Spark plugs are black

[christopher]

I have a 77 gs750 and the spark plugs have been turning really black/burnt and some moisture is on them after just a few minutes of riding. So i took my carbs out and soaked all the jets in chemtool and cleaned everything and put new jets in only one of the carbs. I tested them with the airfilter box off and noticed one was spitting out gas still, so i bent the tab on my floats to specs and backed the air skrews off a whole turn from the bottom. After testing the plugs the were still black. So i rebent the tabs and adjusted the air skrews and my plugs are still black. My bike starts right up but my plugs are black. So as it sits now, my floats are bent even lower to not allow as much gas in and my air skrews are still a whole turn from the bottoming out point. I was about to put in plugs the will handle more heat and the plug wire came out of the plugcap for my sparkplugs. So my question is, could this be caused by faulty coils? Since one sparkplug wire was to the point of breaking off? Im getting tired of taking my carbs out and adjusting the tab on the float. Not sure what else to do? PLease dont tell my to go read the forum because my not good at navigating this site. Any help is appreciated.

 

[TheCafeKid]

Christopher, which way are you bending the tabs? Pics of your plugs would be helpfull. The floats should be right around 26mm in hight (measuring with the carbs upside down, from the gasket mateing surfact to the top of the float...like this

) when in this possition you actually would be bending the tabs in reverse (bending it up moves the float level down, and vice verce) Have you checked that your petcock is funtioning properly? are you getting sufficiant spark to the plugs? Without pics its really hard to tell, but it sounds as if in fact you arent burning all the fuel your carbs are giving..so these things you should check as well.

 

[TheCafeKid]

Sorry for the fuzzy pic btw, apparently my camera thought my lil screwdriver was more interesting. heh

 

[Dave8338]

You have carb adjustment issues. This could be jets (too large), adjustment screws, float height, leaking seats, bunk petcock, ect.

Is your bike stock ie. air box and filter, exhaust stock or 4-1 pipe or some other set-up?

 

[TheCafeKid]

Yes good points also Dave..and too, Chris, when you cleaned them, did you replace ALL of the Orings in them? If not, and i hate to say it, but its time to start over.

If you didnt, and need those orings go here
www.cycleorings.com

These are sold by Mr Robert Barr, a fellow GSR member, at a VERY good price. A service that everyone here absolutely appreciates

Again, i know it can be very frustrating, and i happen to have the same bike and went thru this over the summer, but were i you, i would start fresh from the begining, making sure those rings are replaced, and you might consider replacing your float valves. Those can be purchased at Z1enterprises.com. Cheaply also.

Start from scratch, and provided your bike is stock, set everything at stock settings and work from there.

What sizes are stamped in your jets?

 

[christopher]

Thanks for replying

Thanks for replying

Not sure if im posting in the right spot, but thanks for taking the time to help me out. My bike has the 4/1 pipes. The previous owner also added a baffle i think its called. You know the metal looking silencer on the end of the tailpipe? Its about a foot or so long? Not sure what its called....and yes, i bent the tabs up and measured off the flang where the gasket goes, gasket off at time of measure, to 26mm or just over one inch to the top of the float. And my plugs were still black but not moist now as they were before. I did not replace the o-rings in three of my plugs but did in one, since i only ordered a new set of jets for one carb. That one carbs spark plug was just as black as the other three carbs plugs. Those 3 other carbs were only soaked in cleaner. By the way, my jets and insides looks really clean, as if they had already been cleaned or recently bought.
So back to the floats. When looking at the float in the bowl, i bent the tab up away from the float valve. The 1st time i opened them up and looked at them, most of them were bent closer to the float valve, which correct me if im wrong, would not allow in as much gas. So after bending the float tabs to specs and seeing that the plugs were black, including the porceilan part on the plug, i bent them even closer to the float valve. The tabs are pretty much not level but below level, closer to the float valve and the plugs are black still including the insulator or porceilan part. Something im not sure of is this one jet that i bottomed out then backed off one whole turn on all 4 carbs. Its right above the main jet and has a flathead slot on it to use a skrewdriver on it though the pic in my book shows it with out a slot. Its called the starter jet. I backed it off one whole turn on all four. I havent tried turning the air skrews yet. I know you said to try replacing the o-rings but should i try turning the airskrews first? Ive been told that you should turn them one whole turn from the bottom. I wrote down the position of my starter jets too if i need to turn them back to the positions they were originally in. Does anyone know if my starter jets should be skrewed all the way in or not? One of them was a 1/4 turn from bottoming out and the other was 3/4 of a turn from bottoming out and the other was a whole turn from bottoming out. Like i said i havent even messed with the airskrews yet. So, with all that said, my bike is not surging to 3000-4000rpms when idling at time of start up anymore. And it starts up and stays running while idling. I would attach pics but it wants a url leading to the pics i have. If this would be easier over email, here is my email. Keepaustinsmall@yahoo.com Or can someone tell me how to upload a pic from my pc? I know how to upload pics from my pc but this site asks for a url and that would mean my pics need to be on a website i think. I know this seems like alot of info and i hope we can figure this out. I too am trying to turn my bike into a cafe racer style bike. Ive got the ace bars and cafe windscreen...but i dont want to do anymore cosmetics until i get this thing running better. Im open to ideas too about modifications i can do to it to make it look more cafe racer also. Thinking about lowering the forks and definitely getting rid of the banana seat. But at this point i need to get the carbs set. And about the jets again, they are all stamped with the same numbers. So im assuming they are all correct and my airbox is stock. I probably need to replace the airfilter though because it is saturated in gas. So when i test my carbs, the airfilter box is off so as to see if gas is shooting out my intakes....ok i hope this all helps.

