the road, I will measure the current float level, then maybe set the needles back to stock and move the floats to see how it responds. Until then, I guess Im part of the 20% changing needle settings! Thanks for all your guy’s help. Its appreciated.

[Crazcnuk]

It's not so bad spending the money, when you can actually feel/see the difference.

It's when you spend a whack of cash, and nothing seems different.

Your compression looks good. The leakdown test actually is more for testing the rings, but it tests valves too, and yes it is essentially pumping up the cylinder then timing how long it takes for the compression to escape.l

The main test for rings and valves is the compression test, and yours looks fine.

I would still lean towards dropping the float 2mm and then resetting your needle, but if it's working, no point in playing with it.

I think the needle is actually 5GZ6, and everything else looks stock except maybe the 266 main nozzle, not sure what that is.

Oh, and personally, I would put the snorkel back on.

[psycoreefer]

The 266 refers to the emulsion tubes also sometimes called needle jets, the tube the needles slide up and down in...