Yamaha XJ Thread

Discussion in 'Old's Cool' started by leakypetcock, Sep 7, 2011.

  1. Tosh Togo

    Tosh Togo Long timer

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    Before you use the rebuild kit, check the two screws on the back of the petcock, and see if they have backed out a bit. The only time mine ever dribbled on the floor was due to that problem. If that was the cause, save the new parts for when the petcock finally does begin to drool.

    If you can find one to check for fit, a non-vacuum petcock from a Banshee looks as though it might work. I'm not terribly fond of the vacuum setup either, and fwiw every XJ engine I've checked the compression/leakdown on has it's weakest cylinder on the one that was attached to the petcock. :cry

    If you haven't replaced the vacuum hose that goes to your existing petcock, do that the next time you've got the tank off. :deal
    #21
  2. CatTracker

    CatTracker CatTracker

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    OK, I'll play... Here's my 82 750 Maxim. You might want to check out XJbikes.com if you haven't yet. Loads of good advice on anything XJ related. Also XJ4ever.com for OEM parts at reasonable prices.


    [​IMG]

    [​IMG]
    #22
  3. McJamie

    McJamie STROMINATOR

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    I am looking at picking up an 82 650 Seca, cheap. The guy says it runs, but makes an " odd, non-metallic sound" when running. Pretty vague I know, but I'm going to assume worst possible scenario. The bike has almost 100,k on it, but it's all stock and very clean, right down to the exhaust. So my plan was just find a much lower mileage engine and switch them. I see from other parts of this thread that the 650 and 750 engines are fairly interchangeable, but how similar is the 900. Is it based on the 650/750, or is it altogether different. Just thinking in the same terms as the twin cam Honda's, the 750/900/1100 are all based on the same motor, each one being slightly taller than it's smaller sibling, but sharing many parts. Are the Yamaha engines the same kind of thing?
    I've always liked the 650 Seca's. My favourite out of all the XJ series. I'd like to try to bring it back to life.

    Any guesses on what the noise might be from? I know they are a pretty sturdy motor, not really know for any major problems, but with 100k. I start thinking connecting rods etc....who knows.
    #23
  4. Tosh Togo

    Tosh Togo Long timer

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    The noise is probably the cam chain rattling, and it's normal when they get tired. An aircooled with 100K miles will do that. :D


    The XJ650/750/900 engines all use the same frame mounting points, and the 900 engine will physically fit into the hole. It's a snug fit, but it'll work.

    fyi- the XJ900 engines were just a max bored and stroked 750, and were actually 850's. Slightly bigger valves and taller gearing, beaucoups midrange. Also getting hard to find.

    If you want to use a 900 Seca engine in your 650's frame, there will be some minor issues to deal with: you'll need to toss the air box, install something else for air filters, and probably re-jet. There may be some (curable) exhaust fitment issues getting a 650/750 exhaust to fit as it should with a 900 engine in there, or a 900 pipe to fit all the 650's frame locating points. Very different carbs, so you may need to make up a throttle cable. The 900 oil cooler will not bolt directly to the 650 frame... same-same, but not same-same.:cry

    No deal-breakers, just more things to massage.

    With these engines, the stock pipes made the best/broadest power, so no.... a 4-into-1 pipe is NOT a cure. :puke1

    The 900 into your 650's frame may have a few minor gas tank/valve cover interference points, but nothing that couldn't be cured with a bit of hammer work.

    I'm using a 750 Seca engine in my 650 Seca frame. Stock 650 pipes, 750 ignition and airbox, 650 turbo oil cooler. The 750 airbox fits with some of fiddling, and you need to shave a bit off the leading edge of both sidecovers. Both bikes use the same carbs, so it's just a needle and a main-jet change. :1drink The 650 toolkit tray interferes with 750 airbox snorkel; my cure for now is to keep the toolkit in my tankbag, and the tray's been removed.

    You end up with about the the same top end, but with all the extra mid-range getting there happens a lot faster...most passes don''t require downshifts, and 5th gear works down to under 25 mph. Other than the increased shove, the only other difference is that there's noticeably less room between the petcock and the valve cover when you switch to reserve. There's still enough finger room to easily switch to reserve, but it's just barely enough.

    Aaannnddddd... the XJ750 engine weighs about 5 pounds less than the non-YICS 650. :lol3


    [​IMG]

    650 on the left, 750 on the right.
    #24
  5. Dave in Wi

    Dave in Wi Long timer

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    Just something else to consider, there are a ton of the Maxim 650s out there. Yamaha sold those like hotcakes compared to the Seca. It might be easier to find one of those as an engine donor.

    I've always absolutely loved the look of the Seca 650.
    #25
  6. camgregus

    camgregus riding gently now

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    +1 on the camchain. And what most people don't know that wears them out is that there is a self adjuster. Just loosen a locknut and let it thunk, then tighten back every 10000 or so and you are good....
    #26
  7. McJamie

    McJamie STROMINATOR

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    That's the kind of info I need to know. very helpful. I think I'm going to buy the bike regardless. Like i said, worst case is the whole motor, lots of used ones around.
    Thanks.
    #27
  8. Tosh Togo

    Tosh Togo Long timer

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    True, although the backing-off needs to be done with all the camchain slack at the rear. Under the left engine cover on the end of the crank, there's a stamped "C" mark on the timing plate to line up with the pointer first. :deal

    The XJ750 engine doesn't have one, so I forgot about that adjustment. :cry
    #28
  9. achtung3

    achtung3 Long timer

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    Finally got my Seca 750 ready after messing with the carburator for 2 yrs.

