Has to warm up before all 4 Cylinders fire

[Tim]

It's not the valves, I just finished adjusting them. I had to replace three shims (1 intake & exhaust , 4 intake) all my valves are almost exactly .05 I do see signs of o'ring leaks on the boots going into the heads on all four. I can only afford two of the boots at a time. I've got two on my work bench right now. Next pay day I'll order the other two and if I can afford it I'll get the O'rings also. Once I get that stuff I'm going to pull the carbs off and tear them down. Last summer I had to change the float jets (this problem was still happening before that). I just changed the points also that didn't help. The oil I use is Spectro Golden 4 (Semi-Synthetic). The coil I put on is an Accel Super Coil, I don't know the ohms but it was listed as appropriate for this bike. I might add that two years ago I took the carbs to a local shop and they stripped the carbs down and put them in some kind of Ultra Sonic type of cleaning bath (that's how they described them) and once back on they synced the carbs. This problem was happening before that and continued afterwards. It did run alot better after that.

Thanks in advance for any help you can contribute !!!!

My stable.........
1979 GS850G
2006 ST1300
1995 Z28 ( yeah I know not a bike but it's still one of my babies)

[psyguy]

so, let me ask again... sparkplug caps?

also, you speak of the coil in singular... are they BOTH new?

ultrasonic carb cleaning is good stuff, you should not need another clean if the bike was used regularlly since then

problems that get better (or worse as the bike warms up), other than related to carb problems, are often caused by electrical components that need attention

[renobruce]

I also suggest you do the thorough cleaning, replace carb orings and intake orings.

If the bike is running well after warmed up then the pilot circuit is probably okay. However, if you pull the bowls off you will see a narrow brass tube hanging down. That tube fits into a hole in the float bowl that is fed from a small hole at the bottom of the bowl. I have see both the passage in the bowl and this narrow tube clogged. This narrow tube feeds the choke passage with fuel. If either the hole in the float bowl or the narrow tube are clogged then no gas gets to the choke passage on that carb and that cylinder won't be firing on choke. But, when warmed up and off choke it may run fine.

Chris

Bingo.

I had it happen to mine. The little tube got clogged up, and that cylinder wouldn't run on choke.

Go through the carbs completely. You'll be glad you did. But hey, you might as well wait until the snow starts flying. Get some rides in!

[Tim]

Spark plugs have been changed and problem persisted. Hate to sound dumb here I've worked more on cars than bikes (I'm learning that's why I'm here) what do you mean by spark plug CAPS ?? And yes I changed both coils. I'm curious about what Pacman and renobruce called out about the little tube preventing the choke from working on that cylinder. That makes sense to me. Probably going to take the carbs off in about a week or so. I'm going to see if I can figure out what tubes your talking about. I'm taking note of all the suggestions here and will give them all a try short of a human sacrifice to the Bike Gods. Although who knows sometimes frustration can make you do extreme things. Just kidding..........well maybe........naaah........just kidding.


My stable.........
1979 GS850G
2006 ST1300
1995 Z28 ( yeah I know not a bike but it's still one of my babies)

[Pacman]

Spark plugs have been changed and problem persisted. Hate to sound dumb here I've worked more on cars than bikes (I'm learning that's why I'm here) what do you mean by spark plug CAPS ?? And yes I changed both coils. I'm curious about what Pacman and renobruce called out about the little tube preventing the choke from working on that cylinder. That makes sense to me. Probably going to take the carbs off in about a week or so. I'm going to see if I can figure out what tubes your talking about. I'm taking note of all the suggestions here and will give them all a try short of a human sacrifice to the Bike Gods. Although who knows sometimes frustration can make you do extreme things. Just kidding..........well maybe........naaah........just kidding.


My stable.........
1979 GS850G
2006 ST1300
1995 Z28 ( yeah I know not a bike but it's still one of my babies)

The sparkplug caps are attached to the end of the sparkplug wires and are what slip over the end of the plugs. Most bike shops carry replacement plug caps and you trim off a 1/4" or so from the end of the plug wire and thread the caps on. The part that threads onto the wire has a little brass screw in the end that screws into the end of the plug wire. The center of the plug wire has copper(?) wire that the screw tip screws into to make the electrical connection.

The way I test to see if a cylinder is firing is to hook the inductive pickup for a timing light to each plug wire in turn (with the timing light hooked up as normal) and watch for a consistent smooth light pulse. (The light should pulse each time that plug fires and will not light up if the plug isn't firing). This test is not perfect as it could pickup a plug misfiring through some corrosion on the end and so forth but it is a good test that I have found to be very helpful in finding ignition issues.

For your carbs download this PDF:

http://www.thegsresources.com/files/vm_carb_rebuild.pdf

The fuel feed tube (shown in the PDF above as the "starter jet" & "choke tube") for the choke in your carbs will be very obvious when you take the float bowls off. The tube is about 1/8" diameter and reaches down to about the bottom level of the float bowl. It fits into a hole in the float bowl and that hole is fed by a small hole in the bottom of the float bowl. Use spray carb cleaner and spray into the hole at the bottom of the float bowl and you will see very obviously where it should come out. Then hold the spray tip from the carb cleaner can tightly against the tiny hole at the end of the brass fuel feed tube and spray through that small hole. You should get some carb cleaner to come out of some side holes at the top of the brass tube as well as a rather large hole located on the inside of the throat of the carb. You may have to have the choke open to get it to come out of the neck of the carb but this is the end result that you want. Keep spraying until you get it to come out of the throat of the carb.

This may all not make much sense until you have the carbs off and the float bowl off to see what I'm talking about. However, once you've done that and tried these things it should be pretty evident how the choke system works.

Hopefully, something here helps you get it running better.

Chris

[snowbeard]

hmmm. ya got me then, sounds like you keep up pretty well with it?

[Greg O.]

Mine started missing on #1 when "choked". I put up with it until I had the carbs off for a different reason. while they were off, I gave them a cleaning as best I could with carb cleaner. It must have done the job because now runs on all 4 while choke is on.

Greg