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Newbie
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Discussion Starter · #1 ·
Thanks in no small part to my lurking on this site, I am making some headway on my '93 seca II streetfighter project.


My newest addition is a new exhaust which consists of factory headers, custom 1 7/8" piping into a scorpion slipon (meant for a gsxr 1000). This is the only engine modification done so far.

After getting everything installed, the bike runs poor. I knew this would happen, but I am a novice when it comes to engine tuning. I am trying to hold off rejetting until I do a rebuild this winter. So my knowledge is left with changing heat of spark plugs, and adjusting air fuel mixture. I have been told to just adjust the plug heat to help tune the engine. I tried the search, but didnt come up with much, I'm lookin for any knowledgable advice on this one.

Thanks--Matt
 

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The Soft Serve Enigma
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16,719 Posts
bossmankx said:
I am trying to hold off rejetting until I do a rebuild this winter. So my knowledge is left with changing heat of spark plugs, and adjusting air fuel mixture. I have been told to just adjust the plug heat to help tune the engine.
First off, bike looks good.

That said, if you hold off on jetting too long, you'll be doing a very extensive/expensive rebuild before you plan to. Don't wait, pay the man and get it done proper, on a dyno. Changing heat ranges and idle mixture's will only fuck it up worse. Heat range will hardly do anything, and a/f mixture should be at 2% CO at idle, which can only be done with a gas analyzer. I know someone will disagree with me, but workin with dyno's, carbed bikes, and gas analzyer's everyday, this is my experience.
 

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DIZZLE
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1,446 Posts
all though getting it jetted is the right way to go, if you need a temporary fix than I would change the fuel mixture screws, on a lot of older models they are already set to be to lean. I would back track the screws to see how far they were out and then just turn them a 1/2 or 1/4 turn more from where they were. The new exhuast prolly allowed more air flow so no it is lean.
 

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Senior Member
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890 Posts
The fuel "mixture" screws on CV carbs are only for the idle fuel circuit and adjusting these will not cure lean jetting anywhere else in the rev range. Like endo said, the quickest, most accurate way is to get it dyno'd and have the mains, pilots and needles changed accordingly.

And yeah - your bike looks good. I don't know why, but I really like those little Seca's.
 

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the mad doctor
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3,399 Posts
endo said:
First off, bike looks good.

That said, if you hold off on jetting too long, you'll be doing a very extensive/expensive rebuild before you plan to. Don't wait, pay the man and get it done proper, on a dyno. Changing heat ranges and idle mixture's will only fuck it up worse. Heat range will hardly do anything, and a/f mixture should be at 2% CO at idle, which can only be done with a gas analyzer. I know someone will disagree with me, but workin with dyno's, carbed bikes, and gas analzyer's everyday, this is my experience.

i personally have plenty of experience with gas analyzers, and i don't like them. just persoanl preference though. tuning the idle mixture doesn't accomplish a whole lot, and some bikes just run better when set at something other than 2%. i still tune screws by hear and feel.

dyno tuning, on the other hand, is generally worth every penny if you have a tuner that knows what he's doing, and alot can be gained.

generally, if you have a working knowledge of carbs, you can get away with shimming needles, changing float hieght, adjusting mixture screws, and swapping $5 jets over buying a $120+ jet kit with just a slip-on exhaust, BUT, it does take some fiddling, and if you don't know what you're doing, it's probably best left to a professional. you could seriously hurt a motor if you get it way wrong.
 
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