A Little Help with Jetting?
#22
09-07-2015 | 04:26 PM
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Joined: May 2015
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From: Kenora, NWO, Canada
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Food for thought...
If you're willing to spend $80 to never rejet your carb again, put the lean main back in or even a 125, and get a Dial-A-Jet. I'm at 1000ft elevation and running clean on both my bikes. Went to WV with the big bike and ran clean up in the mountains a few thousand feet higher.
I have run them for the past 20 years in bikes both stock and modified. The KLX650 went with a cut lid, big bore piston, and pipe without any jetting changes, although it could use a bigger pilot since the DAJ works with the slide/needle/needle jet/main jet circuits, not the idle circuit.
I did the KLX300 jetting on my 250, as did my brother, and installed the DAJ, smoothing out the power delivery - I also have the MCM mod. The bike pulls decently over the whole range - for a 250 (riding the 650 kind of jades me on the power). The carb only needed to be apart once to put in the 300 brass, nothing else from there.
On the Thunder products site go read the media comments. The ATV and Snow mobile industries have taken to it whole hog, where the motorcycles are stuck in old school brass. Fact is I had them in a customer's Honda Nighthawk S in place of jetting when he put a Kerker on it back in 1986. Worked perfect without ever removing anything but the gas tank to install them.
Take a serious look, especially if you go into higher altitudes on any frequency. It is a fuel adder powered by the vacuum draw and acoustics of the intake. You jet lean for the high elevation with the brass, then let the DAJ fill in the fuel mix when at lower elevations. It will fill in leanness, doing nothing when running rich - it only works when lean, so you jet lean.
Seems a bit steep to spend the money, but how much would it be worth to not have to take a carb off for jetting again? Plus if you go to a flat slide you can use it with that carb too. Same kit is in both my 250 and 650, the 250 is eventually going to a flat slide and it will be jetted lean and the DAJ in it.
If you're willing to spend $80 to never rejet your carb again, put the lean main back in or even a 125, and get a Dial-A-Jet. I'm at 1000ft elevation and running clean on both my bikes. Went to WV with the big bike and ran clean up in the mountains a few thousand feet higher.
I have run them for the past 20 years in bikes both stock and modified. The KLX650 went with a cut lid, big bore piston, and pipe without any jetting changes, although it could use a bigger pilot since the DAJ works with the slide/needle/needle jet/main jet circuits, not the idle circuit.
I did the KLX300 jetting on my 250, as did my brother, and installed the DAJ, smoothing out the power delivery - I also have the MCM mod. The bike pulls decently over the whole range - for a 250 (riding the 650 kind of jades me on the power). The carb only needed to be apart once to put in the 300 brass, nothing else from there.
On the Thunder products site go read the media comments. The ATV and Snow mobile industries have taken to it whole hog, where the motorcycles are stuck in old school brass. Fact is I had them in a customer's Honda Nighthawk S in place of jetting when he put a Kerker on it back in 1986. Worked perfect without ever removing anything but the gas tank to install them.
Take a serious look, especially if you go into higher altitudes on any frequency. It is a fuel adder powered by the vacuum draw and acoustics of the intake. You jet lean for the high elevation with the brass, then let the DAJ fill in the fuel mix when at lower elevations. It will fill in leanness, doing nothing when running rich - it only works when lean, so you jet lean.
Seems a bit steep to spend the money, but how much would it be worth to not have to take a carb off for jetting again? Plus if you go to a flat slide you can use it with that carb too. Same kit is in both my 250 and 650, the 250 is eventually going to a flat slide and it will be jetted lean and the DAJ in it.
#23
09-07-2015 | 04:49 PM
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Joined: Jun 2013
Posts: 3,231
From: North Texas
1st Gear Member
Ruggy, there was a member that chimed in saying he runs the DJ2152 kit with a drilled slide - and his bike runs fine.. What we are talking about with this issue is the response curve of the slide to the vacuum signaling produced by the engine. To produce the intended response curve with the 2152 kit , you put in the spring.. To produce the intended curve with the 2206 kit, you drill the slide.. (I bet the 2206 kit gave our predecessors the idea to drill the slide without using a the kit.)
#24
09-07-2015 | 05:00 PM
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Joined: Jun 2013
Posts: 3,231
From: North Texas
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Now with the MCM, full exhaust systems, heck even modern slip-ons, we are CHANGING the vacuum signaling that is presented to the CVK compared to what DynoJet expects - they used a KLX250 with STOCK EXHAUST (!!!) to develope the 2152 kit..
Point is, we have to have some kind of "standard/baseline" (and Dyno tested, if you ask me) carb setup for a given set of mods in order to start making sense of what power levels can be reached.. Who knows, it could turn out that someday,@near sea level, we find that your (and mine) mods need the stock spring and lift hole with the 2206 kit but with a DJ144 main jet and the DNO352 needle on 2N (that's the needle in the 2206 kit.).. With a full exhaust system+MCM+lidless, best power levels is still experimental..