 

[TheCafeKid]

Ok. Im not sure, as its kinda hard to read your post, but you say you dont have some of the jets bottomed out? All the interiour jets should be turned untill they seat. There is not a screw type adjustment there. The only screw adjustments are on your air and fuel screws. If your bike no longer has the airbox on it, and the PO put pod airfilters on it, coupled with the 4into1 pipe you have, the STOCK jets will be too lean. This is bad. Can lead to burnt valves. I believe the stock jets in the VM26SS were 115s (main) and 15(pilot) If this is what is stamped on it, its prolly not going to work Likely you will get the pilot jets to work at 15, but not the main. Also, as i said and if it indeed is the case, pods and a pipe will require a needle movement too. Again, i would suggest that you DO replace the orings in the carbs (they are on the pilot screws, the jets and other pieces.) Bad rings mean leaks, whether air or fuel, messing up the delicate balance within the carbs. Intake boot rings are another thing that will likely need replaced, as leaks will cause lean running. A good way to test is as it idles, spray some carb cleaner around where the rubber boot meets the alu head port. if the idle bogs, you are leaking. Leaking there will never allow you to get a correct balance and properly funtioning carbs.

A valve adjustment honestly should have been done first, as if they arent properly adjusted, you'll run around in circles. NONE of this stuff is difficult, but will require patience and time, and a scant amount of money to purchase the correct replacements.

Unfortunately, without doing these things, you may never get this bike running the way it should, aside from stumbling on some silver bullet fix, and you may get discouraged and sell away a perfectly good bike that just needed some TLC. Please take the time to do it right.

 

[paintmann111]

Could the black plugs be caused by oil?

 

[Steve]

Christopher,

What part of the world do you call "home"? There might be somebody close enough to give you a hand.

As Cafe Kid mentioned, ALL screws and jets that are inside the carbs should be snug. The fuel adjustment screw is on the bottom, just forward of the float bowl, and is reachable (with a special tool) without removing the carbs from the bike. The air adjustment screw is on the airbox side of the carbs, usually on the left side of the intake throat.

 

[christopher]

Carb problems

Carb problems

Ok, sorry about my ignorance on all the parts. You just enlighted me a bit more. Your right, that jet, that is not bottomed out, is accessible from the bottom of the carb and there is another skrew also on the side of the carb. Im assuming that the one on the bottom is a gas adjusting skrew and the one on the side is an air skrew? The rest of the jets are inside the float bowl and they are all tight. So the skrew on the bottom of the carbs that is accessible from the bottom, is not all the way in. It is a whole turn out on each carb.
The number 15 is stamped on my pilot jet, if thats what its called. Not sure yet about the main jet until i take my carbs out. My bike has the stock air filter on it. I had just temporarily left the filter box off after i redid my jets so i could visibly see, once i put my carbs back in, if fuel was spitting out into my airfilter box, which it was at that time. Now its not, and my airfilter box is back in.
So all the jets are bottomed out and there are two adjusting brass skrews per carb that i am not sure what they should be set at. So with this info im going to put new o-rings on all my jets. Im getting new clamps that secure my carbs to the engine body because ur right, the clamps i have on there do not tighten securely to form airtight connection. I realized that the other day. Im going to adjust my floats to specs, which is 26mm from the flange to the top of float, because at this point my floats are closer to the needle valve than 26mm. So what about these two adjusting air/gas skrews? I cant find in my Haynes manual where/how to set these? Right now the skrew on the bottom next to float bowl, on each carb, is one whole turn out and i havent messed with the air skrews yet. And to sum it up about my exhaust. It looks like the original exhaust. The PO just added a sound booster/filter? to the end of the tail pipe. Should it be 4/2 pipe? And again, my plugs are blackened without the moisture and according to my Haynes manual, it has a pic of several plugs that have different problems and the one that looks like my plugs are "an over rich fuel air mixture" Thanks for ya's help and patience....
Also i just found in my book that my main jet should be a "102.5". The number stamped on the top part of my main jet says "102". Also, Haynes says the airskrew and pilot skrew are preset. And it says the needle jet should be 0-4 and the jet needle should be 5DL36-2, which im not sure about the last two. I ordered new jets for only one carb off of http://www.oldbikebarn.com/Motorcycle_Parts/Carb-Rebuild-Kit/GS750-E-L-77-79-Suzuki-Carb-Repair-Kit

