DR650SE Index Topic #10- CARBURETOR/INTAKE

Several schools of thinking here. Many opt to stay with exactly what the engineers at Suzuki designed. Others feel the need to make a good thing better, and the intake tinkering can go from mildly tweaking the stock CV carb to opening up the airbox and/or switching to a flatslide pumper. And if you're so inclined, do-it-yourself fuel injection is on the horizon, thanks largely to the relentless efforts of mx_rob.

Intake-wise, what's worked for you?


-AIRBOX MODIFICATION
-AIR FILTERS
-STOCK CARBURETOR [MIKUNI BST40] MODIFICATION
-MIKUNI TM-40 [HSR-40]
-KEIHIN FCR39-MX
-FUEL INJECTION?

my bike had dynojet mods when i bought it. it surged and the power was very abrupt on/off. hated it.

now:
-stock needle & raised up w/ 1 washers for more gas on the main
-stock jetting
-slide NOT drilled w/ an additional hole
-spring not modified
-Procycle fuel screw now set at 1.75 turn out. this is my peak ideal speed.
-carb fully cleaned w/ pine sol soak. this made a huge difference in how much better it ran even though it looked clean. a ton of dirt came out. safe on rubber. search for hondo's post.
-ngk iridium plugs for the best possible fuel burn.
-stock airbox w/ only snorkle gone
-twin-air air filter
-gsxr muffler
-upgraded 2ndary air filter form procycle
-stainless allen bolts on top cap, throttle cables plate and float bowl (heat stock screws 1st w/ a lighter so they come out easier)

bike runs well from sea level to over 13k that i've had it to. pulls strong and linear. i use a 14 tooth cs and i can off-road in 1st and pull 80 all day in top. 50 or so mpg

From the factory, your DR650SE came equipped with a Mikuni BST40 constant velocity (CV) carburetor. You may begin your journey of enlightenment here:


The BST40 Bible

Airbox mod? If you plan to enhance your DR's ability to breathe, you will need to address the restrctive airbox. If your plans to tweak your carb include stay with the factory jetting, you won't likely need to do more than remove the snorkle at the top of the airbox. If you plan on doing more (bigger jets, Dynojet kit, etc.) you'll likely end up doing the "airbox mod".
Here's a picture, from the Keintech website:



www.keintech.com



mx_rob has been a man on a mission to improve the performance of the DR. He is a "fixture" over at ThumperTalk, and his early efforts focused on the BST40.

His website www.mxrob.com, has a BST40 section, including a link to this thread at ThumperTalk, comparing different needles.

