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Discussion Starter · #1 ·
Hello, new to the forum and ay looking for advice! I have been restoring a 82 Suzuki sp500 and have put my heart and soul into this bike and I am still having issue's. I have replaced the rubber intake manifold, exhaust gasket, piston rings, float, jets, head gasket, clutch, coil and spark plug wire, and many other items but do not relate to my issue I'm having. I will say that I have a aftermarket custom exhaust with sound baffles because the stock exhaust cannot be found. And a custom air filter on my carb (I have tried paper and foam) currently have a 3 inch pipe with a foam filter on. I am currently experiencing after firing and sputtering some of the time and other times my bike is running like a champ. The problem seems to happen the most when first started between 10-30 mins of riding and sporadically there after. Cleaned the tank and gas filter and carb several times with no luck. Carb has been adjusted to the lowest setting and everywhere in between but isn't seeming to make a difference. I have my finger on... jetting, new carb in general, or possibly a valve leak? Any thoughts or guidance is much appreciated! The bike has come to far forward to give up on restoring this classic but it was only made for 3 years and there is not much info for them so anything will help me get this issue resolved!
 

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Before the next ride after riding for awhile and the engine has cooled down overnight check the plugs to see if you have any oil on them. If you do then it takes awhile to burn it off and start running better. If you have oil on the plugs let us know. Then we can better diagnose the problem.
Have you checked the timing? Does this model have an automatic advance? I am not familiar with them. Another way to check is to pull the plugs and check them just as soon as the problem starts. This can tell you how well the carbs are doing their job.
 

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Discussion Starter · #3 ·
I went for a ride tonight after tearing my carb apart and cleaning the **** out of it (suggestion from a local motorcycle shop) who i went to see about different jets but they said my jets are good but my throttle slide valve inside the carb was dirty and sticking causing the issue. So far so good! When I first purchased the bike the throttle cylinder wouldn't even budge but with multiple cleanings it's sliding like a champ and the bike is running great! My timing is on I made sure of that when I did the piston rings and I do not have an advance that I know of. I am going to pop out the spark plug tomorrow and see what it looks like but fingers crossed I'm hoping the slide in the carb was the issue! Lots of time into this thing that looked like it should have been in a junk yard to looking like a show room floor bike. I will post what the spark plug looks like tomorrow and take her for a spin to see if the issue act's up again. Thanks for the reply!
 

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Are the slides in your carbs vacuum actuated or are they directly controlled by the throttle cable?
 

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Discussion Starter · #5 ·
Are the slides in your carbs vacuum actuated or are they directly controlled by the throttle cable?
They are vacuumed activated.

Just got back from a ride and compared to a flawless ride yesterday the issue has started up again not as bad but definitely putting a damper on the way home. I'm waiting to let the engine cool down so i can pull the plug and see what it looks like? It's fairly new that's why I haven't pulled it yet trying to get some real indication.
While I was out on the ride I did adjust the fuel ratio needle down 2 clicks ride good, started acting up, down 2 more clicks and was still acting up. Recommend setting 1 and a half (where it sat yesterday) and today got down to 1 full turn with no change to the issue. Maybe the throttle cylinder is dirty again but I am finding it hard to believe after 1 good ride on the street.
 

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Discussion Starter · #6 ·
Before the next ride after riding for awhile and the engine has cooled down overnight check the plugs to see if you have any oil on them. If you do then it takes awhile to burn it off and start running better. If you have oil on the plugs let us know. Then we can better diagnose the problem.
Have you checked the timing? Does this model have an automatic advance? I am not familiar with them. Another way to check is to pull the plugs and check them just as soon as the problem starts. This can tell you how well the carbs are doing their job.
I went for a ride tonight after tearing my carb apart and cleaning the **** out of it (suggestion from a local motorcycle shop) who i went to see about different jets but they said my jets are good but my throttle slide valve inside the carb was dirty and sticking causing the issue. So far so good! When I first purchased the bike the throttle cylinder wouldn't even budge but with multiple cleanings it's sliding like a champ and the bike is running great! My timing is on I made sure of that when I did the piston rings and I do not have an advance that I know of. I am going to pop out the spark plug tomorrow and see what it looks like but fingers crossed I'm hoping the slide in the carb was the issue! Lots of time into this thing that looked like it should have been in a junk yard to looking like a show room floor bike. I will post what the spark plug looks like tomorrow and take her for a spin to see if the issue act's up again. Thanks for the reply!
 

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Discussion Starter · #7 ·
Before the next ride after riding for awhile and the engine has cooled down overnight check the plugs to see if you have any oil on them. If you do then it takes awhile to burn it off and start running better. If you have oil on the plugs let us know. Then we can better diagnose the problem.
Have you checked the timing? Does this model have an automatic advance? I am not familiar with them. Another way to check is to pull the plugs and check them just as soon as the problem starts. This can tell you how well the carbs are doing their job.


Pulled the plug and it looks like it has dry carbon residue all over the igniter and quite a ways up the threads (very grey) like it was dry fouling.

