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Winner So I made it to the salt... but man carbs are terrible lol

Discussion in 'Kawasaki 250cc In-line 4's' started by DamnitLaverty, Aug 12, 2021.

  1. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    After giving up on fuel injected goodness to get to Speedweek, I set to work getting the bike ready to go, some questions here some work there.

    I ordered two sets of jets. One set at about half the altitude between Seattle and Bonneville (what I considered "morning jets"), and one set for 8k ft/2400 meters, because despite the flats being at about 1200 meters altitude... the air gets so hot and thin that by late afternoon the density altitude is closer to 7500 ft than its native 4000 ft.

    if I were smart, it would have twigged that the company kept sending me bigger jets... 127s and 135s. When there's less air in my air, the last thing I needed was more fuel. But, in the rush I was in, I didn't pick up on this. I'm sure you can see where this is going.

    Mods are an open airbox and a Ducati Multistrada backbox with a wideband in the collector. Not nearly enough to need 135s.

    I get the bike to start, but not to idle- throw it in the truck with a manometer set, and aim the truck south for 1300km. Land at the bend, suffer through a night of barbecue-scented air (massive forest fires were blowing down onto the salt- the air was orange.) and get the bike set up in pits. Get the bike running, sync the carbs (which it turned out didn't need anything- they were dead on!) and spend the next two days getting through tech and registration.

    Learned an important lesson, go slow to go fast isn't just for corners. I had to really take about 10 points outta my personal jets and stop letting emotions control me.

    Finally, three days later- the bike was through both tech inspections (new bike required being seen by two people... to my credit my only tech failures were a misunderstanding because of our goofy front axle on the ZXR, and a chase vehicle issue! I read at least part of the book real good- even if I did end up in the wrong class because I didn't read that part particularly good lol)... and I found myself at the line.

    Remember my "ima rejet for mods and altitude?" The one mod I kept from the fuel injection setup was the wideband... which promptly settled at 10.2:1 under load, and above 6k RPM... the bike wouldn't rev past 15!

    I watched the gauge just sit at 15k...14k... the WB getting richer and richer over time until the end of the run. The speedo stuck dead on at 140kph until I turned off.

    It was a lot of work to get a timeslip that read 83mph. I didn't have a good fix other than going back to stock jets, and I wasn't sure that'd make enough difference for the time invested... so I just took my loss- dedicated more than ever to firing these carburetors.

    Ah well, so it goes. Still made for a hell of an adventure!

    IMG_1239_2fifty.jpg IMG_1248_2fifty.jpg IMG_1251_2fifty.jpg IMG_1253.jpg
     
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  2. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    It sounds so good with that Ducati muffler... until it stops revving and starts breaking up.
     
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  3. kiffsta

    kiffsta Senior Member

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    Honestly , that is the greatest zxr pic ever, make sure you get it printed and hung up in the garage

    now 140kms per hour on a zxr is not the best result , I have to ask, why the open airbox ?

    You have stock headers with a twin stack muffler , stock carbs with bigger jets and then you opened the airbox , to me that seems like a massive issue. The cvk-d30 carb is vacuum operated and these carbs perform best with still air , so with the airbox off you would have had turbulent air which could cause issues with the slides. With no metered air coming into the airbox and through the filter before hitting the carbs would lean it out something crazy. What I am trying to say is the airbox is such an important tool in making these carbs work properly. In saying that, I have never built a salt bike, but have had a few zxr’s .

    Now jetting for altitude is usually a 2 stroke thing , but granted you were quite a ways above sea level , but I would have suspected you would have gone down a jet size or 2 to compensate . I have never jetted for altitude , this is just those funny thoughts in my head.

    For your next salt run adventure , I think it is only fair you buy a mobile dyno , and get up there early and get the bike dynoed for the altitude :)

    On a brighter note , how bloody cool is taking your 30 year old jap import 250 to the salt , I’m sure many of the competitors would have never seen or heard of one. The sound of a zxr250 screaming at 15000 rpm would have been amazing.

    You must feel so much richer for the experience … sorry to end on a carb pun, but congrats on having a red hot go.
    44FB9FAA-7EB7-475F-998A-D3AECCEE7D97.jpeg
     
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  4. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    Ironically, I was worried it'd be too rich with an airbox. In short, I ran without a box through pure ignorance. Lesson learned! I'll fix that! I trust your experience with regards to the airbox more than I trust my "building" a bike in a vacuum. Without a box though, I was mid 10's for AF at 6k feet, and mid 9's here at sea level yesterday.

    And yes, the company I was calling on for jets should have sent me smaller, not larger ones. As a result I didn't get to ride very much on the salt- it seemed pointless when the bike started blowing the spark out with fuel.

    For my next salt run adventure, I'd like it to have a MAP sensor so it can adjust for barometric pressure. ;)

    Near as I can tell (especially with COVID closing borders) nobody had ever seen one, I was next to a couple spectators from your end of the world that were surprised to see one, and the guys in tech seemed to dig it.

    The picture is definitely gonna stay with me a long long time. It would be nice if it were on something higher resolution than my iPhone though. I just wish the classification on the bike were correct- I was supposed run MPS-G not M-G. Ah well. :)
     
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  5. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Congrats Laverty. Part of the fun is getting there and Bonneville is a beautiful place. Good job on your bike and don't be ashamed of 83mph on your first visit. Your next visit will be completely different. As Kiffsta said, great pic of your bike on the salt and no airbox was a boo-boo. Just to rub more salt into the wounds (sorry about the pun), the K-RAS sticker on your bike should have given you a clue as it stands for Kawasaki Ram Air System. The inlet on the LHS fairing is designed to push cold air into the airbox. Cold air is denser and even at higher atmosphere, will contain more oxygen. the way KRAS works is the faster you go the more cold air gets pushed into the airbox. The air doesn't swirl in there too much as the filter stops that and the airbox doesn't get over pressurized so the CV carbs still work properly. at 18,000rpm you can work out how often each cylinder wants to take a gulp of air (and fuel) and if you don't give it air the result isn't wonderful. Running your airbox with a course filter and the K-RAS connected wouldn't have fixed your over-fueling issue, but it would have let the bike get a few more revs before fouling your plugs. All good stuff to learn for your next visit. Congrats again on making it to the salt.
     
