1980 GS850GL Need some advice

[Steve]

I'm getting really tired of the tank install/removal.... Somethings going to wear out.

At least you have one of the easiest bikes there is to remove the tank and carbs.

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[jsandidge]

At least you have one of the easiest bikes there is to remove the tank and carbs.

.

Ditto to what Steve said. Had mine out a number of times. Plenty of room to work.

[81GS850]

The only way he is going to be on the main circuit is if he is over half-throttle.

.

You're right, sorry I was thinking about cars. So on these CV carbs can you have the throttle blades opened too much at idle? Is that even possible?


OP, what spring did you have left over? Did you put the one that goes under the mixture screws back in? If not maybe those screws are vibrating around and that would explain the erratic idle.

I would think if you screwed them all the way in and the bike was still running there is definitely something wrong. Mine dies if I screw it in more than 2 turns out.

Steve, is it possible that his needles aren't in the right notch and left a little open at idle allowing fuel to be pulled past them? Sorry for the nomenclature, I mean the needles that affect part throttle operation attached to the sliders.

[Steve]

You're right, sorry I was thinking about cars. So on these CV carbs can you have the throttle blades opened too much at idle? Is that even possible?

Well, let's just put it this way, ... if you open them more than you need for idle, you won't be at "idle" very long. It does not take much of an increase in opening to get the engine racing.

Steve, is it possible that his needles aren't in the right notch and left a little open at idle allowing fuel to be pulled past them? Sorry for the nomenclature, I mean the needles that affect part throttle operation attached to the sliders.

Evidently you don't have a full grasp of how these carbs work. Don't worry, you are not alone.

There is only one notch in the stock needles, so that should not be a problem. And, for those of us who DO have more than one notch or have raise the needle by other means ("shimming"), idle is not affected, so that shouldn't be a problem, either.

The needles are slightly tapered. As the slides rise with increased airflow, the taper on the needle allows more fuel to flow past it into the air stream. The tips of the needles never leave the jets, to ensure that they do not hang up by not fitting back down in the jet.

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[81GS850]

Ok, guess I need to brush up on how these things work, I'm trying to apply automotive carb theory and it doesn't work.

[Uncamitzi]

The idle speed knob probably had a spring on it to maintain it's position. It must have fallen off while I was disassembling the carbs ..as I found a lone spring that was obviously from a carb.... I just had no idea where it went as I was in the middle of dipping and cleaning. When I put the idle adjustment knob back on it felt loose and I was concerned .....but not concerned enough to do anything about it...until it dawned on me while riding last night and having to pull over every 10 miles and turn down the idle again.

I'm going to play the the mixture screws some more.. I'm not getting the results I want with the "fastest idle" method, so I'm going to do some more searching. To 81gs850 Yes all the springs are on the mixture screws but some of the screws seem looser than the others, so I 'm going to pull them all out and look at that again.

[Uncamitzi]

Steve the PO had been in the carbs...he's done some good things (replaced all the bowl and cap screws with stainless steel button head screws) and some dumb things (all of the bowl gaskets were touching and rubbing on the floats) and some things I would have questioned even if I knew what I was doing with these things
He replaced the needles with the dynojet needles and put the largest (165) jets in place of the stock #115's ... I rejetted with the 135's from the dynojet kit he gave me when I got the bike..but I don't think that's the problem I'm having now as most of the missing and erratic idle is with little or no throttle open. The worse performance is at about 1/8-1/4 of the throttle ... and that's in correlation with about 1800rpm to 3500 rpm. I'm going to pull plugs first today... and see what they look like after my ride last night...
I'll be back in a bit.

[Uncamitzi]

ok.... starting to look at things a bit closer now... the spark plug wires are all different. I've got 3 different wires and 3 different boots ... so..before I do any more adjustments I'm going to re wire the plugs...

[Uncamitzi]

New NKG boots, caps and wires.... ran the engine for a short while... even for a short burst # 3 & #4 plugs became coated with carbon.. #1 and #2 clean as a whistle. I'm pretty sure the carbon build up is happening while the engine is idling because it runs so well once the throttle is opened up even a little.

And this is now a bit disconcerting .... after I re-did the plug wires... I accidentally leaned on the right coil..which startled me because it was hot to the touch.. the left coil was cool to the touch... somehow I don't think that's good...

[81GS850]

Check the resistance in the coils... I do wonder... Are you sure the wires are going to their respective holes? Maybe the PO sent both plug wires from one coil to the right and both plug wires from the other coil to the left? 1-4 and 2-3 should be the respective coils, not 1-2 and 3-4.

[Uncamitzi]

Well...that's going to have to wait.. I've got the carbs torn back down and looking for mistakes...here's what I found so far in the carbs. The needle valves were not in straight from the piston ...the snap rings were in crooked and the needles were hanging up on the valve. this was in #3 & #4. so those were hanging up and not moving smoothly. One of the rubber plugs had (I think) come off as well (or I didn't snug it up ). Also I had not tightened up the drain plugs ...they were only finger lose. I have a lot to learn.

