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'82 Seca 750 Refresh Project: Now Scooby's Bike

Discussion in 'XJ Technical Chat' started by Nuch, Aug 24, 2019.

  1. Rooster53

    Rooster53 Well-Known Member Premium Member

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    Normal for a wet clutch on the center stand. If it's on the ground and lurches forward then you have a problem.
     
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  2. Minimutly

    Minimutly Well-Known Member

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    So long as it doesn't creep when your in gear at a standstill, or slip when giving it the beans you're fine. Springy, rubbish outers can cause this.
     
  3. scoobydew

    scoobydew Member

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    I was able to align the splines. Gave a 3mm free play at the lever. This should allow more range to pull the clutch. Yet, the rear wheel still spins. It's fully engaged despite having clutch lever pulled in fully . This is Not a spin that can be stopped by hand, if it was then it would just due to oil. I've made sure to align the dots on the basket when installing new clutch plates. The only thing I can think of is maybe the clutch cable is stretched. But the knurled adjust nut is all the way at the top. It's as tight as can be. Last resort is taking a look at the internals...

    When one problem is solved... another arises...
     
  4. Minimutly

    Minimutly Well-Known Member

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    Tighten up on that free play a little, and put some miles on the clutch before stripping (assuming you can get it to release by the aforementioned tightening free play). My experience with these is that there is very little margin for error - too much free play and it doesn't release, too tight on the adjustment and it will slip. Worn lever pivot, spongy outer cable, bad routing can exacerbate this, so don't rush into taking things apart (again).
     
  5. Polock

    Polock Well-Known Member

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    zero free play gives more travel to the clutch arm.
    can you stop it with the brake? my clutch is adjusted and maybe i could stop it with my hand but my hand would never be the same.
    if the brake can stop it without killing the engine, i would sit on it and start it in gear.
    point it out the door first, just in case :)
     
  6. scoobydew

    scoobydew Member

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    So, I've tightened up the free play on the lever. It's basically zero now. And put some miles on the clutch means I should ride the bike? Isn't it a bit spooky to shift into first and the wheel immediately shoot the bike forward? I'm going to attempt it eventually... the bike is heavy. Maybe the weight will stop the wheel somewhat. I am able to stop the wheel with the footbrake and the engine doesn't stall out. I dont get what's making it spin. I oiled the plates before installation... the only explanation I have is the plates are sticking together?

     

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  7. Minimutly

    Minimutly Well-Known Member

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    Put the bike outside, warm it up. Sit on it, hold the brake (choice of two), pull clutch, bang it into 1st.
    If it stalls you have a clutch problem. If not, go forth....
    You 're overthinking stuff.
     
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  8. Toyobaru866

    Toyobaru866 Active Member

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    So just ride it, no danger there.
     
  9. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    That amount of wheel spin while sitting on the center stand doesn't seem outrageous to me.

    Remember that those clutch plates are still spinning in very close proximity to each other, with oil in between, so it shouldn't be surprising that the rear wheel would spin a little bit without any resistance.

    I would test it by doing the same thing, but sit on the bike and have the rear brake engaged when you shift into first. As @Minimutly said, if it stalls you have a clutch problem.
     
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  10. scoobydew

    scoobydew Member

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    Ran the bike before I left for a bike trip to the Midwest and you guys were right. The spinning was no issue once the bike was on the ground. I took her for a spin but only made it about two blocks until she stalled out and I had to push a 500 lb bike back home. The bike has poor throttle response when blipped. It takes half a second or so for the cylinders to respond when the throttle is opened. So getting the bike rolling can be difficult unless I apply a large amount of throttle. Releasing the clutch slowly doesn't move the bike forward but will stall it out. Even with a tiny bit of throttle applied, the bike stalls. Opening the throttle at least half will get it going.

    I've vacuum synced the carbs using the YICS tool. I also took a look at color tuning. Which is kind of a pain. Should all mixture screws be the same screwed in or out? Or can carb 1 be 2 1/2 turns while carb 4 is 3 turns. As long as they hit that blue color? Or must they all be 3 turns out etc. Because I've turned all the mixture screws out completely to hit an orange color but no matter how far I have them turned out, the color doesn't seem to change.

