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81' XJ750RH Seca Plastic chunks in oil pan.

Discussion in 'XJ Technical Chat' started by Mobius Williams, Aug 7, 2020.

  1. Mobius Williams

    Mobius Williams Member

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    Yup. You read it right. The bike runs superbly. But I did have multiple minor oil leaks here and there. So I finally got the time and developed enough of a distaste for purchasing oil that I have started going through and replacing the majority of my gaskets, seals, o-rings ect. To my dismay when I drop the pan I find multiple black plastic chunks in different locations throughout the pan. I've had the valve cover off a few times to check clearances and whatnot and from that angle my cam chain guides seemed to be intact. I will be double checking them again when I remove the head this time as well. Does anyone know of anything else this may be, or have dealt with this before? I most certainly want to replace the broken part while I have it opened up.
     
  2. Franz

    Franz Well-Known Member

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    It will be your starter chain plastic guide breaking up. Just replaced mine it is necessary to split the cases to change it. Apart from your cam chain guides the other guide is the only other one. They deteriorate with age and the machine develops gear selection problems when bits of the guide lock the selector drum and forks.
     
    Last edited: Aug 7, 2020
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  3. Mobius Williams

    Mobius Williams Member

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    Looks like I have a winter project then. Thank you.
     
  4. Franz

    Franz Well-Known Member

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  5. Mobius Williams

    Mobius Williams Member

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  6. Franz

    Franz Well-Known Member

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    It will cause gear change problems and damage the oil spray nozzle behind the alternator rotor. The nozzle lubricates the starter/alternator chain. With bits of the guide in your sump you should do the work as soon as possible. Follow CDs how to l posted. He explained the process well.
     
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  7. k-moe

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

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    Park her until you can do the work. The oil nozzle runs $100, and that's not the only thing that will be damaged if you keep her as a daily rider.
     
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  8. Mobius Williams

    Mobius Williams Member

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    10/4. Thanks for all the info guys. I love this forum!!
     
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  9. Franz

    Franz Well-Known Member

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    Once you get started it is not so bad, the only problem I had was the three studs at the front of the engine which were seized and I was patient and got them sorted. The crankcases split easily, one bolt is inside the oil filter housing and four are inside the sump the rest are visible. While you are in there to replace the guide, put heat on the old bolts holding the old guide to soften the factory threadlock as they can break otherwise. Get new bolts and medium strength threadlock. Fit new starter clutch dowels and springs, mine were fine but I replaced them anyway as you don't want to split the cases should it fail at a later date.

    One of Mezzmo's videos of his rebuild, gives you a snapshot of the assembly process. He has a series on his XJ conversion you can watch.

     
    Last edited: Aug 7, 2020
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  10. Mobius Williams

    Mobius Williams Member

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    Awesome. Thanks again!!
     
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  11. Rooster53

    Rooster53 Well-Known Member Premium Member

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    Just curious on approximately how big the chunks were and if you had noticed any strange noises (chain rattling) or had shifting issues?
     
  12. Mobius Williams

    Mobius Williams Member

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    Dime sized or a little smaller. A bout 7-8 of them. No shifting issues and no new rattling.
     
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  13. Mezzmo

    Mezzmo Active Member

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    Its likely everything will work fine until the chain stretches to the point where it will rub on the oil feed nozzle. This will be most notable at idle...
     
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  14. Polock

    Polock Well-Known Member

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    make sure the guy behind you at the red light knows you may only go 20 feet and loose all power
     
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  15. k-moe

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

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    The chain will rub on the oil nozzle right away due to the slack not being taken up by the guide (which also acts as a chain tensioner). The chain will also hit the case, though it takes longer for it to wear into the case than through the oil nozzle.
     
    Last edited: Aug 11, 2020
  16. Mezzmo

    Mezzmo Active Member

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    Its not actually a tensioner, its just a guide. I recently fitted an OEM and guide and when new it literally makes no contact with the guide. All that chain does is rotate the alternator rotor and provide drive from the starter motor. To be a tensioner it needs to apply tension via an adjustable bolt or spring and be adjustable like the cam chain tensioner.
    The wear on the nozzle is from the top side of the chain. The guide is protecting the casing, not the nozzle. Some stretch will cause enough slack to hit the oil nozzle and further stretch then damages the guide and if bad enough the casing.

    One weak point on the XJ650 and XJ750 imo is the carby bowl design which creates a perfect spot for the feed to the choke to block.
    Once this happens starting becomes much harder and this is what I think results in chain stretch.
     
  17. Franz

    Franz Well-Known Member

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    The top side of the chain can also hit the case when worn. I head it on mine and I have a video posted on here showing the stretch in the chain. My guide had not broken up but I replaced it anyway and the oil nozzle was fine.
     
  18. Mezzmo

    Mezzmo Active Member

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    Agree Franz. The only positive I guess is that there is usually a rattle warning it’s on it’s way out. It’s unfortunate it’s not a simple job to replace though...
     
  19. Franz

    Franz Well-Known Member

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    Yes Mezzmo mine rattled a bit, and I don't like that but it's sorted now.
     
  20. k-moe

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

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    I’ve done the job to my own bike. I’m not wrong. The guide does apply a slight amount of tension. If your HY-VO chain is worn then it won’t do that. HY-VO chains don’t stretch. Even single-pin chains don’t stretch; the pins and rollers wear.
     

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