81gs850... The plugs are wired 1&4 to the left coil and 2&3 to the right coil. but as I said...I'm going to wait on that until I get the carbs back together.

[60ratrod]

Uncamitzi, any time I need a gasket, I try to go through ebay member janquishmotorsports. They use a felt type gasket material and I have had no issues with their gaskets yet. Also, give what ever you are working on a few light taps to break the seal loose. You'll have better luck at saving the gaskets and not damaging the part or gasket mating surfaces

[Steve]

... because of Steve calling me on it with the idle mixture air screws...I'm afraid to call anything a needle valve anymore...

And yet, it continues ...

... here's what I found so far in the carbs. The needle valves were not in straight from the piston ...

At least we know what you are talking about this time (except for the "pistons").

...the snap rings were in crooked and the needles were hanging up on the valve.

If the snap rings were not in their proper groove, the plastic retainer that it holds could come out of place. However, even when it's in the proper place, there is usually a small nub on its lower surface that will push on one side of the clip, forcing it against the side of the JET (not "valve") to keep it from rattling. Yes, when properly installed, the needle will not hang perfectly perpendicular to the SLIDE (not "valve").

One of the rubber plugs had (I think) come off as well (or I didn't snug it up ).

New plugs will have a bit of tension in them to hold them in place nicely, but even used ones are not in danger of falling out, once the float bowls are installed. There is a nub on the inside of the bowl that holds the plug in place, that is what makes that little round dimple in the top of the plug.

... the PO had been in the carbs...he's done some good things ... and some dumb things ... and some things I would have questioned even if I knew what I was doing with these things
He replaced the needles with the dynojet needles and put the largest (165) jets in place of the stock #115's ... I rejetted with the 135's from the dynojet kit he gave me when I got the bike..but I don't think that's the problem.

This raises a few more questions.

I don't remember seeing mentioned, so will have to ask. You running stock airbox and/or exhaust? Or do you have pods and/or a header?

And, ... if a Dynojet kit was installed earlier, the air correction jets might still be installed. If you are going back to stock, you will not need them and they will certainly affect jetting while they are installed.

Also, if you are going back to somewhat stock, the DJ needles might be a bit too rich.

Please let us know what your setup is regarding intake and exhaust, we can help you a little bit better.

.

[Uncamitzi]

And yet, it continues ...
At least we know what you are talking about this time (except for the "pistons").


If the snap rings were not in their proper groove, the plastic retainer that it holds could come out of place. However, even when it's in the proper place, there is usually a small nub on its lower surface that will push on one side of the clip, forcing it against the side of the JET (not "valve") to keep it from rattling. Yes, when properly installed, the needle will not hang perfectly perpendicular to the SLIDE (not "valve").


New plugs will have a bit of tension in them to hold them in place nicely, but even used ones are not in danger of falling out, once the float bowls are installed. There is a nub on the inside of the bowl that holds the plug in place, that is what makes that little round dimple in the top of the plug.



This raises a few more questions.

I don't remember seeing mentioned, so will have to ask. You running stock airbox and/or exhaust? Or do you have pods and/or a header?

And, ... if a Dynojet kit was installed earlier, the air correction jets might still be installed. If you are going back to stock, you will not need them and they will certainly affect jetting while they are installed.

Also, if you are going back to somewhat stock, the DJ needles might be a bit too rich.

Please let us know what your setup is regarding intake and exhaust, we can help you a little bit better.

.

glad you can mostly figure out what I'm talking about even though I mix the terms and labels around... I'll try to be more careful...

When I re-opened the carbs after my first attempt I found what I described. In my first post I did mention that I had made sure that the airbox was sealed... I am running the stock air box with K&N filter, lightly oiled (as per instructions) with K&N oil. In other posts here I had mentioned that the exhausts seem to have been shortened at some point in the motorcycle's 34 year life by what seems to be about 3 inches... I have NO idea why someone would do that but I'm thinking 3 inches wouldn't effect the jetting too much... I could be wrong.
When I was checking to see where the PO had placed the clips on the needles inside the pistons(sliders) attached to the diaphragm, I must have not seated the #3 & #4 circlips right ..they were crooked and the needle was hanging up in the needle jet. This more than likely accounted for the poor performance and the black soot on the #3 & #4 spark plugs.

Once the float bowl gaskets get here I'll put it all back together again.... As to the jetting... I've got the stock jets and a couple of other sizes from the dynojet kit.. Judging from some of the stuff I've seen on this cycle...the PO was jetting to be jetting... why he did things.... who can guess...?

[Uncamitzi]

The spring there on the idle adjustment knob is the one I was talking about.... I wondered where it went until I did a test drive the other day and had to keep turning down the idle in parking lots along the road...IMAG0085[1].jpg