[SIZE=+2]Mikuni / Dynojet Jet Size Comparison[/SIZE]
[from vmaxoutlaw.com]​

<center> <table bgcolor="#000000" border="0" cellpadding="0" cellspacing="0" height="60%" width="80%"> <tbody> <tr> <td> <center> <table style="border-collapse: collapse;" bgcolor="#000000" border="1" cellpadding="0" cellspacing="0" width="741"> <tbody> <tr> <td align="center" width="56"> [SIZE=-1]Mikuni[/SIZE]</td> <td align="center" width="60">[SIZE=-1]Dynojet[/SIZE]</td> <td rowspan="31" width="4">
</td> <td width="616">
</td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]140[/SIZE]</center></td> <td width="60"> <center>149.3</center></td> <td rowspan="30" align="middle" valign="top" width="616"> <center>
<table border="1" cellpadding="5" cellspacing="5" width="496"> <tbody> <tr> <td align="center" width="472">[SIZE=-1]Flow rates based on size markings of Mikuni and DynoJet jets are not comparable.[/SIZE] [SIZE=-1]As a guide .. the chart to the left indicates equivalent sizes based on the diameter[/SIZE] [SIZE=-1]of hole in the jet. [/SIZE] [SIZE=-1]Mikuni jets are chamfered on the inside opening at the threaded end and [/SIZE]
[SIZE=-1]Dynojets have a machined flat surface. Keep this in mind when using this chart. [/SIZE] [SIZE=-1]These physical differences will never allow an exact comparison.[/SIZE]
[SIZE=-1]This chart is intended to be used as a tool to assist you in making a more [/SIZE]
[SIZE=-1]accurate decision when selecting a jet size range or comparing tuning data[/SIZE] [SIZE=-1]where an opposing brand is being used.[/SIZE]
<center> [SIZE=-1]Actual jet sizes are highlighted with a gray background. [/SIZE]
</center></td></tr> <tr> <td align="center" width="472"> [SIZE=-1]DynoJet jets are marked according to the diameter of the hole in the [/SIZE]
[SIZE=-1]jet .. ie: DJ150 = 1.5mm and DJ175 = 1.75mm. [/SIZE] [SIZE=-1]This is not true for Mikuni or most other OEM equivalent jets. This size[/SIZE]
[SIZE=-1]Mikuni jet, (N102.221 Super BN), is marked according to its' flow rate, [/SIZE]
[SIZE=-1]ie: 150 = a rating of 150 cc of fuel per minute. [/SIZE]
</td></tr></tbody></table></center>
</td></tr> <tr> <td width="56">
</td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]150[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]142.5[/SIZE]</center></td> <td width="60"> <center>152.0</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]145[/SIZE]</center></td> <td width="60"> <center>154.7</center></td></tr> <tr> <td width="56">
</td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]155[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]147.5[/SIZE]</center></td> <td width="60"> <center>157.3</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]150[/SIZE]</center></td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]160[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]152.5[/SIZE]</center></td> <td width="60"> <center>162.7</center></td></tr> <tr> <td width="56">
</td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]165[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]155[/SIZE]</center></td> <td width="60"> <center>165.3</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]157.5[/SIZE]</center></td> <td width="60"> <center>168.0</center></td></tr> <tr> <td width="56">
</td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]170[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]160[/SIZE]</center></td> <td width="60"> <center>170.7</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]162.5[/SIZE]</center></td> <td width="60"> <center>173.3</center></td></tr> <tr> <td width="56">
</td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]175[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]165[/SIZE]</center></td> <td width="60"> <center>176.0</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]167.5[/SIZE]</center></td> <td width="60"> <center>178.7</center></td></tr> <tr> <td width="56">
</td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]180[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]170[/SIZE]</center></td> <td width="60"> <center>181.3</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]172.5[/SIZE]</center></td> <td width="60"> <center>184.0</center></td></tr> <tr> <td width="56">
</td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]185[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]175[/SIZE]</center></td> <td width="60"> <center>186.7</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]177.5[/SIZE]</center></td> <td width="60"> <center>189.3</center></td></tr> <tr> <td width="56">
</td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]190[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]180[/SIZE]</center></td> <td width="60"> <center>192.0</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]182.5[/SIZE]</center></td> <td width="60"> <center>194.7</center></td></tr> <tr> <td width="56">
</td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]195[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]185[/SIZE]</center></td> <td width="60"> <center>197.3</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]187.5[/SIZE]</center></td> <td bgcolor="#c0c0c0" width="60"> <center>[SIZE=-1]200[/SIZE]</center></td></tr> <tr> <td bgcolor="#c0c0c0" width="56"> <center>[SIZE=-1]190[/SIZE]</center></td> <td width="60"> <center>202.7</center></td></tr></tbody></table></center></td></tr> </tbody></table></center>

reference pic
TM-40 & stock

Let's establish one thing up front - My DR doesn't see any dirt at all.
It's a city commuter, which is currently being made even more so (read - being motarded), and a damn good one at that
So, I'm after anyones views or experience on dumping the airbox entirely and running a pod filter or similiar.
In the stock of bits and pieces to play with there's obviously the standard carb and exhaust as well as a TM-40, an FMF Q4, a GSXR titanium can, and finally a FMF oversize front pipe/Hindle rear (to suit the X40X can).
I'll probably end up mucking about with them all but don't mind not having to "re-invent the wheel".

