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.

[psyguy]

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

[rockford]

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

[chef1366]

Do you have the right OHM coils with the points?