Yet another tuning question

So I got the carbs all cleaned up, adjusted the floats, 1, 2, and 3 were all right on, 4 was about 5 mm low. I had to bend the tab quite a bit to get the level close to the other three and now the fuel level is about 1mm lower then the rest. It is bent so far down that when I remove the bowl, the needle falls out when the floats drop. The carbs where bench synced also. That is one issue.
Second is that the plugs are all black, not wet but very black and sooty looking. IE: rich, turned the screws in .5 turn (now at 3 out) and still black but a little better. I had the temp fuel can on when attemping to tune and the only way I can keep it running is to have just a bit of "choke" on. This I think is just a matter of tuning the idle screw a bit. With the temp can on I noticed all of a sudden it started to take a lot of fuel, then it started to flow out of the air box. Thinking the #4 floats are at fault here. I clean it all up, smell the oil, which seems to be ok, and started it up again today, seems to run decent then slowly gets worse. I warm it up then take it for a .5 mile ride to the corner and back and it stalls as the idle is still not set. I pull the plugs to inspect them and they are all dry and black expect #4, it is black and wet with fuel. Scratch my head a bit and then notice fuel dripping out of airbox drain tube. I think #4 floats are going to need to be checked. Arggg! This is frustrating. Any ideas?

 

Where are you getting the specs to adjust your float heights? I had a similar problem when adjusting mine using the specs given in the HBOL. (Haynes Book of Lies)

The floats would hit the top of the float chamber before the needle valve was closed. Petrol would spill out the overflow pipes continually like this. I adjusted them so that the needle valve was closed just before they hit the top of the float chamber.

 

I adjusted them according to the info found on the xjcd. I believe it was from the yamaha service manual. Regardless, I think I have to remove the carbs, yet again, and recheck the float levels.

 

You should be able to check the float levels on the bike, if your drain screws work, you jam a tube into the drain hole, and your reference point is between the front and rear bowl screws.

Anybody have a picture of this?

 

Don't think in terms of FRACTIONS when you are doing the FINAL Adjusting of the Pilot Mixture Screws.
Try to think in terms of DEGREES.

From you Post it sounds like your are still too Rich.
But you need to start tweaking the Mixture Screws instead of turning them.

A turning of the Screw ... 1/4 Turn ... might very well go right through the spot you need for Optimum Tuning. [------] <-- That much might be too much!

A few Degrees --> [-] ... Will have a dramatic effect on the Air-Fuel Mixture when you are close to being in the right spot for Optimum Pilot Mixture.

The Optimum Pilot Mixture is:

Idle + Supplemental Richness

Once you have the Bike Idling OK on the Pilot System ... you need to add a few Degrees of EXTRA Richness to SUSTAIN Combustion during the BRIEF Time between Throttles Opening and the Main Jet Fuel Supply reaching the Combustion Chamber.

Add just enough extra Fuel to provide Richness to the Fresh Air that rushes-in without Fuel ahead of the Main Jet Supply.

This duration is VERY BRIEF.
But, needs the supplemental Richness to avoid Hesitation.

Tuning for that Supplemental Richness is the key to a sweet running bike.
Too much and the Bike boggs-out or dies.
Too little and there's hesitation and backfire.

In the window of Supplemental Richness there is a minute (my-nute) adjustment for performance.

Lean. (But, NOT Critically Lean). Crisp acceleration due to the lean mixture's quick burn resulting in POWER and Fast Acceleration with Heavy engine Braking. Racing and performance outings. Event tuning. Track day.

Rich. (Dark Brown). Velvet smooth application of Power and a degree of engine coasting upon closing the throttles.
Best for touring and long rides. A cooler burn. Smooth all-day cruising!

That "Window" ... Once you find where your Pilot Miixture Screws are within that window ... is a TWEAK. --> "[]" The width of a Nickel. Almost not moving the screw at all.

 

Time2Ride,

I assume that the bike is on the centerstand when testing float level on the bike. Any thing else?

 

Rick,
Thank you for the info. Ok, I understand that I need to turn the Pilot screw in SMALL increments to find the right spot, will do. What do I do first, set the idle, then Pilot screws? Set the idle then sync carbs? What about the fuel flowing into the airbox? I will check the level of the fuel in #4 and make sure that it is correct.

 

Sometimes its not a stuck Carb Float ... but, a leaking-by Petcock that causes that situation.
When the Petcock gets near the end of its lifespan. the vacuum operated valve doesn't fully shut-off the flow of fuel.
Gas will still run down to the Carbs until they overflow.

You have to troubleshoot the problem from both the Petcock and Carbs Floats to be sure.
A leaking Petcock can sometimes be repaired with a Kit ... but, some of the aftermarket Kits leak just as bad as a faulty Petcock.

Since the Petcock lasted 25 years ... I lay the cost of a new on over 25 years to justify replacing the faulty one with new.

 

Rick,
Would the petcock leak with both the vacuum and fuel lines removed? I have had the tank off with fuel in it and left it on the garage floor for two days and did not see any fuel leaking then.

What about the order to tune? Idle, sync, then pilot?

 

If the tank was off and had fuel in it ... the Petcock leaking is moot.
You would have seen gas on the floor.

Bench Sync
Vacuum Sync w/ Tool if so equipped
Mixtures and Idle
Off-Idle
Plug Chops for individual Carb Tuning

 

Weoxstan - - Yes, float level check on center stand, bike on level concrete. It looks like you'll be pulling the rack anyway to adjust that pesky #4 float, so here's a few bright ideas. . .
Know a friend with a digital scale? Weigh all 4 floats.
Take a wooden golf Tee, sharpen the tip, and work it in the "seat" to polish it, and take the "needle" and a bit of 2,000 grit paper, gently polish it.
If that doesn't fix the problem, you're left with ordering new bits from Chacal, or winning an auction on E-Bay, (about $25).

 

ARGGG I figured out why #4 would not stop flowing fuel. The $@%^ float was upside down! Frustrating but at least I figured out that issue.

I also have it sync'ed now using RickCoMatics one gauge method. It is sounding better. Now I just have to get the Pilots set correctly.

Rick:

What is the "off idle"?
When I am setting the mixture how do I go about checking it with my black plugs? Will they clean up as the burn gets hotter? If so, how long do I have to leave it running before I will see any change in plug color?

Thanks for all your help, my smile is getting bigger and bigger the better it runs.