DR650SE Index Topic #10- CARBURETOR/INTAKE

Discussion in 'Thumpers' started by Krusty ..., Nov 8, 2010.

  1. BergDonk

    BergDonk Old Enough to Know Better

    Joined:
    Nov 15, 2010
    Oddometer:
    5,181
    Location:
    Snowy Mountains Oz
    I had a DJ 150 in it and wanted it a bit leaner. Its the smallest the kit comes with. I found an old Mikuni main in my bits and drilled it to 145 with a drill. It feels leaner than the DJ 150, and gave me what I was after.

    I could have soldered up a DJ jet and drilled it out, but I already had the Mikuni jet, so I thought I'd experiment and see what happened. All seat of the pants stuff though, so who knows.

    I also neglected to add that the pipe comprises a FMF Powerbomb header and Megacycle muffler and tailpipe.

    Steve
    #21
  2. NordieBoy

    NordieBoy Armature speller

    Joined:
    Dec 2, 2006
    Oddometer:
    7,172
    Location:
    Kiwiland
    The DJ 150 is the same as a Mikuni 142 I thought?

    A DJ 155 would be about right with a bit of altitude and/or not much air box cutting.

    I was running a larger pilot (+2) and pilot air (+1) too.
    #22
  3. eakins

    eakins Butler Maps

    Joined:
    May 29, 2002
    Oddometer:
    21,632
    Location:
    Fort Collins, Colorado
  4. BergDonk

    BergDonk Old Enough to Know Better

    Joined:
    Nov 15, 2010
    Oddometer:
    5,181
    Location:
    Snowy Mountains Oz
    Now that I've got the FCR humming, I've got a mate with a DR650 who has had the choke sticking open a bit as reported elsewhere. I have since been wondering whether that was a problem with my stock carb and why I kept leaning off the pilot, dealing with a rich condition. I'll probably never know, I like the FCR too much.

    Steve
    #24
  5. TheCowboy

    TheCowboy back in the saddle again

    Joined:
    Feb 15, 2008
    Oddometer:
    611
    Location:
    The frozen tundra - Minny Sota
    Just go my Mikuni BST40SS so-called Carb overhaul kit. Anyway I am looking at the rubber-tipped needle. On other carbs I have overhauled the needle moves up and down with float action. This needle has a pin on the top that moves - it's kinda like a plunger or somthing - when the float moves up and down it just presses on the pin (plunger) and it moves down. The old float pin-needle or whatever you want to call it I removed the pin (plunger) on top does not move at all (of course this may be why it was flooding all the time. Can anyone shed any light on this? I got no instructions with the ProCycle kit.

    TheCowboy
    #25
  6. TheCowboy

    TheCowboy back in the saddle again

    Joined:
    Feb 15, 2008
    Oddometer:
    611
    Location:
    The frozen tundra - Minny Sota
    Disregard last post - I have fuel in the crankcase - a hole new problem
    #26
  7. NordieBoy

    NordieBoy Armature speller

    Joined:
    Dec 2, 2006
    Oddometer:
    7,172
    Location:
    Kiwiland
    Sounds like the same problem.
    #27
  8. 996DL

    996DL Buell me

    Joined:
    Aug 23, 2006
    Oddometer:
    2,397
    Location:
    finally back in paradise...
    #28
  9. LexTalionis

    LexTalionis Inciteful

    Joined:
    Nov 3, 2008
    Oddometer:
    515
    Location:
    San Jose, CA
    Years ago a buddy installed a portable A/F monitor on his flatttracker ATK and was very happy with his tuning result.

    The May issue of Motorcycle Consumer News has, on the back cover, a glowing write-up of the NGK Powered AFX Air-Fuel Monitor.

    Dave Searle at MCN states, "Air-fuel ratios by themselves are not the final answer, but they're close, and from that baseline, additional dyno or stopwatch tuning to totally perfect the setup will require less time and money." My thought, exactly. I'm guessing the tuning arrived at using one of these devices is satisfactory for 98% of DR riders.

    Reading some of the anguished emails from riders soliciting tuning help makes the $260 cost a cheap investment for mental health.

    Searle states 13:1 is the optimal A/F ratio for power and cooling on the DR.

