Sputtering, missing at idle to 1/8, help!

[gs850oregon]

OK, heres what is going on....

(Preface, have ridden and owned countless dirt bikes, 20 or more, first bike with more than ONE cylinder)

History:
New purchase, used bike 80' GS850 with 14,000 miles, bone stock.
Have done the following before riding it
1) Removed carbs and their bowls and sprayed with carb cleaner and air hose. (they were clean when I got inside but you never know so I cleaned em' anyway) carb boots in good shape, breather boots a little stiff but after 15 minutes got em' all on, pulled the air screws and re-set at 2 1/4 turns then siliconed the holes after setting (old trick I learned to keep sloppy air screws from leaking, always do it now need it or not)
1 1/2) Removed tank and petcock and drained old gas, clean as new inside.
2) New plugs, NGK Iridium BR8EIX (very expensive!!! $8 ea.)
3) New oil change (Castrol GT 10-40 Synthetic, PS noticed clutch slip so out it comes)
4) Have pulled plug boot ends off and cut 1/2" off and re-installed. Boots look like new inside but wire did not exactly.(thought I heard intermittent spark and miss at first, just to be sure)

Symptons:
I have a progressively getting worse sputtering, missing issue. It started out by me noticing a slight surge in 5th at about 3,000 rpm, like the wind gusting at you that seemed intermittant, in fact I never noticed it at all for the first 50 miles or so.
Now I have a rough idle and missing below 1500 rpm and an Intermittant miss throughout the range when cruising, runs perfect when under a heavy acceleration or pulling a steep hill.

Possible remedies ?:

A) The plug wires and boots are failing. Can I use automotive style suppression wire? 8mm or 7mm? Can I avoid the stock style plug boots, do they go "bad"? The wires can be "dug" out of the stock coils and replaced, true?
Should I use solid copper core style wires with resistor plugs (radio interference)?

B) The air mixture screws set at 2 1/4 turns is a little off causing a lean mixture. Since these are in front of the carb, I can't remember, do I go in to richen or out?
Since this is all stock I ASSUME no re-jetting is needed, at least I don't want to mess with it since the factory should have gotten all xxxx thousand of these GS's right, right? (I am at sea level)

Thanks guys!

[BRycraft]

Iridium Plugs

My first comment is Iridium plugs, I have not personally used them but everyone I asked gave me the dont waste your money, one person in particular who's opinion I respect said he had tried them on numerous occasions and they kept failing, just a comment to consider.
The coil wires are molded into the coils, however at Z1 they sell a splice that allows you to cut those wires back closer to the coils and splice in a new wire the rest of the way. Personally I would only use bike wires for your bike, different wires have different ohms per foot and if the specs are not right you will only make more problems. Dynatek sells wires for under $20, Z1 Enterprises for like $14, carbon is ok with points but I would recommend the suppression wires if you have an electronic ignition.
I found the plug caps on my wires were way out of specs, they had stamped on them 5K ohms and when I measured they were over 10K and the other 2 were around 8K, the spare set I had were right at 5K, so they can go bad over time. I replaced my coils and wires with Dynatek's and besides finding my inline fuel filter had warped ends due to heat and was restricting fuel flow, this was causing all kinds of intermittant problems with cylinders not firing, removed filter and replaced fuel line, runs perfect.

Did you ever balance the carbs? that could also cause all kinds of problems if they are not in sync with each other...

Good Luck Bill

[bwringer]

You have the textbook signs of bad intake o-rings.

http://cycleorings.com/intake.html

The fix:

http://bwringer.com/gs/intakeorings.html

[bwringer]

I'm also sorry to report that the Iridium plugs are a complete waste, unless you just like the way thtey look or something.

NGK B8-ES are less than $2 each at Advance Auto and Pep Boys, and they are absolutely perfect for your engine, even if it is modified. I change mine every spring just for giggles, but they've never actually needed to be changed after 12,000 - 20,000 miles.

