Plugs going bad, why?

[Anonymous]

Hello folks. This is my first post in this forum but I am an avid reader. I have posted this question in another forum, but I cant seem to get anyone to respond. Maybe you guys can help. I have a 1978 GS750E. It runs great, however, every 4th or 5th day I have to replace the spark plugs. They are fowling out. The gap is set at .25 and when I pull them, they are black and smell like, well duh, fuel. I tried cleaning them and re-installing them and it didnt work. The bike does take a while to warm up and stay running, but after it warms up it runs great. Please help me! Thanks you guys. (V.R., Paul)

 

[Bert Patterson]

I'm not very knowledgeable here - Billy Ricks or one of the others may be able to help. But........I had the same problem, particularly with cylinder #1, but really all plugs were black and sooty. You're running too rich. You need to work on the carb jetting most likely. I had to change mains and pilots. These guys are going to want to know what mods you have - exhaust, air filters, etc.

Bottom line is your mixture's f'd up.

 

[mdole]

Check your air cleaner before you start messing with the carbs. If it is really plugged up it will make you run rich.

I always try to start with whats easiest to take car of.

Mike

 

[earlfor]

Re: Plugs going bad, why?

I have a 79 750, so your bike should be identical.
The problem could be electrical, air intakes or carb adjustment and it could as easily be one thing as another. Do you still have the stock points ignition system and airbox with paper element? When trouble shooting this type of problem, in order, you would verify the ignition working properly, the induction system working correctly and then the carb adjustments. On the left side of the airbox, you will find two screws that hold the airbox endcap on. Remove them, remove the rubber boot underneath and then slide the air filter element out. (the element is in a track and will slide straight out) Check the element for dirt or blockage.
If dirty, blow it clean from INSIDE the element. Its paper, so do NOT oil it. Re install element and airbox cap and rubber boot.

Check your timing to be sure you are on the marks. |F1 for the 1 & 4 cylinders. |F2 for the 2 & 3 cylinders. Also check your maximum point gap. (it should be 14 thousandths) The left pointset is cylinders 1,4. The right pointset is cylinders 2,3. If you havent static timed before and need any instructions, give a yell.

Set the spark plug gaps to 28 thousandths. The 25 you have them set to is a little weak.

Take a voltmeter or multimeter and with the ignition on, check the voltage to the + terminal of your coils. (it will be the orange/white wire) Let us know what voltage you have to the coils. Low voltage and a small plug gap will result in a weak spark and black plugs. Incorrect timing will also have an effect on how the plugs burn.

Once you know you have a correctly functioning ignition system to run the engine, you can move on to other possibilities. I would not touch the carbs until I was sure everything else is as it should be.

Earl

Hello folks. This is my first post in this forum but I am an avid reader. I have posted this question in another forum, but I cant seem to get anyone to respond. Maybe you guys can help. I have a 1978 GS750E. It runs great, however, every 4th or 5th day I have to replace the spark plugs. They are fowling out. The gap is set at .25 and when I pull them, they are black and smell like, well duh, fuel. I tried cleaning them and re-installing them and it didnt work. The bike does take a while to warm up and stay running, but after it warms up it runs great. Please help me! Thanks you guys. (V.R., Paul)

 

[Billy Ricks]

Carbs probably need a good cleaning and float levels checked. As others have said, make sure the filter is clean.

 

[focus frenzy]

I would like to add a question.
How much oil does your bike use?

you can clean those plugs and reuse them, you need to soak the fouled plugs in a jar filled with vinegar for a couple days then rinse in water.
it will clean the carbon right off the insulator, the only draw back is, that the vinegar will also eat the plating off the metal.

this is a old trick for cleaning fouled dirt bike plugs.

 

[Anonymous]

Thank you so much for your replies. My air filter is filthy. Very oily and very old looking. I have only had the bike for a few weeks so I havent really tore into it much. It doesnt use much oil. I have put about 200 miles on it and havent had to add any yet, but there is some buildup on the engine so it must be leaking a little. Im not real concerned about that though. I will start with the air filter and go from there. Im not real sure what all that other stuff is but I think I can figure it out. I aint skeered to tear it apart. If the air filter cleaning doesnt fix the problem, then I will start looking more in depth. Thats when I will ask more questions about the points and timing and all that because I really dont know where that stuff is or what to look for and I dont have a manual. I will be sure and post back with any results. Again, thank you all for your replies, I appreciate them.

