1974 yamaha dt360 carb

Discussion in '2 smokers' started by Kevin 007, Dec 26, 2010.

  1. Kevin 007

    Kevin 007 Adventurer

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    What Mikuni carb is on my 1974 Yamaha dt360a? Is it the 32mm?? Where can I find a rebuild kit for it? or a new carb for that matter...
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  2. Tosh Togo

    Tosh Togo Long timer

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    It's an RT, not a DT...the 'D' prefix in those days referred to a 250... as in TD and DT: all the 350-ish bikes were 'R's...as in TR, RD, RZ, etc.

    Check here for parts- SUDCO
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  3. eric123

    eric123 Gott Mit Uns

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    Then how come Yamaha refers to the 360 as a "DT"?
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  4. Tosh Togo

    Tosh Togo Long timer

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    Because things were changing at that time. I never said that the Yamaha model lettering system was cast in stone. Rules get bent, changed, or forgotten sometimes. In this case it may have been a marketing adjustment.

    Even though I was there, I don't remember the 70's all that well, so don't press me for all the details. :evil

    Medium-bore Yamahas were TD250's, TR350's, DT350's and RT360's until the watercooled engines arrived here in ~1974, and then they all became TZ's or DT's. There was even a DT400 for a while. :huh

    Ask an old dirt rider what a DT-1 is. :D
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  5. concours

    concours WFO for 44 years

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    Yup, for a few years they called ALL the enduro's "DT's", it was kinda lame. Really, the model designations are as follows... JT=60cc. AT=125cc, CT=175cc, DT=250cc, RT=360cc. They even called the street bikes by the same letter design for a couple years, all two strokes were RD's, and all four strokes were TX's. Then they woke up and dropped the designation after the TX750 was a steaming fizzle.
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  6. davevv

    davevv One more old rider

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    The '74 model is in fact a DT360A. This is mine.
    [​IMG]
    Prior to '74 the the models were JT100, AT125, CT175, DT250, and RT360.

    The '74 DT360A was a one year only bike. The engine is different from the earlier RTs but similar to the later DT400s. It was also the first year with CDI ignition instead of points. There was also a MX360 that was not street legal, and one other even rarer model that I can't remember the details on.

    As far as the carb goes, it is a 30mm Mikuni, model VM30ss. I have not been able to find anyone that has a stock parts rebuild kit for them as set up for the DT360A. This is actually a very common carb and is still in production, but there is a world of different combinations of slides, needles and jets. You pretty much have to buy individual parts wherever you can find them. I also have not been able to find the original needle and needle jet (I don't recall their numbers offhand). There is someone on Ebay who advertises custom jet kits for them. I haven't tried them yet, but may be forced to eventually.
    http://cgi.ebay.com/ebaymotors/Yamaha-DT360-DT-360-Carburetor-Carb-Perform-Jet-Kit-/230555365469?pt=Motorcycles_Parts_Accessories&hash=item35ae2bb05d

    By the way, the best place for info on these bikes is YamahaEnduro.com. Kind of the advrider of old Yamaha ATs, CTs, DTs, and RTs. Great forum with lots of info.
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  7. advNZer?

    advNZer? Long timer

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    actually it wasnt quite as straught forward as that.
    this is a dt3 the 250 of about 73
    [​IMG]

    this is a dt250
    [​IMG]

    the rt3 was the same as the dt3 but bronze and a 360
    the dt 360 looked exactly the same as the dt250 but was of course a 360
    #7
  8. Kevin 007

    Kevin 007 Adventurer

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    Mine is a DT360. Ok a 30mm eh? At least that gives me a starting point, thanks
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  9. AC Swank

    AC Swank Banned

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    You don't say where your at but if you are serious about getting a new carb, visit Vintage Iron. They can set one up to run right out of the box.
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  10. concours

    concours WFO for 44 years

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    A new carb would be crazy expensive. The Chinese copies don't work at all. These people have all the parts for all the Mikuni's. No kidding. http://www.sudco.com/
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  11. AC Swank

    AC Swank Banned

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    189.95 from Vintage Iron, plug and play.

    Riding and maintaining these old bikes is not an inexpensive sport/hobby. If you want cheap, buy the chinese clones.
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  12. stainlesscycle

    stainlesscycle Long timer

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    that's crazy for a 30mm mik vm. should be $89.95

    and 30mm seems awful small to me for a 360. i generally put 32's on 200, and 34/36 on 250's...


