Idle Frustrations

Ok...almost feel beatin down over this bike and I've never struggled so much be it bike or car...just seems hard to figure it out.

First what's been done, carbs house of clean preformed, throttle shaft seals replaced, float levels set and double checked..if its off by 1mm I'd accept that..but still just does not add up.

Idles fine when holding throttle but using the idle adustment either a has almost no effect, or will put the idle at 4k then back down a quarter at a time will eventually just drop all the way down to nothing and die.

had it at idle at one point so synced em and was doing good...color tuned still a bit off, but very close.

New plugs gapped right, no air leaks found, running stock airbox. Even road this weekend, good throttle ressponse..got back running good...then tried to run again this am and wouldn't idle after warm up. just at a stand still now. any insight?? Really hitting a wall with this project.

 

Try setting all your mixture screws 2 1/2 turns out from seated...I had a different problem...all my plugs were different colors and now they are all perfect. Don't know if it will fix your problem but its worth a try.

Good Luck!

 

Sounds like it might need a valve adjustment, or it's still a sync issue (or both, since out of spec valves will throw off your vac sync.)

What method are you using to vacuum sync the carbs?

 

Using a 4 vac sync setup, adjustable restrictors for a perfect view...plan right now is to take a look at the valves, had planned on doing so, just kind of suprised me it would have this kind of an effect on a motor with 15k on it...I realize they need to be checked and could be a bit off, but I assumed it would throw this big of a monkey wrench in things.

Guess I have to stay after it, but man I have to admit this project has pushed my normally great patience to its limits...I should have long been moving on to paint and fender mock up, but such is life...it was easy anyone could do it.


Had the idle screws set at 2.5 turns, but seemed to like being set at 3.5 which is closer to where they were from the factory.

 

SAVED by the bell! Hopefully anyway.

On the airheads, the original valve adjustment was to have been done at 3000 miles. Most owners ran the warranty period out time-wise long before they put 3K on the bike, so they didn't take it back to the dealer for an expensive procedure they didn't see a need for.

Adjustment interval is every 5000 miles after the initial 3000. As the bike changed hands, as long as it was running "ok" nobody ever bothered. How many miles have you added?

At 15K you are getting right to the point where if the valves have never been touched, you've got one or two that are critical (if you haven't burned one yet.)

I got my '83 with 7100 miles on it, valves untouched (thankfully.) Never done, not at 3000, never. Seven of the eight were tight, two getting critical. 7100 miles.

If yours have never been touched, you're 12K overdue. If they were done at 3000 like they should have been, you're only 7000 OVERdue.

So yes, it can and will have a major effect. And you'll need to re-sync after you adjust them.

Don't put it off any longer, you're jeopardizing your motor.

 

Is there a shim set to buy?

How long does it take to shim them in?

 

set the idle after it's good and warm, at least 10 min of riding, then when it's cold use the "choke" till it warms up

 

You generally do valve adjustments in two steps: Teardown, measure, order shims; replace shims. Kind of hard to buy a "set" without going broke.

How long does it take? A couple hours, total once you've done it a couple times.

Read: http://xjbikes.com/Forums/viewtopic/t=14827.html

And: http://xjbikes.com/Forums/viewtopic/t=29209.html

 

Hi. I've had the same problem with idling speed - I think most of us have, I think it's a symptom of this engine.

When adjusting the little wheel a quarter-turn at a time, allow a couple of seconds for your adjustment to take effect... I think there's some kind of built-in delay, or there seems to be.

Also check your mixtures (using the plug colour to judge). from the standard 2 and a half turns out.

After lumpy idling issues with mine, I adjusted one screw in a quarter turn and another in a half turn (one partially sooty and one sooty plug).

After doing that the bike seems to start up and idle more cleanly (time will tell).

PS. I re-shimmed my motor last year. If you're lucky some might swap positions, otherwise genuine Yamaha ones worked out around £8 each. Do them all at once - and you will need the shim tool.

PPS. I met a guy at a bike show last year who had owned his XJ from new. At 50-odd thousand miles he reckoned he'd never even lifted the cam cover, let alone changed any shims. It was still running.

With shims, the thing is that due to wear making things thinner rather than thicker, you're unlikely to get a valve not seating properly. The only problem you'd find would be a minute difference in valve opening/closing time (ie: less duration) which would be a problem if really slack.

