This Bike hates me - a tale of hateful carburetors.

Worn throttle shaft seals look just like brand-new throttle shaft seals, except they leak.

 

Carburetors on bike, tried to start it, it caught once but I killed it taking it off of idle in haste, and I killed the battery trying to get it to start. Took out battery, put in trickle charger, went to work, six hours later I reinstall the battery and I kill it again, it isn't catching. Going to have to go over everything with a fine toothed comb when I just want to ride.

 

What is the air temperature? Are you using the choke?

 

Air temperature is comfortable, maybe 75 or so by feel, and I was using the choke. Battery's back on the tender, going to try again tomorrow when I wake up. I'm thinking if it might have something to do with the idle setting. I bench synced them but I'm not sure how open I set them all with the idle screw because I'm not sure how much is required. Would completely closed butterfly valves keep the engine from getting enough air to catch and start, or are there other circuits or ways for the engine to get air to idle?

 

If #3 is set the same as the rest then the idle screw is where it needs to be for the initial startup. The throttle plates are supposed to be nearly closed at idle.

 

How old is that battery? You say you killed it trying to start the bike... which, if the battery is strong should have taken many, many attempts at starting. If it died out quickly, it may not be strong enough to give you the initial power you need to get her going.

As an example, before I went to church, my 700 was very hard to start. Vacuum leaks, etc. It would take 18-20 tries (this past winter) to get her going... choke, no choke or a combo of the two... to the point I thought I'd ruin something else just trying to get her going. The battery never gave up.

 

Your on the right track, with that kind of bench sync the idle will be very low. Give the idle a half turn.

 

just hope she does not cook your carb parts into the pudding for the special treat..

 

The battery was bought new last year. I've tried to keep it charged ever since, I brought it in and had it on the charger/maintainer all winter, etc. It's possible the battery just doesn't want to do the work needed to get a less than optimally set engine to catch, though that's somewhat disappointing. Neighbor has a machine which is a charger/tender but can also act as a starter boost, maybe I'll give that thing a go if I can get a hold of him.

 

use some starter fluid.
check the voltage drop on your battery when you press the start button

 

Battery is tired again. Battery is likely going to get itself replaced very soon if it keeps this up. Bloody thing was fine a week and a half ago.
I was able to get it to catch finally, was not easy at all, catches when I let go of the starter button instead of while I'm depressing it. Runs pretty terribly, I'm assuming due to the bench sync. I was trying to work with the idle speed and the choke, a bit less choke, listen, adjust idle, a bit less choke, listen, adjust, etc but even following that method once the choke was gone, the bike kept on poorly for a bit and then died on me. I'm going to have to give it a dynamic sync with partial choke or a high idle because it won't run without one or both yet.

 

Once it's running wait for it to warm up before adjusting anything. The idle speed will come up as it warms. When it idels around 2,000 RPM, then you can ease off the choke and set the idle speed. You can then do a running synch, but you will have to keep adjusting the idle speed as you go, and will need to do a final idle speed adjustment during your first ride when the engine is at normal operating tempaerature.

Not starrting until letting off the starter button is a clue to something, but I can't remember exactly what it is. @Polock? @hogfiddles?

 

When I have full choke the bike idles around 3-4k depending on the idle setting. Once I get get access to the neighbors electrical rig so I don't have to worry about killing the battery I'll get it running with as reasonable an idle as I can manage and I'll give it a running tune. Hopefully that will give it what it needs.

 

low battery, starter stops drawing current and the TCI gets enough to fire the plugs.
your mixture screws are 2.5 turns out?
you can start a running sync at 3k, it's going to change as you get it dialed in but you have to start somewhere
is your charger on the battery now? put it on and leave it there while you tune it

 

One other thing I have noticed in starting - if you get a "pop" but not a start, your headlight will come on. Then it will still crank, but may not have enough voltage for TCI to fire.

I find turning key off and on again, to shut off headlight, often helps it to start on the next attempt.

 

Alright, so with the neighbors machine to assist my aged battery, I was able to do running sync. Kind of Sort of. Turns out the single line of clear vinyl tubing doesn't exactly work very well, it's very (far too) sensitive and the fuel was getting sucked into one of the manifolds pretty much immediately so my friend and I had to experiment with kinking the line here there and everywhere to slow the transfer of fluid ((we used old gas) which I got a good mouth full of) to the point where we could actually follow the fluid with the screw, but with not being sure if everything was kinked evenly and other stuff I now know why the baby bottle device is better.
In the end, the bike now runs. To me, it sounds a little funny, but for everyone else it seems fine. For now, I'm just very relieved because I can actually ride it, I was able to get a decent idle over 1k. The rolling, chugging hesitation on idle doesn't seem to be there anymore at all, I suppose it was those blasted throttle shaft seals. You have my thanks for recommending that.
I think that all that the bike needs now is a better sync, and eventually I'll play with the air mixture screws, but naturally, ebay and amazon and I think everyone else seem to not have colortunes in stock, it's sounding a bit like they aren't being made anymore, so I'll have to wait til I can get my hands on the tool to do it justice. For the engine sync, I might break down and buy carbsticks, or see about a pair or two pair of vacuum gauges, or I might even make the baby bottle device if I can get parts for it.
For now it runs, I'm no longer stuck walking across town for everything, so I'm pretty happy about things.

