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Discussion Starter · #1 ·
Well, I finally got around to addressing the lean condition on my 02 today. I felt that it was really rough in the midrange, so I wanted to shim the needle to get it right. I took the washer off the top of the clip and put it underneath, and wow... what a difference. A whole new bike, really. Now, with the Scorpion its still backfiring, which I seem to be able to stop by pulling on the choke a bit. So, I've decided to throw another washer shim in there to see how it takes.

My question is this. When I took the washer off the top of the clip, the spring stopped seating well on top of it. It seems like the spring wants the washer there so it has a nice smooth surface to mate with. When I get another washer for underneath the clip, should I get a replacement for up top, too? Will a washer on top of the clip have any effect on the bike performance-wise?

Thanks for any advice.
 

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Im not sure how much difference the washer on the top makes but I would still get at least 2 washers for each needle and put that one back on top. I think you will sleep better at night that way :D
 

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Discussion Starter · #3 ·
Throttlecrazed said:
I think you will sleep better at night that way :D
lol

Hopefully it won't affect my beauty sleep - god knows I need it.
 

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Instead of adding another shim just move the clip down one spot & put the shim back on top. Don't see how raising your needles is going to stop backfiring though.
 

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Discussion Starter · #5 ·
Good point... but it will help finish smoothing out the midrange :) I must not be getting enough sleep or something. Anyhow, the backfiring is another issue... only exacerbated by riching up the mixture, I'd imagine. Anyway, I've seen the needles with multiple clip positions in a jet kit I got for my old GS500, but my SV doesn't have them. Just one slot for the clip, nothing more. Is that different than everyone elses'?
 

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ejl10 said:
Good point... but it will help finish smoothing out the midrange :) I must not be getting enough sleep or something. Anyhow, the backfiring is another issue... only exacerbated by riching up the mixture, I'd imagine. Anyway, I've seen the needles with multiple clip positions in a jet kit I got for my old GS500, but my SV doesn't have them. Just one slot for the clip, nothing more. Is that different than everyone elses'?
No, those are stock needles. This is why people use a "shim stack" to jet the bike.

To fix backfire you will have to adjust A/F idle screw. Im guessing you need out .5 turn :)
 

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Discussion Starter · #7 ·
I thought that needle was stock!

I was planning to try some larger pilot jets (17.5). I'm about 120' above sea level... pretty low and my first thought was that it's starving for fuel when I quickly shut down the throttle. I've set the mixture screw already... 2.5 turns out I think.

Then again, it has some kick at low revs. It isn't bogging down or anything, so you may be right... bigger pilots might not be the best approach. Anyone else worked through a similar situation? Stock jetting right now with 2 shims, 2.5 turns. Stock airbox, no tank risers, Scorpion high mount slip on.
 

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Dont go bigger pilots unless you are going to desnorkle the air filter. Stock filter doesnt need 17.5s

There is no real set mix screw setting, just general starting point. 2.5 turns out is a good starting point, adjust until you think it idles right.
You can always try richer w/out hurting motor, mabye foul a plug but wont damage anything so there is little harm in playing with it.

First though, shim needle... then ride... then mess with mixture screw. You may find that the needle fixes some of your problem. :)
 

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Discussion Starter · #9 ·
I shimmed the needle yesterday. It is much better, but still shows evidence of struggle at the low end. The high end, too, for that matter.... but I hardly ever push it at the high end. I'll try another 1/4 turn and see how it feels. Then maybe another 1/4 to see if its better or worse. Thanks!
 

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We did my roommates bike with two shims and 3 turns out and it made a world of difference. The bike runs great, but if you lay into it hard it will sputter sometimes for some reason. Ideas?
 

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ejl10 said:
I shimmed the needle yesterday. It is much better, but still shows evidence of struggle at the low end. The high end, too, for that matter.... but I hardly ever push it at the high end.
I am going to assume you mean top of RPM range and not top of needle range...
To fix that Im betting you need larger mains. You might try a DJ 140, or DJ 142. Those are dynojet mains, Mikuni also makes them they start with MK XXX These numbers do not equal each other. The sizes in brands dont match.


RedAggie03 said:
We did my roommates bike with two shims and 3 turns out and it made a world of difference. The bike runs great, but if you lay into it hard it will sputter sometimes for some reason. Ideas?
Yeah, be smoother on the throttle.
If you drilled the slides they open faster so you can actually bog the motor a little... its better if you control the throttle anyway, even on FI bike. Even if you didnt drill the slides, smoother throttle operation is always better.

Basically its getting too much fuel when you do that. On CV (Constant Velocity) carbs (like SV has) a vacuum controls the slide (and needle) position. The slide wont start to come back until more air is flowing into the carb... get a smooth operation. The downside is that it does not make as much power and its not as quick on the power b/c the vacuum takes a sec to work which leads to a slight lag in response. So if you make carbs to where they open faster and give better response you loose the ability to just wack the throttle open. I think the trade off is more than worth it.

On my bike it is like this, if I just wack it open it doesnt do so well because the slides open faster. See if you can find that "sweet spot" right before it starts to loose ground, where it is the strongest. The trick is to keep it there as you accelerate. I actually love to do this, it feels really cool to me.

An interesting side note... if you had flatside carbs (like racers use) on the bike and wack the throttle open, the bike dies because it just dumps so much fuel into the cylinder so you always have to be smooth the throttle with those.
 
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