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XJ 650 Marvin 4 into 2 collector box

Discussion in 'XJ Technical Chat' started by tx1, Aug 5, 2020.

  1. tx1

    tx1 New Member

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    Hello still new to the site but have started to restore a 1980 XJ 650 from the frame-up and this site has helped me in many ways so a big thanks to all of you, I was looking at purchasing a Marvin 4 into 2 collector box has anybody on here ever fitted one and did you have any problems or snags along the way. Thanks in advance for any info you may have.
     
  2. Timbox

    Timbox Well-Known Member

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    tx 1,
    The carbs on this bike are CV or continuous velocity carbs, I am not too sure using a collector box that changed that is a good idea if you want good motor performance? Once you have removed and installed the carbs a few times, you will learn the tricks to getting the rubber boots back on more or less easy. It just takes time and a little strength and good lighting. Is there a reason you want to put the collector box in? Someone told you of a performance change or enhancement?
     
  3. jayrodoh

    jayrodoh YimYam Premium Member

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    tx1 likes this.
  4. hogfiddles

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

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    Keep in mind that the OP is in the UK......so his Xj650 is probably what we in the US call the Xj650r non-Turbo.so, his has a collector box.
    Since it’s a 1980, it’s going to be different than our 1980. We had the 1980 Xj650 Maxim-I. Those did NOT have a collector box. The 650 Maxim is a 4-into-2 with just a crossover pipe. The mufflers are a single-unit-per-side from the exhaust pipe inlet to the end of the muffler, with a slip-joint in the middle of the crossover pipe.
     
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  5. tx1

    tx1 New Member

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    [​IMG]

    This is the collector box that I am planning on fitting to the original downpipes on my XJ 650 was just curious if anybody had fitted one and thanks to jayrodoh for the link and hoggfiddles for his translation I think that his downpipes were not genuine Yamaha not sure if its the same over the pond but my headers are numbered 1 2 3 4 with the model number mine being 4K0 I will see if anybody else has tried them before I commit (Birthday soon) and the last collector box for sale over here I saw was on e***y XJ750 £845.00 let you brainy people work out what that is in dollars but its still a lot of money. Thanks again
     
  6. Simmy

    Simmy Well-Known Member

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    your downpipes are meant to slip into the collector.
    The above collector has 4 ends meant to slip inside the downpipes.
    How are you going to make this work?
     
  7. Simmy

    Simmy Well-Known Member

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    actually these may accept an internal fit, they're just missing the external clamps.
     
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  8. tx1

    tx1 New Member

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    I think with the collector pipes split it would be an internal fit with clamps on the outside not sure if they take the crush gaskets though. and my downpipes do taper into the collector box.
     
  9. chips

    chips New Member

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    Hello i agree im sure with the taper on std XJ down pipes they will slide inside the 4 split openings and then be clamped with the clamps supplied from marvins web site , to locate the down pipes , if this type of collector with crossover pipe works for XJ 650 MAXIM it should work for XJ 650 4k0 as its nearly a replica of the Maxim collector , unless anyone knows different

    Thanks Chips (steve)
     
  10. chips

    chips New Member

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    [​IMG]
     
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  11. chips

    chips New Member

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  12. chips

    chips New Member

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    Hello all , yip just checked as i am restoring a STD 4ko collector just now.

    Std 4K0 collector ID is 33 mm reduced down to 28 mm ID with crush gaskets, to 28 mm OD taper end of STD 4k0 down pipes , marving collector accepts 28mm and no need for expensive gaskets , high temp silicone and then clamped up tight, just like collector for XJR 1300 from black widow.
    cheers

    Chips
     
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  13. chips

    chips New Member

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    Hello all

    Can anyone please advise if 4H7 1980 MAXIM exaust headers can be used on a 1980 4k0 model.
    The MAXIM headers have got drain bolts.
    The 4K0s don't.

    Thanks

    Steve
     
  14. tx1

    tx1 New Member

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    Hi and just an update I did purchase the Marvin collector box and have fitted it but I did need to heat up the number 2 pipe and bend it on the collector box to make it fit as it did not line up with the downpipe and you don't need the crush gaskets will take a few photos and post them when I get a chance and Steve my pipes also have drain bolts on them and I am pretty sure that they are stamped 4KO on the downpipes.
     
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  15. DaygloDavid

    DaygloDavid Active Member

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    From new, my 1980 4K0 (UK) XJ650 header pipes didn't have the emission analysis sample points (drain bolts).

    In 1990, the header pipes were replaced, they were ordered & supplied by a Yamaha dealer. They are genuine parts but this time they had the sample points on them but as above, stamped 4K0. I've often wondered if these are from a US spec. (Seca) bike where exhaust emission regulations may apply.
     
    Last edited: Mar 18, 2021
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  16. tx1

    tx1 New Member

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    Here we go a few photos of the pipes and collector box fitted to the bike and no exhaust leaks if you notice I have also changed the rear mudguard(fender) for a maxim one I think it looks better than the plastic one, the shocks are off a Harley Sportster and the silencers are peashooters from a 1978 MK3 Norton Commando. Still need to make a couple of brackets for the rear of the silencers and mount them to the rear footpegs.
     

    Attached Files:

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  17. DaygloDavid

    DaygloDavid Active Member

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    Is this a 4K0 (UK) XJ650 model.
     
  18. tx1

    tx1 New Member

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    Yes, it is DaygloDavid.
     
  19. DaygloDavid

    DaygloDavid Active Member

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    This is a photo of a Maxim header against the Marving 4-2 collector box for a 4K0 model, it doesn't fit.
    [​IMG]

    I now understand that the Maxims have 2 x 2-1 silencers with a balance pipe between the two sides.
    [​IMG]

    Whilst the header pipes for a Maxim may appear to be the same as those for a 4K0 model, the OD (28mm) to the 4-2 collector box or Maxim 2 x 2 -1 silencers isn't.
    (Don't know what the Maxim OD is).

    What are you trying to match the headers up to?
     
    Last edited: Mar 18, 2021
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  20. tx1

    tx1 New Member

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    Just to back Dave up my downpipes ends are tapered to fit the Marvin collector box.
     

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