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highly modded 650 Seca

Discussion in 'XJ Modifications' started by Simmy, Mar 25, 2016.

  1. Simmy

    Simmy Well-Known Member

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    Hey Quixote, I just recently joined this forum so I missed your posts in 2013. For some reason your pics didn't come up, could be our work system here while I'm on lunch. Really curious to see your bike.
    Interesting to read your approach to the cooling as I remember dealing with the same dilemmas. I used a Honda thermostat housing which had no filler neck so it fit neatly inside the frame neck. It's still the highest point in the system so I need to hoist the front wheel on a stand to fill the coolant. I wouldn't worry about the smaller drive shaft of the Seca, something I wasn't even aware of but if mine stands up to sidecar duty a solo bike should have no problems. I've pushed this thing past 160 kph with a friend in the chair, (yes he's still a friend:rolleyes:). With the standard 650 Seca powering the sidecar my top speed I think was about 130-140 kph but I had to kick it into 4th as 5th was too tall to pull.
    I found some room with the 650 Seca airbox but I had to shorten the connectors between the carbs and the airbox but had trouble sealing them so eventually went to the foam Uni filters like you. Currently running Chinese pods scrunched to fit the frame rails, it's never run better than present. My bike (the red one) came with electronic tach so that was one less thing to mod.
    Let me know when you're ready to tackle the 911 big bore, I'll keep an eye out for good pistons and block.;)
     
  2. Quixote

    Quixote Active Member

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    I've recently upgraded my cooling system (again) and I think I've got it right this time. I had a new custom rad made, even bigger than the last one. It still doesn't have a fan, but there is now room to put a small one on each side outboard of the frame tubes if I need to. So far I haven't needed to, but then again I haven't really tested it in slow traffic on a hot day.
    Besides putting in a bigger rad I also made some changes to reduce heat transfer to the rad when the bike isn't moving - I wrapped the header pipes and re-routed the return line from the rad to the water pump so that it doesn't route right between the header pipes like it used to.
    This iteration of the plumbing has eliminated the stock thermostat housing in favour of one from Summit Racing that uses a Chevy thermostat. Bigger than necessary but it works, and as a bonus it's shiny. Under the tank is a wye made from copper plumbing pieces to join the 2 lines coming off the engine into one larger hose to the new thermostat housing. That fitting is also drilled and tapped for the temperature sensor.
    The filler is now directly on the rad, on the right side so that it is the high point when the bike is on the side stand.
    Also, there is a bit of genuine Canadian engineering in there. I wanted to make a rubber mount for the rad for vibration isolation and the solution was to 'machine' it out of a hockey puck
    Still to come: a new overflow tank to replace the stock one which currently lives where the air filter used to be.
    [​IMG][​IMG][/URL][/IMG] Side.jpg Front.jpg Left.jpg Right.jpg Radiator Mounts.jpg
     
    Last edited: Nov 22, 2016
  3. Quixote

    Quixote Active Member

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    And thanks for the offer of to look out for big bore cylinders and pistons, but I'll pass on that! You deserve to be the only one who has those bragging rights.
     
  4. k-moe

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

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    Does the fender not kiss the rad under hard braking?
     
  5. Quixote

    Quixote Active Member

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    No, but it's close. Less than a quarter inch clearance at full suspension compression.
     
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  6. Simmy

    Simmy Well-Known Member

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    You have an astute mind k-moe. My fender has fouled my Honda rad after landing some sloppy wheelies riding solo without the chair. The scratches buffed out. I may have extra clearance from Al's bike with my 16" wheel. You might want to add the oil cooler Al if you're still boiling coolant.
     
  7. Quixote

    Quixote Active Member

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    Some of those pictures make the clearance look worse than it is. Here's a better angle.

    20161122_085634.jpg
     
  8. Simmy

    Simmy Well-Known Member

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    1982SecaXproject.jpg
    I just found this photo surfing the net.
    I took this photo around 1999 I think. I haven't lived in that house since 2001 so its going back a while.
    It was still a 750 here, before I put the FZR1000 block in. I replaced the Maxim-X valve cover with the FZR when I did that and this pic still has the X cover. I powder coated the crank ends black then to.
    Also had the complete Supertrapp header back then. Now I use a Turbo collector and XJ750 head pipes.
    Back then I still rode this as a solo bike without the chair.
    This is the money shot but the pipe is always hidden by the chair.
    I think this is about as close to making your 650 Seca look like a Lawson Replica and appearance wise all I changed were the wheels and front fender.
    This is basically what I want my Turbo I'm working on to look like. Pipe will be exiting on the left though.
     
  9. Quixote

    Quixote Active Member

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    Nice pic! But then I would like it - other than the colour and the wheels it looks a lot like mine. I even have the same Supertrapp.
    Where did you hide the coolant reservoir?
     
