Running lean with sooty plugs

[Guest]

Hello everyone, I've just recently finished my first (and only) cafe build of my gs650E. if anyone's interested here are some pics of the build (https://plus.google.com/photos/11131...70858866789745).

I've installed pod filters on it, the cheapo kind. The photos show taped pods which was my initial remedy for rejetting but i've since untaped and unrestricted them. Initially the bike was idling well but running poorly when throttle opened, the engine would bog down rather badly and pop on acceleration. So i figured it was running lean (which is what you expect after pods) but the spark plugs were super sooty (not oily just sooty). This confused me but i still went ahead and upped the main jets from the stock #110 to #120. NOw the bike pulls on acceleration for 50% on throttle opening but there's still some slight hesitation, so I'm thinking to go up a size more maybe on the mains. THis indicates that the bike was indeed lean before rejetting, yet the spark plugs are still sooty black now just like before. Also the rpm hang around 3K when the bike is warm (and only when the bike is warm) which i think means too small on the idle jet so i was thinking to go up one size on them as well to see if they cure the hanging rpms. I've unscrewed the idle screw at 3 turns and it doesn't seem to make the problem much better. I've checked for leaks and replaced the o-rings on the intake boots, no cracks in the vacuum diaphragms either, so i don't think it's an air leak.

So my question is why are the spark plugs sooty when all the indicators are that the bike is running lean. I haven't done a sparkplug chop test yet so it's arguably the idling circuit that's making them rich somehow since i check the sparkplugs after idle running. could it be my cheapo pods that are dirtying the incoming air? I am not prepare to shelf out on a set of K&Ns yet, maybe next season. My ignition is stock but the spark is strong and I have great compression. Any ideas or input would be appreciated.

thanks!

[Steve]

Proper plug chops are going to tell you a LOT about what's happening.

Your adjustments don't sound too bad, but your "cheapo" pods are not going to affect jetting at idle. If there is no change in response with the pilot screws (or mixture screws, but not 'idle screws') turned out 3 turns, try turning them out to 4 or 5. If you get a change there, you will need to up your pilot jet size. If not, I would suspect plugged pilot ports. No way of telling from here whether they are plugged due to improper carb cleaning or broken screw tips, but it's definitely something that needs to be checked.

What spark plugs are you running? Improper heat range can also show up as sooty plugs, but you should not change plugs to fix that problem, you should fix the problem so your plugs look 'right'.

You can get quality pods without the expense of K&Ns. Check out the APE pods. They look (and work) just like K&N, but you don't get that fancy K&N logo, and you get them for half the cost, or less.

.

[Big T]

Take a minute and read the Pipes, Pods, Panic stickie

[badeaslava]

ok, i've checked my plugs they're NGK D8EA which is what the manual says so they should be good. I've unscrewed my mixture screws to 4 turns and the largest difference that i saw was that the bike started to die at stop lights, so then i unscrewed the idle adjust screw to open the butterflies up a bit and in result i got the same hanging idle. I guess the carbs are really susceptible to the nominal setting of the idle adjust screw

The other thing i noticed today is that my fuel mileage is horrible, i don't get anything near the nominal 40mpg, but much less maybe around 20? I filled up a gallon today and will see how much that will last me. I don't ride it really hard but do give some throttle now and again to get some acceleration adrenalin could it be that somehow i'm loosing fuel through the idle mixture screw due to the mating surfaces being worn? I've also changed my needle valves to new ones since the old ones were leaking gas into the cylinders, but i don't seem to have that now (my oil level is constant), is there any better way to check without draining the oil?

But if i'm loosing fuel somehow through the carb and thus fouling my plugs why does the bike have lean running symptoms??

sorry about the long post, i'm super perplexed here, looking for some input... thanks to everyone for pitching in

[chuck hahn]

RAISE the float hts by 1 MM. this will lower the fuel in the bowls..which makes them run leaner.

Check the rubber plugs over the pilot jets..MUST be supple and well seated. Hard and unseated plugs allow fuel to bypass them and enter he circuit..thus runs rich.

Check the voltage to the coils and freshen the ends where they screw into the caps.

Sooty black plugs is a rich condition. So, it stands to reason that going up in jets is just compiling more and more fuel into an already out of whack system. Go back to the stock jets if you have them and set the top mixture screws at about 2 1/2 out and restart the process after you have rechecked the floats and the rubber caps. And while the bowls are off, work the floats up and down and see that they do not scrape or rub against the gaskets.

[badeaslava]

I know that sooty plugs indicate rich running which is what confused me in the beginning, however i did go to smaller jetting than stock and the bike constantly sputtered and backfired during acceleration. When i switched to larger main jets it ran much much better, no backfiring and lots of power delivered, which leads me to think that indeed it was running lean with stock jetting. Another interesting fact is that with stock jetting the plugs were still black sooty, so the only explanation i have is that fuel may be somehow ending up in the combustion chamber but not burning completely.

My rubber plugs on the idle jets are new and sitting well in the float bowls.

Maybe my ignition timing is off. I have the stock advancer setup on the bike, is there any way to check the timing on the ignition? It's a mechanical advancer with magnetic pickups. I've checked valve timing per manual instruction and they are fine so my valves are opening at the right time.

I've also done the bypass mod to get 12v directly from the battery to the ignition coils so my spark should be strong. It starts up pretty easily anyways indicating that the spark is strong (i think).

[tom203]

".....I've also changed my needle valves to new ones since the old ones were leaking gas into the cylinders, but i don't seem to have that now (my oil level is constant"

plus this...

