I need enlightenment on CV carbs :: tuning...

I had resigned myself to finally fine tuning my carbs next riding season, but the last couple weeks here in Utah have been unseasonably warm.... Here is where I am at...

Cleaned carbs as per Rick's article. They were relatively clean, but now are spakly.

Checked float levels....all spot on.

Synced Carbs, replaced a leaking airbox boot, new plugs, and shortened a fuel line that i suspected was slowing my rate of fuel.

All pilot screws were set to 3 turns out (as a starting point)

Fuel filter is stock (I also have a higher flow Uni....more on this...)

So...my pilot screws are easily movable, so it is easy for me to set them. I pull off for a couple minutes, lift the tank, and i can use a bit to set them with my fingers. After setting them to 3 turns out, I went on a little ride. Idle was good, no stumble coming off idle. There was a pretty good stumble starting at 4k rpm.

Also, when idling, full choke would kill it.

So i figured it was too rich.

I slowly backed off the pilot screws a quarter turn at a time, til I was at 2.5 turns out. The stumble was still there, though not as bad, but the enrichment on full still killed it.

So i put in the Uni filter (that was on the bike when I got it.) and reset the pilot screws to 3 turns out. Enrichment doesn't kill it anymore, and it doesn't overheat. There is still the same hesitation at 4k to 5.5k. If i accelerate through it, there is not a problem above about 5k.

So my question about CV carbs.....they are operated by engine speed, not throttle position, right? If so, what is actually supplying fuel at around 4k. I'm figuring that at 4k it is off of idle and the needle is operating. I'm not sure what to adjust here.

To the plugs....

This is what is really weirding me out. After a 30 minute ride with the stock filter, with the pilot screws setting that kills the bike at idle with enrichment on (very rich). I pulled the plugs and the insulators are still bright white. They are brand new.... but they should change some color right? After seeing this, i took the bike, and ran at WOT for about 10 seconds, killed it and coasted to the road. Still the same.

I can't figure it out. By all indications, it is running rich, yet the plugs are saying extreme lean. There is a miss/boh/stumble at about 4-5k.

It is not overheating. It drops back to idle normally (no hanging) There are no signs of a lean mixture. Beside the 4-5k problem, the bike can be ridden for an hour with no change in symptoms. The temperature stays steady and it idles and cruises fine.

Today as I was adjusting the #1 idle screw, I'm pretty sure some fuel was leaking up as I turned it out. I'm wondering if that particular cylinder is leaking air in through the pilot screw. Even that still leaves some things unexplained though.

Ideas? Sorry for the long post....I just want to cover all of the symptoms.

Thanks in advance...

Kellen

 

sorry, I can;t help, but I'm interested to see the responses from people that can....

 

Don't think in FRACTIONS anymore.
Think in DEGREES

The Optimum Pilot Mixture Screw Setting is within 3 ~ 4 Degrees.
Go back to where you were Idling OK ... what was that ... ?? Three turns?

Lean the Mix Screws IN ... 2 or 3 Degrees.

A quarter turn is 90 - Degrees
An eight = 45 Degrees.

The right setting is going to be found within a "Window" of just a few degrees. The width of a Nickel. The Screw barely moves. But adjusting it this tiny amount is EASY because the Screw is Ultra-fine threaded.

Once you begin the process of FINE-tuning ... Read the Plugs and LISTEN to the engine.

The Plugs will tell you if you are too Rich or To Lean.

The engine will "Talk" to you while you are fine tuning.

Tune-out the the roughness. Mini-mini-tweaks.
Eventually you will find "The Sweet Spot"

Idling like an Atomic Clock.
Lean tweaked for rapid acceleration and dynamic engine braking ...
Or, ...
Rich tweaked for smooth acceleration and engine coasting.

The two extremes are within 3-Degrees.
Outside the 3-Degrees is:

Too Lean ... not a good place to be.
Potentially harmful overheating and Plug Damage.

Too Rich ... Bogging-out and No getting "Out of the hole".

Degrees.
Not Big Fractions!

 

RickCoMatic

The CARB WHISPERER...