This is the actual pic of the parts. My main jet wasnt included, just the brass part that skrews to the top of it. That was stamped 102.
Ok, i hope i made this easier to understand.

 

[BassCliff]

Hey howdy hey!

Hey howdy hey!

Mr. christopher,

Here's the "official" unofficial welcome! I hope you can find some information that's useful. Do you have a manual for your bike? Suzuki Shop Manual? Clymer? Haynes?

Let it be known that on this day you are cordially and formally welcomed to the GSR Forum as a Junior Member in good standing with all the rights and privileges thereof. Further let it be known that your good standing can be improved with pictures (not you, your bike)! :-D

Perhaps you've already seen these, but I like to remind all the new members. In addition to the carb rebuild series, I recommend visiting the garage section via the GSR Hompage and check out the Stator Papers. There's also a lot of great information in the Old Q&A section. I have some documentation on my little BikeCliff website to help get you familiar with doing routine maintenance tasks (note that it is 850G-specific but many tasks are common to all GS bikes). Other "user contributed" informational sites include those of Mr. bwringer, Mr. tfb and Mr. robertbarr.

And here are some quotes from one of our dear beloved gurus, Mr. bwringer, with ideas on basic maintenance needs (depending on initial condition), parts, and accessories.

***********Quoted from Mr. bwringer************
Carburetor maintenance:

Replace the intake boot o-rings, and possibly the intake boots. Here's the procedure:
http://bwringer.com/gs/intakeorings.html

Here's an overview of what happens with this particular problem:
http://cycleorings.com/intake.html

You'll also want to examine the boots between the carbs and the airbox. There's a good chance these are OK, but check them over.

And finally, if things still aren't exactly right, you'll want to order a set of o-rings for BS carbs from the GS owner's best friend, Robert Barr:
http://cycleorings.com

Once you receive these rare rings of delight, then you'll want to thoroughly clean and rebuild your carburetors. Here are step-by-step instructions that make this simple:
http://thegsresources.com/gs_carbrebuild.htm
*************End Quote*************
**********Quoted from Mr. bwringer**********
Every GS850 has (or had) a set of well-known issues that MUST be addressed before you have a solid baseline for further troubleshooting.

It's a vintage bike, and it's quite common (as in, every single GS850 I have had contact with) that there are multiple problems that have crept up and slowly gotten worse over the years.

It's not like a newer vehicle, where there's generally one problem at a time.

These common issues are:

Intake O-rings (install NEW OEM or Viton only - common nitrile o-rings will quickly deteriorate from heat)

Intake Boots (install NEW -- these cannot be repaired)

Valve clearances (more important than most people think)

Carb/airbox boots

Airbox sealing

Air filter sealing

Petcock (install a NEW one)

On '79 models, install new points or Dyna electronic ignition (or at least verify that the old points are working correctly)

On all models, it's fairly common to have problems with the spark plug caps. These are $3 or $4 each, and often worth replacing if you're keeping the stock coils/wires.

Stock exhaust with NO leaks or holes -- good seals at the head and at the junctions underneath.
**********End Quote**********
***********Quoted from Mr. bwringer***************
http://denniskirk.com
Put in your bike model and see what they have.

