A Favor: Carb Rebuild Gone Wrong

[jrazz]

Okay, I have a GS 850 GN (79 model). It has Mikuni VM26SS carbs and I replaced the o-rings in it last fall and we could never get it to run right afterwards. Maybe I need to get some o-rings again? However, confusion is compounded due to all the mixture screws and adjustments. I printed off all of the papers on the carbs and I have the Haynes manual but still can't get a concrete number on the screw settings.

I have the bike out at a buddy's who works on cars and can fix any make or model with just about any problem, but this bike has thrown him for a loop.

Here is where the favor comes in: Would anyone who owns a GS850 GN or is knowledgeable about the carbs on one be willing to allow me to call them to see if we can work through this and get this bike back on the road? I HAVE SPRING FEVER!!!!

Thanks guys,

j razz

[jrazz]

I guess I should explain "...never got it to run right afterwards."- we got it to where it would run at higher rpms but not idle and then we got it to idle but not run at higher rpms.

j razz

[Nessism]

A good starting point is to set the pilot fuel screws at roughly 3/4 of a turn and the air screw at 1.5 turns. Check your fuel screws to make sure the tips are not broken off in the carb bodies. Also, the carbs need to be spotless on the inside; remove all the pilot jets and hold them up to a light to make sure the small orifice is open.

Good luck.

[Larry D]

Does it run now ?? Do you have a stock setup ? Meaning airbox and jetting.

I'm guessing screws of which you speak are the idle air screws. These are normally set around 2.5 turns out from lightly seated. This should get you in the ballpark for more finer tuning. So....lightly seated is finger tight, DON'T crank down on them or the tip of the screw will break off in the carb body...not good.

The racing idle you describe could be that the screws weren't set properly, or, an air leak.

Good Luck.

EDIT::Silly me.....different carbys. Sorry 'bout that one........

[nisom512]

the specs for your may be in here I know the 80-83 modle ones are so your may be too.

http://www.thegsresources.com/_forum/showthread.php?t=73723

[jrazz]

Thanks guys-

The carbs have been soaked, bathed, brushed, poked, prodded, violated... er, what I'm trying to say is, they are clean!

As per screws- I was referencing the air, the fuel, and the carbs themselves. There is a lot to get right and oh so much to get wrong!

Thanks guys.

j razz

[nisom512]

Thanks guys-

The carbs have been soaked, bathed, brushed, poked, prodded, violated... er, what I'm trying to say is, they are clean!

As per screws- I was referencing the air, the fuel, and the carbs themselves. There is a lot to get right and oh so much to get wrong!

Thanks guys.

j razz

the specs on how far to turn out your air/fuel screw should be in the link I gave you to set it to spec

[jrazz]

Thanks- Got it:
GS850 (77-79) the specs are for the VM's

idle r/min........... 950-1150
carb................... mik vm26ss
id no................... 45060
bore size ............ 26 (1.0)
float height ......... 23-25. (0.91" - 0.98")
fuel level ............ 3.0 - 5.0 (0.12" +/-0.20")
pilot air screw ..... 1.25 turns out
pilot screw........... 5/8 turns out
pilot air jet........... 1.2
pilot jet............... #15
cut away............. 1.5
jet needle........... 5DL36-2 (the -2 2nd notch)
needle jet .......... 0 - 6
pilot outlet........... 0.6
by pass ............. 0.8
main jet............. #102.5

j razz

[mcloud]

Hi Jrazz,
-Intake boots and o'ring new?
Spray carb cleaner to check if sucking air, revs should increase from idle.
-Cleaned and properly positionned air filter ?
Don't assume it's clean. Dirt can get in it, specially if snorkel is dry and not in place, wich brings next point
-Sealed airbox?
For the life of me, I can't locate that tutorial
-Contact breaker points or up grade to electronic ignition?

http://www.bwringer.com/gs/tdc.html