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Help me ID these? and can they be tuned? Mikunis

Discussion in 'The Garage' started by gggGary, Mar 4, 2011.

  1. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Well, you learn something new every day. Pulled this off a 2-stroke website:

    Slide cutaway is not in mm as many think.
    It is the size of the gap under the slide front in 1/16ths of an inch.
    A 2.0 is 0.125" a 2.5 is 0.156"
    This is a leftover from Amal which Mikuni took over long ago.

    So, your 2.47mm cutaway is about .094", or 3/32", or 1.5/16", which makes it a #1.5
    Guess that makes mine 6.0mm, .240", or about 4/16", which makes them #4.0 (actually #3.8)
     
    Last edited: Jul 19, 2015
    gggGary likes this.
  2. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Ah that makes sense now (kinda sorta LOL) Got busy changing pipes and didn't measure one of the other slides to compare. I'm thinking next up is bolting on the MM 34's and see where that puts me. If I "change the cutaway" any howto's? sandpaper on a flat surface? Stay parallel moving the whole angle back or change the angle so the start of the cutaway stays where it is? ie take off a "pie cut not a slice of slide. Guess I gotta get the mains dialed in first, That's the proper sequence? Get the main right then work backward towards the lower end running?
     
  3. grizld1

    grizld1 Grumpy old man Top Contributor

    Thanks, Gary and TwoMany. Somehow I'd never bothered to do what Gary did and measure the cutaway--just assumed it was specced in millimeters, and we know where that leads....
     
    gggGary likes this.
  4. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Yeah, even THAT stuff is ancient knowledge for me. Wonder if it's in imperial inches, or Whitworth, or Royal king's knuckle, or 3 barleycorns???

    When I did slide cutaways, I maintained angle center, pie cuts, using tilt-table sander.

    As far as sequence, well, I didn't use one. Started with idle, so it would at least kickstart and not foul the plugs for later reading. Then small tweaks, plug readings, gut feel, sound, gas mileage, over a period of time, slowly crawling to desired results. Can't put metal back on an over-cut slide...
     
    Last edited: Jun 26, 2013
    gggGary likes this.
  5. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Well that's good info and some progress. Guess the loud mufflers need to go back on for now.
    Here's a shot of a slide marked 2.5 from the MM MV34
    slides 005.jpg

    I think it confirms what TMXS1B is saying about the height.

    Found on CL locally; big sorted bunch of VM jets/parts but checking to see if they are in the sizes that would help me.
     
    Last edited: Mar 31, 2019
  6. 5twins

    5twins XS650 Guru Top Contributor

    18,335
    8,579
    688
    Yes, those mufflers you tried are the pits. That's the exact kind I had on my 650 when I 1st got it running. Very restrictive and quiet. I switched to Commandos and never looked back.
     
  7. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    I have one set of commandos love em but they have a too small neck for these headers will just a order a set of the bigger neck ones from mikes. But I never get away from his site without a $500 hole in my pocket...
     
  8. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    tonight. loud pipes 200 mains



     
  9. grizld1

    grizld1 Grumpy old man Top Contributor

    That motor sure isn't falling on its face! If you had the throttle all the way open you're either there on the mains or real close to it. BTW, those look like 1-3/4" head pipes. Are you sure about that 2-1/4" OD I thought you mentioned--or did I misread?
     
  10. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Yeah I screwed up on that, mentioned the error in the slide height post. Yes 1 3/4" OD on the headers. Yes the 200's seem very close now, the plugs even were slightly tan I am thinking about getting 190's 210s and 220s and see where it's happiest. That fuggled float valve was messing with me, I have two new ones coming, will probably change the other side too. The idle isn't half bad for not far from random slide settings so far. I think the mid range is a bit on the rich side yet. perhaps raise the cutaways, do I have that right? the PJ are 25 which seems on the small end? Anyways, I'm even kinda getting used to the noise. It's a hot rod not a touring mount.

    That road is a fairly steep uphill run and yes I had the throttle nailed 2nd, 3rd, 4th
    You might notice I am not practised on fast launches, LOL the 18 tooth front sprocket makes it harder too.
     
  11. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    You are having way too much fun!

    Listened to your 2nd video several times. Coming toward the camera, just at the very end of 3rd gear, just before shifting into 4th, thought I heard a hint of lean clipping.