TM40-6 (HS40) manual from Mikuni:
http://www.zodiac.nl/instructions/234862.pdf

I'm pretty happy with the stock carb/airbox set up on the DR. It has been totally reliable and I never have to mess with it. I live at 7500 feet and ride above 11,000 feet on Colorado passes often, and have put in many miles at sea level as well. The bike always starts and runs well with no hesitation or misses from idle to redline. (If I want more power, I usually choose my other bike.)

Just my .02.............shu

cut box/ twin-air AF
39mm fcr-mx, jetted normal except:
38pilot 50leak EMP-3 magic-racing screw 1.0 turns out

07 DR650 with stock exhaust at 2200 ft asl...

Full Jesse/Kientech airbox mod, TwinAir foam air filter, Uni pleated filter replacing useless oem foam cannister, drilled slide, exposed oem mixture screw @ 1 turn out, Jesse's recommendation of 155 DynoJet mainjet for oem exhaust, and Most Importantly in my case: DynoJet needle set one step leaner than instructions, to Completely Cure the common off extended idling flat spot: (DJ needle's clip set at 3 down from top).

This setup performs perfectly and routinely yields 60mpg Imp gal / 48mpg US gal. My DR is used as a "roadie" with a taller 16 tooth frt sprkt and ridden like I want to keep it for the long run, with no banging off the rev limiter, nor treating the transmission like a 125 motocrosser.

996DL

Bump

Coz my bike only gets 40-45 mpg and i dunno why.

I have a question, my carb doesn't seem to shut down quite quick enough between shifts. The only mods done are air/mix screw 1-1/2 turs out and shimmed needle. .32/.09 mm. Any thoughts?

start by cleaning it with pine sol soak (google for hondo's thread)

you might have sticky/gummed throttle cables or throttle tube.

What size washers did you use?

Fuel Consumption Numbers

Thanks to Northyork:
http://www.advrider.com/forums/showpost.php?p=13004862&postcount=35442

Idle speed adjustment:
The idle speed knob adjusts the inner post, once the throttle stop is hitting the outer threaded barrel, you've lost that adjustment. At that time you need to adjust the outer barrel (lower) to expose the inner post to allow more adjustment.


Suzuki Manual error. When shimming the needle, it goes between #4 and #5. (.020"-.030" recommended)

Thank you.

I did the jesse mod on my previous Dr and transferred everything back to stock but the slide piston with the extra hole drilled in it. The throttle seemed to be a bit to abrupt on deceleration. The throttle is very snappy as for as the thottle body spring back is conserned, it just seems to be a little long on deceleration. this bike only had 495miles put on it from oct 08 unil now so no telling what might have a little gum still holding on in the carb. Maybe it will subside once it has some real miles put on it.

I removed the airbox snorkel and opened up the top.
After much experimenting, including initially making up my own needle from and old FCR needle I had lying about, I got a Dynojet kit from Procycle.

Much more experimenting, and this is where I'm at:
Main 145
Pilot 37.5
FS 0.875 turns
DJ needle 4th clip from bottom
drilled slide

800 m

Leaner than most, but now working well with no surging and good economy, and pretty clean roll on from a closed throttle. Still no FCR, so I'll do that next. Nevertheless its the best DR650 with BST40 I've tried to date.

More of my DR650 stuff if you follow the link in my signature.

Steve

DJ or Mikuni main jet?

Good question, a drilled Mikuni. I have experimented with DJ vs Mikuni and Keihin previously in other bikes and although I'm aware of the supposed differences re approach and departure profiles, they all seem to work pretty much the same for me over the years. All I do is gauge them with my jet drills, and that works for me. I leaned off the main from the supplied DJ jets to my drilled 145 and its leaner, although the 'book' says it should be richer.

A stick of solder and a set of jet drills and you can have most mains to play with.

Dunno
Steve

So basically close to a DJ 155?