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carb issue?

  • Thread starter Thread starter luketorjesen
  • Start date Start date
L

luketorjesen

Guest
when sufficiently warmed up, my bike hangs at around 2500 rpms, then returns to a good idle slowly. PO put in a new jet kit to increase fuel and added cone filters. i think the hanging means its lean, do airscrews go in or out? i always get it backwards.


fun fact, no. 1 plug is black, no.4 plug is white.....
 
Out means youre adding air....In retards the amount coming in...
 
Air leaks = bad!

Air leaks = bad!

Mr. luketorjesen,

These 850s are very picky about air leaks in the intake system. Have you sealed up your airbox and made sure there are no air leaks around the rubber boots on both sides of the carburetors?

The airbox probably needs new weatherstripping around both side covers and on top of the air filter cage. Also the intake boot O-rings may be suspect, unless you've replaced them recently. Make sure your breather hose is properly connected. I'm sure others will add to the list.

Thank you for your indulgence,

BassCliff
 
TheCafeKid said:
Out means youre adding air....In retards the amount coming in...
Click to expand...
Carefull there, TCK. Assuming he's talking about the '80 850 in his sig line, there is only one adjustment screw, not two, like yours. That is an idle mixture screw on the top of the carb outlet. Turning the screw out (counter-clockwise) will richen the mixture. Start by turning these screws in (clockwise) slowly, while counting the turns until they seat LIGHTLY. Record the number of turns so you can go back to that point, if necessary. Turn them all about 2 full turns as a starting point.

Of course, some of this will depend on what jets were installed. Are they stock (but new) or are they larger than stock? Do you have stock exhaust or just the addition of pod air filters? All of these will determine what jets should be in there. Best situation would be to open up the carbs and see what is in there. Let us know what's there and we can make better suggestions.

The hanging idle problem is likely a lean mixture, but you need to determine why it's lean. Could be the wrong jet size, could be a bad o-ring or a cracked intake tube. Rarer, but also possible, is a torn diaphragm in the top of the carb, but they usually affect lack of power, due to that slide not opening, not a hanging idle.

Oh, and just to be sure ... #1 is under the clutch hand, #4 is under the throttle hand. Is that the way you are counting?


.
 
Probably leaky intake rubber somewhere but it might also be a carb balance issue - one or more carbs might be sitting open a fraction. I had this problem with a GS550 which was oh so sensitive to balancing.

Wally
 
Steve said:
Carefull there, TCK. Assuming he's talking about the '80 850 in his sig line, there is only one adjustment screw, not two, like yours. That is an idle mixture screw on the top of the carb outlet. Turning the screw out (counter-clockwise) will richen the mixture. Start by turning these screws in (clockwise) slowly, while counting the turns until they seat LIGHTLY. Record the number of turns so you can go back to that point, if necessary. Turn them all about 2 full turns as a starting point.

Of course, some of this will depend on what jets were installed. Are they stock (but new) or are they larger than stock? Do you have stock exhaust or just the addition of pod air filters? All of these will determine what jets should be in there. Best situation would be to open up the carbs and see what is in there. Let us know what's there and we can make better suggestions.

The hanging idle problem is likely a lean mixture, but you need to determine why it's lean. Could be the wrong jet size, could be a bad o-ring or a cracked intake tube. Rarer, but also possible, is a torn diaphragm in the top of the carb, but they usually affect lack of power, due to that slide not opening, not a hanging idle.

Oh, and just to be sure ... #1 is under the clutch hand, #4 is under the throttle hand. Is that the way you are counting?


.
Click to expand...

Ahh my bad...and thanks for that too steve that will help with my CVs on my yammie...
 
Also...he mentioned that he was running pods. Must be o-rings if the intake tubes are in good shape, balancing act, or likely both. Sounds like the carbies should come off.......:-s
 
thanks steve

thanks steve

Steve said:
Carefull there, TCK. Assuming he's talking about the '80 850 in his sig line, there is only one adjustment screw, not two, like yours. That is an idle mixture screw on the top of the carb outlet. Turning the screw out (counter-clockwise) will richen the mixture. Start by turning these screws in (clockwise) slowly, while counting the turns until they seat LIGHTLY. Record the number of turns so you can go back to that point, if necessary. Turn them all about 2 full turns as a starting point.

Of course, some of this will depend on what jets were installed. Are they stock (but new) or are they larger than stock? Do you have stock exhaust or just the addition of pod air filters? All of these will determine what jets should be in there. Best situation would be to open up the carbs and see what is in there. Let us know what's there and we can make better suggestions.

The hanging idle problem is likely a lean mixture, but you need to determine why it's lean. Could be the wrong jet size, could be a bad o-ring or a cracked intake tube. Rarer, but also possible, is a torn diaphragm in the top of the carb, but they usually affect lack of power, due to that slide not opening, not a hanging idle.

Oh, and just to be sure ... #1 is under the clutch hand, #4 is under the throttle hand. Is that the way you are counting?


.
Click to expand...


ive turned in the air screws and back them out to 3.5 turns, as i read they were supposed to be. i think im going to try and back them a half turn from where they are as a starting point.

i am counting #1 as clutch side, but the plug may be going black b/c the choke rod on that carb doesnt always go all they way back in. the rest are white only on the top of the tip, not all over. other than the tip they have that gold-brown hue.

ill check the boots and o rings, i doubt its the box, as the bike has pods on it. The jet kit was actually done by the PPO and i heard through the grapevine it was for more fuel, hense the pods. the the PPO didnt do aftermarket exhausts.

im a bit timid about opening up the carbs. im afraid that theres going to be a lot of stuck bolts for me to strip and not get back together right. she HAS been living outside for a couple yrs. shes still a beauty though, just not on the outside. but ill get to that.

oh and i finnally got to take here through the motions yesterday, and im pretty sure theyres no power loss, shes a screamer! if there is, id actually be stoked.
 
I'm sorry I missed the part about the "cone filters". :oops:

But I think everybody concurs that it's carburetion with the possibility of air leaks in the intake boots. Jetting and needle adjustments are beyond the scope of my experience at this point in my motorcycle wrenching career. But I hope to grow up someday. 8-[

Keep us informed. There are some carb gurus around here who can help.

I think I have PDF documentation for the BS series of carbs if you need it. Let me know. It might help.

Thank you for your indulgence,

BassCliff
 
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