 

First let's go back to the start and rethink. You cleaned the carbs and reset the mixture screws to a general setting. So you don't know if they are rich or lean. The only indication that it is rich is the application of choke. Which is not an indication of richness. My well tuned bike will die with choke on when idling. I have to open it slowly and even goose the throttle to keep it running at first. The plugs show lean. The stumble sounds like a lean stumble if it happens at the first opening of the throttle. So I would bet that a colortune plug would show you lean on one or more carbs.
The carbs are running on both idle jet and main jet at 4k. So it is the transition from idle to main circuit that is the problem. Since the main jet and needle are fixed, this makes the pilot mixture screw the varible along with sync. Float height is good, so not suspect. If you haven't rejetted for the uni filter then it could cause a lean condition at WOT. Remember at WOT you are on the main jet alone. So the plugs will tell you nothing about idle to main transition. So using the stock filter is best, while doing the plug chop at about 4.5k.
The idle circuit needs to be set in order to proceed. There are only two tools that can set it, a colortune plug or exhaust gas analyzer. Other than that you have to guess it by ear. Rick can help with that but personally I don't believe in that method. I believe in using the colortune with a YICS tool. I prefer doing this along with a vacuum sync tool like the Carbtune II so I can set both at the same time. Which is what I do at carb clinics because sync affects mixture and mixture affects sync. You did sync the carbs but did so with the mixture not dialed in. So that could be contributing to the problem. Since you don' t have a colortune then you need to determine whether the carbs are lean or rich by other methods. Plugs and throttle response are the primary means. With CV carbs there is no fuel pump on the carb as with autos. So when you open the throttle you open the butterflies and let air in first. This reduces pressure and pulls fuel into the air stream. If the fuel is lean then not enough fuel gets there initially and the engine stumbles. If the fuel is set rich then the air leans things back down initially and if it does so enough the bike will pick up instead of stumble and run better until the mixture evens back out.
So open the throttle a bit and get a stumble, means lean. Open the throttle a bit and get a surge, means rich. Plugs will help confirm. Think in degrees like Rick said and let us know what worked and what didn't.
For those who are strapped for funds and can't affort the $60 for a colortune there is a cheat. You can buy just the colortune plug for about $36 USD. All you get is the plug. No wire to attach it to the plug lead and no tube for easier viewing. Most can fabricate a jumper wire to the plug lead and the periscope tube is not necessary. The plug alone can be used in your garage at "night" which will make the flame much easier to see. I actually prefer to do my bike like this.

 

cool...i'll look for one of those colortunes.

From idle to throttle on there is no stumble. If i accelerate slowly and never get the engine speed above 4k (which is hard) there is no stumble whatsover. Same above 5k. If i'm really accelerating and never dip below 5 (again, hard) it is perfect.

When engine braking there is no pop. I will put the stock air filter back in though, I just put in the UNI filter to see if it solved the richness problem. I wasn't aware that the choke could kill a properly tuned bike.

My main question about the CV carbs was answered...thanks.

I've had the bike extremely lean before, and know how it responds, smells, and heats up, etc. It is not doing that now. It is running pretty happily, I would just like to fix the little stumble it has so that I can for once ride a fully tuned bike (or at least where it operates somewhat normally.) I'm gonna look for one of those colortunes right now, seeing as that will solve my problem without resorting to subjective methods.

Thanks for your help.

 

Sounds like im gonna have fun this week... valve's then carb synch, then colortune for mixture, synch then mixture, ect... With Ricks method (I think Ricks... have to check on that) of the single vacume gauge carb synch... This will be a first for me, so wish me luck! (probably need plenty...)

 

A word about Colortuning:

ColorTuning is a Shortcut. It's a great Visual reference to where there is a well-balanced Air-Fuel Mixture.

You can bring-in the Colortune "Lean" if your Mixture Screws are set Lean and you bring it out to Blue.

The Blue ... or, "First Blue" comes in (or at least it did on my Bike) ... Lean.

The trick is to add a few degrees to the Blue and GO PAST the Blue on the Lean Side ... and, ... Come BACK for the Blue on the Rich Side.

Utilizing the ColorTune Plug will then have you exceptionally close to the "Window" I have eluded to in other Posts.

