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4 into 1 carb

Discussion in 'XJ DIY How-To Instructions' started by cruiserlover, Feb 7, 2018.

  1. cruiserlover

    cruiserlover Active Member

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    I spent some time messing with 4 cylinder goldwings.The rebuild kit for those carbs cost $188. Plus seldom does anyone get it right the first time they try.Some of the forum members came up with a single carb modification.Using a custom made manifold and either a volkswagen carb or a weber.The weber is not as expensive as one might think.The manifold and volkstyle carb cost about $150. One guy made a manifold out of pvc. The goal was to make a single carb to tune and deal with, maintain,clean, and use without hurting performance and fuel economy. They accomplished that.Purists cringe, but nonpurists like myself liked the idea.I was wondering if anyone tried that with an xj.The stock airbox would not be useable but the aircleaner on the carb should eliminate the need. The more I read about the engineering of the xj the more impressed I am.However, the ujms of that era all had 4 carbs and most with either single or double overhead cams. I know a guy that could fabricate a manifold. Anyone care to offer their opinion.I am going to have a nonuseable head soon and it would serve as a platform to try and make the setup.
     
  2. MattiThundrrr

    MattiThundrrr Not a guru

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    A couple of years ago, a guy did just that with his xj. Might have been @Orange-n-Black . If I recall, he melted the PVC intake due to gas fumes. I think he was forced to abandon the project for medical reasons. It seems that a proper tune of the stock carbs would be simpler and cheaper. The resources are available at xj4ever.com
     
  3. cruiserlover

    cruiserlover Active Member

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    I dont think much tuning is necessary.They are all connected most likely by 1 or 2 bolts or screws along along a common linkage rod.With one having a screw to turn for a fluid filled balancer device. And then adjust the other 3 to match. I intend restoring one of the 2 i will own. More or less.If the original engine is too far gone the transplant will be done.I actually prefer restomods over restorations on a couple points.First, is the bike going to be valuable, a collector item.The answer here is no. Will changing some configurations enhance the performance, or upgrade an antiquated system to a more serviceable durable version? Then yes do that.Plus some ergonomic issues for me personally.No buckhorn handlebars. A better horn.Forward controls adapted from dime city components.No humpty seat found on the specials,dehump it.

    Some details of the xj that are appealing to me.I love the stock wheels. I like the stock megaphone mufflers.It would be terrible to put a 4 into 1 on these bikes. I wish the rear drum could be eliminated, but thats not a doable item, especially on a thousand dollar bike.Use the original color and emblems. Upgrade the fuse box.diy for that here on the forum.steel brake lines if possible. I never ride without a small windscreen.Those are easy to find. A full radical custom of one of these only creates a moneypit that only the owner will appreciate in its final rendering. I live in the dallas metroplex.One of the international shows is here every year.I saw one bike, so unrecognizeable from the jap bike it started with i am not sure what it was.Possibly a roadstar.One of the ugliest bikes i have seen. I have been on the GS resources site for 15 years.Those bikes its all about the engine. The xj is similar, except for plain bearings not rollerbearings. But the alternator behind the engine instead of hanging out increasing engine width is fantastic in my opinion. Lots to learn here.I love this stuff.
     
    Last edited: Feb 7, 2018
  4. cruiserlover

    cruiserlover Active Member

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    Once again I am told to go to xj4ever.he has fantastic writeups and explanations.But i need parts.Not explanations.Surely there is a order section I havent found yet.
     
  5. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Start a conversation with Chacal.
     
  6. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    One of the main problems with using a single carb (besides the fabrication work, etc.) is that you then have unequal manifold lengths for the inner vs. outer carbs.....and that will create a tuning "challenge" (another word that could be used is "nightmare"). As you've noted. the Yamaha engine is cleverly engineered in a number of ways, and the fuel system is no exception. It is somewhat doubtful that you'll get the same performance (power and economy) out of a different design. Others have tried and gone down swinging. About the only realistic improvement is the adaptation of a fuel-injection system, and a few people have accomplished that successfully, but not without a whole boatload of effort and $$$.
     
  7. cruiserlover

    cruiserlover Active Member

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    I agree with what you say. I do not need to re-engineer what is working.I am dwelling on the nightmare of the 4 cylinder goldwing carbs.A single setup is easier and less problematic with those bikes. I also have learned stick with the stock jets and airbox.never put pods unless you love constantly trial and error want to use different size jets trying to get a bike to run correctly.
     
