gs 850 cyl 4 lean

[Guest]

airbox is completely seal, no exhaust leaks...carbs have been dipped an all passages blow out with air, all new o rings etc...

all the maintence has been done on this bike...carbs have been jetted for 4-1 header

cyl 4 is still lean others are brownish grey..what else causes a lean condition?

[Nessism]

Possible reasons:
- dirty carb
- weak spark (maybe plug cap, wire)
- exhaust leak
- vacuum leak
- carb sync (maybe, not positive)

[gs850cafe]

Possible reasons:
- dirty carb
- weak spark (maybe plug cap, wire)
- exhaust leak
- vacuum leak
- carb sync (maybe, not positive)

no vac leak that i found...i sprayed a lubricant all over the carb area(made it nice an shiny) and got nothing...i spayed just a small bit in the snorkel an it about killed it..so im sure as much as i sprayed over the intake boots, carbs and box boots something would have changed..

took header off...nice an clean no signs of exhaust leak on any cyl's

new plug caps about 1000 or so miles ago ( can i test spark?)

carb sync...did it a while ago...before rejet...will try that again today

carbs might be dirty? but was clean 8k miles ago lol

plugs have been changed but once (about 5k or more miles ago)...

[twotimeGSr]

I'm no expert on this, but if you did the sync before you re-jetted maybe you should recheck it afterwards.

[gs850cafe]

I'm no expert on this, but if you did the sync before you re-jetted maybe you should recheck it afterwards.

but would that cause a lean all the time?

[Nessism]

You can't judge vacuum leaks using spray on the outside.

When removing the exhaust pipes it's best to replace the gaskets to avoid leaks.

I'm not sure what the problem is, but clearly, something is not as you expect so don't overlook the obvious.

[gs850cafe]

carbs are in sync like i figured...cyl 4 was a hair off...just not even an 1/8th of a turn...

cleaned plugs went for a 10 mile ride...cyl 4 plug was still siverish with black around the thread part...at wot an normal driving...

less decel popping...

im about to just let it run lean on that cyl...no tellin how long it has been anyways

[tkent02]

Have you checked the fuel levels in the float bowls?

A low level would cause that cylinder to run lean.

[gs850cafe]

Have you checked the fuel levels in the float bowls?

A low level would cause that cylinder to run lean.

i was just thinking that...its been a while since ive done it...beginning of the year at least

[tkent02]

It could also be a partial blockage of the screen over the needle valve, I had the same problem once, it was a tiny chunk of wood blocking the screen. Don't know how a piece of wood got past the petcock screen, but there it was.

[gs850cafe]

It could also be a partial blockage of the screen over the needle valve, I had the same problem once, it was a tiny chunk of wood blocking the screen. Don't know how a piece of wood got past the petcock screen, but there it was.

that was my other thought....ill tear it down an post if i run into more issues

[tkent02]

I would check the fuel levels first, just because it's easier than pulling the carbs..

[gs850cafe]

I would check the fuel levels first, just because it's easier than pulling the carbs..

checked cyl number 1 level...didnt write measurement down, but had enough to fill the bowl up im sure...

used cyl 1 as a reference...cyl number 4 was more then half of then cyl 1 (which cyl 1 runs good)...if that didnt make sense it had much less fuel in the bowl then number 1

so id say thats my issue no?

[tkent02]

Probably, but do the fuel level check in the service manual to be sure. The one with the hoses....

You still need to find the cause of the low level.

I guess on an 850 the carbs pop off in a few seconds anyway, no big deal, maybe you will find something obvious (like my chuck of wood) in there.

[gs850cafe]

Probably, but do the fuel level check in the service manual to be sure. The one with the hoses....

You still need to find the cause of the low level.

I guess on an 850 the carbs pop off in a few seconds anyway, no big deal, maybe you will find something obvious (like my chuck of wood) in there.

ah gotcha...least i got a starting spot...ill post results another day probably..

thanks for the info