"...Another interesting fact is that with stock jetting the plugs were still black sooty, so the only explanation i have is that fuel may be somehow ending up in the combustion chamber but not burning completely. "


Eliminate this problem 100% by getting new petcock-
maybe your choke plungers are leaking, so make sure cable is not holding them open
what main jet size are you running now? My shafty uses 110 with stock airbox stuff

[gustovh]

Your pilot circuit deals with your low speed, idle-4000, turn each pilot jet in 1/4 turn at idle until it either rises and then drops off or the idle starts to drop, then back each pilot needle off 1/8 to 1/4 turn and adjust your idle screw. Each needle needs to start from the same turns out, my base is 2 1/2 turns and usually end up around 3/4 to 1 1/2 turns out. Next go take it for a ride and check your plugs when you get back...each of them. You might have a carb or two that will need to be tweeked. If you have a good sync you should have good results.

[badeaslava]

"Eliminate this problem 100% by getting new petcock- "

I've installed a petcock kit that replaces the diaphragm and orings so those should be good. The choke plungers i;ve checked the cable has play so they appear all to be closed. My stock jetting was indeed 110 on the mains with the stock airbox, now i'm running 120 main jets. I have bench synced the carbs but not vacuum yet, maybe i should do that soon.

Somehow i'm burning waaaaaay tooo much fuel (my mpg is 18 or so), yet the bike still doesn't provide much power above 4k rpm, can't get it to rev to redline when going. I has an rpm hang above 2.5k or so, in other words once it revs above that value the rpms just climb to 4k and hang there, when its below it, the rpms fall back down. This only happens when the bike is warm. Is there a possiblity that there's a crack the block somewhere which expands as the bike warms up such that it allows air to rush in even when the throttle plates are closed?

I ordered new throttle shaft rubber seals which are the last rubber parts in the carbs that i have not replaced with new ones. I suspect maybe it's leaking air trough there which is giving me the hanging idle. Although i can't find any info on the forums that would indicate anyone else having this issue. I've had a carb mechanic guy take a look at my carbs and he can't make ends meet either. SHould i just bite the bullet and go with the dynojet kit, except that i think the main jetting is just way to big on that? What do you guys think?

[thd]

It may seem unlikely, but I recently fixed a similar problem on my GS1000 by changing the o-rings that seal the rubber intake manifolds to the cylinder head. The old ones were cracked and allowing air to be sucked in ahead of the carbs. After changing them I retuned the bike to find out just how big of a difference those leaks were making.

[badeaslava]

Thanks for the suggestion THD, i've actually replaced those o-rings a while back, so they're new, i don't think the leak is through there.

However i did notice some oil leaking through what seems to be the head gasket. It's hard to say for sure where they're coming from but the engine block has traces of oil below the head gasket right next to the exhaust manifolds on the left side (i suspect because i lean it on its side stand a lot) Could a leaky head gasket cause my hanging rpm issue and sooty plugs? Would a compression test show a leak in the head gasket?

I replaced every seal in the carbs to new ones, even the throttle shaft seals, so at this point its all new rubber in it. I even bought the dynojet kit for its "amazing" needle shape, it didn't make a difference. I think i have a gross air leak or dysfunction somewhere because nothing i do with the carbs seems to change the bike behavior. When it warms up it gains a massive rpm hang (climbing rpms). I haven't vacuum synced the engine, only bench sync, should i do that before i do anything else?

THe dynojet uses massive 155 size (dynojet size) main jets that when i plug them in, the bike pulls hard but i get massive black smoke from the tailpipe when i rev it up. So now i'm running with 125 size main jets (mikuni sizing). The smoke i see from the tailpipe is grayish in color in normal running, but when i rev it up suddenly to 6k rpm close to redline, it just becomes black smoke. Floats are set within spec. My idle mixture screw is set 1 turn out right now, at 0.5 turns the bike doesn't start. I still have black sooty plugs. Has anyone experienced leaking fuel through the choke system from imperfect sealing?

[GSX1000E]

I do not know how to undo any damage that drilling the slide as those dynajet kits call for because I have never needed one of those kits on any of my bikes.
But, on my '82 650, I had the cheapo pod filters and it ran great with 117.5 main jets. Perhaps you should try those. Mine averaged 54 mpg.

[Joe Guilbeau]

The following is assuming that the engine is stock with with pods.

Your Technical Service Manual indicates the following...
GS650 Carb Specs.jpg

http://www.mtsac.edu/~cliff/storage/gs/GS650E_Service_Manual.pdf

Reduce the Main Jet size, try #105 or so.

My 1981 GS1100EX has a Wiesco 1166 Big Bore Kit, Air Filter Pods and a Vance & Hines 4-1 exhaust and my Main Jet is #138.

Pull the diaphragm's and using Snap Ring Pliers check the Jet Needle position, two or three positions from the top should get you in the ball park.

If you can see your Pilot Air Jets try reseating them all the way in (very light pressure or damage will occur) and back them out 2 1/2 turns.

You should pull the carbs and go through them with Ed Ness's tutorial for visual aid on the above suggestions.

http://www.mtsac.edu/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

[BigD_83]

Would a compression test show a leak in the head gasket? A leakdown test would be more appropriate for this

I haven't vacuum synced the engine, only bench sync, should i do that before i do anything else? Vacuum synch would be a great idea.

So now i'm running with 125 size main jets (mikuni sizing). Has anyone experienced leaking fuel through the choke system from imperfect sealing?

Yes, due to a cracked choke plunger seal, but not to the extent you are describing. That is a VERY large main jet you have. I've settled in at (IIRC) Mikuni 110s with my 4 into 1 on stock airbox, and I could drop back to 107.5 as it is running a tad rich

[tirebiter]

Do all 4 spark plugs look exactly the same everytime - dry but sooty ?