Slide is still spotless and is moving easy when pushed up with my finger and slides evenly down. I'm going to pull it all apart tomorrow and give it another cleaning just in case???
 

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Discussion Starter · #8 ·
I was just drinking my morning coffee trying to do some more research and after looking at my plug and researching the stock plug for my sp500 it looks like I have been using the ngk d9ea but my bikes stock plug is the ngk dr8ea. After reading about the difference in plugs I'm going to go to the part's store and get the stock plug and try that out. Hopefully this will solve the issue, I don't know why the plug got switched to the 9 but fingers crossed this is why it is fouling up on me!
 

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By the color of your plug it is running lean. Try turning the carb or carbs, screws out 1/4 turn. Clean the plugs and run the bike again at least a couple of miles. Pull the plugs and check again. Look on the internet somewhere and find what the plugs should look like. But this doesn't sound like it is causing your problem. I would totally disassemble your carbs and petcock which involves emptying the tank before hand. If you are running out of gas this would cause the lean colored plugs and the miss that you have. Most petcocks have a screen in them. Do you have a filter inline? How old is it? If you don't know change it after cleaning everything.
 

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Discussion Starter · #10 ·
By the color of your plug it is running lean. Try turning the carb or carbs, screws out 1/4 turn. Clean the plugs and run the bike again at least a couple of miles. Pull the plugs and check again. Look on the internet somewhere and find what the plugs should look like. But this doesn't sound like it is causing your problem. I would totally disassemble your carbs and petcock which involves emptying the tank before hand. If you are running out of gas this would cause the lean colored plugs and the miss that you have. Most petcocks have a screen in them. Do you have a filter inline? How old is it? If you don't know change it after cleaning everything.
I painted my tank pre season and have chemically cleaned the inside of the tank, then soap water and dried the tank and petcock there was some build up and was defiantly an issue at one point in time. Maybe throw a in line filter in cause i have read many times it's good to have on. The issue is getting better but not 100% yet. I had my air fuel screw out 2.5 turns and ran like a champ for about 50 mins then I started getting a light sputter on my way home.
I just went on a ride after switching my pilot jet to the one that was in when I bought the bike (larger port). This really lowered my idle but ran good, but still having a little miss now on the lower end of the throttle or when I release the gas. Gonna see what the spark plug says in the morning but I'm thinking back to stock pilot jet, lower the idle screw and have the air fuel mixture screw to 3 turns out (pending plug) ??
 

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Discussion Starter · #11 ·
pulled the plug this morning and found it black from the larger pilot jet, switched it back to the stock jet ran it around with the same issue. Went to my shop to too off my oil and plug the plug again. Plug looked clean so I decided to switch back to the coil and plug wire that came with the bike (much tighter fit) when I wad dissembling everything I found a wire was pinched on the positive screw and was rubbing bare wire on the spark plug cool. I did switch out to the better fitting coil and it seems to be running strong now that the spark plug power is not interfered on a random wire. We will see how it goes...
 

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Discussion Starter · #12 ·
By the color of your plug it is running lean. Try turning the carb or carbs, screws out 1/4 turn. Clean the plugs and run the bike again at least a couple of miles. Pull the plugs and check again. Look on the internet somewhere and find what the plugs should look like. But this doesn't sound like it is causing your problem. I would totally disassemble your carbs and petcock which involves emptying the tank before hand. If you are running out of gas this would cause the lean colored plugs and the miss that you have. Most petcocks have a screen in them. Do you have a filter inline? How old is it? If you don't know change it after cleaning everything.
I painted my tank pre season and have chemically cleaned the inside of the tank, then soap water and dried the tank and petcock there was some build up and was defiantly an issue at one point in time. Maybe throw a in line filter in cause i have read many times it's good to have on. The issue is getting better but not 100% yet. I had my air fuel screw out 2.5 turns and ran like a champ for about 50 mins then I started getting a light sputter on my way home.
I just went on a ride after switching my pilot jet to the one that was in when I bought the bike (larger port). This really lowered my idle but ran good, but still having a little miss now on the lower end of the throttle or when I release the gas. Gonna see what the spark plug says in the morning but I'm thinking back to stock pilot jet, lower the idle screw and have the air fuel mixture screw to 3 turns out (pending plug) ??

So I have done all of that, my plugs look normal added a in line filter, cleaned the petcock, cleaned the gas tank, ran the air fuel mixture screw 1.5, 2, 2.5, 3 turns open ran the best at 2 turns for about 2 rides before the issue started again. I'm too a dead end and thinking of purchasing a new aftermarket carberator because it seems to run fine after a good cleaning but soon after just act's up again. I maybe get 1 good ride before its back firing and spitting flames out the exhaust. That or I'm going to take it to someone cause I just don't know anymore I have tried so many things and have got close (it sure is fun when she is running right) but I just don't know anymore? Any thoughts or ideas are appreciated, thank you!
 
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