[jbuddo]

I have an 81 GL500 that sat idle for 15 years. With the help of this forum I have it running at 80/90% after about 2 weeks of riding/tuning.



The problem I have now is that the left side spark plug keeps dying on me. I have replaced it 4 times in two weeks. Each time I put in a new one it runs like a charm for a day or two and then it starts to spark intermittently and then not at all. I can't find anything on this forum that will point me in the right direction so I am starting a new post in the hopes that someone has encountered this before and can tell me what the heck is going on.



I was using the ngk spark plugs and tried a different brand from a different store, just to make sure it wasn't a bad batch I was buying from, but the problem continues.



Has anyone encountered this? Tips/hints/suggestions?



John

Vancouver, BC Canada

 

[jbuddo]

Thanks David,



I'll look at that link. The plugs are coming out carbon fouled.



John

 

[jbuddo]

Capt Frank - I hope that's not the case as we have a short riding season in Vancouver! If I can get through the next three months, I'll be happy to work on the engine during the fall and winter.



David - the plugs are dry & black. They were wet before I worked on the carburetor last week, but coming out dry and jet black after just a day of riding right now. I'll post some pictures tomorrow as I would like to get to the bottom of this. I did the aluminum rod replacement for the resistors tonight. I'll throw a new plug in that left side tomorrow and see what happens. I have the mixture screws set to 2.5 turns out. I'm sure this will sound like a stupid question, but do I turn them in or out to get it leaner?



John

 

[jbuddo]

Capt Frank - the odometer reads 20,000 miles, but I have no idea if that is accurate. I have had the bike for a year, but just on the road for a few weeks. One owner before me and he had it parked for the past 15 years. It looks like he took great care of it.

 

[jbuddo]

I originally posted the problem I am having (spark plug issues after just a day of riding) was always in the left cylinder, but it has happened in the right as well.



I'm having trouble getting a clear image of a spark plug with my cellphone cam, but the shot below gives you a pretty good idea. After just one ride, my plugs come out dry and black. I checked my mixture screw and set it to 2 turns out. I checked my air filter and it looks good. I'm not riding at low rpms so that doesn't explain the black plugs and even if I was, it shouldn't happen in less than an hour.

I put in a new set of plugs and the bike runs great - smooth idle, power right through from idle to 9000rpm. Took it out on the hwy and got it up to 75mph, rode it for about 30 minutes with a mix of hwy and city and then it started giving me trouble again. On the way home I had to rev the engine at stop lights to keep from stalling.



The manual says carbon fouled plugs are from too cold a plug (running the NGK DR8ES-L in 65 degree weather in Vancouver Canada), weak ignition (I recently did the brass rod fix and tested my ignition with a multimeter - everything appears to be to spec), dirty air cleaner (I'm not sure where to get a new one, but the one I have looks pretty good), too rich a fuel mixture (I'm set at 2 turns out), or excessive idling (not a chance).



When I checked the spark plugs after last night's ride, one was sparking from everywhere but the tip due to the excessive buildup of carbon. A quick clean and it was working fine again, so the problem would seem to be caused by excessive carbon buildup.



Has anyone experienced carbon buildup this quick and this bad?



I don't have a history on the bike, but the PO clearly took great care of it, then parked it for 15 years. I got it running easily after cleaning the carbs and changing the oil. The exhaust coming out of the tailpipe looks good, no blue and very little black (shouldn't I see a lot of black with how quick the plugs get coated?).



I'm lost and appreciate any more advice. The bike is a pleasure to ride but I can't afford to change the spark plugs daily!!



John

 

[jbuddo]

The choke and throttle butterflies check out ok. I just pulled out the carburetor and the choke is full open and the throttle butterflies open when I crack the throttle.



I'm curious now though about the throttle pistons. They don't appear to be connected the actual throttle in any way, so how do they work - on vacuum or air pressure?? I would have thought that the throttle would lift this piston, but all I can see that the throttle does is control the butterfly.



Shep, I went through carb sections after following your link, and I realized that I didn't remove the black banana cover and clean down the air jets. I'm not sure how these might affect the lean/rich mixture, but I'm going to clean them and see what happens.