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Discussion Starter · #1 ·
I bought two motorcycles, an 86 and a 93 ninja 250. I took parts off of the 86 to make the 93 run. I rebuilt the 93 engine and have it completed except for one little problem. I had to use the carbs off of the 86, which are a larger size. I had a professional clean, install, and sync the carbs and when he did I believe he used the jets out of the 93 carbs and put them into the 86 carbs. During the summer the bike wouldn't idle and it would always die, unless i set the idle to 5,000+ rpm, but as long as i gave it a little gas it would run fine. Now that it is winter I use the choke to start it up like normal and when it warms up and i take the choke off, it idles fine at low rpm. I was wondering would would cause this. Could the i need a smaller pilot jet, perhaps the original that came in the carbs, to offset the the change in air temperature?
 

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It sounds like it may be running too rich. Have you noticed any black smoke out of the exhaust in the summer when it's trying to idle normally? Have you pulled the plugs to see what they look like?
 

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Discussion Starter · #3 ·
The plugs look fine and i don't really notice any smoke. I am thinking that because it has a k&n the top end and mid-range are right, but my idle may be rich. Not sure
 

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Since the problem seems to go away at 5k ish rpm, it could be a problem with the pilot jets being the wrong size. If it were running too rich though, I'd expect you could see that when you looked at the plugs. Do you have the original jets that were pulled out of those carbs? You could always try putting the original pilots back in if you do.
 

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Discussion Starter · #5 ·
I'll probably run it until it until it stops idling and then ill look up what the stock pilot size is.
 

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Discussion Starter · #6 ·
Another Idea

Just got another idea. I have the spare mufflers off of the 86, which are basically the same. Could I bore the exhaust whole bigger to get some more air flow? Is that possible?
 

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If you had a flat on your car would you let the air out of the other 3 tires so they all rolled the same or fix the problem? :roll:
 

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Discussion Starter · #8 ·
Well my carbs are a pain in the a** to get to. Getting the air boot hooked back up is also a pain. I don't mind a little extra power and noise if that would fix the problem but I'm not sure if it will. When I take off my fairings, the bolts that holds the plastics on leak gas out when i take them off and spill gas all over my paint job and messes it up.
 

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Well just for the sake of answering your ?, yes you could get more air flow through the engine if you start drilling holes in the exhaust. The problem with doing that would be that the "5000+ rpm running fine" will no longer be the same. So it may solve the low rpm problem, it will create a leaner condition in the higher rpm ranges and might burn a hole in a piston if it's too lean. Have you considered draining part of the fuel from the tank so it is below the hole that is leaking?

I've read about others having that problem with the hole in the tank from the screw for the plastics. If I remember correctly there was supposedly a recall for that problem for some year models and there were also cases where the problem was caused by the owner installing the wrong length screw that caused it. But for recall purposes, it may be too late in your case since it's a 93.
 

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Well my carbs are a pain in the a** to get to. Getting the air boot hooked back up is also a pain. I don't mind a little extra power and noise if that would fix the problem but I'm not sure if it will. When I take off my fairings, the bolts that holds the plastics on leak gas out when i take them off and spill gas all over my paint job and messes it up.
It maybe a little work to RE & RE the carbs, but at least it would be done right.
very simple really, just take your time and do it right.
 
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