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mixture adjust

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gs850cmc

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Finally up and running stock 1980 GS850G (45k miles). Performed complete carb tear down and rebuild, replaced all o-rings, intake manifolds, air box manifolds. Had the bike since 2000. Now it starts w/o choke, it never did that before..very happy and it settles quickly down to 1000rpm. Thanks to all on this site for their tips and expertise. I have one minor concern, it seems that the pipes are coloring faster than they ever did before, in fact the pipes on this bike never colored at all, almost perfectly chromed. I preset air screws 2.25t turns from seated. Could this be my issue? Should I back them out a bit while striving for max idle. Thanks again, trying to attach a picture
 
YES! Set the mixture screws with the engine idling to get the fastest idle on each carb. The mixture screws are the easiest circuit on the carbs to tune as the motor will "tell" you where it wants them. Ray.
 
I would raise the needle a bit with washers to richen the needle circuit.
 
Thanks for the tips,

I will first sync my carbs, I just received motion pro sync tool. Although it is running pretty good, I did not even bench sync so I think I will be able to get running even better after sync then do adjustments.

Will post on how things work out.

Thanks again.

Charlie
 
That's a beautiful bike. Brings back lots of memories. I had one nearly identical to that and like a dummy, I sold it after I got my Honda ST1100.

I just didn't like the high rpms on the highway and went to the Honda. Lower rpms and quiet as all get out.

Sold it in 1997 and sure would like to get it back today. Man I miss that girl.
 
rapidray said:
YES! Set the mixture screws with the engine idling to get the fastest idle on each carb. The mixture screws are the easiest circuit on the carbs to tune as the motor will "tell" you where it wants them. Ray.
Click to expand...

BassCliff has the instructions for the 'highest rpm' method on his website, this is what you are referring to right?

Also, for a newb like me - where are the mixture screws located? I know, I know...gotta learn sometime I guess.
 
This is on an 850, but they are almost all the same:
IMG_2958.jpg


.
 
Thanks...

Follow up question - BassCliff's instructions say to do it with the tank off and an alternate fuel supply. Is there an easy way to rig a homemade fuel set up? What do you guys reccommend?
 
Hi,

The next time you pass by an auto wrecking yard, stop in and pick up an old windshield washer fluid tank.

Or, I use my regular tank with an extra length of fuel hose and a 5/16" brass barb connector/splicer thingy.

hose_fittings4.jpg


Remove the tank, set it on something solid near your bike (higher than the carbs), attach the extra length of fuel hose to the tank's petcock, use the connector to splice into the fuel line on the bike, set the petcock to prime, away you go.

Thank you for your indulgence,

BassCliff
 
Last edited:
BassCliff said:
Hi,

The next time you pass by an auto wrecking yard, stop in and pick up an old windshield washer fluid tank.


Thank you for your indulgence,

BassCliff
Click to expand...

Good call...

If one doesn't have that available can a milk jug or other gallon size jug be used somehow?
 
lilbilly said:
Good call...

If one doesn't have that available can a milk jug or other gallon size jug be used somehow?
Click to expand...

I edited in another, very cheap, solution.

Sure, you can use just about any bottle or jug that will hold gasoline safely. The trick is finding the right fitting for the fuel line.


Thank you for your indulgence,

BassCliff
 
BassCliff said:
Hi,

The next time you pass by an auto wrecking yard, stop in and pick up an old windshield washer fluid tank.

Or, I use my regular tank with an extra length of fuel hose and a 5/16" brass barb connector/splicer thingy.

hose_fittings4.jpg


Remove the tank, set it on something solid near your bike (higher than the carbs), attach the extra length of fuel hose to the tank's petcock, use the connector to splice into the fuel line on the bike, set the petcock to prime, away you go.

Thank you for your indulgence,

BassCliff
Click to expand...

Okay, I see how this would be pretty simple.

Another (:D:o) follow up question. You say set the petcock to prime - set it to prime for the entire time while doing the tuning?
 
Hi,

Yes, plug the vacuum line to the carb. Set the petcock to prime so that fuel will flow. The vacuum petcock will not flow fuel without vacuum applied. Setting the petcock to "Prime" allows fuel to flow via gravity.


Thank you for your indulgence,

BassCliff
 
BassCliff said:
Hi,

Yes, plug the vacuum line to the carb. Set the petcock to prime so that fuel will flow. The vacuum petcock will not flow fuel without vacuum applied. Setting the petcock to "Prime" allows fuel to flow via gravity.


Thank you for your indulgence,

BassCliff
Click to expand...

Okay, now I'm definitely still lost - sorry for the sudden confusion, I'm not by my bike and I'm forgetting how it looks.

Vacuum line/fuel line are the same or different?
 
The vacuum line is smaller than the fuel line, both of them connect to the petcock.

When you remove the tank, the vacuum line will be a SERIOUS leak, so plug it with a golf tee or a Philips screwdriver. Extend your gas line from the tank to the bike, connect with the splicer.

NOTE: when you have your tank off the bike, don't put it much higher than the stock height, or you may overpower the float valves, changing the fuel level in the bowls. :eek:

.
 
Steve said:
The vacuum line is smaller than the fuel line, both of them connect to the petcock.

When you remove the tank, the vacuum line will be a SERIOUS leak, so plug it with a golf tee or a Philips screwdriver. Extend your gas line from the tank to the bike, connect with the splicer.

NOTE: when you have your tank off the bike, don't put it much higher than the stock height, or you may overpower the float valves, changing the fuel level in the bowls. :eek:

.
Click to expand...

I see, so I need to extend both the fuel line and vacuum line with a splicer? Or just one or the other?
 
lilbilly said:
I see, so I need to extend both the fuel line and vacuum line with a splicer? Or just one or the other?
Click to expand...

Okay, so if I use the vacuum line then I gotta splice both right? And if I use PRIME then I plug the vacuum and extend the fuel line?
 
Thanks for the tips. I have the tank off and have an external gas tank, plastic bottle with hose and valve..paid too much for this but it works. After I warmed bike I tried adjusting, I found that the idle change was very subtle and didn't increase much on any of the carbs. But when I turned them back in from about 2.5 turns the idle did go down which leads me to believe that the presets of 2.5 turns are pretty accurate. I will now check basscliff's procedure to see if I missed something, will also be synching carbs later on using a motion pro manometer.
 
lilbilly said:
I see, so I need to extend both the fuel line and vacuum line with a splicer? Or just one or the other?
Click to expand...

No need to extend the vacuum line. Just stick something in it (like a golf tee) to plug it. Hook up your extended fuel line. Then set the petcock to "Prime". On the "Prime" setting, the petcock does NOT need a vacuum to allow fuel to flow.

Take a look at this: Where Do These Hoses Go?

I found it on some guy's website. :D


Thank you for your indulgence,

BassCliff
 
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