    Those mufflers sound great!
     
  12. grizld1

    grizld1 Grumpy old man Top Contributor

    Actually I'd expect the #25 PJ to be about right, but you won't really know until you finalize MJ selection and the needle/needle position; secondary effects are heavy in the old VM's. Judge PJ choice by where your air screws wind up. Re. the cutaway, yeah, needs to be higher. Reducing the cutaway to richen the slide by taking the flat bottom edge down is a common mod, cutting a new radius to lean it as TwoMany has done takes skill that most (including Yrs. Truly) don't have.
     
  13. racerdave

    racerdave ^ Gone not forgotten ^

    Gary, I have a new set of those EPO headpipe inserts if you are interested in them. Some say they work, some say hocus pocus. I make no claims except that I have a unneeded pair.
     
    gggGary likes this.
  14. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    I am interested, PM sent!
     
  15. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Got sets of 205 to 240 jets in the mail I put in the 220's and put 150 miles on the bike yesterday. Last 50 miles at sunset saw AT LEAST 10 deer. Stopped and moved stuff around so I had FULL front brake lever range, it was hitting the throttle tube. Getting the bike slowed down while bambi is making up her mind whether or not to cross seems like it goes on for hours!
    But the plugs look good, light tan and I am back to overpowering the clutch at about 5K.
    THINKING about a wideband O2 gauge.....
    Ordered the commando's this morning. What? What did you say? I just spent a few hours with basically open pipes, huh??
    I am strongly thinking about trying to recut the slides the mid range FEELS and sounds drippy wet. It's the area where the throttle sits a lot about an 1/8 to 1/4 turn loafing at 60MPH. Yeah this engine is pretty much loafing at 60 The idle is near spectacular, one half hearted kick (well half hearted to get 200PSI over the top) no throttle and it starts and immediately idles. Easy to lug away from a stop and just open it up and power off. I am about shocked I can get this much tractability out of the big honker VM38s. It pulls without hiccup from nearly any RPM.
    I see flat slide 38mm Mikuni dual carb racks used on Vmax 600 snowmobiles, linked throttles looks like the spacing is close to the XS spacing...... available for $100ish the pair.
    What fire? I'm busy hopping out of this frying pan.
     
    jasidok likes this.
  16. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Was chatting with my button-buck the other day, he says his relatives are fed-up with the heat, so they migrated to Wisconsin to the summer camps. They love headlights, will stand there and watch 'em for hours.

    A couple of years ago, was doing a slow cruise thru the backroads, a herd flowed out in front of me, so I came to a full stop, while they scampered back-and-forth trying to figure out which way to run. My full stop must've confused them (most folks just slow down a little), and one seriously confused doe ran smack-dab into ME! Now she's got a good story for her grandkids...

    I'd wait on the slide cutaway until those commandos are on, and you've gathered some gas mileage numbers at that sedate 60 mph. Been so long, fuzzy memory, but I believe either the vm34 and vm36 Mikunis or the vm36 and vm38 Mikunis share the same slide. Could be handy if searching for a spare pair. Nothing wrong with planning-out a jig fixture now. I crawled-up to the final cutaway a couple of degrees at a time, spread-out over a couple weeks riding...
     
    gggGary likes this.
  17. racerdave

    racerdave ^ Gone not forgotten ^

    TwoManyXS1Bs and gggGary like this.
  18. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Still wrastling with this bike.


    I removed the 38's and bolted on a brand new set of MM VM34s but ended up with it running about the same, fine till about 4K then not so good. Currently getting a Pamco with e-advance and an Accel coil. Mufflers are now drilled out emgo's which have about the right amount of noise for my taste on a "hotrod" type bike.

    It's on the lift but not quite the priority project right now.
     
  19. grizld1

    grizld1 Grumpy old man Top Contributor

    Betcha wind up dropping those NJ's to P-6 before that cruising-range fat spot slims down.
     
    gggGary likes this.
  20. james c

    james c XS650 Member

    help please i got a 1982 650 with bs34mm mikuniss do these have a plug in the pilet jets inside the float area if so what do they do and what if i leave them out i have a set of 1980 carbs also but in the coarse of haveing both sets apart i forgot which set the plugs belong to any info would be fantastic thanks james
     

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