Dyna ignition coils would be an excellent investment. The wires eventually always go bad and cause problems. You can use virtually any spark plug wires with the Dyna coils -- I bought a universal V8 set in a groovy bright yellow from the auto parts store, so I also have a spare set in my garage.

[gs850oregon]

It could be the o-rings, never thought about that.

The problem is, is that it is the weekend and suppose to be really nice weather....so, I am a little impatient, like I want it to run today of course.

I am suspecting a combination of lean idle (could be o-rings) AND some worn out plug boots. The wires appear to be solid wound copper so I imagine they are o.k.

The Iridiums simply state that they are "lower voltage" so I thought they would be easier on an aging bike.

So I think I am going to do the following.....

1) Apply vaccum to the petcock and check for good fuel flow.
2) Pull carbs and check o-rings, what the heck, I'll just replace them.
3) New plug boots.
4) New B8ES plugs.
5) Adjust air screw for best rev's at idle.
6) Cross my fingers and see if it runs better.


Thanks

[gs850oregon]

Just pulled my plug boots to check them.....

#1 = 10.10k ohms
#2 = (no continuty whatsoever, my tick I thought I heard?)
#3 = 14.73k ohms
#4 = 05.57k ohms (NGK plug boot)

I am guessing I have found part of the problem.

[semerm]

Check to make sure your carb ends are really tight against the air box. You could be getting extra air and it causing these issues. It is an easy check loosen the clamps, make sure they butt against and are inside and then tighten. It is really easy to have them not on correctly and not even know it. After this if it is still doing it, start the bike, idle it, spray carb cleaner near this joint, if the rpm's go up, they are leaking, if not you are probably good in this area.

Good luck and post your results.

[bwringer]

You should be able to find the spark plug boots locally -- you might have to poke around in a few motorcycle shops. Someone also mentioned a butt connector you can use with stock coils. You cut the original wires off a few inches from the coils, then use the connector to splice on new spark plug wires.

The fancy spark plugs will work fine and should last a long time. You might as well use them now that you have them! I was just pointing out that there's no real benefit to them over the original spec plug. They're still perfectly fine spark plugs. You might actually get several years out of them if the engine runs fine and never fouls them.

To answer another question, the normal settings for the air screws are between 1-1/4 to 2-1/2 turns out. In makes the idle mixture leaner, out makes it richer. I confess that I never could tell much difference in the idle when twiddling these screws on my bike, so I set 'em all at 2 turns out and stopped worrying about it.

[BRycraft]

Replace Boots

Just pulled my plug boots to check them.....

#1 = 10.10k ohms
#2 = (no continuty whatsoever, my tick I thought I heard?)
#3 = 14.73k ohms
#4 = 05.57k ohms (NGK plug boot)

I am guessing I have found part of the problem.

That was just how my boots tested out at, only 1 was right one, ended up replaceing the coils and wires and major improvement, you have to fix that problem otherwise any other troubleshooting is really moot until that problem is taken care of.

Bill

[Pharkmeh]

You have the textbook signs of bad intake o-rings.
http://cycleorings.com/intake.html

The fix:
http://bwringer.com/gs/intakeorings.html

excellent post - thx m8 - this may be some of the issues Im starting to get..

cheers

Phark

[gs850oregon]

I replaced all of the plug caps with new NGK caps. The spark tick has vanished.

I removed the carbs and found the o-rings to be firm but not broken or brittle. I replaced them anyway and also added some "Ultra Copper" to the joint.

I adjusted the mixture crews for fastest idle and it seems to like 3 1/2 turns the best. Any above this and it really does not seem to improve that much more.

I believe 3 1/2 turns are a little out further than they ought to be so I am guessing that my pilot jets need to be increased by one size.
The bike runs well but has a slight studder and intermittant missing in from idle to 3,500 rpm range. Above this range the bike pulls very hard and shows no signs of any issues.

