Extreme Rich condition

[HobieSun]

1980 GS750L (TSCC) 17.5k miles
Ok, I think I have finally fixed my charging problem, (Knock, Knock) Now I am having a very rich condition. The bike pulls strong until about 6,000RPM and won't go any further then 7k maybe 7.5krpm in any gear. At idle, it emits black smoke, if you rev it it will go very quickly to 9k along with a big cloud of black smoke. I am going to make sure that all of the float levels are good tomorrow and adjust. I will probably end up taking the entire carb setup off and inspect everything. Should it be obvious if there is any wear on the needle and seat? I am not a huge carburetor buff, but I am learning along the way. Is there anything else that I should be looking for as far as wear and the actual need to rebuild the carbs? It has 17, 500 miles. I plan on adjusting the mixture screws and after I am done synchronizing the carbs as well. I am really hoping that it is a simple float adjustment problem, but I have not had much simple things wrong with this bike yet so...

I know that I have to figure out the initial fuel problem, but, it takes a spark plug (NGK)d8ea or (ND)X24ES-U. I am currently using new NGK's, I would like to use a hotter plug. Does anyone know what a few plugs hotter then these would be?

 

[ruddy]

Check your air filter. The foam disintegrates over time and can block air flow. If that's not the problem, then it's time to pull the carbs. Check the Garage section on this site for carb cleaning step-by-step.

 

[HobieSun]

Its an 80 TSCC, it comes with a paper element which looks good. I am pretty sure that the carbs are very clean, but I know it doesn't take much. I will pull them in the morning. It would be nice if they were simply dirty. I basically have a good midrange with very poor low and highend. That along with hitious gas milege.

 

[Jethro]

Have you read the plugs to see if all cyls are running rich? Sometimes the #2 carb can get flooded if the petcock diaphragm is leaking. Make sure you check the needles for the floats, they may not be seating correctly.

 

[HobieSun]

I just checked the petcock, doesn't seem to be leaking. All plugs are sooty and black. One thing that I am wondering now that I have read a few problems with the petcock, I notice that mine makes a clunky noise at idle, you can hear it through the tank when it is coming down to idle. I know that it is the petcock opening and closing, but I was wondering if any one else's does that. I took it apart and everything looks ok...

 

[KEITH KRAUSE]

Did you inherit this problem or did the bike run well earlier?
Any mods or completely stock?
Did the bike sit for awhile with gas in it?

 

[HobieSun]

Well, about two months ago I got the bike and it didnt run. I took the bowls off and found that the rubber plugs that where in the pilot jet holes had melted into the bowls. I asked a few people on this site what the heck they where and they said that it was for emissions and that I didn't need them. I have the carbs off now and I am a little confused from that information. They say to turn these in all of the way and then back them out 2 full turns. It seems as if it is way too loose, not to mention, that it is an actual jet and that there used to be a plug there. I am confused.

 

[HobieSun]

sorry, got off of the subject a little. After I cleaned out the carbs with the carbs on the bike I managed to get it to run. No mods or anything other then fixing the charging system. It seemed to run well, I had figured that the charging problem was why it was running rich and didn't have any top end at all. It ran rich before but it seems worse now. I have only gotten into the first carb and everything looked good. I am going to check the float level and wait to hear what the hell to do with the mixture(pilot jet).

 

[KEITH KRAUSE]

The pilot jets should be firmly tightened.
The mixture screws, on top/engine side of carbs, should be adjusted for highest rpm. I'd set them initially about 1 1/2 turns out from lightly seated and go from there. At 1 1/2 turns, any excessive richness problems will not be because of the mixture screws though they may need fine tuning. As long as everything else is good with the carbs.
Check the floats as you planned. Measure from the bowl surface, gasket removed, to the top of the curved float body, not to the top of the arm that supports the float body. If your float valves have weak pins and they sag too much under the float weight, you should replace the float needle valves or accurate adjustments will be impossible.
With the bike sitting, gas can varnish up the passages everywhere. With your possible rich condition, pay special attention to the pilot and primary air jets at the filter side of carbs. Clean with cleaner and blow out with hi-pressure.

 

[KEITH KRAUSE]

Also pay attention to the many small holes in the needle jets/bleed pipes. Plugged holes will compromise fuel atomization and cause a rich mixture too.
I have to wonder if the PO made any jetting changes, though they shouldn't have if the bike is completely stock.

 

[HobieSun]

I believe that the main jet is 112, the air jet is 170. I took everything apart and cleaned every little orfice and valley. The needle and seat looks good to me. Everything seems ok, on the first one anyhow. Thanks for your help, I will let you know what else I find.

 

[minutemen]

Put the rubber plugs back in.

 

[HobieSun]

I am going to. The old ones melted for some reason. So I am off to find some new ones.

 

[Guest]

I also have an 80 petcock and it also made the same sound. I thought it was alright because it appeared to be working properly. I spent way too much time messing with carbs and such when all I needed was a new petcock.

 

[HobieSun]

What did your bike do with the bad petcock?

 

[Guest]

It would die on the side of the road and not start for a few minutes.

 

[HobieSun]

Ok, I bypassed the petcock, not a difference at all. Put back together, readjusted the float level on the fatter side, didn't make a damn bit of difference. Thought that I may have some air leaks between the airbox and the carbs so I sealed it up tight with a few different things, not a damn bit of difference. I can hold my hand over the airbox hole a certain way and get it to rev hard all the way to 10k, if I take my hand off of it, it will bogg, if I put the airfilter box in it will bogg. I have good spark, new plugs, timing matches, getting plenty of fuel through numerous ways, no air leaks, everything has been looked over and/or adjusted. Complete charging system is new, battery, regulator, stator. I am done. Trading the POS in. I have never had anything give me so much S^&! and run so badly.

P.S. Anyone want a 1980GS750L in perfect running condition, that just happens to run ****ty? I have $800 in it.

 

[frosty5011]

Did you ever replace the 4 rubber plugs that cover the idle jets ?(Not the plugs which covered the mixture screws on top of the carbs.....I saw that there was some misunderstanding about which plug(s) you were talking about in an earlier post).

 

[HobieSun]

Yes, After I figured out what someone told me awhile ago was incorrect, I replaced the plugs. Thank you though.

 

[KEITH KRAUSE]

Placing your hand over the airbox hole forces the jets to draw fuel, at least momentarily. The bike will rev better.
Because the bike wasn't running right from the PO, the sky's the limit as to what could be done wrong. You've checked many things but there's still more possibilities.
You may have a vacuum issue here because the carbs seem fuel starved...but at the same time you have black/sooty plugs. It seems like more than one problem.
The airbox may have poor seals or a fit problem somewhere and this would effect vacuum. It could even be the wrong airbox, off a different year/model. I assume you still use the lid.
A poor bench synch/vacuum synch can cause vacuum problems.
I also wonder if the carbs are the correct ones and the jetting is stock, especially the jet needle position. If a PO played around for whatever reason and raised (shimmed) the needles or re-assembled parts wrong, you'd be rich.
These things would explain all your problems. I'm not saying it's these things but there are a lot of things that can go wrong.
A faulty ignitor could explain a poor spark resulting in a "rich" condition.

I don't know why you set the float levels richer with your symptoms.
Also, you said you though you had air leaks between the box and carbs and you "sealed it up tight with a few different things". Not sure what your attempts were but you can't expect a bike to run right with "home fix its". Your words make it sound like you improvised. That generally doesn't work, or certainly not for long when dealing with intake problems.