    With 3k on the odometer I hope it will last for a while.

    It purrs and runs smooth like silk, and roars when needed.

    [​IMG]
    #29
  10. gunnabuild1

    gunnabuild1 Been here awhile

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    Wow Achtung thats super clean,and yes it's an XJ! last the rest of your life with just regular maintenance.
    I like them too.:ricky One of my 900's
    [​IMG]


    And parts bike that was to good to part

    [​IMG]

    The 750 I still have [the first 900 was bought as a parts bike as well]:fpalm

    [​IMG]

    My wife is very understanding .......mostly.
    [​IMG]
    #30
  11. johns

    johns Been here awhile

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    Bought this XJ900 (1992) in 2011 as a replacement for a burned BMW K75S but I like this one better :). Needed new wireing, steering head bearings cleaned and adjusted but now it runs well. Installed a YICS eliminator but I don't notice much difference.

    Only need to replace the fork seals. They are starting to leak.


    [​IMG]
    #31
  12. BIG ED XT FAN

    BIG ED XT FAN Long timer

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    Thats way cool!!! Love the color.
    #32
  13. Andyvh1959

    Andyvh1959 Cheesehead Klompen

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    Da frozen tundra eh? 1.5 mile west of Lambeau
    My brother has his sweet 80 XJ650RJ for sale. I know the bike very well because I did all the wrenching on it over the years, I did the following:

    • Tapered steering head bearings
    • Dynojet carb jet kit, balanced the carbs with mercury sticks
    • KN filter in the stock airbox, some additional "breathing" holes
    • Replaced the crappy fuse panel with a newer automotiv blade style fuse panel and all new fuses
    • Went through every electrical connection, cleaned all terminals, sealed the back of all connections with silicon caulk
    • Krauser Starlet saddlebags with very solid mounts
    • Custom made, water-jetted aluminum tail-rack integrated into the the Krauser bag mounts, seat still tips up normally. The pic below shows the bike without the completed rack, we were just finishing it up that night.
    • LED rear turn signals
    • Rifle handlebar mounted fairing (quite nice really)
    • Replaced the plug caps with new NGK caps
    • Hagon replacement rear shocks
    This is a great bike. Starts easily all the time, warms quickly and runs strong. $1500, in Appleton Wisconsin. 2nd owner and I know the 1st owner.
    [​IMG]
    #33
  14. gunnabuild1

    gunnabuild1 Been here awhile

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    Johns, do you have anymore pics' curious about your colour scheme?I don't think we got that one here.
    #34
  15. johns

    johns Been here awhile

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    It's black(ish), purple, grey. 4bb colors used in the early 90's afaik. We got the XJ900/N/F from 83 up to 92, after which it got replaced by the diversion (seca-2).

    This one is not mine, but it's got the same colors:

    [​IMG]
    #35
  16. svs

    svs All Hands on Deck!

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    Mine back in the day...

    [​IMG]
    #36
  17. gunnabuild1

    gunnabuild1 Been here awhile

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    Thanks Johns,we sure didn't get that colour scheme.
    #37
  18. Jumping Jack Flash

    Jumping Jack Flash Vagabond

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    Hi,

    Another inmate helped my find my new-to-me 1985 XJ700NC. Aside from a pretty good size dent in the tank Jackie (all proper scoots should have a name right?) is in pretty good shape with character to match the present owner.

    I treated the XJ to a bit of time in the local shop (TCP Cycles in Chambersburg...highly recommend Tony) as the carbs needed a full yank clean and tweak as well as other minor stuff that a pro can knock out in a morning and I would take weeks to do....and probably poorly!

    Fully inspected and purring like a kitten! Even treated to a nice little wind screen. Not too shabby for having been built the year after I graduated high school :raabia. A very comfortable riding position and I have already gotten nice comments on the retro style which I think is pretty damn cool.

    I didn't realize I could not post an image from work....I will sort that out later on this weekend. I think I am going to run through Gettysburg and on down to Point Of Rocks on Sunday....perhaps that will yield a good photo op.

    Cheers

    Ted
    #38
  19. Thumpermeister

    Thumpermeister roost maker

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    I had one of these wobblers for about two months. I don't even have a pic of my own bike. A great looking, reasonably quick and good handling bike until the speeds got up there.
    After that, a serious (handlebar fairing induced) high speed weave. I came across a couple other owners complaining about the same thing so I didn't keep it.

    [​IMG]
    #39
  20. johns

    johns Been here awhile

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    As I recall Yamaha had a kit to mount the fairing to the frame. My 4bb has a frame mounted fairing. I had it up to about 120mph and it's not unstable at that speed. That's including the leaking fork seal (and probably by now empty left fork leg :) )

    But it's an old design, it will never be nowhere as stable as newer bikes. Crosswinds have a disturbing influence on these, and at least my, bike.
    #40