'78 GS1000 Idling Issue

[paulkdx220]

hello!

K&N pods, unknown 4 into 1 exhaust, mains 120, pilots 15 (stock). new o-rings on boots, cabs cleaned and float levels set. valve adjustments all in spec, read the newbie mistakes thread and i think i am in the clear.

should the pilots go up in size with pods?

when bike is fully warmed up it still likes about 1/2 choke and revs pick up quite a bit. i leave it off when riding however. plugs are sooty but not to the point where they foul.

bike idle rpm wanders a bit after warm which to me indicates an air leak. i tried to search for leaks using a propane torch but didn't seem to affect rpms.

bike runs very well off idle.

regards,

paul

[MisterCinders]

Propane torch for hunting air leaks seems . . . scary.

Although not related to the idle issue, you should also make sure your needle is adjusted for the added air flow.

If your idle wanders, you are right to be hunting air leaks. With sooty plugs, however, see if your idle isn't sagging when warm (i.e., RPMs dropping, tries to bog out), as that would be a richness issue and line up with what your plugs are showing.

Where are your air and fuel screws set?

If you checked through the Newb Mistakes list, I assume you also addressed all the usual suspects (valve adjustment, strip and dip carbs, etc.). If not, do that too.

Some people increase the pilot jets for pods and pipe. I have tried that a few times, but it always ended up being too rich at idle. YMMV.

[RobG1970]

Very scary -

propane torch for hunting air leaks seems . . . Scary.

Although not related to the idle issue, you should also make sure your needle is adjusted for the added air flow.

If your idle wanders, you are right to be hunting air leaks. With sooty plugs, however, see if your idle isn't sagging when warm (i.e., rpms dropping, tries to bog out), as that would be a richness issue and line up with what your plugs are showing.

Where are your air and fuel screws set?

If you checked through the newb mistakes list, i assume you also addressed all the usual suspects (valve adjustment, strip and dip carbs, etc.). If not, do that too.

Some people increase the pilot jets for pods and pipe. I have tried that a few times, but it always ended up being too rich at idle. Ymmv.

[OldVet66]

How many turns out from lightly seated on the fuel needle screws? One turn out would be a good starting point. They will most likely end up between three quarters and one turn out. The air screws roughly twice that. You'll most likely have to play with main jet needle height and size. A Dynojet stage three jet kit will save you a lot of time and angst, if not money in the long run. The Mikuni needle taper is not right for pipes and pods, though some have luck with it.

[hampshirehog]

The propane torch trick works fine and it's not dangerous if you use common sense.

No need to change your pilot jets - it should run fine on 15s. I would start by looking at how clean your carbs are. You might find a blocked pilot jet or 2 in there. Plus were the fuel screws ok - all in one piece and not with broken tips still stuck in the body?

[paulkdx220]

i just took another look at the carbs...

pilots are 17.5, not the aforementioned 15.

this must be an air leak issue... if i grab the carbs and flex them up and down, rpm's change, i'm going to do the propane thing again this time when it's not so windy. i also have try pressurizing the intake rubbers and do a soap and water check.

just to elaborate on the 1/2 choke thing: the rpm's climb up to about 5500 rpm.

there is quite a bit of popping in the exhaust when rolling off the throttle and decelerating while riding, to me that's indicated an over rich condition. which isn't congruent with a lean condition that is seemingly indicated by the use of choke mentioned above.

what and where is the adjustment for air jets? i don't think my carbs have them. i just see the brass idle mixture screw on the sides of the carb.

on my '79 GS1000 parts bike the carbs look different slightly. the float bowls on it have hex plugs on the bottom for drains/acess to main jet. they also have brass floats as opposed to the black plastic ones in my '78. what is up with that? also there is and adjustment if i recall on the '79's carbs under the carb where as the '78 doesn't. air screw? just to clarify, neither carbs is a CV style... they are VM's

man, i miss my kawi H1, so simple to tune!

[OldVet66]

Go back to the stock #15 pilot jets If those are VM 26 carbs. The stage three kit even recommends them and they work. The air screws are on the outboard sides of the carbs and the fuel needle screws are on the front side of the float bowls under the carbs. They were painted in by the factory, so it looks like you are in for a carb rebuild. If you haven't found them, a total tear down is in order, soaking in carb dip and all O-rings replaced. Check out the carbs on the parts bike and send pictures. You might have a $600.00 set of VM 29's there If you're lucky. The '78 and '79 both had the bottom adjustment, fuel needle screw. I don't know if you all got the VM 28's in Canada, but from what I remember of the one set I saw they looked like the VM26 except for some brass passages that were on the intake side that weren't on the 26.