Nige

 

Except that's incorrect, sorry. The shims and cams don't wear appreciably; that's not why regular checking and adjusting is needed.

What happens is the valves pound themselves into their seats, so as things wear, they tighten up, not get looser.

Once a valve gets to the point of being "dead" tight when cold, it won't seat properly once the motor is warmed up, and you end up burning a valve.

 

Go to your local bike shop with the shims you need to replace and 9 times out of 10 they will swap them for the ones you need for free.

The shop I go to said they haven't had anyone come in for the shims required for our bikes in a long time...hence them swapping with a smile!

 

I'll bow to your experience on that one Fitz..., though I'd have thought that valve-stem ends, both sides of the shim and the cam lobes would wear thinner too? I just know you're going to tell me that they are hardened to minimise wear.

Nige

 

Yep.

The "wear points" in the valve train are the valves themselves and the valve seats. So, as they wear, the valve clearances tighten up, counter-intuitive to what you'd assume.

Which is why checking clearances regularly is so important. As the clearances tighten, the valves are held open longer than they should be, decreasing compression, and eventually failing to seat fully; and that's when you burn a valve.

It really does work that way, too. I had one "getting quite close" valve the first time I did my '81; the next time I did the check, it had tightened beyond spec.

When I adjusted the clearances in my '83 for the first time at 7100 miles, seven of eight were tight. I'm interested to see where we are at the second check, at 12K.

One thing to note: This "pounding in" process seems to taper off as the motor ages; by that I mean once they've been through a couple of adjustments, they seem to "hold" for longer and longer. Once again, stressing the importance of the initial and follow-up checks, at 3000 and 5000 miles. You will find that fewer and fewer need actual adjusting with each subsequent check; but they have to be checked as specified or you're taking chances with the motor.

 

Check again for vacuum leaks. Take a can of carb cleaner and just start spraying around while the bike is running. If the RPM rises after you spray, then you found a vacuum leak. Spray the couplers between the carb and motor, spray the block, spray by the plugs, any head bolts, etc. I had a very similar problem and it turned out to be a vacuum leak.

 

:lol: Now Im looking forward to doing the shim work!

 

I think you have better local bike shops than I do. We have two big ones here in Colorado Springs. One sometimes will have a needed size shim in stock - better chances with the 13mm ones than the 29mm ones Yamaha uses. Even so, at least half the time they have to order it.

The other shop is very proud of the fact that they stock NOTHING for any bike older than 10 years. Since all the newer bikes use 9mm or so shims, that's all they stock.

The little shops don't stock much in the way of these kinds of parts, except one smaller one that's good for some used parts, some generic parts, and a lot of Harley parts.... still don't recall having much luck with shims there.

I got mine from Len.

 

I guess I am lucky then.

 

These bikes are not the only ones that use that size shim

 

I know that, and I didn't say they were. I didn't mean to confuse anyone on that. However, I still had better luck finding the 13mm ones my GPz uses in stock (at least used) than I did the 29mm ones the Seca uses.

But again, different shops, different cities (Colorado Springs is relatively small), different results.

I don't know how common it is to have a place like this (Rocky Mountain Cycle Plaza) that won't carry parts for or work on anything older than 10 years. (I forgot to mention before that they flat out will not work on old bikes.)

The other big place, Apex Sports, will work on older bikes, but only in the off season. In the summer they won't touch them. Period.

 

It is very common that bike shops wont work on the older bikes or stock the parts for them actually it is very rare that a shop will even touch one of these and to tell you the truth I do not really want anyone else touching any of my rides that includes my cars too

 

r u snapping the throttle after each carb adjustment.

cuz if you just adjust and leave it alone. the sync isn't getting done properly.

i did my ninja 5 times before i tried that method. adjust. throttle snap. adjust. throttle snap again.

before i was just adjusting. and calling it good. but the idle never worked right. by snapping the throttle you can see the sync go out again. usually takes a couple of adjustments before you can snap the throttle and have it come back to sync. then you've got a perfect sync.

now, i make adjustment and do throttle snap after each adjustment. no problems since.

perfect idle every time.