    Edit: I tried starting the bike this morning and... it's seized. I was gone for two weeks and I guess the rings got stuck or something. If the starter motor can't free up the crank with it's torque, how could I with a wrench?
     
    Last edited: Sep 12, 2021
  11. Toyobaru866

    Toyobaru866 Active Member

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    No, the setting can be different. The way I do it (if I use the colortune because I found it hard to use with an X) is turn the screws out until an orange color, then turn them back in until the blue color and then turn them back out 1/4.
    Are you sure the engine seized? Is the battery voltage okay? Did the carbs flood and do you have vapor lock?
     
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  12. scoobydew

    scoobydew Member

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    Nice to know. I'll keep that in mind when I color tune the bike.

    I did a little diagnosis to see if the engine was seized...Before I left, it was having starter motor issue, no mechanical issue at all so I replaced the starter motor and went on a 2 week trip. When I got back, the engine wouldn't turn over. So I opened the governor cover and tried to turn by hand. It would move clockwise but not counter-clockwise. I check the cylinders through the spark plug holes and I see an intake valve inside cylinder 4.

    I don't know HOW it got in there and it certainly didn't happened while the engine was running or I would've noticed a huge BANG BANG BANG and my entire engine would be destroyed. My only guess is I never replaced the valve springs and they could be the originals from '82. Perhaps one of them broke under tension for so long. Luckily it didn't break while the engine was running. There's no way to know for sure until I open the engine up. But since the engine can't turn over... I can't reach the sprocket bolts to take off the chain... Which means I have to break the cam chain and replace it just to check the valve stems....
     
  13. Franz

    Franz Well-Known Member

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    That's a pity the valve dropped. Splitting the cam chain is the solution if you cannot get to the sprocket bolts.
     
    Last edited: Sep 12, 2021
  14. Toyobaru866

    Toyobaru866 Active Member

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    That's a PITA but you're also very lucky...
     
  15. scoobydew

    scoobydew Member

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    Haven't taken the cylinder head apart yet but here's the culprit. Snapped at the cotters. When I pull the valve out I guess we'll find out what happened to the lower part of the valve stem.
     

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  16. Minimutly

    Minimutly Well-Known Member

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    Don't know about lucky... I would say this is very rare, non existent even on a standard road bike, unless something else caused it.
    I suspect you'll need a piston, maybe a barrel and head, but you never know. Rebuild carefully and go again.
     
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  17. scoobydew

    scoobydew Member

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    You're right, def not lucky. As this is gonna cost a lot of cash... but lucky enough that I think there is no head damage.

    Took off the head to inspect the damage. The piston is a bit chewed up. Since I'm already down into the guts, I'll probably just replace the piston. The valve guides look good though only way to know is when I put a different valve in and see if there's any resistance. The port next to the valve guide looks like it took the damage. If the valve guide is good then I'm guessing the valve dropped and chewed the piston when using the starter motor.

    My only guess is the springs were installed incorrectly. So the top of the valve stem was shaking back and forth until it broke off.
     

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  18. Toyobaru866

    Toyobaru866 Active Member

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    Well I would say lucky that this did not happen to you on the highway in a corner. But for the rest, of course not lucky...
     
  19. Minimutly

    Minimutly Well-Known Member

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    Sure thing there..
    @scoobydew , turn the engine over to check the bore for damage - that piston looks fine to me, I've peened far worse with a ball pein hammer and left as is.
    I don't know where you get the valve springs installed incorrectly - if the collets are in then that's it. I would be looking closely at that cam lobe - didn't you have an issue with cams at one point?
     
  20. scoobydew

    scoobydew Member

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    Hey all,

    Bores look good. Everything looks fine from what I can see. except for the little dent on the piston. The old cams had an issue. The new ones were in spec. They turned over fine but there's no way to tell if they have bad runout. Gonna take them to a motor shop to check.

    Right now I'm stuck on a little issue. Since I'm not splitting the crankcase, I split the chain and intend to use a master link. Issue is, every chain split kit comes with a pressure plate too big for a cam chain. They are obviously intended for a drive chain. Where can I find a kit that can install master link for the cam chain?
     

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