 

[Anonymous]

Ok, I have an update. After I read your advice, I went out and looked around. The #1 plug (assuming #1 is far left) is completely black. I only had the bike running on the new plugs for maybe 5 minutes. The others are black too but not as bad as #1. The air filter is saturated with oil and grime. I tried blowing it out but nothing came out, so it is packed in there pretty good. I need a new one. The air filter box is oily also. Question: When starting the bike, should I have the choke all the way up until the bike runs steady without dying, or just long enough to get it to fire up and then kill the choke and rev the engine to keep it running until steady? I keep the choke all the way up for a while because if I lower it, and dont rev the bike, it dies until it gets real warm, and that takes a while. My point being, am I choking this engine to death? Somedays, I will have the choke up for more than 5 minutes to keep the bike running. Thanks!

 

[Anonymous]

You could try to wash your filter with soap and water (assuming it is foam). After you do that you have to re-oil it with SAE30 or 80w90, otherwise dust will just blow through it rather than get caught in the oil.

As for warming up your bike here's what I do.
-Put on full choke and start the bike.
-After a few seconds I will push in the choke a bit which causes the RPM to rise (full choke starts the bike well but makes it idle poorly for me)
-wait a few more seconds as the RPM climbs to 3-4000 and push the choke in more to drop it down to 2000
-put on my helmet, etc.
-turn off the choke while keeping the revs up a little
-ride up a few ramps to get to my parking garage door
-take my hand off the throttle to unlock the door (bike usually keeps running 8))
-from then on I don't need to use the choke after parking the bike for a few hours before returning to it. It idles fine as it quickly warms up on its own.

 

[Anonymous]

I have a paper filter, so I cant wash it unless I let it dry for a few days. I have never tried to wash a paper filter before, I guess it could'nt hurt. Your bike warms up a lot faster than mine. It takes about 5 minutes or so to get a steady idle above 3000 rpm with the choke full on, and with me rev'ving the motor. I attribute that to the cold weather mostly, but even on warm days it takes a few minutes. Once it holds an idle, I push the choke all the way off and keep the motor rev'ed up until I take off. After about a mile or so, it's good to go. I was just wandering if I am choking it too much, the bike that is. Thanks for the input bro. Where online can I get a filter? Nobody in this area carries one.

 

[earlfor]

You can not wash a paper filter, it must be replaced. The normal starting routine on my 750 is pull choke all the way out, (dont touch throttle) crank bike for 1 second until it starts. RPM will immediately increase and I push choke in to keep rpm at 1500 for about 5 seconds, then push choke off and open throttle. Warm bike for about 30 seconds and at that point it will sit and idle without choke or my touching the throttle. I can start it and ride away in one minute. It is not a good idea to cold start an engine and warm it up in the 3-4000 rpm range.

Air filters are not very expensive, so I would probably go to my local motorcycle shop and have them order one. You can probably order one through Bikebandit online. When I needed one, I was impatient, so I took the filter element to a local lawnmower shop and had them match the size with one for a riding mower. I had to pop rivet a cover plate and track to it and make gaskets from a couple of old mouse pads and it works fine, but its a lot of work for something you can easily order for not much money.

Earl

I have a paper filter, so I cant wash it unless I let it dry for a few days. I have never tried to wash a paper filter before, I guess it could'nt hurt. Your bike warms up a lot faster than mine. It takes about 5 minutes or so to get a steady idle above 3000 rpm with the choke full on, and with me rev'ving the motor. I attribute that to the cold weather mostly, but even on warm days it takes a few minutes. Once it holds an idle, I push the choke all the way off and keep the motor rev'ed up until I take off. After about a mile or so, it's good to go. I was just wandering if I am choking it too much, the bike that is. Thanks for the input bro. Where online can I get a filter? Nobody in this area carries one.

 

[AOD]

is the 750 air filter the same as a 550? if so, i have an old one i dont need anymore sitting in my trunk...

if you do get the air filter cleaned out, let it run, then check the plugs again. i've had the same experience with my bike...which was running a little too rich on the pilot screw on the bottom of the carbs. it requires you remove the carbs to adjust (unless you have a really small screwdriver). you need to tightened them to lean the engine out on the pilot circuit (idle to 4000 RPM). i would suggest going 1/8th turn 2,3,4 and 1/4 turn on the #1 carb since its really black.

