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Old 11-08-2010, 10:16 PM   #1
Krusty ... OP
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Joined: Dec 2004
Location: Richardson, TX
Oddometer: 7,600
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?
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SUZUKI DR650SE INFORMATION INDEX
"...choosing a DR indicates an affinity for peace, harmony and enlightenment. Serenity lies in accepting it as it is, changing what you want, and the wisdom of knowing it ain't orange." -psmcd
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Old 11-08-2010, 10:32 PM   #2
eakins
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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
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eakins screwed with this post 05-11-2015 at 11:10 PM
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Old 11-09-2010, 06:43 AM   #3
Krusty ... OP
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Location: Richardson, TX
Oddometer: 7,600
Bst40

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.




Mikuni / Dynojet Jet Size Comparison
[from vmaxoutlaw.com]

Mikuni Dynojet

140
149.3

Flow rates based on size markings of Mikuni and DynoJet jets are not comparable. As a guide .. the chart to the left indicates equivalent sizes based on the diameter of hole in the jet. Mikuni jets are chamfered on the inside opening at the threaded end and
Dynojets have a machined flat surface. Keep this in mind when using this chart. These physical differences will never allow an exact comparison.
This chart is intended to be used as a tool to assist you in making a more
accurate decision when selecting a jet size range or comparing tuning data where an opposing brand is being used.
Actual jet sizes are highlighted with a gray background.
DynoJet jets are marked according to the diameter of the hole in the
jet .. ie: DJ150 = 1.5mm and DJ175 = 1.75mm. This is not true for Mikuni or most other OEM equivalent jets. This size
Mikuni jet, (N102.221 Super BN), is marked according to its' flow rate,
ie: 150 = a rating of 150 cc of fuel per minute.


150
142.5
152.0
145
154.7

155
147.5
157.3
150
160
152.5
162.7

165
155
165.3
157.5
168.0

170
160
170.7
162.5
173.3

175
165
176.0
167.5
178.7

180
170
181.3
172.5
184.0

185
175
186.7
177.5
189.3

190
180
192.0
182.5
194.7

195
185
197.3
187.5
200
190
202.7
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SUZUKI DR650SE INFORMATION INDEX
"...choosing a DR indicates an affinity for peace, harmony and enlightenment. Serenity lies in accepting it as it is, changing what you want, and the wisdom of knowing it ain't orange." -psmcd

Krusty ... screwed with this post 05-04-2011 at 11:35 PM
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Old 11-09-2010, 08:17 AM   #4
SkunkWizard
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reference pic
TM-40 & stock

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Old 11-23-2010, 01:04 PM   #5
macdesign
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Location: Melbourne, Australia
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What about a road only set up?

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".
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Old 12-08-2010, 08:13 AM   #6
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Quote:
Originally Posted by eakins View Post
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/ 2 washers for more gas on the main
-stock jetting
-1 additional hole drilled in the slide for better throttle response
-spring not modified
-jesse's fuel screw now set at 1 turn out. had it out more for better idle but off-idle bog. now off idle bog at 1.
-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
-upgraded 2ndary air filter form procycle

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
What size washers did you use?
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Old 12-12-2010, 02:53 PM   #7
ER70S-2
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Fuel Chart

Thanks to Northyork:

http://www.advrider.com/forums/showp...ostcount=35442
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SUZUKI DR650SE INFORMATION INDEX
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Old 12-12-2010, 06:47 PM   #8
kalsop
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1

Thank you.
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Old 05-05-2011, 05:52 PM   #9
Ladd
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Tried Dynojet kit and airbox mod - better throttle response but still surged no matter what I tried. Got the TM40 and it is awesome, so smooth. I can lug around in 5th at 30mph and roll on throttle with no bucking and no surging on interstate. Fuel economy suffered a little bit but it is worth it.
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Old 03-12-2015, 09:26 AM   #10
ryder1
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My 2013 dr has a bit of a stumble just off of idle while in first gear. I checked out the clymer manual bit could not find an air fuel mixture screw. Did i just miss it or has it gone the way of the do-do bird?