 

The Gunson Colortune is still being made. Sometimes it's out of stock at several places due to demand. I'm pretty sure Chacal has some on hand. Start a converasation with him.

I'd like to caution future readers (not you; what's done is done) against using gasoline to do a carb synch. The results of a backfire will not be pleasant. Automatic transmission fluid is much preferable, and not at all expensive.

 

In hindsight, using fuel wasn't the best idea, I'll definitely agree to that. Stuff's far too thin anyway, I'd rather something that flowed slower, at least for the bare-bones line only approach I used. The potential for the line to go up in flames or worse doesn't sound too fun, though I'll admit it has that sense of danger I've missed since I've been unable to ride the last few weeks, heh.
I'll see about finding the tools for the job of getting the bike tuned, the right way. We'll make a smooth runner of this bike.

 

here ya go' save your money. read this thread. pay attention to the guy called "takingabreak".
http://xlforum.net/vbportal/forums/showthread.php?t=31262
when you get it to stumble going in and you start back out, go s l o w. three alligators between tweaks back out and a tweak is 1/8 of a revolution

 

two snapple bottles and some water work for me

 

What's being said in that thread definitely makes sense, sounds like it could very well work for me as long as I can correctly document exactly where my bike is set right now. I'd rather have those numbers just in case, since it's seemingly run pretty well, though a little lean and hot unsurprisingly. Sounds like getting the cylinders as close to perfectly synced as possible has to be the first step though if I'm going to use that method, since it relies on a slow, consistent, sure idle.
Snapple bottles sound doable. More available to me than glass baby bottles seem to be. I imagine there's a range of vessel diameters where a good working tool can be made, larger diameters resulting in a slower moving fluid. I want it to be reactive, just not so much so that the tubes empty by the time I let go of the starter button to glance down at it as was the case with 3/16 ID clear line. There's also the matter of having to seal all of this up in a functional way, but I'm sure I'll get creative with it.

 

The key is restrictors in the line between the vacuum port and the bottle.

 

only fill one bottle up half way, that way no water can get sucked up the line, then you can take your time and watch the bubbles
to seal them just drill the hole a little small and force the hose through.
plastic bottles can work but they may collapse, ignore that just keep working

 

Alright, So, a better manometer was built with a brace of mason jars and the same tubing I used for the rough tune. I was able to get it close, about as close as I think it was before all of this happened. I just took a quick 20 mile jaunt to feel how it's running, it's pretty much exactly as it was before, smooth idle, no real hesitation off of idle, smooth until around 4k, small vibration til 5k, by 6k it's smooth and continues that way until redline. I don't feel any real hangups at any point in the RPM range, needle tracked across the gauge without slowing down at any point in an idle to redline pull. It sounds as it always has.
I'm thinking it's running a little hot, I'm still dealing with the situation where after a nice ride at full speed, the idle will hang at around 2k for a while before finally descending to 1.5 or somewhere in that area. I'm thinking the balance is good enough for a little bit of air mixture tuning, but I've had my fill of wrenching this month. That's a project for another day, and another thread. For now, I can get to work, I can ride out to Fitchburg with the friend with the now repaired Subaru, can cruise about with the neighbor on the 84 ironhead I've been helping him work on.
Life can be good sometimes.
Thank you all for your advice, your suggestions, your help. I'd be lost in the pits of despair without it.

Good riding.

 

Sounds like synch still a little off...but at least it runs now....

 

if it works for you, it's ok with me. remember, Aim small, Miss small

 

^ This is truly the voice of genius.

