DR650 790 Big Bore Installation and Review

Discussion in 'Thumpers' started by planemanx15, Feb 5, 2013.

  1. gregdee

    gregdee Motocampist

    Joined:
    Oct 30, 2011
    Oddometer:
    514
    Location:
    Tijeras, NM
    Yeah, this thread got me thinking that I need to put a 790 kit in my wife's DR. Then I had a better idea: sell my KLR 688, buy my own DR and do the kit. :d

    Thanks for this thread - good stuff. I love ADVRIDER:clap:clap:clap:clap:clap
  2. planemanx15

    planemanx15 Long timer

    Joined:
    Dec 4, 2009
    Oddometer:
    1,009
    Location:
    Long Island, NY
    Another MPG report... 40mpg. I think its time to take out the carb tuning handbooks.

    That was riding it a bit aggressive, but thats how I normally ride. Highway \ city about 50\50. and on the highway I usually keep it about 75 mph.Hit reserve at 170 miles, I went another 16 miles before gas. The IMS tank took 4.6 gallons. Before the kit, i was in the 45-48 range with mixed driving.

    Currently I'm on the second notch down from the top on the needle. As for the jets, I really don't remember.

    I usually get lower fuel economy in the winter, and it is still pretty cold when I've been riding. I also have been letting the bike warm up a lot before riding, which is a factor that contributes. I'm not sure if I'm going to touch it yet, or just leave it for now and see if it gets better as the temps climb back up.
  3. davesupreme

    davesupreme grand poobah

    Joined:
    May 1, 2011
    Oddometer:
    1,794
    Location:
    palm harbor, fla
    40 don't sound bad, but i don't have your bike.... i don't get 40 on my 450 KTM, but i gotta accelerator pump/41mm FCR, so...

    cold dry air is denser than warm humid air, bike carburates(sp?) better in cold dry... look up relative air density....Merge Racing has an air density calculator on their website...

    you totally changed your engine, so you're gonna have to experiment some to get it right... that procycle guy sounds pretty smart, i'm sure he must have some baseline jetting for his kit..... i think fat is where it's at, and if you ride hard, you wanna stay away from lean, cause' detonation is bad.... though i dunno if you could ever detonate that motor that bad.... plus fat runs cooler....

    i dunno how hard it is to change jets/needles in your bike?... do the butt dyno, and where it pulls the best, leave it... you just gotta experiment some, and some bikes it's easier than others to change jets.... mines really simple, my buddy's '10 450 Six Days is a pain, so YMMV....

    old school.... find someplace where you can run WFO for awhile, doesn't have to be that long.... keep the main jet that runs/pulls the best WFO...if you try it, you'll be able to tell.... then mess w/the needle position for the midrange... then mess w/the pilot... pilot's pretty much just for starting/idle/barely off throttle.... you gotta go top to bottom though, WFO first, or you'll start chasing your tail.... not that i ever did that....:evil
  4. Idle

    Idle Been here awhile

    Joined:
    Jun 16, 2011
    Oddometer:
    721
    Location:
    Northern California
    Stop letting it idle so long. Start it, run it for 3-5 minutes max, then ride it or shut it off. I read back on page 1 or 2 that you (quote) ran it at idle for 20 minutes after you did the clutch.

    That's about as dumb of an idea as I've evers herds. There's no good that can come from prolonged idling. Low oil pressure and flow, so oil starvation is highly possible, no air flow whatsoever. All bad...


    Perhaps if the carb is the same you might mirror the DRbig DR800 jetting specs.

    My guess is it's lean at idle and rich and richer as the throttle is opened more and more.

    Hope you can get it to a dyno to check the air fuel ratio. Bring smaller main jets and a bigger pilot jet when you do.

