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GS1100E update - conversation with Dynojet

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    GS1100E update - conversation with Dynojet

    So my '82 1100E is running better, but not great. For background, K&N pods and a Kerker pipe straight out of the 1980's with a huge clear bore down the megaphone "muffler" with all the sound you could love (and hate! ). The bike starts and idles just fine, revs, and runs like stink on full throttle, but partial throttle settings and she kind of misses and surges, most noticeable from 4-7,000 rpm which indicates a pilot circuit problem. If she didn't run so good WFO up to redline and I didn't know how much carb trouble I've had, I'd think it was an ignition problem.

    Bike has a Dynojet stage III kit in it and I've taken the needles up and down, with them now raised TWO FULL CLIPS above the Dynojet recommended initial settings. This surprised me that they'd need them raised so high (only one clip higher is left!), but this setting has minimized the width of the band where she spits at partial throttle and massively reduced the spitting compared to other settings. No amount of fiddling with the mixture screw has helped this poor midrange/partial throttle performance.

    I had a good conversation with "Mike" at Dynojet last night and it sure sounds like the man knows his stuff. He said it's unusual to need the needles that high, but not unheard of for this motor, and I might even need them up to the top notch. (sigh of relief)

    His main recommendation was to go ahead and install the smaller pilot air jets which are recommended as "optional" in the Dynojet kit instructions. I had these in earlier before raising the needles, but they didn't help anything so I took them out. The smaller air jets should richen the pilot circuit up throughout the band, unlike the mixture screws which really work down low. With this, I should be able to adjust the mixture screws to "best idle" and not need to enrichen them to try and fatten the midrange mixture.

    Two interesting notes: Mike told me that the Dynojet air screws are sized identically with the Mikuni air jet sizes, unlike the Dynojet fuel jets where numbers don't correlate with Mikuni jets. Also, the purpose of drilling out the air hole in the vacuum slide is to increase the rate at which the slide can rise and fall, increasing throttle response. I was speculating on this in another thread, so now we know.

    I have some new socket head screws on order since the JIS phillips heads are getting all beat up, so I'll probably wait to make the mods suggested by Dynojet. The main point of this post is to let folks know that if you're having troubles like this with Dynojet kits, 1) the recommended settings aren't gospel and 2) the folks there are knowledgeable and helpful if you need to speak with them.

    Will report back on results.

    #3
    Good ref. thanks!

    Comment


      #4
      Some updates. After speaking with the Dynojet, I installed the smaller air jets, but no real improvement getting her smooth from 3 to 7,000 RPM.

      Finally decided to raise the needles to the highest notch and that was the cure - smooth power throughout the entire RPM range. Was able to screw my idle mixture screws back down and achieve a nice idle.

      Still, I was not happy. Doing some more research, I discovered there are actually three baffles that Kerker offers, the standard 1.5" ID, a competition 2.0" ID, and a closed course racing baffle with a humongous 2.5" ID bore. So guess which one I had... yep, the big one that says "extremely loud" on the Supertrapp/Kerker website. This explains why it's been such a bear to get my carbs working right - no backpressure.

      Besides the loudness which I truly hated, the bike also has somewhat anemic midrange grunt for an 1100, although she screams like a banshee WFO at redline. I'm thinking the only purpose for that 2.5" pipe is dragracing where midrange is less of an issue.

      In the interest of better neighborliness and protecting my hearing, I bought the standard 1.5" ID baffle and installed it last night. Unfortunately, with that pipe installed, I could not even get it off choke and she wouldn't rev past 3000 rpm. I'm thinking the needles have to be dropped back down because she's getting too much gas for the flow at the lower rpm. Planning to go back to the recommended "base settings" for the Dynojet kit.

      Will report back when I get the next adjustments made. L8R

      Comment


        #5
        The Kerker comp baffle is nearly running a straigh pipe. I have a Kerker, it won't run right with that baffle. Dragbikes run WFO from jump street, that's what it's made for.

        On my 1100Es I ran stage three, 138DJ main (there's a conversion formula to get Mikuni numbers out of them By the way) stock pilots, DJ air jet (150 or 160 I believe) mix screws 3 turns out, needle clip in the 2.5 position from the point (you can shim to a half step, which is what you'll probably have to do to get it perfecto) 36mm 1150 carbs Yosh full race exhaust, ape pods. Ran like a scalded rat... Awesome.

        Comment


          #6
          Thanks for the notes, Kid. All the Kerker short baffles are straight through pipes, but the one I took out was so big you could practically put a soup can through it. I had the carbs pretty good, smooth all the way through, but look at the settings I had to go to for it. And the midrange was lame at best.