 

I agree. I used the bottles, 1-2, 3-4, 2-3, and then I tweaked 1-2 and only had to check 2-3.
I got it to the point for each pair where the levels will even out, the force of gravity balancing the water levels was greater than the force of unequal vacuum, so the fluid would flatten out and stay there. My only issue was that after so much time running, the sound would change a bit and then one of the cylinders would end up pulling just a little harder than the other, after 10 to 30 seconds of evenness, even with a couple of blips of throttle. I had a fan running to cool the bike, but that only does so much, so it's not like I could have the entire synchronisation done in one go while it was at perfect running temperature and no more, I would have to turn the bike off after so long, then start it up again and start making adjustments when I felt the bike was where it should be. I could see a better sync job being done, but I'd want an actual four carburetor tool of one type or another, enough fans to keep the bike running at perfect temperature more or less indefinitely, and most likely something to disable YICS with.
I shouldn't have any air leaks at this point, I replaced all of the throttle shaft seals and I couldn't get any change in anything spraying the boots with WD40 or carburetor cleaner. I'll be tackling the air mixture as my next project, which will be after I've had some fun actually riding the bike for a few weeks.

 

Is your throttle tube clean and lubricated with graphite, or other dry-film lubricant?

Why you wanna disable the YICS? It provides a fuel economy and power gain over the non-YICS engine ( a small one, but a free gain is a free gain).

 

I think he meant for when he does a better running synch. At least that's how I read it.

 

My Seca is running great after synching ...NO YICS tool used

 

After rebuilding my carbs, I decided to try a synch without the YICS blocked off first. It showed that it was pretty close already and sounded fine. I then did a synch with the YICS blocked off. It required a good bit of adjustment still and sounded much smoother when I finished. The YICS system masks out of synch carbs which I guess is it's purpose. I know this thread isn't about the YICS tool but thought I'd share the test I just did.

 

That 2k rpm idle hang- just open the mixture screws another 1/4 turn or so. That'll clear it up.

 

I did mean as waldreps took it, to disable YICS while I'm tuning. My understanding is that while we know what Yamaha tried to do with YICS, jury's still out on what it actually does, for at least some people. I've got no problem with it other than the fact that it complicates tuning.
The throttle cable has been lubricated with what I understand was dry film lubricant. My throttle cable broke a month or so ago, and since I was in a bit of a rush to get the bike back in useable condition, when I chose to either order a new one and wait two weeks for delivery, or buy one from the salvage yard 15 miles away, I chose the salvaged part. I saw the owner of the yard spray something into it, though I cant recall what the can was labeled as.
I'd meant to replace the used cable with new eventually, but that thought was put to the side when the carburetor issues showed up. Thanks for reminding me, I now have a new one on the way.
For the fuel air mixture, I do think that it's likely running lean, jetted so from the factory. My understanding is that the air screws are pretty bloody sensitive, so couldn't a quarter turn be a bit much? I don't know what they are set to at the moment, what method was used to set them. I know someone pulled the security caps out of them and it wasn't me. I want to try to document where they are now as a reference, take pictures and then try to bottom them out and start tweaking, but then I hear about people breaking the tips of the needles off doing so and messing up the opening in the carb throat the needle interacts with and generally making a big costly mess I'm not aching to deal with after having been without a running bike for half a month.

 

Ok, so first, you did all that work with disassembling the carbs, but didnt pull the screws out to clean behind them? What!?

Second...count the turns as you screw them in to lightly seated if you want your reference point. No damage will be done if those directions are followed. Everyone says 2.5 is the place to start. Regarding sensitivity, some of it depends on the coarse or fine thread screws, and some of it is relative as there is no measurement for "sensitivity", just opinion. And if you open them a 1/4 turn nd its a bit too much, you just close them, back a bit, right? Its not brain surgery...just idle mixture. If it were my bike, and it was behaving as you described, that's how I would handle it. You could go "the width of a dime" at a time as some others have suggested if you felt so inclined, but to me a 1/4 turn is pretty fine adjustment. If you had the colortune, the fine adjustment might be warranted, but for a seat-of-the-pants feel, a 1/4 turn will solve the hanging idle (more than likely) and get you on your way.

 

this is a test, what is the YICS system for?

 

1. Lowered emissions.
2. Improved fuel economy.
3. A bit more power (factory claimed 15% increase over non YICS).

Trenchcoat, the jury isn't out about what the YICS system does. It "borrows" otherwise unused fuel charge from the three "resting" carburetors to induce a swirl in the combustion chamber that improves the completeness of combustion, which provides the (admittedly modest by modern standards) gains mentioned above.
http://www.xjbikes.com/forums/threads/yikes-all-about-the-yics-system.14757/

There is benefit to using the blanking tool during carb synchronization, but it's a minuscule gain (mainly to engine smoothness and emissions) and not really necessary.
Fitz would point out that using the blanking tool during a synch all-but-eliminates that annoying buzz in the huevos that most XJs have at 4k RPM.