~Adam

 

[Anonymous]

I have an update. I changed the air filter, oil and filter, and put in some new plugs. (I have like 24 plugs in my shed now, vinegar isnt getting them clean). I rode the bike for about an hour, very hard too. Pulled the plugs and they werent that bad, but still black. I have ridden 5 times on these plugs though. Thats a new record. So it did get better, but still needs a good carb cleaning. Oh well, talk at ya later.

 

[redliner1973]

Make sure the petcock is not leaking fuel into teh cylinders. :twisted:

 

[argonsagas]

I haven't seen a response to Earl's suggestions:

Check your timing to be sure you are on the marks. |F1 for the 1 & 4 cylinders. |F2 for the 2 & 3 cylinders. Also check your maximum point gap. (it should be 14 thousandths) The left pointset is cylinders 1,4. The right pointset is cylinders 2,3. If you havent static timed before and need any instructions, give a yell.

Set the spark plug gaps to 28 thousandths. The 25 you have them set to is a little weak.

Take a voltmeter or multimeter and with the ignition on, check the voltage to the + terminal of your coils. (it will be the orange/white wire) Let us know what voltage you have to the coils. Low voltage and a small plug gap will result in a weak spark and black plugs. Incorrect timing will also have an effect on how the plugs burn.



Since you have the same problem with all four plugs, and the air filter issue has been resolved, try the net step, as above.


Vinegar is not likely to do much for your plugs, unless you mix them with fries.

Try soaking them in Varsol, then wire brush them lightly....a brass brush is best, but I have used a steel one for years.

You can use an oven to bake them....expect the wife to complain about the smell....or you can use a propane torch and heat them individually until the oil becomes ash, then wire brush them and carry on.

If using the propane method, do NOT use maximum flame....that may superheat one part and crack or shatter the porcelain. Use a medium flame and twist the plug over the flame as it heats. Takes only a few seconds.

 

[KEITH KRAUSE]

HootiHoos, try to get yourself a factory manual or at least some kind of repair book. We can help you with your questions but you need to become familiar with your bike's parts or you'll have problems.

 

[Anonymous]

HootiHoos, try to get yourself a factory manual or at least some kind of repair book. We can help you with your questions but you need to become familiar with your bike's parts or you'll have problems.

You hit it on the head. I need to get a manual. I am an aircraft mechanic by trade so I can read a manual. I thought I could figure all this stuff out without a book, who would have thought that a 25 year old motorcycle could be so confussing? However, now when I get my book, and thanks to yalls help, I know what I need to look for, I just have to look it up in the book. The air filter did do a magical trick on the bike though. Today was day 6 on the new plugs and it ran fine. The plug base is still black but the electrode and point is fine. On the others, the whole plug was black. So I will go until these plugs foul out. Im gonna try that torch trick on the old plugs. I really hope that works. Thanks for the replies fellas, and talk at ya soon.

 

[earlfor]

"Reading the plugs" refers to the color on the center ceramic of the plug.
It should be a tan to medium brown, preferably more towards brown.

Earl

The plug base is still black but the electrode and point is fine. On the others, the whole plug was black. So I will go until these plugs foul out.

 

[earlfor]

Apparently, its easier to replace plugs than to isolate and eliminate the cause.


Earl

I haven't seen a response to Earl's suggestions:

 

[Anonymous]

For now, it is easier to replace the plugs. I will isolate and elliminate once I get a manual. I know that reading the plugs refer's to the ceramic electrode, but the base of the plugs being black after a few minutes of operation? That's a problem. However, the ceramic is lightly browned and the bike has ran fine now for 6 days, so maybe the air filter did the trick. I would be amazed if it did. I will keep yall posted and let you know when it fails to start. Thanks for the replies though, at least someone is trying to help. I think I am going to order a manual right now. I wish BikeBandit was a little faster with their shipping. It takes them 3 to 5 business days to ship even on express orders. There must be another company out there with our parts that ships a little faster. Oh well, at least SOMEBODY has our parts!