Colortune - How to ?

I have a question... Can one of the techs make a "how to" with pics the next time you colortune and sync up your bike? I'm curious how this works.. I'm not that fluent in some of the terminology for certain parts of the carbs and engine... so if you can break it down "barney style" and maybe take a video or walk us noobs through it... that would be awesome!! :lol:

 

Grainy video, poor audio, no commentary, but better than nothing!:

http://www.gadgetjq.com/ctune.htm

 

I can follow everything up to the adjustment.. i don't know what screw to turn or what... it don't show how or where to make adjustments.. just that blue is good

 

You use it to adjust the mixture at idle with the idle mixture screw so there isn't much to see and not a lot to know about using it. Turn the screw in or out to get the correct blue color then go on the the next cylinder. I don't recommend trying the Poor Man's Dyno since it's dangerous and the engine doesn't run that well with a Colortune in place of a spark plug anyway.

 

Dustball... top of the carbs on the air intake side is a small screw or a plate covering the small brass screw... This is you mixture at idle screw

 

Actually....it's on the cylinder head "side" of the carbs (towards the front of the bike) and there is a lone cast passage that terminates in the very top, front, centerline of each carb.....that's where the idle mixture screw lives.

As Alive points out, it may be covered by a small (1/4" diameter) brass or aluminum flush-at-the-top-edge-of-that-passage disc that is an "anti-tamper" cap, so that the average Joe or Jane wouldn't go trying to adjust the idle mixture screw way back in the days when the bikes were new, and Federal emission regs needed to be met, and Yamaha was scared that they would be sued by the EPA is they made it too easy to allow said average Joe/Jane to reach that mixture screw.

The cap, if in place, needs to be removed, which is normally done by drilling a tiny hole in it VERY CAREFULLY and then prying it out. If you puncture the cap with the drill bit fully, just remember that the head of the idle mixture screw is DIRECTLY below the bottom of that cap.

All of which means that you have to remove the carbs from the bike to be able to drill out those caps if they are still in place.

And once they're out, you'll need to replace the idle mixture screw O-Rings, Washers, and probably the Springs, too (and the screws, if their heads get messed up during drilling or removal).

 

Each of the four Carbs has a Pilot Mixture Screw either visible or hidden below an Anti-tamper Plug on the top of the Carb ... to the right of the Enrichment Valve, right next to the Pillar Post that the Enrichment Circuit Operating Rod is contained.

The Pilot Mixture Screw regulates how much AIR is allowed to enter the Combustion Chamber with the Throttle Butterfly Closed.
Because this Air that is allowed to be drawn-in to the Combustion Chamber is under the Full force of the Vacuum drawn on the Cylinders INTAKE Stroke,, there is sufficient force to allow the volume to be regulated by the Position of the Pilot Mixture Screws Needle Tipped End at the orifice from which it slightly protrudes when the Screw is "Bottomed Out"

The Air Passage from the Pilot Mixture Screw to the Pilot Air Jet passes over a narrowly drilled Port connecting the Air Passage to the Pilot Fuel Jet's Passage which starts in the bottom of the Carb within the level of Fuel when there is Fuel Present in the Fuel Bowl.

The Air from the Pilot AIR Jet rushes by the Port drilled from the FUEL Jet.
The Airs speed causes a pressure differential to occur and the Fuel from Pilot Jet Passage rises and joins the AIR rushing to fill the Vacuum.

That the AIR can be regulated by the position of the Needle-end of the Screw therefore determines how much FUEL will be drawn-up from the Pilot Jet Supply and allowed to enter the Combustion Chamber.
The combined Air and Fuel is referred to as MIXTURE.
There can be a MIXTURE which is predominately just AIR ... or,
There can be a MIXTURE which is predominately Fuel.

Depending on the sizes of the Fuel and Air Jets.

Regulating the MIXTURE to be of the right blend of AIR and FUEL to be ignited by the Spark Plug is called Air~Fuel Ratio Tuning.

The variables are:
The size of the Pilot Fuel Jet
The size of the Pilot Air Jet
The size and position of the Pilot Mixture Screw.

 

I've been working on my Mikuni's for too long :lol:

 

I thought it was that those down-under Mikuni's were oriented backwards.......

Doesn't the water swirl counterclockwise in the drain down South, too?