    Lex
    #29
  10. NordieBoy

    NordieBoy Armature speller

    Joined:
    Dec 2, 2006
    Oddometer:
    7,172
    Location:
    Kiwiland
    Carb MainJet equivalents...
    PHP:
    hole     Kehein      DynoJet     Mikuni
    0.0570    147.5       136        127.5
    0.0580    150         138        129.4
    0.0590    152.5       140        131.3
    0.0600    155         142        133.1
    0.0610    157.5       144        135.0
    0.0620    160         146        136.9
    0.0630    162.5       148        138.8
    0.0640    165         150        140.6
    0.0650    167.5       152        142.5
    0.0660    170         154        144.4
    0.0670    172.5       156        146.3
    0.0680    175         158        148.1
    0.0690    177.5       160        150.0
    0.0700    180         162        151.9
    #30
  11. Ladd

    Ladd Big Bad nOOb

    Joined:
    Jan 21, 2007
    Oddometer:
    25
    Location:
    Asheville
    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.
    #31
  12. Dakar Dan

    Dakar Dan Long timer

    Joined:
    Feb 4, 2007
    Oddometer:
    1,058
    Location:
    Bendigonia
    I'd recommend staying with the stock set-up with only light mods (snorkel out, drilled slide and raised clip, adjustable air-fuel screw and hex-key carb bolts) in conjunction with the stock pipe as a reliable, economical ride. I also replaced my cable choke with a manual one due to sticking early on, as well as ditching the vacuum petcock when I got an IMS tank. Think of this as an easy "Stage 1" step.

    The DynoJet kit is only adequate at addressing some of the stock carb's shortcomings and if you're going to go down the path of fettling, then save your bucks towards the FCR carb. IMHO "Stage 2" mods like this are really still a compromise around the BST-40's CV design.

    As for "Stage 3", if you fit an aftermarket pipe and perform any airbox surgery, you really begin to out-gun the CV carb. It's then a slippery slope of experimentation unless you commit to a pumper carb as well. I now run a TK alloy pipe with stock header (will have weld ground down when I get it ceramic coated later), FCR39_MX carb (ex-MxRob), open top airbox with Twin Air filter. Bear in mind that this is all bolt-on work without any internal engine mods (cams, piston etc.) or porting/ valve jobs as a true Stage 3 progression would entail.

    This combo makes the DR a different bike altogether. It doesn't transform it into a snarling, ill-mannered beast but certainly gives it more of an iron fist in a velvet glove feeling. Starts easy, runs smooth, no more farting at the table and excellent throttle response all the way through the range. Economy has dipped slightly but with the better tractability, I'll be returning to the higher stock ratio at chain & sprocket change time, which will restore some fuel range again. It's been said many times before but the overwhelming feeling is that this is the carb that the bike should have left the factory with in the first place, making it into a true thumper.
    #32
  13. Rumlover

    Rumlover Ed

    Joined:
    Sep 2, 2010
    Oddometer:
    707
    Location:
    Utah
    I pretty much agree with most of what you said. However I would give the BST carb a little more credit. I think with some basic mods as you mentioned, and include a few bucks for a few jets and an adjustable needle (or jet kit if prefered), the stock carb can be made to purr and provide some pretty good bang for the buck. I think some just don't have the patience/desire to keep tinkering with it to get it right. I will certainly agree that it will never have the immediate punch of a pumper carb, but it can make good power and run pretty much flawlessly with some careful tuning. For me it's just not worth the dollars to get a pumper (for now anyway :wink:)

    Current setup:
    Main - 142.5
    needle - stock (modified/improved taper with one .040 shim)
    Slide drilled with second hole (same size as original)
    fixed D shelf problem with plastic washer cut to size
    K&N filter
    No backfire screen
    Air box open about twice original hole size
    Stock muffler
    14/43 sprockets

    Edit: Thanks 996DL and NordieBoy for posting those jet comparison charts here.
    #33
  14. TripTheNinja

    TripTheNinja New to Seattle

    Joined:
    Mar 10, 2010
    Oddometer:
    10
    Location:
    Maple Valley, WA
    First of all, thanks to everyone who contributes to this website chock full of information. I've gained a lot of knowledge from here and hope to contribute where I can. I'm doing my best to do all of my own maintenance, etc. so that I can be confident of fixing anything while out in the mountains or on long hauls away from home. Hopefully this question can help others as well.

    I have an '08 DR that I bought used and in mostly stock form. I'm not doing any mods that require me to crack the case.
    Last month, in an attempt to wake this bike up I purchased the FMF-Q4 exhaust, K&N filter and the "ASM-Jetkit" from Procycle. I stuck to the instructions that came with the jet kit. I'm currently riding in the humid climate of South Carolina mostly at 1000 feet elevation with weekend rides ranging up to 7000 feet.

    I drilled the slide and did the air box mod (cut a big hole in the top). Procycle recommends using the #150 main jet for free flowing exhaust, setting the e-clip in the 4th groove from the top of the slide, and starting with the extended idle fuel mixture screw at two turns out.

