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gs 850 cyl 4 lean

  • Thread starter Thread starter gs850cafe
  • Start date Start date
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gs850cafe

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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?
 
Possible reasons:
- dirty carb
- weak spark (maybe plug cap, wire)
- exhaust leak
- vacuum leak
- carb sync (maybe, not positive)
 
Nessism said:
Possible reasons:
- dirty carb
- weak spark (maybe plug cap, wire)
- exhaust leak
- vacuum leak
- carb sync (maybe, not positive)
Click to expand...


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)...
 
Last edited:
I'm no expert on this, but if you did the sync before you re-jetted maybe you should recheck it afterwards.
 
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.
 
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
 
Have you checked the fuel levels in the float bowls?

A low level would cause that cylinder to run lean.
 
tkent02 said:
Have you checked the fuel levels in the float bowls?

A low level would cause that cylinder to run lean.
Click to expand...

i was just thinking that...its been a while since ive done it...beginning of the year at least
 
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.
 
tkent02 said:
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.
Click to expand...

that was my other thought....ill tear it down an post if i run into more issues
 
I would check the fuel levels first, just because it's easier than pulling the carbs..
 
tkent02 said:
I would check the fuel levels first, just because it's easier than pulling the carbs..
Click to expand...

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?
 
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.
 
tkent02 said:
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.
Click to expand...

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

thanks for the info
 
well im never buying box boots from Z-1 again...cyl 3 had a gap around the boot...then i couldnt get the boots back on...so i trashed them

my buddy had a set of soft used gs1000 boots (a hair larger) but the fit very snugly inside the box and with my smaller 850 carb clamps they fit very snugly on the carbs...

i did go out an boy she pulled great...really great...pulled the plug and its still on the lean side i think but not near as bad....i cleaned the plug an it still looks clean...so im guessing it runs lean still...

but it runs super good so i dont care no more...its just gonna run little lean


*edit** put the bike upright an checked fuel level...all 4 was the same....not sure what i did wrong yesterday
 
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