WE KNOW IT'S NOT IGNITION .. CHECKING CARBs

[79XS11F]

Hey TC .. Here's the new address for motorcycle carbs site. It was moved.



http://www.motorcyclecarbs.com/Parts_W122.cfm

Rob

[79XS11F]

Well it's a new day and I will try to get this bike running again. Yesterday the idle was so lumpy that I could not even sync the carbs. I was missing and back firing way too much to do anything constructive with it. I think this morning I will do a compression test, Check the spark again on all 4 cylinders. I will lay the plugs out on the head and turn it over a lot and see what happens at the plugs on several turn overs. If that stuff checks out I will be content that the issue is carbs and then I will be stumped pretty good. I'm not sure what the heck else i can do with the carbs to see what is wrong with them.
Rob

[79XS11F]

TEST RESULTS

PLUGS:
All plugs firing on several turn overs and firing together as paired.

COMPRESSION:
Run 2 tests per cylinder with Throttle wide open.

#1 = 145 + 160 = 152.50 Avg.

#2 = 160 + 155 = 157.50 Avg.

#3 = 160 + 155 = 157.50 Avg.

#4 = 150 + 150 = 150.00 Avg.

All Average = 154.37 PSI

These numbers are just a little high as per the manual that states a Max reading of 156 PSI with no difference between cylinders of more then 14 PSI. Given that the gauge I used is not a "shop" quality unit i will conclude that the valves are closing and the rings are good to go.

Based on the above this issue MUST be carb related and that's where my effort will remain until I get this bike running.
Rob

[79XS11F]

I have the carbs off the bike again. G I will soon be a carb Re & Re pro.
I just posted a PIC of the diaphragms at the link below. Can some one with carb experience check this out and tell me if these diaphragms look "normal"
thanks
Rob

http://www.ott-motorcycles.ca/mambo/...g2_itemId=1662

[wingnut]

From what I can see in the pictures they look ok but that does not mean much. Take them out and hold them up to the light if you can see thru them any where on the diaphram you have a leak if no light or tears you are good to go. Also when they are assembled if you hold your finger over the vent port for the diaphram chamber after pushing then up they should come down slowly if at all. If the fall like a common house brick you have a leak.

[79XS11F]

Originally posted by wingnut
From what I can see in the pictures they look ok but that does not mean much. Take them out and hold them up to the light if you can see thru them any where on the diaphram you have a leak if no light or tears you are good to go. Also when they are assembled if you hold your finger over the vent port for the diaphram chamber after pushing then up they should come down slowly if at all. If the fall like a common house brick you have a leak.

Good to go. I was thinking they looked a little on the "dry" side so I used some auto shop quality "rubber renewer" that I have for detailing the car. This stuff removes oxidization and it did a good job on the diaphragms. They are now very supple and soft. When I cover the diaphragm vent holes the slides stay up. Now I did notice an odd thing. As you know there is a tab on the diaphragms to make sure they are installed in the right position. I noticed that on #3 carb when the tab is in its location the slide on that carb is not in the same position as the other 3 carbs. The small hole under the plastic tower was about 20 degrees off center. I couldn't adjust the diaphragm on the slide so I cut the tab off so I could rotate the slide to the same position as the others.
I also took everything apart again and used my compressor to blow out every channel . There were no blockages anywhere.
I however am on hold now because I will wait for my pod filters to arrive. I have had it with that blasted air box. It's too tight a fit for easy carb removal and these carbs seem to be coming off the bike a lot.
Rob

[randy]

Rob,

It would be a good idea to hold off on intake / fuel changes until you get the bike running right. Too many changes at once and you can get confused about the cause of problems.

Try to get it right with the stock equipment, then go ahead and make your changes.

[79XS11F]

Ya I know, your right on that Randy but it's such a pain in the behind to re & re the carbs with that air box there. But I will hold off until this issue is solved.
QUESTION ... Even if this issue is not an ignition issue should I use the solid copper plug wire over the graphite wire that came with the coils.
Rob

[cruiser]

In your cleaning and blowing out ports, any chance o-ring and washer in bottom of idle mix screws was lost on any of carbs?

To help narrow down if possible, try removing one spark plug wire at a time when running ( if possble) to find out which cylinders are not working properly. Insulated pliers save on the heart rate.

Ramp the idle up if it stalls disconnecting wires, Be sure to ground out plug wire when disconnecting.

Just sounds like idle circuit problem.

[79XS11F]

Thanks Cruiser however my bike (1979 XS1100F) does not use O-Rings and washers in the Idle screw holes.

NEW INFO
I set my gas tank up on a table with petcocks turned off and have gas lines attached but sealed at other end. There is since about 12:30 about 2 inches of fuel at the bottom of the hose so the fuel petcocks are leaking. Perhaps when the bike sits more then a day it gets flooded badly.. could it be that simple??? 4 days is the longest the bike had sat unused since I built it.
I rebuilt the right side petcock but could not build the left side one because they are not the same. Right side is a 1978 unit and the left is a 1979 unit.
Rob

[79XS11F]

FUEL HEIGHT IN BOWLS IS WAY OUT !!!

All righty then ... I just checked fuel height in the bowls with the existing fuel supply lines for the Dial-A-Jets and only 1 of all 4 is correct. All the others have a fuel level very close to the gasket seal surface. I set the floats up with a mirco meter and they were all at 1 inch on the nose when I put the bowls on.

So .. Any ideas as to about how much at a time I shoud adjust the tang on the floats during the correction process? I can see that this will be time consuming as it is. I may even use a few wood working clamps to hold the bowls on instead of dealing with all those screws every time I make an adjustment.

Rob

[TopCatGr58]

Hey Rob,

A further review and remeasurement of my carb bowls shows that the shoulder of the bowl is ~0.25" below the sealing surface. The manual says that the fuel level should be ~3mm below that surface, so when you say that the levels are close to the sealing/mating surface, how close??

Adjust the floats about 1mm at a time, use the float height, not just how far to bend the tang....that's too hard!

BTW, when you had the pilot jets out, did you notice whether they had the vent holes in their sides? Secondly.....may be a dumb question, but does your's have the screw caps for the pilot jet towers, or rubber plugs? IF they had NO caps/plugs, that would also contribute to an overly rich condition allowing the pilot circuit to suck up fuel thru the top of the pilot tower instead of thru the main tower and their shared tunnel!
T.C.

[79XS11F]

Thanks TC
OK MM is .1181 inches so we'll say 1/12 of an inch below the bowls gasket surface. I will check and adjust tomorrow.
The pilot jets are the ones with holes in the sides and the top of the tower is sealed with a steel screw and a washer.
I do believe that once I adjust the fuel level in the bowls I will have done everything that I can to confirm that the carbs are set up correctly and I will see what I got sometime tomorrow evening
Rob

[skids]

25.4mm per inch. What is MM?

Originally posted by 79XS11F
Thanks TC
OK MM is .1181 inches so we'll say 1/12 of an inch below the bowls gasket surface. (snip)

[randy]

Like Skids wrote, there are 25.4 millimeters to the inch.

1 millimeter is approx. equal to .03937 inches.

**** millimeters, if you set your floats to 1 inch you should be fine!