    I'm a little late to the party, but I'm glad your bike is back together and have to say you handled the bumps very well.
  5. sandwash

    sandwash Long timer

    Joined:
    Oct 26, 2007
    Oddometer:
    1,379
    Location:
    Flagstaff Az
    How does the plug look? No bog when throttling,try going one up on the clip(making the needle lower)
    Plugs can be tough to read these days.May have to wait till you get some more miles on it to try to make changes.Still a little tightish ?
    Really no need to let idle so long.5 min max and then get going somewhat easy for a few miles.
  6. planemanx15

    planemanx15 Long timer

    Joined:
    Dec 4, 2009
    Oddometer:
    1,009
    Location:
    Long Island, NY

    Sorry for the long delay. According to the butt dyno the bike is pulling hard in all throttle positions. I have been commuting with it every day trying to rack on some miles and see mileage figures as the engine continues to break in. I just purchased ricor intimidators in order to solve my brake dive problem under heavy braking and under two up braking. I also believe this will help solve some of my poor handling on the front end. I notice at some points the forks don't compress, and when they do its not a fluid motion. It's a hard initial dive.

    In other news, I took off my windscreen. What a different type of handling the bike has. It handles like my friends ducati monster. The bike is much more nimble, I assume because the windscreen was attached to the handlebars and was creating drag on the bars
  7. Rob.G

    Rob.G Mostly Harmless

    Joined:
    Jan 14, 2010
    Oddometer:
    2,288
    Location:
    Fulltiming in an RV! Currently NW Oregon
    If you want some decent wind protection, look at the Screens for Bikes (.com) screen... a little pricey, but it works great for what it is. Gets the air off your chest but doesn't drag on the bars because it isn't all that wide.

    It'll be hard to relate mileage since you have the TM-40, and some of use have the FCR-MX, while others still have the stock carb. I get 45-48 now, so it stands to reason I'd see similar mileage if I did the 790 (which will eventually happen unless I somehow end up with a new KTM 1190R).

    I agree about the idling... keep it to a minimum. Even in cold weather, I'll start mine, idle it maybe 1-2 minutes at most before riding away (gently). Same with my commute bike (FZ1).

    If the Intiminators don't do as much for your brake dive as you'd like, drop in some stiffer springs. I used to have Intiminators with stock springs and recently sold them off and went to Gold Valves and 0.47's and the difference is quite remarkable. Even less brake dive, and better handling.

    Rob
  8. planemanx15

    planemanx15 Long timer

    Joined:
    Dec 4, 2009
    Oddometer:
    1,009
    Location:
    Long Island, NY
    Thanks for the advice Rob I have been doing a lot less Idling and I only keep the choke on for about a minute or two before I start riding away. I also realize while I was washing my bike and I have an exhaust leak coming from where the header meets the cylinder. I need to go get a new gasket for there. I don't remember there being a gasket when I reinstalled. That could also be contributing to my low fuel mileage. Also, my homemade Midpipe absolutely sucks. LOL
  9. davesupreme

    davesupreme grand poobah

    Joined:
    May 1, 2011
    Oddometer:
    1,794
    Location:
    palm harbor, fla
    'yer only gonna be able to reckon the butt dyno if you change the main, and then do WFO.... hell, if that 800 cc thumper runs at all, it's gonna pull hard.... 'yer just lookin' for where it pulls the best, and you don't know where that is til' you make it pull worse, either fatter or thinner.... you dig?....
  10. planemanx15

    planemanx15 Long timer

    Joined:
    Dec 4, 2009
    Oddometer:
    1,009
    Location:
    Long Island, NY
    Took a few times to read it, but I dig!
  11. uraberg

    uraberg whosaberg?

    Joined:
    Apr 21, 2009
    Oddometer:
    700
    Location:
    Durham, NC
    As far as the mileage goes, if everything stays the same, and the only thing that changes is the displacement of the motor, then it is not uncommon to go down on the main, or drop the needle.

    If you run a cv carb, then an argument can be made that increased vacuum signal makes the slide ride higher than it normally would. If not a cv carb, then you could still argue that a larger displacement sucks more fuel through a given jet size than a smaller displacement.

    I went through just this on my klx 650 (now a 678)). And I am not quite done yet, but dropping the main from a 160 to a 150 makes it run much better at full throttle, and replacing the klx needle with a klr needle got me 8mpg alone. (from 38 to 46).

    I do need to go up slightly on the pilot to cure a little lean surging, because the thicker needle, and the smaller main jet allow for less fuel when cruising.

