Has to warm up before all 4 Cylinders fire

[Tim]

79 GS850G If I start the bike cold it only fires on the left side until it warms up. I'll feel hot exhaust on the left side and cold air on the right side. She'll sputter here and there and as she warms up she'll start to smooth out and I start feeling hot air coming out of the right exhaust. Any ideas ? Once she's warm I can shut her off and she'll fire up perfect, let the engine get cold and the whole sputtering warm up starts all over again. And I might add it needs full choke just to warm up. even in warm weather (of course it will warm up quicker). The bike runs good once warmed up, I just believe if I can fix this warming up issue she'll be even better !!

Bike has 19,000 miles. My father was the original owner and now it's mine. Was garaged always and consistant oil changes. I put on Accel coil, new points, Valve adjustment and some typical seals. Other than that it's stock.

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)

 

[almarconi]

If I had to guess, I'd say the carbs probably need a good cleaning.

 

[Guest]

sparkplug caps?

 

[tkent02]

Why guess, go through it all, troubleshoot everything, the results will be well worth the effort.

 

[TheCafeKid]

I agree with TKent, but If i had to put my finger on one thing, you've got crap in your pilot circuit of the carbs, likely picked up from the tank. Number one will generally be worse than the others, as all the crap will settle over there on the side stand...

 

[Old Colt]

I look at this from a very different side. I expect you are using regular mineral oil, not a synthetic. I used to deal with this and a change in oil made the difference. The synthetics do not load the plugs on first start.

 

[Nessism]

Problem is not oil. Problem is that you have a 30 year old mototcycle that needs maintenance. Pull the carbs and go through them proper like: dissasemble and soak the bodies in carb dip, replace the o-rings with a VM kit from cycleorings.com, replace the intake pipe boot O-rings, and sync the carbs. This is the right of passage with any old bike.

Good luck

 

[rodm850g]

Has to warm up before all 4 Cylinders fire

Tim,
+1 on what previous poster said, having had a 25 year relationship with the same bike, this is most sound advice. Depending on where you want to start...carbs are prolly the most likely culprit. When you soak them ,use a welders torch cleaner to route out all residue....this is essentially a mini file...you don't want to try to up size the jets use appropriate size for each jet. if you want to try some newer cleaner try the new Yamaha carb cleaner...the one you cut with water...there may be some of the old stuff that you mixed gas but the new uses h2o much safer and worked well for me...mine had been in storage til recently I've brought it back out for duty round town. Back to cleaning the jets...take them all out and put them in this soution and during the course of other work you can do while the jets soak....walk by now and then and swirl them around ...after about half a day or more if you want ....use air if you have compressor if not the tip cleaner and some "gumout "carb cleaner will sufice...wear gloves of some kind...nitrile will last better trhan latex.....check plugs, another poster mentioned plug caps,fairly inexpensive too....do you have point file? Snap on used to sell one that was an abrasive glued to a fiberglass piece...dress up the points...After all this you should notice a real difference in the 850....after sitting nearly 5 years and doing pretty much what I have written here...mu old buddy fired up and was running as good as when it went into storage....Good luck with your 850...when its right its a great bike to ride on....and will give you some good mileage back too....
Rodm850g

 

[TheCafeKid]

Tim,
+1 on what previous poster said, having had a 25 year relationship with the same bike, this is most sound advice. Depending on where you want to start...carbs are prolly the most likely culprit. When you soak them ,use a welders torch cleaner to route out all residue....this is essentially a mini file...you don't want to try to up size the jets use appropriate size for each jet. if you want to try some newer cleaner try the new Yamaha carb cleaner...the one you cut with water...there may be some of the old stuff that you mixed gas but the new uses h2o much safer and worked well for me...mine had been in storage til recently I've brought it back out for duty round town. Back to cleaning the jets...take them all out and put them in this soution and during the course of other work you can do while the jets soak....walk by now and then and swirl them around ...after about half a day or more if you want ....use air if you have compressor if not the tip cleaner and some "gumout "carb cleaner will sufice...wear gloves of some kind...nitrile will last better trhan latex.....check plugs, another poster mentioned plug caps,fairly inexpensive too....do you have point file? Snap on used to sell one that was an abrasive glued to a fiberglass piece...dress up the points...After all this you should notice a real difference in the 850....after sitting nearly 5 years and doing pretty much what I have written here...mu old buddy fired up and was running as good as when it went into storage....Good luck with your 850...when its right its a great bike to ride on....and will give you some good mileage back too....
Rodm850g