I would definitely double and triple the recommendations to use Cycle Recycle II and Z1 Enterprises as much as possible. These guys are priceless resources. Z1 tends to have slightly better prices, CRC2 has a wider range of goodies available. If you're near Indy and can bring in an old part to match, CRC2 has a vast inventory of used parts.

http://oldbikebarn.com seems to be slowly regaining a decent reputation, but it's still caveat emptor. They don't have anything you can't get elsewhere at a better price anyway.

OEM Parts/Online Fiches:

http://www.babbittsonline.com/
Decent parts prices. Spendy shipping. Don't give you part numbers at all. Useful cross-reference if you obtain a part number elsewhere. Efficient service.

http://bikebandit.com
Fastest. Middlin' prices. Uses their own parts numbering system to obfuscate price comparisons -- can be very confusing for large orders. Cheapest shipping, so total cost usually isn't too bad.

http://flatoutmotorcycles.com
Slow. Cheapest parts prices, crazy shipping costs. Don't expect progress updates or much communication. Real Suzuki part numbers.

http://alpha-sports.com
Exorbitant parts prices. Different type of fiche interface that's quite useful at times, especially with superceded part numbers. Real parts numbers. Shipping cost and speed unknown due to insane, unholy pricing.

Stainless Bolts, Viton o-rings, metric taps, dies, assorted hard-to-find supplies and materials, etc.:
http://mcmaster.com
Fast, cheap shipping, good prices. No order minimum, but many items like bolts come in packs of 25 or 50. Excellent resource.

http://motorcycleseatcovers.com
Great quality, perfect fit (on original seat foam), and available for pretty much every bike ever made. Avoid the textured vinyl -- it's perforated.

http://newenough.com
You DO have riding gear, don't you? Great clearances, always outstanding prices and impeccable service.
***************End Quote**********************

Here are a few extra links:

Cycle-Re-Cycle Part 2
http://crc2onlinecatalog.com/

The ever popular Z1 Enterprises
http://www.z1enterprises.com

The Rice Paddy (salvage/used)
http://www.ricepaddymotorcycles.com

Ron Ayers Motorsports
http://www.ronayers.com

Lots of info/pictures here:
http://www.suzukicycles.org

Thanks for joining us. Keep us informed of your progress. There's lots of good folk with good experience here.

Thank you for your indulgence,

BassCliff
(The unofficial GSR greeter)

 

[Suzuki_Don]

Hey Cliff you put the wrong Carb Rebuild Series on there for Chris. He has VM carbs not CVs. (Joke) I know. I have too much time on my hands and I should be in the shed putting the 550 back together. Don

 

[BassCliff]

Close enough, you get the idea!

Close enough, you get the idea!

Hey Cliff you put the wrong Carb Rebuild Series on there for Chris. He has VM carbs not CVs. (Joke) I know. I have too much time on my hands and I should be in the shed putting the 550 back together. Don

Hey Mr. Suzuki_Don,

Unfortunately, that's the best carb rebuild series I know of. You should be documenting some of the cool things you fabricate for your bike. You, my good man, are an arteest!

Thank you for your indulgence,

BassCliff

 

[Suzuki_Don]

Hey Mr. Suzuki_Don,

Unfortunately, that's the best carb rebuild series I know of. You should be documenting some of the cool things you fabricate for your bike. You, my good man, are an arteest!

Thank you for your indulgence,

BassCliff

Cliff try this shortcut, it is a great rebuild article on the VM series.
http://www.thegsresources.com/files/vm_carb_rebuild.pdf

This is the best carb rebuild series that I know.

Cheers
Don

 

[Pete Logan]

I would attach pics but it wants a url leading to the pics i have. If this would be easier over email, here is my email. Keepaustinsmall@yahoo.com Or can someone tell me how to upload a pic from my pc? I know how to upload pics from my pc but this site asks for a url and that would mean my pics need to be on a website i think.

If it would help you can email them to me as attachments and I'll put them up on my site for you - logan@pt.lu

 

[christopher]

Have a gas/air skrew question

Have a gas/air skrew question

My Haynes manual only specifies for the british suzuki release and not the american for the number of turns to back off the air skrew on the carbs. Does anyone know how many turns to back off the gas skrew and the air skrew for a 77 suzuki gs750? Im going to assume the air skrew is 1 and 1/4 turn from the bottom. Does anyone know how many turns to back off the gas skrew? Thanks for your help

 

[KEITH KRAUSE]