    My way of doing a carb tune:

    Set your needle as high as it will go, and change main jets that will give you the highest top speed. If mileage is a concern, go with the leanest jet that makes "no difference".
    Then adjust your pilot (and this is where it differs from other guides). find the pilot that gives you best (highest, most solid) idle at fuel screw out between 1.75 and 2.75. (Or something in that range, but you should notice a very definite response. take time in between 1/4 turns). If you need to turn the fuel screw out more than that, go up a size. If the other way around, go down.

    After you've found the best pilot, drop your needle until it starts lean surging at cruise. (make sure the engine is up to temp.) and then go back up on the clip.
  12. 805gregg

    805gregg Long timer

    Joined:
    Jan 14, 2006
    Oddometer:
    1,608
    Location:
    Ojai, Ca
    Great write up thanks, looks like a 790 in my future
  13. planemanx15

    planemanx15 Long timer

    Joined:
    Dec 4, 2009
    Oddometer:
    1,009
    Location:
    Long Island, NY
    Got the intimidators in today.. What a difference! Very little brake dive and far more control in bumps. Highly recommended.
  14. planemanx15

    planemanx15 Long timer

    Joined:
    Dec 4, 2009
    Oddometer:
    1,009
    Location:
    Long Island, NY
    2 fill ups, one mixed milage 40 mpg, the other after a highway biased trip, with speeds over 70 for most of the time 47 mpg
  15. refokus

    refokus Just Learning

    Joined:
    Jun 7, 2007
    Oddometer:
    2,560
    Location:
    North Phoenix
    So do tell how is the bike running? How smooth is the throttle response, and how much pull? Please do tell......
  16. planemanx15

    planemanx15 Long timer

    Joined:
    Dec 4, 2009
    Oddometer:
    1,009
    Location:
    Long Island, NY
    Bike is running great. I think I'm going to start doing some carb work soon. Maybe go a size down on the pilot jet to increase mpg. My needle is on the second notch from the top, so there isn't much more to go there. The throttle response is outstanding, just twist and go. On the highway where I would normally be shifting between 4-5 I can go keep it in fifth to accelerate and just boogie. Did a top speed run today with 17/42 gear. In the low ninties. I'm a bit upset about that, I thought for sure I could break 100. In fact at the end of the stretch of road where I had it pinned, was a slight up hill. With the throttle fully opened it couldn't hold the speed and just decelerated a few mph.

    I'm going to try to go down a size on both jets and see what that does. If I remember correctly, pilot is low throttle, needle is the mid range and the main is the top end.
  17. planemanx15

    planemanx15 Long timer

    Joined:
    Dec 4, 2009
    Oddometer:
    1,009
    Location:
    Long Island, NY
    Update, went a size down on both jets and the bike actually pulls better. I have been running too rich. Ill get back with mpg when I use up this tank.
  18. davesupreme

    davesupreme grand poobah

    Joined:
    May 1, 2011
    Oddometer:
    1,794
    Location:
    palm harbor, fla
    izzit poppin' when you chop the throttle?....
  19. planemanx15

    planemanx15 Long timer

    Joined:
    Dec 4, 2009
    Oddometer:
    1,009
    Location:
    Long Island, NY
    yes, but its done that since putting the Hayabusa muffler on it.
  20. davesupreme

    davesupreme grand poobah

    Joined:
    May 1, 2011
    Oddometer:
    1,794
    Location:
    palm harbor, fla
    it's not the muffler... the muffler lets more air thru, so you're gonna go lean.... if you're popping on decel, it's cause' your pilot is too small, going lean when you close the carb slide, and it's detonating.... every one of those pops is a miniscule piece of your piston going out the back...:deal....

    the pilot pretty much just starts the bike... it's what the carb is using when it's idling... too big a pilot, and it will flood real easy when it's hot.... maybe at the bottom of the rpm range it's significant, but not even that much there.... it ain't good to go too big, but that detonation ain't a good thing... sounds cool, but....

    i dunno if you can get a finger adjustable pilot needle for your bike?... they work great, if you can....

    all the racy guys wanna jet way down, supposedly that's where the max power is.... they also rebuild their top ends like they change their underwear...

    and needle taper has alot to do w/jetting too... dunno if you can get different needle tapers/diameters for your carb....