OK - I searched, really... I did. But I STILL have a jetting question on 2001 640
I found a nice thread on jetting, and it made sense.
But, I still have a question....
I have a 2001 640 Adventure. I opened the airbox, have a IDS2 can on order, and my question is....
What jets sizes should I have on hand to properly tune/jet the thing? I believe the 2001 has the Mikuni.
Also, when popping in jets, other than sputtering (lean?) or maybe blowing black smoke (rich) (note - I've never jetted anything) how do I know I've got the optimal configuration beyond dyno and exhaust gas analyzing???
Thanks to all of you for your patience and indulgence. I'm so stoked about uncorking this beast.
#1- yes, your bike has the Mikuni BST-40 CV Carb, unless of course it's been changed from stock
#2- you will probably be running a 165-175 main jet, they run in units of 2.5 (ie. 160, 162.5, 165, 167.5, ... ) , and make sure you get the large round headed jets, not the small headed ones.
#3- you may want to also jump to the larger secondary jet of 47.5, the stock is 45. these are the only 2 options.
#4- here is a great site for explaining how to jet, it is for a Kawasucki but the principles are all the same http://justkdx.dirtrider.net/carbtuning.html
#5- since messing with the stock jetting, replacing the stock silencer (IDS2 with 12 disks), using racing airbox cover instead of stock, my bike always pops on decel. i've asked about this several times and read manya post about it and have come to the conclusion that it's due to the CV carb and not poor jetting.
good luck and have fun! your bike is going to feel like and sound like a monster when your done!!
Head over to ktmtalk.com and search the dual-sport area for "jetting". You'll have hours of fun.
Here's one thread started by Laramie hisself....
p.s. I'm guessing the right main jet for your bike at sea level will be about 157.5 (everybody here tends to go a little fat... :thumb )
I figured you guys had already decided on the optimal configuration.
1) What does the secondary jet do???
2) If I remove the floatbowl, I'll just see the jets there and be able to unscrew them?
First of all, just for reference, your stock main jet should be a 142.5. I'm near sea level and run a 157.5 (open airbox, SXC muffler) most of the time. For our mountain/desert adventures, I drop in a 155 or so, depending on the season. A selection of sizes say from 150~ish to 165 will give ya plenty to work with to dial yours in. Stock up - they're cheap.
Getting at the main is easy on the '01 because there's plenty of clearance beneath the carb, so just remove the big nut on the bottom of the float bowl and there's your main jet right there. There'll be a little collar that comes off with it, so be careful not to lose that. I've done it a bunch of times with a stubby screwdriver, but using Motion Pro's main jet wrench makes it even easier. "8mm Round Part Number: 08-0024" as shown on http://www.motionpro.com/Docs/convtools_2.html. After a few times, you should be able to swap a main jet out in a couple of minutes, start to finish.
The air jet is located in the carb's bellmouth, recessed into one of a couple of holes, with its screw slot facing the airbox. You'll wanna put a 1.1 in there. Here's an easy carb access tip: Remove the exhaust mount bolt just above the chain roller, along with the muffler's springs. Then loosen the clamp that secures the airbox to the carb and remove the subframe's upper mount bolts. Slowly pivot the subframe down towards the tire while watching to see which (if any) of the electrical connectors need to be unplugged to avoid pulling. The airbox will pop off the carb and you'll be able to remove it (the carb) with ease. Be VERY careful with the tiny air jet's threads and screwdriver slot.
Then just dial in the mixture screw like on most any other bike. Turns are counted outwards from lightly seated. Here's a handy guide...
Some relevant threads...
I believe in supporting your local shop, but here's a nice online resource for part numbers and schematics...
Specific to your carb...
Also, since the bike is new to you, here's a blurb about friendly gearing in case you ever feel the need: To keep your chain length the same and be able to easily swap street/dirt gearing as needed, go up one tooth in the front, and down two in the rear.
17t countershaft sprocket, ktm part # 58033029017.
40t rear sprocket, ktm part # 58310151040.
You'll need to take a belt sander to the removable case protector to fit the larger countershaft sprocket, or order up the one that they use on the duke (ktm part # 58430047000). Either way it's a no-brainer.
Soooooo, long story short, here's my typical setup and few part numbers...
17t countershaft sprocket, KTM part #58033029017.
40t rear sprocket. KTM part #58310151040.
KTM SXC muffler is part #58305081300.
Open airbox cover is part # 58406003200.
Main jet 157.5-ish, air jet 1.1.
Euro tool carrier thingy is KTM part #58012058000.
YMMV, and then some.
but, what does the 1.1 jet thingy do? is that idle?
OK - I got all the jets in or ordered. The 1.1 air jet isn't listed. They show a 1.0 and 1.2. I got one of each coming.
How critical is this mod and what's it do ?
I did the carb mods on my bike when it had over 8K on it and wondered why the hell I hadn't done it sooner. The bike runs much smoother and has more power. A couple of other things I have done to my carb are to drill the slide holes to 3mm and cut two coils from the diaphram spring. Both of these mods increase throttle response as the slide moves quicker and easier. On my engine, I also installed a thinner base gasket to increase compression which made a noticeable difference.
If your locals can't help, try..
Thanks to all for the flood of info...
I'll be pasting a lot of the thread into a LC4 folder on my hard-drive when I get home.
Great links, great info.
I'll post this in Equipment as well but its a question I have had for a bit. While looking thru Arch's stuff I came across this at Sudco:
(editor's note: HTTP tag is correct... why doesn't it load the pic Arch?)
K&N Air/Fuel Monitor
The K&N Air/Fuel Monitor is a precision instrument designed to aid in making correct jetting decisions. The monitor measures the oxygen content of the exhaust gas and displays the relative air/fule ratio information on an LED display. This device is an economical way to analyze exaust gases, enabling a tuner to see at a glance what the Air/Fuel ratio of an engine is at any RPM or throttle position. Can be mounted on bike for perminent installation, or used temporarily during tuning.
Order No. 005-200
Anyone have any experience with one of these? I think I am interested. Alternatively, this looks like a pennytech solution also on the Sudco page:
Sudco/Mikuni Pocket Carb Tuner
A handy pocket-size slide calculator which can be used to determine required jetting changes in Mikuni carburetors due to ambient temperature, altitude, or both. It also provides a guide for determining rich or lean carburetor conditions. The Pocket Tuner is applicable to both single and multi-carburetor applications on two stroke and four-stroke engines.
Order No. 002-430
The reason that the link doesn't work is because vBulletin replaces special ASCII characters with their HTML character codes so that the special ASCII character displays correctly. Specifically, it converts the ampersand to the equivalent HTML character codes and, as an unintended consequence, breaks the link by changing the URL that your web browser sends to the www.sudco.com web server when it tries to retrieve/display the image. (To see how vBulletin has mangled the original URL, select View -> Page Source from your browser's menu. You can find the HTML quickly by selecting Edit -> Find from the viewer's menu and searching for the word "editor".)
Use the "Insert Image" icon in the message composer (i.e., the little icon that looks like a post card with two mountains) and vBulletin should leave it alone.
That image should display right there in line with the message. e.g.,
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