Black plugs can be caused by many things. Some common basic checks...
If you have a compression tester, is compression within specs?
Are you burning oil? Whitish smoke or black plugs the don't dry in the air means you're burning oil. This must be fixed before anything else.
Are the plugs NGK B8ES?
Are the plugs gapped approx' .027"?
Under dark conditions, and with a new plug, turn the crank and check spark color. Is it a decent bluish color or weaker and orange?
If weak/orange, then you need to verify battery voltage, check/clean all connections including the plug caps, clean points and adjust the dwell if you still have points, and check timing and ignition advance action. You also need to verify coil resistance at the primary side of coils and secondary side (plug cap to plug cap). Even if a good bluish spark is present at all cylinders, the above should be checked.
This is basic maintanance and should be done regardless of what you may think is the problem.
If all above are serviced correctly then you can go on to the intake/carbs.
Verify the filter is clean and the entire intake is in good condition, including the rubber boots (filter side) and the manifolds and their o-rings(engine side).
Check fuel tank venting to be sure it's clear.
Make sure both float bowl vent lines are 100% clear and routed without kinks.
If you can be sure any problem is the carbs, clean completely and install Robert Barrs inner o-ring kit, adjust floats to factory setting (about .95") but verify float needle valve/spring tension condition first. Any worn valve tips and/or sloppy springs must be replaced. Verify choke plungers seat well and the rubber tips are not allowing leakage.
Since it appears the pilot jet and main jet are stock, I'd GUESS the jet needles are at the factory position too but you should verify this. Also verify with a factory manual or trusted source that ALL jet needle assembly parts are present and in factory assembled order.
As for pilot fuel screw (underneath) and side air screw settings, try 3/4 turn out for the pilot fuel screws from LIGHTLY seated and 1 1/2 turns initially on the air screws.
You must then bench synch the carbs as best you can.
If all above is good, the bike should start and you can adjust the air screws using the highest rpm method.
Then you must vacuum tool synch.
To back up just a bit, if you have a 4-1 pipe as your only mod, and it flows better than stock, I'd try 5 to 7.5 larger on your mains. Leave the pilot jet and jet needle stock unless further testing says to richen them.
Lot of work I know, but basic maintanance. Do/check all the above and it will probably save time and frustration.

 

[Suzuki_Don]

Link To Carb Rebuild Series

Link To Carb Rebuild Series

Chris this is the link to the carb rebuild series for the VM type carby, the ones that are on your bike.

http://www.thegsresources.com/files/vm_carb_rebuild.pdf

Cheers
Don

 

[christopher]

Float valves

Float valves

Ok, thanks for the advice. There is alot of work to do. I believe all my questions have been answered but one was raised with the last post. I have four float valves and only one is brand new. It has more resistance than the other 3 when pushed in by hand because its new. Should i replace the other 3 since there is not as much resistance as the new one? There is spring action there, just not as much resistance. And thanks again for all ya's help.

 

[KEITH KRAUSE]

Ok, thanks for the advice. There is alot of work to do. I believe all my questions have been answered but one was raised with the last post. I have four float valves and only one is brand new. It has more resistance than the other 3 when pushed in by hand because its new. Should i replace the other 3 since there is not as much resistance as the new one? There is spring action there, just not as much resistance. And thanks again for all ya's help.

Hard to say without seeing them for myself.
Many replacement valves out there are made cheap and I've seen new bargain brand valves leak immediately. I don't know if yours are original or how many miles on them. The best quality factory valves are a good $35/40 each I believe.
First test for any valve is the leak test. If you know for a fact the float level/float assembly action is correct and the valve seat washer (fiber or metal) is good or the valve seat o-ring is good, and that carb still overflows even a little after shut off, then the valve is bad. The valve tip can also groove too deeply and it will need replacing. A slight groove is normal.
If that carb doesn't show any signs of leaking...
As for the spring, in my opinion, if the spring has tension along its entire length then it's probably OK. But if you can gently push it in 1/2 way (no more or you can damage it), gently release it, and then pull up some slack, then it's sagged and needs replacing. The spring would never be fully compressed during its normal life so I'd never push it all the way in, even just playing with it.
Springs can have no sag but still be too weak. Even normal riding/vibration can result in the valve sealing poorly and the bowl level will be higher than intended. A weak spring will allow some leaking.
A sticking/leaking valve may be from a small burr and that can sometimes be gently filed off.
In short, if there are no leaks while off or during riding, you're probably good. But the valves can be hard to determine sometimes, especially for adequate spring strength. Best thing you can do is make a fuel level checker out of an extra bowl drain bolt and some clear tubing. Start the bike, let it idle, and place the tester against the rear 1/3 of each bowl as indicated in the factory manual and see if the level is within that specified range.