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    Last edited: Aug 13, 2021
  6. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    I’m a little ashamed of 83, but largely because of things around it, not the speed. I’m just glad I got there, and actually raced instead of spectating like all the other years I’ve gone.
     
  7. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    Also, keep the puns coming lol it’s totally worth it.
    Worst part is I even had the airbox with me. I just ran the bottom plate with no top to preserve the bell mouths molded into it.
     
  8. thebeefsalad

    thebeefsalad Well-Known Member

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    4 strokes get away without jetting better than 2 strokes, but when going for the most power across the entire rev range (or top end) you must tweak the hell out of jetting. 2-3hp low to mid-range might not mean much to some people, but when roadracing minis it can make a hell of a difference and I imagine LSR is much the same even though it's a top end game. If I could show you GordonsXRs collection of needles and jets and tell you the number of hours he spends tweaking carb settings, and then show you how much pull his XRs produce over a carb that "works" you'd likely be quite surprised.
     
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  9. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    My ZXR was good for an indicated 210km/h and it was standard air box and jetting with an open muffler. Jealous of the salt action.
     
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  10. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Congrats to getting there and doing a run. Salt is always slower than bitumen.
    Big jets, my pet hate.
     
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  11. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Worst part is I even had the airbox with me. I just ran the bottom plate with no top to preserve the bell mouths molded into it.

    Sorry Laverty, I probably should have posted a pic of the LHS of my salt bike. Even though I ran in an 'altered' class, I made sure to keep some form of direct cold air system in place for the ZXR250 engine. Helped me get to just over 180kph with 5,000 rpm left on a very bumpy bit of salt.

    ZXR250F 2fiftycc DLRA 2019.jpg 180+kph.JPG

    I'm going back to the salt in the near future. I was hoping to run a ZXR250T (turbo), but that's looking less likely, so I'll probably have another go at the normally-aspirated class.
     
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  12. Gen

    Gen Well-Known Member

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    "Helped me get to just over 180kph with 5,000 rpm left on a very bumpy bit of salt."
    Last time I went down the salt, speedo readings didn't count as anything Frankster ;)
     
  13. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    They do when they're calibrated on a drag strip and GPS. I'm just going to run the GPS speedo next time and throw the mechanical speedo drive in the bin. One less thing to worry about.
     
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  14. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    this is my plan too. Ran out of time and mental health. Next year maybe. I have the turbo on the shelf waiting.
     
  15. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    this is my plan too

    In Australia, 2020 was cancelled due to COVID, but they managed to get the 2021 event in, so I'm assuming 2022 will go ahead. I didn't think 2021 would go ahead, so I never even thought about going. I think I was racing in NSW the week the DLRA 2021 event was on.

    I'll try to get the turbo engine sorted, but I'll prep a normally-aspirated engine and bike as I'm more confident/competent with carbs and have zero knowledge of turbocharging and not a lot of coin to pay someone to get the current turbo setup working properly.

    Keep posting about your turbo build as I'll be learning as you go along.

    ZXR250T...

    IMG_2251.JPG
     
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  16. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    for sure man- I’ve got a build thread going, it’s been concerned with the fuel injection leading up to the turbo so far.

    the only reason I haven’t done it was because I want to build a motor before I add boost- and I can’t get to yalls corner of the world to get a spare motor to build.

    I had a quick chat with Nick Arias III at Bonneville re: teeny tiny pistons. They can’t make me forged ones but billet are an option. Just gotta get a spare longblock or two before I get toooooo wild.
     
  17. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    My engine builder went down the Turbo/Carb setup as this was what he felt comfortable with. Unfortunately, he has had so many issues with that setup and some recent health issues means he can no longer work on the setup. I have to go and get the bike once all of our crazy border closures are lifted and see if the combination can actually be tuned, as it's currently either flooding or it won't start. There's a crowd in Sydney that I might have to leave the bike with, but we'll see what they say when I drop by their shop with the bike.

    Most shops that I've spoken to have said that turbo with a draw through carb should work easily, but here we are. I guess if you get your Turbo/EFI setup working, I could copy what you do and retrofit it to my bike. I'll be using a ZXR250A engine (48mm x 34.5mm) so that would be the major difference to your turbo build. The engine in your bike (49mm x 33mm) is basically the same as the engine in the Kawasaki Balius, so not sure if they're available over there, but you could use one of those engines for your turbo setup. I'll start posting on your other thread, so this conversation is in the right place.
     
  18. Big Balls

    Big Balls Active Member

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    Well done. Burt Munro would have been impressed. Love the sound of the muffler. Which model are they from?
     
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  19. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    So yeah, my friend wants me to go blow-thru as well, but I dont wanna change jets at altitude. That's the sole reason I'm going FI. No Balius available here, so my current plan is take a vacation and break a couple bikes off gumtree. I got a buddy in NZ I'd love to go hang out with for a bit so two birds, one stone. Pack a bag or two home with engines in. Maybe a spare pair of forks.

    they're off Multistrada, MY2010 to 2015 or so.
     
  20. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    I went with my office instead, but:

    E9518E0D-15FD-405C-A3C2-8CBE400F1EDD.jpeg
     
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