    I did just that and it ran like a raped ape. Only problem was that it backfired real bad on deceleration and when switching gears. I played around with just about every combination of jets (145, 150, 155), 3rd and 4th grooves in the needle, and idle screw adjustments (adjusting from 2 turns out after 10 minutes of riding). All of the settings provide better performance from stock, however...

    -The 145 main jet backfires the least (at the 4th groove in the slide) and has the least power and response. Barely better than stock.

    -The 150 main jet set at the 3rd groove has the better power however backfiring a bit more.

    -The 155 main jet set at either the 3rd or 4th groove run good however it smells rich in any setting.

    My goal is to get the best performance with no backfiring. If it's not possible to rid the bike of backfiring I can live with it. Any suggestions?

    Thank you. :D
    #34
  15. NordieBoy

    NordieBoy Armature speller

    Joined:
    Dec 2, 2006
    Oddometer:
    7,172
    Location:
    Kiwiland
    The only way with an aftermarket pipe is putting on a Keihin FCR39MX carb with the air cut valve.

    The stock carb has no air cut valve/coasting enrichener.
    #35
  16. ER70S-2

    ER70S-2 Long timer

    Joined:
    Sep 30, 2009
    Oddometer:
    10,224
    Location:
    SE Denver-ish
    Deceleration popping:

    Originally posted by LexTalionis:

    "Two or three posters yesterday asked about DR’s backfiring, probably on deceleration. Didn’t see an answer, so here’s mine.

    Most street bikes with carburetors have a decel circuit built into the carb to meter in a bit of fuel on closed throttle, to prevent or greatly reduce backfiring on deceleration. My KLR has this, as has every pure street bike I’ve owned. The simpler DR carb does not have this circuit, hence you will be hearing more backfiring than other bikes you may own or have owned.

    This is not a problem, rather it is simply a characteristic.

    Lex

    P.S. As an aside, the rubber diaphragm in the decel circuit of my KLR has a tear in it, and so my KLR now backfires almost as much as my DR."
    #36
  17. sagedrifter

    sagedrifter Southern Explorer

    Joined:
    Apr 23, 2006
    Oddometer:
    1,533
    Location:
    Jacksonville, Alabama
    Make sure your pilot jet is really clean, what your describing is a back fire or decel pop?

    If its back firing at idle through the carb its the pilot circuit or an air leak at the carb boots.

    If its popping through the exhaust on decel, thats normal. 2 1/2 turns out on the pilot should help in the decel popping. A 150 main jet is all you need with exhaust and a cut air box. Mine popped very little at 2 1/2 turns out while living in Florida. But, it is pretty rich, 1 1/2 to 2 turns out is better usually.

    The Q4 is loud compared to stock and your probably just hearing the pop from a straight through exhaust. The Q4 is at least 10db louder and it keeps getting louder with use.
    #37
  18. TripTheNinja

    TripTheNinja New to Seattle

    Joined:
    Mar 10, 2010
    Oddometer:
    10
    Location:
    Maple Valley, WA
    It's popping through deceleration. After working through the many variations of jets and settings and riding from 700 to 6500 feel in elevation, I believe that the 150 jet is the way to go. Funny how I started with the suggested settings and played around with every variation. Now I'm back to the original suggested settings. I just didn't expect the pop.

    So far:
    Pro's
    - Louder / safer
    - Much better throttle response
    - Overall a more exciting bike to ride
    - Improved low and mid range power

    Con's
    - Top end power struggles from 70-75mph. Could still need some fine tuning
    - Deceleration pop
    - Loss of stealthiness while exploring in the mountains
    - Have to upgrade to a better carb. to hit the sweet spot

    Thanks for everyone's answers and advice! :freaky
    #38
  19. sagedrifter

    sagedrifter Southern Explorer

    Joined:
    Apr 23, 2006
    Oddometer:
    1,533
    Location:
    Jacksonville, Alabama
    Well, we are only talking around 38 hp or so... Depending on load, 70 indicated will not come instantly.

    If you can get 47 mpg or better your carb is probably good. I get 47 to 53 mpg depending on load and my mood. I find the bike likes 75 mph indicated or less. When traveling I run about 64 mph (around 70 indicated) on the GPS and get 50 mpg or better. My bike pops on decel and smoothly pulls to the rev limiter.... :lol3
    #39
  20. twigsnapper

    twigsnapper How did I get here?

    Joined:
    Aug 23, 2009
    Oddometer:
    651
    Location:
    Westsylvania
    My popping decreased significantly when I repacked the Q4. Kinda miss it tho.
    #40