  8. MattiThundrrr

    MattiThundrrr Not a guru

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  9. REUBEN

    REUBEN Member

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  10. Jetfixer

    Jetfixer Well-Known Member

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    A big challenge ,the XJ uses a side draft style carb , the Goldwing is a boxer style engine so you can do this with a downdraft carb, My 71 Super beetle has a 1776 with a Weber 2 barrel progressive carb . If you tried this you run into clearance issues with the tank, frame and as chacal stated unequal fuel delivery your inner might get more than outer . Years ago I had a Virago 750 and was on the Virago forum several tried to make a one carb set up with varying results , most made out of PVC , usually resulted in vacuum leaks and melting . My thought do your carbs at church of clean ,synch them right , and do not use pods and bike will run great.
     
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  11. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    The last time I serviced my carbs.....

    650 Maxim - 2001, when I got it
    700 maxim - 2009, when I got it
    900rk - 2010, when I got it

    All still running strong
     
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  12. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    No doubt.......
     
  13. Orange-n-Black

    Orange-n-Black Well-Known Member

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    I'm Back!
    I did make 2-2 into 1 manifolds out of PVC for 2 34mm Mikuni Round Slide carbs that I got from CycleX. First you need to block off the YICS channel. I blocked mine off with a 3/8ths" steel rod.

    I made 2 versions of the intakes trying to get the right amount of fuel mix to each cylinder. The carb was pushed out towards the outer cylinder a bit (half way between the outer cylinder intake port and the mid point between the 2 ports). I tested it for a month with good results until the PVC started to melt from the fuel and heat.

    Then I made they new manifolds out of steel square tubing I got from work. Can't remember now what size they were, 1 & 1/8" or 1 & 1/4" square tubing at 1/8" thick that I mig welded. Used a short piece of 1" round pipe to attach the carbs with generic boots That I got from Cycle X with the carbs.

    It worked great after putting 7 series plugs in the middle cylinders that were running slightly richer than the outer with the original 8 series plugs.
    At first I had 2 pod filters that gave me problems in wet whether, so I changed to 1 larger pod towards the center. Had short pipes running to drag style silencers. I ran it that way for a couple seasons til my health problems got in the way, now my Son In Law has the setup on his bike.

    You could just use 4 - 32mm round slide carbs and use a 4 wheeler throttle cable.
     
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  14. Dave in Ireland

    Dave in Ireland Well-Known Member

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    Excellent news.
    I've been pondering the dual carb setup for the XJ when the carbs finally wear out. Hopefully not for a long time yet, but they will eventually, and by that time rebuild parts might be unobtainable.
    My single-carbed GS is still running fine and incremental improvements over the years have it running better than ever. It goes like a scalded rat up to redline in the bottom four gears and my butt dyno tells me it's not far short of the original power. In top, it runs out of steam at 95-ish, but I know the manifold (with the larger carb I had on there previously) can flow up to 115mph without trouble.
    The reason I fitted a single carb (SU in this case) was the rebuild cost of a bank of carbs back then, and because I knew SU carbs quite well, having been working with them for years.
    While a single SU setup is as reliable as a stone, twin SU setups are problematical and the Japanese are a better option for reliability. Apart from that, the recent selling prices of twin SU rigs on ebay make me blink. They're simply not worth what they sell for. It's all these people trying to restore classic Minis and the like, are bumping up prices. They'd be better off fitting a rack of carbs from a bike, ironically.
     
  15. Minimutly

    Minimutly Well-Known Member

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    Better off fitting a rack of carbs off a bike?
    What would they do with the two spare carbs then?
    Oddly enough it is being done - but not on minis - vauxhall red tops, peugot 1400s, pretty much any 2l and below engine - bogg brothers are experts on it. I made and fitted a set of trumpets, inserted at 30 degrees into a Peugot 1100 autograss engine some years ago, made big power, still around, winning too. Strange thing is, all these ran K&N air filters, without issues, once set up. Not a std plastic airbox in sight..
    For the humble xj, if you're worried about worn out carbs (I wouldn't be), go megasquirt efi - its a learning curve, but not much money once you have the throttle bodies.
     
  16. Dave in Ireland

    Dave in Ireland Well-Known Member

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    Oh, I dunno - they could take them off the rack. Sheesh.
    Not interested in megasquirt.
     
  17. Honeybadger01

    Honeybadger01 New Member

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    I recently just bought a sand rail with what I believe is a xj550 engine it runs on a single vw bug carb. It was not runing when I bought it was scoping this form for info on the carb itself it is runing great now if you guys need in info on the single carb part numbers ect let me know.
     
  18. Honeybadger01

    Honeybadger01 New Member

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  19. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Well THAT’s got my attention!!
     

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