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keeps fouling plugs

  • Thread starter Thread starter Anonymous
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Anonymous

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Hi everyone, I'm new here. I've been reading these forums for a few months now, lots of useful info. Anyway, heres my problem. I bought a gs 750e from my brother about 5 months ago. The specs on my bike are in my sig. Ran great while he owned it for 2 years. Then i bought it. Was fine at first, then i changed the plugs, not because they were bad, just because i didnt know how old they were. I put the same new plugs in (ngk d7ea) and it ran great for about four hours then slowly started to foul the plugs. Got so bad i barely made it home. Has steadily been getting worse. I was buying plugs every couple days. Spark plugs seem to be carbon fouled, like its too rich. Carbs have never been messed with since my brother bought it. I have asked plenty of people their opinion on what it is. Some say carb problems, like float height adjustment. Others say stator, igniter, coils... What do you guys think i should do? Any input would help. Thank you all.
 
If it started when you swapped the plugs, put the old plugs back (if you kept them) and see if it goes away.

It looks like standard plugs for the GS750 are D8EA (according to NGK), so D7EA are hotter than standard. My guess is the PO (your brother?) over-compensated the jetting after adding the aftermarket equipment. Maybe one of the carb gurus can get you on the right track.
 
I second what Flying ace says about those plugs being one step hotter then what normally goes into the bike... check the gap? on the old and new.. ?
 
WELL THE 2 VALVE MOTOR(77-79) TAKES B8ES. I AM NOT SURE ABOUT THE 4 VALVE(80 AND UP) PLUGS BUT I KNOW THEY ARE DEFINATELY A SMALLER SPARK PLUG.
 
Well I tried the D8EA plugs with no success. I rode for under 1 hour until it fouled them. Hard to believe it would just start fouling plugs left and right, nothing changed on the bike. I never touched the carbs, or the 2 years my brother owned it he never did either. Sounds like something electrical to me. Any other ideas? Carbon fouled, dry black carbon that wipes right off. They dont work, even after cleaning the plugs.
 
As I said before, I believe your brother (or some other PO) added after market pods and exhaust. Looks like he changed the jetting too (which you should do after adding those things). However, I think he over-jetted the carbs and tried to compensate by going to one range hotter plugs. Soot on plugs is an over-rich condition, and it's unlikely that all the carbs would have needle/seat problems at the same time. Find out what mods he made to the carbs and try to get a carb guru here to determine if it was correct or not.
 
My brother had the bike for around 2 years. It came with the 4 into 1 header and jet kit when he bought it. He never touched the carbs or anything else. It always ran like a champ. It ran great when i got it off of him, then suddenly began to foul plugs. What could have changed if nothing was ever adjusted? Thats what makes me think its electrical. I just dont know where to start troubleshooting it. Coils all spark the same when i test it against the engine. I had a rectifier put on around 3 weeks ago, but it was fouling before that. I dont really want to mess with the carbs since it ran fine with the current jetting. Dont know what happened.
 
Carbs are too rich. Either the needles are set too high, mains could be too rich, and/or the fuel level in the bowls is too high. Start by measuring float height. If they are right try dropping the needles a notch.
 
I'm not really familiar with taking the carbs apart. I heard that you can leave the carbs on the bike when adjusting the needle height. Anyone know of any step by step instructions for mikuni carbs?
 
Thanks you all for your help. I moved the e-clip up one notch in all of the carbs. The plugs are now light brown...yippee! Its back to running like a raped ape again. Guess you never learn until you get in there and try it yourself. This site is the best! I read it daily, like the paper. Thanks again.
 
what is an e clip i have an gs 450L that is fouling both plugs carbon black i replaced the seal in the pitcock it was leaking thats when my problems started!
 
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