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  13. AC Swank

    AC Swank Banned

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    So you have little to no experience with piston port and early reed valve 2 stroke motors?

    BTW, the price is for a plug and play carb, no trial period of selecting the idle jet, main jet, slide, needle, etc. to get the bike to run correctly.
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  14. stainlesscycle

    stainlesscycle Long timer

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    yep, no experience at all. :D
    just put these on in the last 2 months.
    32mm on 200cc bultaco
    36mm on 2 different 250cc bultaco
    34mm on 175 can-am (rotax)
    36mm on 250 husky

    there's no such thing as a plug and play carb. there's so many variables. sure it might be close out of the box, but most likely you will still need to jet.

    i'd have to look, but i still think 30mm is small for 360cc..i am not a believer in bigger is better, i'm not saying go bigger just randomly. we don't know if it's a stock motor with stock jets,reed and pipe. we don't know elevation and temperature. there is no hard and fast rule for what carb size will work best. i have on occasion gone with a smaller than stock carb if original carb was obviously too big, and i wanted to get more intake velocity. i do realize it's a trail bike that may have been restricted a bit with carb size...

    and vintage iron i believe is charging $199 (unless it's a typo) according to their site, and it appears to be a stock jetted carb for that price. that's more than DOUBLE the going rate. i got nothing against vintage iron, i just think that's ridiculous pricing. even hugh's bultaco (not known for being cheap) will sell pre-jetted (foir your model) mikuni's for $150ish. that's with a non standard slide and needle. i don't buy them pre-jetted to someone else's guesstimation. i buy them stock jetted and go from there. maybe vintage iron has done some research and figured what works best for a dt360 - but i seriously doubt it. there's just not a lot of people changing carbs on a model as uncommon as this. i have worked on several rt-3's and know that they're set up goofy stock.
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  15. davevv

    davevv One more old rider

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    From page 105 of the service manual, carb specifics:

    Manufacturer/model = Mikuni VM30SS
    I.D. number = 44560
    Venturi size = 30mm
    Main jet = #180
    Needle jet = 0-8
    Jet needle = 5EJ8
    Cutaway = 3.0
    Pilot jet = #50
    Starter jet = #60
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  16. AC Swank

    AC Swank Banned

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    Good reply Stainlesscycle.

    My reply was in response to the OP and his appearent lack of knowledge so as to give him an easy solution. Too bad he does not say where he is located as I'm sure one or two members here could come over and help out.

    I have bought several carbs from Vintage Iron, the last one was for a 1972 CZ400. Like the others before it, it was plug and play. YMMV.

    I hope the OP sees this and replies.
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  17. Kevin 007

    Kevin 007 Adventurer

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    Im in Nelson B.C Canada.
    Well I just had this bike bored 2nd oversize with a NOS Wiseco piston kit in it, new reeds etc... I had the carb completely apart again with thorough cleaning and the problem is still there.
    The current jetting has always been the way it is and the bike is from the area...no altitude changes. So should I go and get a new needle and needle jet and see where that takes me? Im guessing my problem lies in that area. Idles great..mid range to WOT is great; just that one certain trouble spot at low throttle.
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  18. stainlesscycle

    stainlesscycle Long timer

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    when you change the needle position does the problem move to a lower/higher rev range?
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  19. Kevin 007

    Kevin 007 Adventurer

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    I don't know how to adjust the needle position.
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  20. stainlesscycle

    stainlesscycle Long timer

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    remove carb top. take slide out.
    remove throttle cable from slide.
    remove spring, remove retainer plate (may or may not have one - depends on carb model)

    push needle out of slide from the bottom.
    there's a clip on the needle.

    which position is it in? needle has either 3,4, or 5 grooves in it. moving the clip UP lowers the needle and leans it out. moving the clip DOWN raises the needle a richens it.

    here's a pic of a needle in position 4 - the richest position on this particular needle.

    you mention it has problems at 1/8-1/4 throttle ? that's either pilot jet or needle positon/taper USUALLY. it could be airscrew too....

    you're in canada. it's probably cold there :) i'm betting richening up the pilot one step, and maybe raising the needle up a notch will compensate for the cold. but it may be too rich when the temperature increases. you say it runs great a wot? with how cold it is it may be slightly lean on the main too. don't forget 2 strokes run the best right before they blow up :)

    you need to google '2 stroke jetting' and go through the whole process. keep in mind, that your proper jetting at current temperature will most likely be too rich when the ambient temperatures increase. keep in mind it's really hard to jet over the internet.

    [​IMG]
    #20