Visualize the Tip of the Mixture Screw. It's a Pin Head. Visualize the Threads of the Mixture Screw. They are Ultra-Fine Threads.

Once you get the Bike -- ColorTuned -- and the Mixture Screws in a position where you have a good Idle ... you must abandon your thinking that the Carbs are all too be adjusted the SAME.

NOW, you have to treat EACH Carb individually. You are Tweaking SINGLE Carbs.

Work-out the Idle for it's Maximum smoothness. Do NOT make more than ONE adjustment at a time.

Error on the RICH Side. See how #-1 handles a couple of degrees of Richness.
If the Idle INCREASES slow it down with the Idle Adjustment Rod.

You WANT the Bike to Idle with as little assist from the Idle Rod as Possible.

Chart what you do so that you can do a GO-Back.

Simple notation will keep you from getting messed up.
1) +2
2) +3
3) +1
4 -0-

When you have it so that the Bike Idles real smoothly and accelerates ~> Immediately upon opening the Throttles <~

Thats HOME.
The degrees are reset to Zero ... and PLUG READS determine what you will do next.

Plug a little too Dark ...
(Example
3 is a bit too dark and running rich.
3) -2

KNOW right where you are and it wont be too long before you are looking at a set of Plugs that are indicating that you can't tune that engine any better if you wanted too.

Twilight Zone.
Tweaker's Heaven.

+2 Across the Board ... Smooth Crusing and Coasting
-0- Midrange Tuned. Best of both Worlds.
-2 Sport Tuned. Heavy acceleration and Engine Braking. (My favorite!)

Go get some.
You got pllenty of time between now and Easter to nail it!

 

Rick, I must admit I get confused. Not a rare state.

Turning the pilot screw -out- (lefty, loosy) makes it more rich? Turning it to the right (righty, tighty) makes it lean?

Correct?

 

Righty; Leany ... right.

I think my way of expressing it was the confusion factor.

Sorry about that.

 

i've looked all over for that cheaper colortune and I can find it no-where. Where available. I looked for about a half hour online last night. Is there a parts store that carries these? Also, I need a 12mm colortune for a 550 right? Its a D8EA NGK plug stock.

I eliminated one possible problem today by plugging the pilot screw ports with some silicone ear plugs (for swimming. air tight seal, and comes out without residue.) There was no change in performance, so I know I don't have an air leak through the pilot screw o-rings. I think its more fine tuning the mixture. I need a colortune, hope i can locate one soon.

I live in Utah, and its supposed to be colder right now, but it will be in the 50's through next week. I had my bike in storage already to start winter projects, but this weather is amazing, so i'm putting a few more miles on her, and trying to tweak the carbs a bit. With some luck, I can put the bike in hibernation mode while i work on some cosmetics, and come back in the spring without having to do much work to just get out and ride.

thanks for the help thus far. if anyone knows where to get that stripped down colortune let me know.

kellen

 

Chacal has the Colortune you need Kellen, at a reasonable price (less than other stores). I think your right about the 12mm (I'm not a 550 type).

 

I carry them!


j5) Morgan Colortune Tuning Spark Plug ....brand new, no display box, includes all accessories and instructions. If you really want to tune your multi-carbs to perfection, you'll have to use this unique "see-through" spark plug that allows you to view the combustion chamber flame color in real-time, thus allowing accurate (rather than guesswork) adjustments to your idle mixture screws. Use it once and you won't believe how you ever got by without it, and will pity those who don't have one of their own. Beware: you'll find that a lot of people now want to be your "friend" and have you come and tune on their bikes, once they find out you have a Colortune!


NOTE: 12mm plugs are used on all XJ550 and XJ700-X models.
14mm plugs are used on all XJ650/XJ700 non-X/XJ750/XJ900/XJ1100 models. No XJ bikes from this era used 10mm plugs!