 

Thanks as always for the advice and idea's...I've gone over the bike I don't think its a air leak..so I will go after the valves and see where things are at...makes the most logically sense to me as I'm sure its not been done..have no history on the bike, but still nothing else has shown signs of being touched so I'll go that route then see where things lead me.

 

Post results after you check them for discussions sake.

Keep in mind that you will need to do a vacuum sync afterward.

 

As promised my follow up.

Valve adjustment turned up to have one intake with zero clerence and an exhaust well out as well...so popped the shims went down to the yama dealer and they were happy to do a swap...btw without a swap they were 25 each!.

So that all went well...bike ran bettter but still have my problems, so it was back to the bench with the carbs..thought about it and only float levels were to be rechecked...low and behold I found my problem.

Technique is often a factor in working on thing I find and this is what bit me in the butt more than once. When I was setting and checking I would turn on the fuel to fill the bowls then when I saw the flow stop I would shut down the flow....wow big big mistake.

What I figured out is the bowls will fill and stop..then after waiting about 30 seconds they would settle and take a little more in...so I was getting false readings.

In the end I learned just how damn hard it is to get these set right on spec...took about 12 tries per carb...must be me and my big ham hands the just kept going over
then under, but patience and a gallon of fuel won out and the bike ran like a dream...sync perfect..all blue on the colortune...nice idle and great response!

So this morning I got up to find fuel dripping out...not sure what's up but I am using the kickstand not the center so maybe one isn't perfect..not sure what's up but
know I've still got something wrong!!! This machine has pushed my limits with being so particular...but I will find out what's going on and resolve it.

 

No leak when the selector on normal...not sure whats up with this. bike won't leak when level guess I just need to keep the petcok set to norm and it should be fine..going to see if the crank got fillted up just in case its levels still bitting me.

 

Sounds like one or more float needles don't like to work properly when the bike is on the sidestand, or you have a float binding.

With your fuel lever set to "ON" there should be no (new) fuel flow when the motor isn't running, just what's in the bowls.

 

From what you are saying, I understand that with the selector in the run position there is no leak. The selector has three positions, Run where fuel flows when the engine is running due to vacuum, Reserve for when you run low, and prime. The only time you need to prime is in the event the tank was empty or you drained the carbs. If there is no leak in the run position, no problem. The only time I ever change the position is when I run low on fuel.

 

I FEEL your pain BRO. I have countless hours on my buddies, xj700x
I had to replace one carb (float stand broken) and repair the 2 outside carbs bodies . the were dropped or something and small pieces were broken causing air leaks due to shaft seals to be exposed..that was and easy repair part of it.
i pulled all the butterflies apart and replaced all the o rings. Thanks Mike for the carb body, screws, and O rings. there will be a a little something special in your X Mas stocking this year. ;-}.
after all this I put the rack back in the bike. it fired right up! I re synced the carbs and #%())%%#@! same problem. won't Idle when warm #&^%)%&!!!!
the only saving grace here is that i have determined by reading posts that it is "The Valve's" that are the cause of all this.
Now I'm gonna load the bike on a trailer and take it back to buddy with the names and #'s of 2 good local mech's who he can Pay! to adjust the valves.
thanks for all the help
LB

 

Two things I've found that might help.

1, polish the float pins just as you would the throttle body's on
the carbs. Makes a world of diff in how the float valve operates.

2, on m 700, once tuned you only need to barely turn the idle adj
screw to make a change. Just like Rick suggests wih the pilot screws.
Very small change in settings is all thats needed most of the time.

 

Once you have the Pilot Mixture Screw close to where it needs to be for Ideal Idle and Off-Idle Tuning, ... Further adjustments to Precisely FINE-TUNE the Pilot Mixture, ...
(From
|<--Too Lean<>Performance Lean<>Normal<>Slight Rich<>Too Rich-->|
Will be a matter of Adjusting the Pilot Mixture Screw VERY SLIGHTLY.

Picture the Sweep Hand on a Stop Watch.
One Revolution - One Turn = 60 Seconds.

Once you get the Pilot Mixture Optimally Set, ... the further adjustment to Perfectly Tuned will involve moving the Mixture Screw within 0 -to- 10 seconds.
(That's less than the Width of 2-Dimes)

<><><><><><><><>

ColorTuning:

The IDEAL Color for having the Bike IDLE is:
Bunsen Burner Blue.

