long time reader/first post

[Guest]

amongst the annals
I read something like
twins don't need a tool to balance the carbs

that's what I'm trying to do
so how do I do it
please phrase any & all explanations in the "dummy" style

'86 gs450L

recently lost some left side compression
& gained some left side smoke out the exhaust
- said smoke only appears after the bike is hot & only at low rpm/idle

I'm betting on a lack of carb coordination 'cause this started after I "cleaned" the carbs & reinstalled

(quoted because it's the first time I've ever cleaned a carburetor. ever)

despite these symptoms this bike runs very very strong

[tom203]

dummy style? OK, you want both carbs to do equal work. The throttle plates need to be matched similar -at idle,they are just open a sliver,then as you twist throttle,they open hopefully the same. Did you bench sync them after your cleaning? A vacuum sync gets them closer - unless the bike has mechanical issues, i.e. Low compression in one cylinder.

[tkent02]

On a twin you can raise the idle up to where it idles smoothly on one cylinder, pull one spark plug lead then the other, adjust the synch to where it idles at the same speed on either cylinder. Usually this will get it close enough, perhaps not perfect but running very well.

As far as your smoking and compression, what other maintenance has been done?

[sanozz]

honestly I don't know what a bench sync is, so no

as far as other maintenance I have adjusted the valves, but nothing else major
again, these symptoms manifested when I put the carbs back on

right now I've got some mikunis from an '81 450 on there but it's worse,
so I'm diving into the original carbs again, & by the book this time
with these carbs on her she's very slow to return to idle, and these forums provide solutions to this, but for the life of me I cannot locate the pilot screw. I see it on the diagram, but not on those older carbs nor my original ones

so how does one bench sync

much thanks, gentlemen

- Brett in Seattle

[sanozz]

may I clarify?
so I would
pull the boot off the left plug
then raise the idle close to smooth on right side
& vice-versa?
am I raising the idle by the idle adjuster on the bottom?

thanks again, good sir

[tkent02]

No, raise the idle so it won't quit with either cylinder' spark plug wire unplugged. Pull one, watch the tach. Put it back on, pull the other and watch the tach again. Adjust the synch screw so both cylinders idle at the same RPM when the other cylinder's spark plug wire is unplugged.

Once they are even, lower the idle back to a normal idle RPM. Then adjust the mixture screws.

May have to go through both of these adjustments a couple times if the mixture screws are all screwed up.

[sanozz]

thanks
now I don't ask this next question without some embarrassment
nor without a great deal of research to find out on my own
but these '86 carbs I think are different
so:

where are the sync & mixture screws?

[tkent02]

I don't know, never worked on an '86 450. You may find out here:

http://members.dslextreme.com/users/bikecliff/

[Big Rich]

If you have the carbs off the bike, look at where the throttle cable hooks up to them. The cable pulls up on a bracket attached to both carbs, which open up the butterfly valves. Now, that bracket should have an adjustment screw somewhere near the middle (said screw controls the balancing between the left and right carbs).

The mixture screws almost definitely had a brass plug covering them when they left the factory (EPA requirements ....). Just guessing, but look on the underside of the carbs, especially on the engine side (not the air filter side). There may be brass plugs there unless somebody already removed them.