  10. Simmy

    Simmy Well-Known Member

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    I used 1/2 litre bottle container (I think it was from fork oil) and hid this under the seat.
     
  11. Simmy

    Simmy Well-Known Member

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    I was just going through my old mags and found the Cycle Canada article with my bike in it.
    Nov/Dec 1993, hard to believe this was 25 years ago.
    I've made a few changes to the bike since this article.

    IMG_0160.jpg
     
  12. Polock

    Polock Well-Known Member

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    what color is that, really. kind of liking pale mint with dark green stripes
     
  13. Simmy

    Simmy Well-Known Member

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    I had an antique car calendar hanging at work when I decided on the color.
    There was a 55 T-Bird which influenced me.
    I think what I love most about the 50's autos were the wild pastels.
    Even cream pink is cool but I don't have the balls to paint anything that colour, LOL.
    280px-T-bird.jpg
     
    Last edited: Jul 11, 2018
  14. Simmy

    Simmy Well-Known Member

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    I dug out my old files from the dyno runs I did with this bike from 1992.
    This 1st graph are the results I got with stock 750-X motor and jetting with pods.
    The top curve is torque and the lower curve is hp.
    Typical of bikes running without the airbox they fall flat at 5,000 rpm.
    It maxed out at about 76 hp but the dip at 5,000 was terrible for pulling a sidecar

    XJ750X dyno run before.jpg

    This 2nd graph were the results after I got professional help.
    Changes included alternate jetting, softer slide springs and drilling the holes to the diaphragm chamber larger.
    The drop off in power at 5,000 disappeared and this is mainly corrected by the softer springs.
    Peak hp climbed to 82 hp, this is actually better than what I've seen stock FZ750's achieve.
    (the 1st run was a Dynojet model 100 dynamometer and the 2nd run was a 150, whatever that matters, both graphs are 4th gear roll-ons).
    Since this I installed the pistons and cylinder block from the 87/88 FZR1000. Other than mixture screws and synching I haven't made any further changes to the carbs.
    Never put it on a dyno in the 911 configuration, always been afraid of blowing it up.
    XJ750X dyno run after.jpg
     
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  15. MattiThundrrr

    MattiThundrrr Not a guru

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    Wow that's a big hole in the "pods" graph. I wish you had one with the stock intake for the purpose of comparison.
     
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  16. k-moe

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

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    Here's one for the FZ750 (note it has an aftermarket exhaust, but stock jets: green plot line). Numbers will be different, but the curve shape will be nearly identical to the stock Maxim-X.
    4102.pdf
    Also keep in mind that (as with most test equipment) the numbers you see for a machine on any given day, and a particular location, will not necessarily be identical to those measured on a different day or location. The overall curve shape should be near identical however.
     
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  17. 50gary

    50gary Active Member

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    Hey Moe, that's for an XJ750 right? Stock they're listed as 82 bhp, I have an '82 just wondering.
    Cheers, 50gary
     
  18. Simmy

    Simmy Well-Known Member

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    The part number K-Moe referenced is an XJ750 but the fine print states 'This graph shows a typical gain with a Dynojet jet kit.'
    They depict typical gains for an FZ750 but it is purely sales embellishment. There's no way in hell you're going to see almost 100 hp from an FZ750.
    I used to attend a lot of rallies in the early 90's and a Dyno was always present, I knew the operator well, he's actually an Iron Butt Rally winner.
    I saw just about everything on the dyno back then. An XJ650 was typically 48-50, XJ750 55-58, this is rear wheel hp, delivered through a shaft drive.
    Other bikes I've owned and put through dyno runs, 87 CBR1000 - 110hp, ST1100 - 88 hp, VTR1000 stock 100 hp, then Yosh slip-ons and Dynojet Stage 1 104 hp.
    I paid about $1600 for those 4 extra horses on that VTR, LOL!
     
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  19. Simmy

    Simmy Well-Known Member

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    When I first installed the 750-X motor I had the 650 Seca airbox hooked up. The X carbs are further from the motor to clear the water pump so I had to modify the rubbers to the airbox to make them fit.
    It never sealed properly so that's why I went with the pods. In hindsight I should have tried the rubbers from a Maxim-X, they might have fit, but then again I'm not sure if a 650Seca airbox has equal volume to the Maxim-X air box. I did learn a lot through the process and eventually did get it running great without an air box. Now that I have a 911 sucking through the 750 carbs I'm getting really great response, even at 4 grand I can roll the throttle on with a loaded up sidecar and it pulls real strong without any hesitation.

    I would expect a stock XJ750-X on a rear wheel dyno would be somewhere between 75-80 hp. It will be less than an FZ, 34 mm down draft carbs and chain drive being advantages.
     
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  20. k-moe

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

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    I referenced the shape of the curve, not the total HP,
     

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