HCP95A Morgan Colortune Spark Plug Tool, for 10mm spark plugs:
NOTE: NGK plugs that begin with the letter "C" are 10mm. No XJ-series bikes from this era used 10mm plugs!
$ 49.00

HCP95B Morgan Colortune Spark Plug Tool, for 12mm spark plugs:
NOTE: NGK plugs that begin with the letter "D" are 12mm, and are used on all XJ550 models and all XJ700 "X" model bikes.
$ 49.00

HCP95C Morgan Colortune Spark Plug Tool, for 14mm spark plugs:
NOTE: NGK plugs that begin with the letter "B" are 14mm, and are used on all XJ650, XJ700 non-X models, and all XJ750/900/1100 models.
$ 47.00


You can see my ad over at:

http://www.xjbikes.com/Forums/viewtopic ... t=120.html

 

The ColorTune Plug Kit is worth every penny of the cost in saving you plenty of time bringing-in the Pilot Mixtures to where you need them to be for fine tuning.

In some cases, the ColorTune Plug will have you right on the money and you need not have to further play with the Mixtures.

Others will use the ColorTune to get within the window of Ultra-fine Tuning and further adjust the Mixes after Reading the Plugs a few times.

Either way, the quess-work is eliminated and the Mixtures are going to be where you need to have them for an enjoyable experience having the Bike tuned to near perfection.

 

Hey Rick, that was very funny about Easter.... I am in So Cal and use my bike for commute to work 4 days a week. I have two days to fab a single vacume gauge tool restriction valve, do the valves and the synch ect before I go to work on Friday. First time with all, bet I finish it all in 1! (At least if the used parts store has some shims, pretty sure they do..)

 

http://www.ekmpowershop.com/ekmps/shops ... ne-8-c.asp
This is what I was refering to. Go there and you will see that once you include shipping, Chacal has the better deal.

 

Here's a free idea-- someone make a kit to replace the pilot jet
with 4 new ones. Then just drill out the old ones and clean the
passages, and press in the new ones. Kit includes the sweet stainless
drain screws and gaskets. Send me a kit for the idea, I'm waiting.

 

Don't let the Cam pop-out of the bearing if you have to lift the Cam to get to a Shim that needs to be exchanged. The Tensioner is just waiting to gobble-up the slack if it does.

If the Tensioner Auto-takes-up the slack ... you have to remove the tensioner to reset it. Not a fun job to do. You may have to make a gasket and remove the Carbs if it does get away on you.

I have the Factory Shim Bucket Tool for 750 & 900. It doesn't work on 750 Max's. I had to lift the Cams to do my Shims. One of the Cams rolled toward the middle and the Tensioner moved out.

There was no way to get the Cam back in place without removing the Tensioner.
And, that little slip cost me 4 Hours of extra work because I got careless and let the Cam move on me.

 

Not only do I have a better deal with shipping, even without the shipping I'm still far cheaper. Remember, those units at ekmpowershop are priced in British Pounds, and current exchange rate is about $2.08 pounds for a dollar, so their US price on a colortune is $ 72.80 and then you add shipping, too.

I'm holding tight at $49.00 US plus shipping.....

*****************

Rick, I'm confused as to why the shim tool won't work on the 750's? I've used them on 550 and 650 engines before with no problem....should be the same on 750 and 900 models????

BTW, I stock the cam tensioner case-to-block gasket, no need to make your own! But hope you don't ever need to replace it, like you say it's a time-consuming job to replace that little sucker!

 

I'm getting ready to use the shim tool ha ha ha, hopefully with a little more luck than Rick, otherwise I will be stuck in my car this week... Now I am a little bit nervous doing the valves lol!

 

The "Reach" for the stem on the tool that holds down the Bucket is a few mm's longer on the 750.

The tool will hold down the Bucket ... but, there isn't enough room to get the Shim out.

It don't miss by much. I had considered altering the tool. But, then I abandoned the idea of machining the tool for lifting the Cams out of the way.

The Outside edge of the head is just a little bit higher ... me thinks!

 

hmm.. you can always use the doubled-up zip tie trick... worked like a charm for me, with no risk of damaging the valve or the head.

 

Thanks for the info......do you remember who you got the tool from? I think there are 2 different manufacturers of it (besides the Yamaha OEM tool) and perhaps one versions isn't quite right.........

 

I think mine's "Motion-Pro"

And, ... I tried it every which way on that 750 and couldn't get enough room to extract the Shim.
It held down the Bucket; fine.
Just not far enough!