As far as i know the bike is stock except for he new handlebars.
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Old 05-14-2015, 02:45 AM   #11
eakins
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Quote:
Originally Posted by kalsop View Post
What size washers did you use?
Same size as white spacer. Stainless steel.
Found at my local ace.
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Old 05-11-2015, 11:08 PM   #12
eakins
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I just picked up a used BST (unmodified) w/ 4-5k from an inmate.
I decided to tune different this time.

-1 (.3mm ideal) washer under the white spacer on the needle...was 2 before. Motolabs recommends the adjustable non-USA needle on the 4th clip.
He feels this additional washer creates more pre-load on the spring.

-Procycle D shelf spacer down in that pocket. white spacer now sits on a flat surface! the needle now is centered (in the slide) and does not press against the needle jet. Motolab does not like this spacer? To me this is a much better setup vrs constantly wearing against the needle jet opening (& wearing it out there). No idea why Mikuni puts that d shelf their...it's been heavily discussed in the past.

-non-drilled slide...was drilled before. Motolab is against drilling the slide w/ additional hole. Others have said the additional holes does cause the engine to hammer more.

-had a Jesse extended fuel screw...now a Procycle. Much easier to use.

My rides as good as it ever has!!!
Only 1 washer and not drilling the slide is key for the BST for my bike.
Start with this and an extended fuel screw.

Quote:
Originally Posted by eakins View Post
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 idle 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
__________________
Butler Maps - motorcycle maps for riders by riders -
Alaska
NM map COBDR AZBDR IDBDR South East map
http://www.advrider.com/forums/showthread.php?t=598717
Butler Maps website:
http://www.butlermaps.com
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Old 05-12-2015, 08:37 AM   #13
motolab
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Quote:
Originally Posted by eakins View Post
He feels this additional washer creates more pre-load on the spring.
This has nothing to do with feelings. It's a fact that a washer under the clip increases the preload on the slide spring by the thickness of the washer.
Quote:
Motolab does not like this spacer?
Correct.
Quote:
To me this is a much better setup vrs constantly wearing against the needle jet opening (& wearing it out there). No idea why Mikuni puts that d shelf their...it's been heavily discussed in the past.
Installing a d-shaped spacer that is the same height as the shelf in the floor of the slide means that the needle is no longer preloaded in the downstream direction, and will therefore be more prone to orbiting/otherwise gyrating inside the emulsion tube. It also means that the needle will not be able to pivot out of the way as the slide guide wears. Both of these factors equate accelerated emulsion tube wear.
Quote:
Motolab is against drilling the slide w/ additional hole.
Correct. Slide guide wear is pretty much proportional to lift hole area, so drilling the slide will dramatically increase slide guide, emulsion tube and slide wear. Dynamometer testing I have performed on a late model DR650 also showed that it caused a loss in hp at 1/4 opening and richened the mixture at 1/8 opening in a not easily correctable manner.

Regards,

Derek
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Old 05-13-2015, 02:52 PM   #14
rvt
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main jet size

Hello boffins!
I recently opened up the airbox on the dr650 with 2x 45mm holes. One of these is where the snorkel used to live.

For jetting, I installed a 145 mikuni jet (because I had one) and raised the stock needle one slot. Fuel screw at 2 turns out. Slide not drilled. Aftermarket foam "funnelweb" filter.
Looks like this:http://www.advrider.com/forums/showp...ostcount=14932

It performs really well, with no surging or bogging at any points that I can notice. The exhaust is a staintune, which I tried with insert in and out. Will be leaving the insert in, although it ran fine both ways. Fuel consumption over 100km of mixed riding was like stock, about 5L/100km.

Others seem to be using larger main jets, as do the common jet kits. My concern is, even though it rides OK, could it be lean enough to damage anything long term? I don't have access to a dyno or gas monitor at the moment. Time and $$$ limit the purchase and testing of multiple jets.

Suggestions appreciated.
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Old 05-13-2015, 03:54 PM   #15
BergDonk
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Bum test. Get up to speed, say 80 kph in 4th gear and hold the thrrottle full on (WFO). If it pulls cleanly, keeps accelerating, and doesn't surge, that's promising.

When you roll off, it does just that and doesn't momentarily acelerate, then its not too lean. If it does, try one size richer main and test again. If it doesn't, try leaner.
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