Bunsen Burner Blue --> IS NOT the IDEAL MIXTURE for Tuning.

The Blue is an Ideal Air~Fuel Ratio for Idle.
You NEED the IDLE MIXTURE slightly RICH.

You have to make the Idle Mixture Rich enough to support the INSTANT that you move the Throttles ==>> OFF IDLE.

When you Transition from IDLE to OFF IDLE. (i.e. Getting out of the hole.)
You NEED "Supplementary Richness"
Enough to SUSTAIN COMBUSTION for the RUSH of Intake AIR that will NEED Fuel which precedes the MAIN Jet Supply.

The DURATION is Short.
6 -or- 8 "Rapid-Eye-Blinks"

Too Lean and you Hesitate.
Too Rich and you'll Bogg-Out.

 

Rick, would you mind expanding on this topic, I respect your opinion and insight.

I had a bit more time with the bike now, I do notice some slight hesitation and not everytime, I'm use to working with fuel injection bikes and carbs on my old cars, its almost like I'm really close but still I know it can be better.

I've noticed the hesitation primarily after a longer idle time...kind of feels more like loading up....couple of blips seems to clear and then I don't notice it..but still wondering about that perfect tune.

So at idle I was at blue with 2.5 turns, so I turned out till I saw a bit of orange...then backed off until she went blue. Just seems right to me that way...but I'm still learning after all these years.

Rick your talking about the transitional tune...so I'd like to hear more on how your going about that part...if you wouldnt mind sir.

 

Oh and yes no leaks at all when in the normal run position, so that's all good. I am happy to report she's all clear...started doing some cutting yesterday...so at least now I can move on to body and paint. as I continue working towards a completed project.

Thanks again for everyone's input. Hey and for the record...do your own valve adjustment...its way easier than getting the carbs right....and it took the popping I had right out. Just think what a zero clearance valve is doing, its a short amount of time that not only needs to be done, but could save you a bunch of money...the only thing I paid for was the tool..the rest was just time...and not that much of that.

 

The Pilot Mixture Screw.

The Pilot Mixture Screw is an AIR Metering Needle jet.
When AIR flows into the Carb, Metered by that Screw, it brings-along FUEL, ... because the Passages meet.

The Pilot Mixture. AIR and FUEL enter the Carb from inside the Throttle Plate.
The Factory Pre-set for these AIR Screws was 2.5 turns Out.
The 2.5 Turns satisfied California EPA, where the Bikes came ashore.
Most dealers added, ... just short of another 1/4 Turn and Re-plugged them.

The YAHAHA EGA Machines, made to aid Fine Tuning, broke-down and the process was done, ... "By EAR"
Still in use.
By those places that WILL service the Bike.

Find the Fastest Idle using the least Throttles or none.
Let the Idle rise as the SCREW is turned OUT
Continue until the Idle NO LONGER quickens.
+> This Point is IDLE.
>>(||)<< IDLE
Remember this spot.
Continue until the Cylinder BEGINS to MISS because the Mixture is too Rich.
>>(|| + X = Miss)<<

Turn IN -- 1/2 the distance between (||) and (||X) = Pre-set.

Fine Tune as needed depending upon Plug Color for Individual Cylinders.

Along comes ColorTune to help find the Sweet Spot.

Coloortune finds IDLE (||) ... Right on the nose.
IDLE!

You need to TUNE for what happens at the INSTANT the Bike is TRANSITIONED.

From IDLE -to- GO.

If you ColorTune ... BLUE.
You get enough Gas in the Air to let the Bike IDLE.
Not enough to GO.

The surge of fresh air brought-in at the INSTANT the Throttles Open needs that extra bit of Fuel.

 

Thanks Rick, I think you confirmed my setup technique and now I have no complaints about the response...its as snappy as could be. Thanks for sharing the info and insights.

Now off to beat a fender into submission

 

I'm awaiting my colortune plug from Len now. This information will be very helpful. Thanks for the insight.

 

Hey Rick; the BLUE you mention, is it by any chance the BUNSEN BLUE people seem to be so hung up in?

N'er mind, I just read page two and noticed we're indeed talking about Bunsen Blue....