Adj Pilot Screws vs Synch

Which one is done first......

Does one adjust all pilot screws first with Colortube plug & then the synch is done afterwards ??????

or Vice Versa....... & explanation please as to why if possible......

Sorry if this is a dumb question or has been answered previously......

It will be my first time adjusting the pilot screws & synching with Morgan Carbtune Pro......

Last time, about 7 years ago, it was done by the Yamaha stealership........

Thanks in Advance.....

 

The proper procedure would be to first perform a running synch on the engine, and then do an iterative process of:

Step zero: check and adjust valve clearances.
Step 1: clean the carbs
Step 3: bench synch carbs
Step 4:
a) colortune cylinder #1
b) re-synch the engine
c) colortune cylinder #2
d) re-synch the engine
e) colortune cylinder #3
f) re-synch the engine
g) colortune cylinder #4
h) re-synch the engine

and then, start at Step 4a again and do a second go-round.


Changing the pilot screw settings (when using the colortune) will change the engine synch, since your just-adjusted cylinder now produces more or less power than it did before the adjustment....and that throws off the engine synch. So that's why you should re-synch after each cylinder adjustment.

 

Thanks for the explanation....makes perfect sense.....

valves have been adjusted, carbs have been cleaned & rebuilt, bench synch has been performed......

Looking forward to next weekend for the intial startup & colortune & synch....

Thanks Chacal for your concise explanation.....

 

Chacal, so you can leave the sync tool connected the whole time right?

 

You can leave the gauges hooked up the entire time during the procedure, just don't forget to set the petcock to PRime position.

For engines with YICS, you should keep the blanking tool in the YICS chamber, and as long as you work quickly, do it all in one shot. However. I wouldn't leave the port blanking tool in the ppassage for over 10 minutes at a time, as you run the risk of melting the seals.

If it takes longer. shut off the engine and extract the tool and allow it a few minutes to cool down, re-insert and pick-up where you left off.

 

I found a good rhytm, I think - after having experienced a "seal-meltdown" (probably helped by the fact that I forgot to lock the tool with the flip-lever - couldn´t understand the odd behaviour of the idle and sync... :roll:

2 out of 3 seals were shot and one left a bit of silicone in the YICS-cahannel, no problem getting it out though, when the engine cooled down.

So now - at least like now with temps above 25C - I shut off the engine and removed the tool while I was reinstalling the colortuneplug to a new cylinder. That also gave me time to verify my newly adjusted pilot screw settings (turns out from bottoming).

Less stressful this way, I think.

 

Chacal,

Your instructions that come with YICS blanking tool that you sell indicates if the engine synch lasts for more than a few minutes, to remove the tool & let engine cool down.....

But above you indicate about 10 minutes......

Is a few minutes the norm or just a conservative number.......so 10 minutes would be max ??????

Would hate to melt these new seals on this tool I bought from you.....lol

 

Well, it depends on how hot the engine is, what the ambient temp. outside is, whether you have a cooling fan blowing on the engine, etc.....

The seals we use are rated for about 400-F, and cylinder jugs tend to be the hottest parts of the entire engine.

So 10 minutes would be the maximum I would leave it in, under ideal conditions.


How Hot is Hot?:

The following information was measured on a stock, un-modified XJ650 YICS engine, with the air temperature between 60- to 70-F. Modified engines, engine tune conditions, different air temperatures and humidity levels, etc. will affect these readings up or down.

Using our HCP9959 Digital Infrared Heat Thermometer, we verify that the cylinders and the valve cover are the hottest part of the engine, with the front of the cylinder jugs (exhaust port side) reaching almost 390-F during and immediately after spirited riding, while the intake side of the cylinders were consistently 50-degrees cooler (350-F). Cylinder heads, surprisingly, remain much cooler, just barely breaking the 280-F mark.

Engine upper case and engine side covers vary in their readings depending on which cover and where on the engine case the reading is taken, but in all cases are substantially cooler than the cylinder head, valvecover, or jugs.

Brake rotors were measured at 300-F or more after 10 consecutive maximum-force braking events from 50mph. Calipers were approximately 50-F cooler.

Rear final drive units are like refrigerators, and were never measured at over 140-F.

 

Thanks for the clarification.....

 

I don't think it's necessary to go-over and over Colortuning to get the Bike Tuned.

Colortuning ONLY get you into the Ball Park ... faster than tuning by ear or settling for something close to a factory Preset"

Once you Colortune for IDLE ... Colortuning is Over.

Once you get the Bike to IDLE ... you adjust the Idle for the rpm's that you will Vacuum Sync too and get the Rack balanced across the board.

When the Carb are Synchronized ... you are done with the YICS Tool.
You are also done with the Colortune Plug.

The "Fine Tuning" is going to get done the way the Bike is run.
No YICS Tool.
No Colortune Plug.

You treat each hole independently and Enrich or Lean-Out each Hole according to how the Mixture is colorizing the Spark Plugs.

If you were diligent and Colortuned to the "Back-side" of the Blue; you won't have much to do but Tweak the Mixtures to get the ones too Lean a bit more fuel and the ones too dark; less.

 

You're both right; chacal is pointing out that with every cylinder that has been colortuned you throw the sync off a tad so it pays to resync after colotuning each cylinder; you CAN just colortune all 4 and then go back and touch up the vac sync (the lazy Fitz method) but chacal's method as outlined is more precise.

All that being said, as Rick points out, once colortuned and final vac sync is done, the rest of the tweaking comes from riding the bike and reading the plugs.

I'm saving up for a modern, easy to use EGA.

 

EGA ?????

Acronym for ??????

 

E-xhaust
G-as
A-nalizer

The 4 Hex Bolts at the bottom of most Yamaha's Late-70's `thru the Mid-80's Exhaust Header Pipes were access ports for probes to an EGA Machine. The EGA Machines were Yamaha'a until Yamaha got sick and tired of servicing and calibrating the damn things so they gave the EGA Machines to the Dealerships.

At one place I know of ... it was there on Friday and gone on Monday. Nobody knew nothing about where it went.

 

Yep. The way Yamaha wanted the bikes to be adusted, to make the EPA happy (lean.) But the only TRUE way to read the combustion mixture at idle AND at 5000rpm (as specified in the Yamaha EGA manual.) Colortune gives us a visual approximation; and it's the best we can do.

Rick is right; unfortunately, back in the early '80s the EGA was in its infancy and DID NOT WORK the least bit correctly unless continually calibrated and operated by a qualified (and patient) operator. Which is why they got shoved in the corner to collect dust (or "disappeared.")

I wanna nice new spiffy digital EGA that works better than 1980 ever dreamed for 1/8 the price. Until then, I Colortune.

 

I was wondering what those 4 hex bolts were for at the bottom of the exhaust header pipes....

Thanks Rick.....

 

Mine were seized.
I drilled 'em out and went to the next size.

Every now and then I pull those guys and run-around sounding like a Ferrari.
They rumble nice when you engine brake.