          The new baffle is also straight through, but more like the roll from paper towels. It's a ton quieter. Now all I gotta do is rejet to get it right.

          Thanks again for your setup notes. It's good to have those handy for reference. Right now I'm just going to drop the needles, since I know those are way too high.

          Comment


            #7
            Mikuni = 93.75 X Dynojet

            Comment


              #8
              Originally posted by Katarat View Post
              Mikuni = 93.75 X Dynojet
              That's not correct...
              Example-
              DJ 138 main x 95.37 = 13,161.06. Not quite.

              Correct formula is DJ x .9375 = Mikuni (round up to next Mikuni size)
              DJ 138 x .9375= Mikuni 130 (129.blah blah)

              Comment


                #9
                Re. the conversions equivalent DynaJet and Mikuni jets, the fuel jets ARE different, per the discussion above. However, the AIR jets for the pilot circuit are identical, that is, the 160 air jet DynaJet supplies is the same size as a Mikuni 160 air jet. That comes from DynaJet, and as measured by me using numbered pin drills.

                For the record, the setup I'm at now is:

                K&N pods on 34mm Mikuni CV carbs.
                Kerker pipe with standard 1.5" baffle.
                DJ 138 main jet. (approx same as Mikuni 130, per discussion below)
                Needle raised to next-to-last position (#5 position of 6 avaliable. Instructions say to start with #3 midpoint)
                Pilot air jet is the DJ #160 (richer than stock, one size smaller than the Mikuni #170)
                Mixture screws 2.5 turns out.

                This setup is pretty close. I initially went to the recommended DJ stage III settings with the needles at #3 midpoint, but could not get the transition from from the pilot circuit to the main circuit (3000 to 5000 rpm) going well and was getting surging at low throttle settings that the mixture screw alone could not cure, and I was already with a richer pilot air jet. Had to raise the needles two notches (meaning I had to open the carb tops two more times today! Note, I found I could do this without even pulling the carbs. Got to the point where I could change all four needles from gas tank-off to tank-on in about 30 minutes!).

                With the above setup, it is mostly good. Overall midrange power is way up over the huge "competition" exhaust baffle and anything the top end lost is not noticeable. Haven't ridden it enough to verify it's good under all conditions, but it is very rideable. I wouldn't have thought the needles would be so influential at such low RPM and low throttle settings, but it was definitely the needles that needed adjusting.

                Anyway, there's probably more that I can tweak in these carbs, but it's pretty good for now, almost "Busa-like" in power and desire to pop wheelies. Coming along. Coming along....
                Last edited by Guest; 04-02-2012, 07:32 AM.

                Comment


                  #10
                  I put the decimal point in the wrong place, big deal, no where did I write 95.37. Like no one could figure that out

                  Comment


                    #11
                    Originally posted by Katarat View Post
                    I put the decimal point in the wrong place, big deal, no where did I write 95.37. Like no one could figure that out
                    I noticed that and should have mentioned it. Thanks for your help, Katarat. You were making an important (and helpful) note. Cheers!

                    Comment


                      #12
                      Took some pics of the old and new baffles. It's pretty amazing to seem them side by side. I've done a little more tweaking and it's running quite well, very enjoyable. She's a lot quieter, but still has a hearty growl when you wind her out.

                      Comment


                        #13
                        And one looking down the ends...

                        Comment


                          #14
                          Originally posted by Katarat View Post
                          I put the decimal point in the wrong place, big deal, no where did I write 95.37. Like no one could figure that out
                          Wasnt busting your balls mate, just clarifying for perhaps the new guys who might believe/try everything they read. No offense meant...

                          Comment


                            #15
                            Originally posted by Ajay View Post
                            And one looking down the ends...
                            Sheesh! I'd say it was a bit loud eh? Barely room to wrap it and still fit it in the can hahaha! I know the Yosh race pipe I had on my now ex 1100ES was loud before I wrapped it extra stuffing style. I used stainless steel batting (which is excellent By the way. Lasts damn near forever and doesn't rust out or burn up)

                            I like me some bark wih the bite, but when it's so loud on a long trip that YOU even get annoyed, you know it's too loud hahaha. But the Yosh has a great sound. Dunno how it's tuned to have that wonderful note..nice deep liter bike burble at idle, a nice growl on throttle and then the sound of what I can only describe as a whole battalion of really ****ed off hornets at full chat.
                            The Kerker on my ZRX sounds nice, different, but nice. But not as nice as that Yosh did.

                            The smaller baffle should restore some of that "light to light" grunt she may have been missing with that "Sarlac Pit" you had in there before. Top end "retro rocket" like rush might decrease a little, but really, short of a drag strip where do you really get to open her up for long like that??

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