Agreed, tho I would be VERY VERY VERY (as in i wouldnt advise using) Careful about using any type of "file" in the jets. Most use one or two strands of copper wire. The jets are brass, and VERY soft. even a file of the same size risks wallering out a jet, and even a minute change in your jet size can make a HUGE difference in how the bike runs, plus if they arent done uniformly, you'll never get it running right on all four. I have had GREAT success simply soaking the disassembled carbs and jets OVERNIGHT, in Berrymans parts dip, (all plastic and rubber parts need to be removed) and then cleaning any, if any (seriously this stuff is pretty potent) remaining gunk out with some thin copper wire. Then use carb spray to rinse and rinse again in warm water. Dry thoroughly with compressed air if available, or shoot again with carb spray. Pay attention to all those little holes, shooting some spray in each and assuring that it comes out the other side smoothly (wear safety glasses, those ports sometimes come right back around at your face) Pay particular attention to the two holes in the FLOAT BOWL, as this is part of your enrichener/choke/pilot circuit. Copper wire is best to use because its softer than the brass, and wont damage the jets....

There is a COMPLETE and THOROUGH write up on cleaning carbs on the forum home page under the Garage section...

Good luck! Its not as daunting as you might think....


TCK

 

[Guest]

Most likely

Most likely

I agree with TKent, but If i had to put my finger on one thing, you've got crap in your pilot circuit of the carbs, likely picked up from the tank. Number one will generally be worse than the others, as all the crap will settle over there on the side stand...

I'd bet that's correct.

 

[Old Colt]

Isn't #1 on the left, the side he said is running?

 

[Pacman]

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

 

[TheCafeKid]

Indeed all these are possibilities. If one and two are running, perhaps you arent getting enough fuel to three and four....

My suggestions:

The usual suspects

Check and or replace the petcock,
Valve adjustment,
replace the intake boot Orings (this could be a distinct cause as well, as it may be lean enough not to fire when cold due to leakage around the intake boots, but as the bike warms up, the metal expands a bit and seals them a little better??)
disassemble and thoroughly CLEAN the carbs and replace all the orings
check electrical connections, including plug caps and wires

If, once youve done that, it still runs like this, we can start to look at other possibilities. But untill youve done these things, you're likely chasing your tail, and throwing money at a problem hoping you get lucky and fix it.
These are common issues and often need to be addressed on these old bikes, as usually they never have.
You need three things to make the motor run: Spark, Fuel and Air. You evidently arent getting one or more of those....

 

[snowbeard]

Ok, I'm in agreement that most of these little problems are common and easy fixes. I thought I had holed a piston when my petcock diaphram was leaking, but I wonder on this issue if maybe it isn't the valves?

I have issues starting my bike cold, the puff of air thru the carb vents works alright most times, but I know the valves need to be adjusted. I think the fact that it changes with engine temp points to something besides carbs (but it never hurts to clean them anyways) I've felt like the vacuum is poorer when the engine is cold, therefore not pulling as hard on all the carbs. once it's hot the valves close tighter and it pulls better again.

I always get a surge when I start 'er up, it runs kinda poorly, then after half a minute with the throttle just cracked, it runs up to 4K RPM's on all cylinders and is good to go.

best o' luck there!
'beard

 

[Guest]

Do you have the right OHM coils with the points?

 

[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)

 

[Guest]

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

 

[Guest]

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