Point is, we have to have some kind of "standard/baseline" (and Dyno tested, if you ask me) carb setup for a given set of mods in order to start making sense of what power levels can be reached.. Who knows, it could turn out that someday,@near sea level, we find that your (and mine) mods need the stock spring and lift hole with the 2206 kit but with a DJ144 main jet and the DNO352 needle on 2N (that's the needle in the 2206 kit.).. With a full exhaust system+MCM+lidless, best power levels is still experimental..
Last edited by Klxster; 09-07-2015 at 05:10 PM.
#26
09-07-2015 | 05:27 PM
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Joined: May 2015
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From: Kenora, NWO, Canada
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Ok slightly cofused. The 2206 is for the 300 and the 2152 is for the 250. The 2206 you drill the slide and the 2152 you don't drill but some have. So the questions are: If using the 2206 and drilling do you use the stock spring or the DJ spring? If using the 2152 kit you drill but what spring is used? Of the two DJ kits, 2206 and 2152, which kit is the preferred DJ kit to use with a drilled slide and my modes?
I'm getting really quick at taking the carb on and off but really would like to get this right.
Thanks for your help.
I'm getting really quick at taking the carb on and off but really would like to get this right.
Thanks for your help.
#27
09-07-2015 | 05:48 PM
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Joined: Jun 2013
Posts: 3,231
From: North Texas
1st Gear Member
To use as intended:
2206 with drilled slide and stock spring. This kit works with the KLX250 as well as KLX300.
2152 with undrilled slide and DJ spring.
However, as I said, "intended use" is based on a stock exhaust on a stock airbox (stage1 with snorkel or stage 2 without the snorkel).
So, "intended use" is only a suggestion for our modified 250's - there is no reason other combinations couldn't work - Perhaps work better... it is just that with the "intended use" setup on the slide spring and lift hole, we have a starting point to tune from...
You increase the vacuum signalling most with MCM+stock header+ slipon. I found that, on the dyno, near sea level, with lid off, such mods can be fueled correctly for max power using 2152 stage 2, with a DJ140 main and the needle on 2N.. Now you need 2N in order to not overfuel the low and mid RPM range, It could be that same results could be had with the stock spring and 3N... While I don't know how much of this you can understand, the point is that other spring/lift hole combinations COULD work well - we just don't have Dyno Charts proving them...
2206 with drilled slide and stock spring. This kit works with the KLX250 as well as KLX300.
2152 with undrilled slide and DJ spring.
However, as I said, "intended use" is based on a stock exhaust on a stock airbox (stage1 with snorkel or stage 2 without the snorkel).
So, "intended use" is only a suggestion for our modified 250's - there is no reason other combinations couldn't work - Perhaps work better... it is just that with the "intended use" setup on the slide spring and lift hole, we have a starting point to tune from...
You increase the vacuum signalling most with MCM+stock header+ slipon. I found that, on the dyno, near sea level, with lid off, such mods can be fueled correctly for max power using 2152 stage 2, with a DJ140 main and the needle on 2N.. Now you need 2N in order to not overfuel the low and mid RPM range, It could be that same results could be had with the stock spring and 3N... While I don't know how much of this you can understand, the point is that other spring/lift hole combinations COULD work well - we just don't have Dyno Charts proving them...
#29
09-07-2015 | 08:36 PM
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Senior Member
Joined: May 2015
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From: Kenora, NWO, Canada
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So just on a whim here's what I did. I put in an adjustable air pilot needle, basically soldered on a brass extention. I thought maybe the pilot was too big so adjusting it near closed might reveal that. I put back in the 128 and left the needle in the N2 position. Got the bike started up and lowered the RPM to around 1G to detect changes in the rpm as I adjusted the pilot. The pilot needle achieved the highest rpm at around 1 1/4 turns out. I turned it to the 1 1/2 position and turned the RPMs back up to 1700. One thing I did notice was that with the needle turn all the way in and all the way out there was only around 200 rpm difference. I expect the bike to stall with the needle all the was in. Anyhow took the bike for a quick ride on my gravel road and pretty much the same. Missing the big wheelie power but was able to lift the wheel maybe a foot in first, hopeless in second. I seem to still have a small dead spot when I Crack the throttle. Maybe the slide is not acting quick enough. Does drilling the slide slow down or speed up the action of the slide?
#30
09-07-2015 | 08:51 PM
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Joined: Jun 2013
Posts: 3,231
From: North Texas
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Well I think you need a primer on how to set the fuel screw..
Also, with the idle set to 1300 rpm, it certainly should die when you seat the fuel screw closed. If not, then you have a problem.
So - lightly seat the fuel screw, turn out 1 turn, fire up bike and set idle to 1300 rpm, turn in the screw until idle drops then back out until idle returns, then give it another tiny 1/8 - 1/4th turn out, leave it there.
Also, with the idle set to 1300 rpm, it certainly should die when you seat the fuel screw closed. If not, then you have a problem.
So - lightly seat the fuel screw, turn out 1 turn, fire up bike and set idle to 1300 rpm, turn in the screw until idle drops then back out until idle returns, then give it another tiny 1/8 - 1/4th turn out, leave it there.