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Old 01-16-2013, 09:04 AM   #72916
motolab
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Quote:
Originally Posted by procycle View Post
I'm waiting for someone to show us how that can be done.
Correspondences on CV carbs:

Low rpm all throttle positions: float height, needle base diameter, emulsion tube outlet size
WOT operation overall: main jet
WOT operation between HP peak and red line: main air corrector
WOT operation below red line: jet needle shape
1/4 throttle opening: jet needle clip position
1/8 throttle opening: pilot jet size
1/16 throttle opening: pilot jet size
idle: mixture screw adjustment

Put some tape on the throttle housing and the edge of the grip. Mark zero throttle with a sharpie. This is best done with the engine idling, so you can tell when the slack in the cable has just been taken up. Turn off the engine and mark wide open. Now take a tape measure (metric works best in my opinion) and measure the length of the arc. Put a mark at the mid point. Duplicate this procedure to mark the mid-point between here and zero throttle opening to get 1/4 open. Repeat for 1/8 and 1/16 openings. Don't have an accident trying to look at the marks while riding. If you do, I'm not responsible!

Tune from the top down, i.e. get the right main jet in it for proper wide open throttle operation, then set the needle clip position for correct operation at 1/4 opening, then install the correct pilot jet for proper operation at 1/16-1/8 opening. Readjust the idle mixture after every jetting change. Without the ability to dyno with 5-gas analysis, I would go progressively leaner until there was just the very beginning of a discernible misbehavior. On the main jet, I would then go 2-3 sizes richer. On the needle clip, I would then adjust 1-2 positions richer. On the pilot jet, I would install 1-2 sizes larger. Please do bear in mind that if you have high compression, poor exhaust flow, low octane fuel, and/or ignition timing that is either correct or overadvanced for the correct mixture, tuning via this method could cause detonation and therefore engine damage.

Regards,

Derek
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Old 01-16-2013, 11:14 AM   #72917
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Quote:
Originally Posted by motolab View Post
Correspondences on CV carbs:
-Snip-
blah blah blah
-Snip-
I'm pretty sure I said show us not tell us.

.
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Old 01-16-2013, 11:16 AM   #72918
motolab
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Quote:
Originally Posted by procycle View Post
I'm pretty sure I said show us not tell us.

.
I'm not sure what you mean. Are you saying that someone owes you a CV carburetor tuning how-to video?

Regards,

Derek
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Old 01-16-2013, 11:50 AM   #72919
LucasLeader
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Chain Guide

My chain guide disappeared this morning on the way to work. I haven't thrashed the DR off road for a while so I'm not sure what happened. Does anyone that has upgraded theirs have a stock piece in decent condition they would like to sell?
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Old 01-16-2013, 12:28 PM   #72920
Rob.G
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Intiminators

Shameless Plug: I just posted a set of Intiminators for sale in the Flea Market. Nothing wrong, just switching to Gold Valves as my riding skills have changed.

Rob
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Old 01-16-2013, 12:30 PM   #72921
TinkerinWstuff
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so much humor in this thread today
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Old 01-16-2013, 01:51 PM   #72922
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Quote:
Originally Posted by motolab View Post
I'm not sure what you mean. Are you saying that someone owes you a CV carburetor tuning how-to video?
No, I was trying to (in a polite way) say "put up or shut up"
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Old 01-16-2013, 01:52 PM   #72923
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Quote:
Originally Posted by procycle View Post
No, I was trying to (in a polite way) say "put up or shut up"
I don't follow.

Regards,

Derek
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Old 01-16-2013, 02:33 PM   #72924
TinkerinWstuff
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Quote:
Originally Posted by motolab View Post
I don't follow.

Regards,

Derek

He's saying theory is all well and good but none of us are aware of anyone who's used the stock needle IN CV carb WITH modified airbox AND achieved optimum results.

let's see where it's been done successfully. Many of us here are well familiar with the practice of how to tune - especially procycle.
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Old 01-16-2013, 03:14 PM   #72925
procycle
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Quote:
Originally Posted by motolab View Post
I don't follow.
You keep saying how much better the OEM needle will work with an open airbox than the DynoJet needle. But you have no hands on experience tuning a DR650 with an open airbox.

The problem with the OEM needle and open airbox is that the needle will have to be raised about 4-6mm to have any hope of running well enough to make the bike rideable in the mid-range. Raising the needle that much causes the beginning of the taper to rise out of the needle jet way too early causing a low end bog.

In the real world the only viable solution available is the DynoJet needle.

I'd like to see you show that there are other options and I've even offered to foot the bill to give you that chance.
I'd also like to stop hearing about how much better OEM needle is until there is some proof to back it up.
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Old 01-16-2013, 03:20 PM   #72926
motolab
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Quote:
Originally Posted by TinkerinWstuff View Post
He's saying theory is all well and good but none of us are aware of anyone who's used the stock needle IN CV carb WITH modified airbox AND achieved optimum results.
He can speak for himself.

If, however, you yourself are saying that none of you (who?) are aware of anyone who has used the stock needle with a modified airbox and achieved optimum results, I agree that with the USA needle, the possibility is slim (no need to shout BTW). If you are asserting that no one has used the non-USA stock needle with a modified airbox and achieved optimum results, then that's either because no one has tried, because whoever did try doesn't know how to tune, or because there is a better needle profile yet.
Quote:
let's see where it's been done successfully.
Sure, let's!

The point I have been trying to make is that, based on the chart I have posted several times now, the results when using the DJ needle can hardly be called optimal, and that experience with many different needle profiles (including many of my own) on many different motorcycles has shown me that a profile such as the DJ needle has is likely to produce a wonky CO trace such as the DJ needle does in fact in practice produce. The same experience has shown me that a shape more like the non-USA adjustable needle has will in fact flatten the CO trace vs. what a needle with a shape like the DJ produces. I suppose there is always the possibility of an anomaly, but I can't see how the non-USA adjustable needle would not be an improvement over the DJ.
Quote:
Many of us here are well familiar with the practice of how to tune - especially procycle.
I think that depends on the definition of the phrase "familiar with the practice of how to tune". I'm not saying that to be rude. It's just that there are different levels of experience and different levels of tuning (some of which are equipment-dependent). Unfortunately there's no way around that.

Regards,

Derek
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Old 01-16-2013, 03:25 PM   #72927
barko1
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Quote:
Originally Posted by motolab View Post
I'm not sure what you mean. Are you saying that someone owes you a CV carburetor tuning how-to video?

Regards,

Derek
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Old 01-16-2013, 03:31 PM   #72928
TinkerinWstuff
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New topic anyone?

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Old 01-16-2013, 03:41 PM   #72929
Carl Childers
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Header Grind

My GSXR can showed up today so I pulled the stock exhaust off to get ready for the install and one of the first things I did was dremel out some of the weld out of the header pipe. I've gone from a trapazoidal opening to a round hole now that looks pretty good in comparison. I want to get the optimal opening without taking too much out so I was wondering if anyone could post a nice close up picture of the right amount of metal removal on this pipe?
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Old 01-16-2013, 03:45 PM   #72930
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Mmmm, more power!!
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