 

1979
http://www.yamaha-motor.com/corporate/historytimeline.aspx

 

better low and mid range power, peak power is not higher, lower emissions and increases fuel economy

 

excuse me while i get the worms back in the can

 

Oh man. This is what I meant when I said "for at least some people". There is still some disagreement in whether YICS does what it was advertised to do or not.
I don't intend to disable yics, at least not permanently.

I do have that 4k vibration, and I would like to get rid of it eventually, but you are saying that a unblocked sync should in fact be good enough for now? If that's the case then I'll relegate it to "when I feel like" instead of "when I can", because I figure if it's easy I may well do it, though I'm still not sure how I'd want to do it. I've heard some good things achieved with Marvel soaked teeshirts and even bare threaded rod of a close enough diameter. What is the diameter of that passage, anyway?

Riding home from work, I was able to get more of a feel for how the bike is running. It does hang up around 2k after having been moving for a while pretty consistently, and if I let it get close enough to 1k while I'm at a stop, it does seem to hesitate a little bit off of idle. Nothing like before, but it's there. I might need to check for more air leaks, though I really don't want to use Carb clean, given how it eats rubber and I don't want it damaging old boots or new throttle seals. Would WD-40 or something else work for testing for air leaks, something that won't have the same potential to do damage?

 

Unlit propane torch.

Gary H.

 

Not any informed disagreement. Lots of uninformed disagreement.

The 4k buzz never goes away entirely, but it can be minimized. You can put off the blocked synch to a date of "someday" without any concerns whatsoever.

 

The hang at 2k man...thats not bad enough to be an air leak IMO. You have not messed with the mixture screws at all in my understanding, and that is really a pretty critical error. Its easy to do and easily reversible. Just open them a bit, the idle hang will go away. Its a very slight hang, so a 1/4 turn or less ought to take care of it just fine. A little richer at idle, thats all. And it will solve the hesitation too.

 

Nope his carbs are nor fully synched ...all opening mixture screw will do is let a little more fuel in. This is what he is fighting now if you have 4 carbs and one is admitting a little more fuel than the other 3 hence hanging idle ( and yes eventually it may idle where you want it ,but when you open throttle it won't idle back down where it should quickly). He should have made double sure in his bench synch , and then done a running synch WITH some type of synch tool ( 4 vacuum gauge/2 bottle manometer) . Just my 2 cents or nickels worth .

 

I did use a two bottle setup for my running synch. I used polocks method for the bench sync, lining up the butterfly valves in reference to the pair of ports in the top of the carburetor throats. It's possible the sync is still a bit off, but I'm trying my best to chase that zero and get all of the cylinders agreeing with one another.
I do intend to do some work with the mixture screws, probably today, once I've bottomed them and figured out what they've been set to, we'll know if I can afford to loosen them more, if they're already past three turns out my understanding is that it's better to jet up or there's something wrong, shouldn't need to richen it that much with stock jets. Once I've bottomed them and gotten my baseline info I can even unscrew them and make sure I don't have any broken needles.

 

I'm not doubting your work ,just know from experience I had a hanging idle , ended up my synch was off . I have the 4 gauge vacuum gauge set up , had trouble getting #3 to play nice . The other 3 were pulling their own weight , but where the others pulled 5 hg #3 was about 1 hg . Pulled carbs ended up butterfly was not perfectly centered, loosed screws moved plate till it centered . I then used 2 business cards cut in half( so you have 1 piece per carb) put under the butterflys adjusted synch screws until I could not pull card stock out, then backed out screw until it slid with a slight drag. Put Carbs back on . After wards only had to do a slight turn on each screw now all measure 5 hg on my gauges , it idles at 1100rpm . This was my experience and my bike would not idle right before you could back knob out and it would not drop below 1500 rpm so it would not die ( no vacuum leaks either ) .

 

A stumble just off idle can be from carbs that are set just a bit too lean. When the plates open, extra air is introduced to the cylinder before the mixture can change.
This causes a stumble until the carb can catch up with the demand.
Solution, open the mixture screws a eighth of a turn.
Thank Rick o matic for that.

 

What, no thanks to me either? 1/8 turn or a 1/4 turn, either way- its lean at idle. And the simple fix is to richen it a hair, via the pilot screws. Don't get hung up on where they are set, just open them a bit until the bike runs right.

Right right, it may be a clue that something else is off if the screws are set to more than 2.5 turns out. Mine are set to 4.5 turns out, and it runs great. Idles smooth and even wherever I want it to, no hanging idle, no hesitation, no missing or popping, just smooth acceleration that makes my eyes water. Plugs look real nice. What more does one need?

 

Gentlemen. There are a lot of things that can cause a hanging idle. Let the man work through the suggestions offered instead of arguing over what the cause is.