We traveled up a small mountain yesterday (about 4,000 feet) and the problem really was hardly noticeable. I assumed the leaner mixture was working at the higher altitude.

One point to inform all the troubleshooters, my air box is stock but the black boots can be spun inside the metal. I do not know if these were glued in like some or just stuck in there. Do you suppose that any air leaking at this point on the intake could be causing the mixture to be lean enough to cause these issues? Someone stated in one of the forums that Suzuki had these bikes jetted to lean from the factory to help with emissions.

I am wondering now if the box needs sealed (if it was factory) do I just go ahead and increase the pilot jet if it is to lean from the factory while I have everything apart or just do the box first and then see.

Thanks

[Billy Ricks]

3 1/2 turns is still on the jet so I wouldn't worry about it. If you go up a size on the pilot then you probably won't even get a full turn out to be where you are now.

[gs850oregon]

Another point I should make for those who know, it almost feels like a two stroke power band. It really comes on after 3,500 through the top. Below that and it is weaker and not real clean on hitting on all 4 all the time. Some intermittant missing and surging in this lower range.

I know that these jets overlap somewhat and as the last post indicates, it is probably still in range for the jet it has.

I would raise the needle a notch except it pulls so strong after an 1/8th throttle that I do not believe this is it. Just puttering around in first gear at an idle, to just enough throttle to keep moving, it misses intermitantly almost like a loping aftermarket camshaft in a car. A slight twist of the throttle, a short hesistation, and it clears right up and start to pull. It has this little hesitation in all gears at all speeds below 3,000 rpm and below 1/4 throttle.

When cruising at say 50 mph and the revs are at around 3,000 to 3,500 rpm and about an 1/8 to 1/4 throttle, holding steady speed and rpms, it has the intermittant miss. This is when it is most noticable and annoying.

Apparantly these old GS's are very finicky to jetting.

Thanks

[gs850oregon]

One more, I just noticed these spec's on this site:

GS850 (80) the specs are for the CV's

idle.................... 1050 +/- 100 r/min
carb................... mik BS32SS
id no................... 45120
bore size ............ 32 (1.26)
float height ......... 22.4 +/- 1.0 (0.88 +/- 0.04)
fuel level ............ 5.0 +/- 0.5 (0.20" +/-0.02")
VALVE SEAT........ 2.0
STARTER JET....... 32.5
PILOT SCREW ..... 3.5
PILOT AIR JET ..... #200
pilot jet............... #42.5
jet needle........... 5D57-3 (the -3 3rd notch)
needle jet .......... X - 6
pilot outlet........... 0.7
BY PASS............. 1.0, 0.8, 0.8
MAIN AIR JET...... 1.7
main jet............. #115

I assume that the jet in the back of the carb you can see when the air box is off are the ones called "Pilot Air Jet".

I know mine are all 180's and the ones spec'd here say 200 so I think I may be on to something...... [-o< maybe someone else has been changing things.

[gs850oregon]

I rejetted per the spec shown. I noticed later when I went to the Alpha-Parts.com site, fische has different jets than what is posted on the site. For instance....
Stock is 190 on the air jet, the site indicates 200 (mine was 180)
Stock is 40 on the pilot, site indicates 42.5 (mine was 40)
There are other differences as well on the jetting shown (like the needle).

Anyway, the bike is running much better on the bottom after an 80 mile round trip tonite. However it is now a little rich and I can even smell it when idling. The bike ran best again at 3 1/2 turns after running for 5 minutes. I now believe that the engine must be hot, hot, hot before adjusting the air screws or otherwise you'll be rich after riding for while.

I plan on rejetting again for 190 and 42.5. The reason on not going back to the 40's is that I feel that it is a little lean at 1/8 on acceleration and also when cruising in this throttle range. Maybe the air jet has something to do with this range as well, I just don't know so I am in that experimental stage.

Has anyone jetted an 80' 850 with similar results? if so what did you wind up for a stock setup?

I'll post my results.