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A handy guide to not rebuilding your slipping starter clutch.

Discussion in 'XJ Technical Chat' started by k-moe, Sep 19, 2021.

  1. k-moe

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

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    Is your starter clutch slipping?
    Check these things before assuming that it needs rebuilt, and tearing into the engine.

    This list includes a issue that I recently encountered, but had never considered as a possible culprit before.

    1. Make sure that you are using oil with a JASO MA rating or better.Such oils are engineered to work with wet clutches in older motorcycles, and do not contain the friction modifiers that will cause the starter clutch rollers to slip.
    Choosing the correct Oil for a wet-clutch Motorcycle
    If you do have a friction-modified oil in the sump, drain it. Replace it with a cheap oil of the correct specification, and dose the oil with Seafoam (or similar) to clear out the remains of the too-slippery oil. You can also pull the starter motor and spray carb cleaner towards the front of the engine case to help clean the starter clutch of the too-slippery oil. Do an oil change again after the slipping stops.

    2. Make sure that your battery and starter motor are in top-condition. The battery should not drop below 10 volts when trying to start the bike, and the starter motor brushes should be inspected and the motor cleaned (especially if the bike is new to you) with electric motor cleaner. A starter that does not spin fast enough will cause the starter clutch rollers to slip.

    3. The new-to-me-issue that I mentioned earlier:
    Make sure that the problem isn't your clutch plates sticking together. Even with the clutch lever pulled in it is possible for an older set of clutch plates to remain in contact with one-another, which causes the poor starter motor to have to try and spin the transmission along with the engine. The starter clutch will slip in this case. The immediate remedy is to roll the bike forward while pulling in the clutch lever. That will break the clutch plates free and allow the bike to be started without any problem. This issue will turn up even when the transmission is in neutral.
     
    Last edited: Sep 24, 2021
    hogfiddles, PJC750, cgutz and 4 others like this.
  2. Carl LaFong

    Carl LaFong Member

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    Thanks for this. I wondered about the starter clutch issue since I got this bike last fall. No issues so far.
     
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  3. cgutz

    cgutz Well-Known Member

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    Good write up, and an exhortation to use oil rate properly for wet clutch motorcycles!
     
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  4. PJC750

    PJC750 Member

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    Last edited: Oct 7, 2021
  5. k-moe

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

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    Please start a thread about your problems. Better yet, add to any existing thread about your motorcycle.
    I don't know what videos you watched, but there is no way to turn around the idler gear in a shaft-driven XJ without splitting the engine cases.

    If your battery is draining during a ride you have a charging issue. Worn alternator brushes are the most common cause and easy to fix.
     
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  6. PJC750

    PJC750 Member

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    Thanks Kmoe, prob will start with new brushes,ck teeth etc.
     
  7. Huntchuks

    Huntchuks Well-Known Member

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    Next, check the rectifier.
     
  8. PJC750

    PJC750 Member

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    Thanks, HC ...did solenoid, will pu bat on load with meter. I should expect 13-14 v while running correct?
    Its just annoying to get quick clean starts when cold outta garage....but after everything warms up....it decides to mis-behave.
     
  9. swingmanu

    swingmanu Member

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    Thanks for the write up!
    I have that issue since i bought the bike, changed with oil for proper jaso, but still can't crank. Rebuilt the starter motor and it just spins the engine a little then slips and spins in the air... I will try the other fix you mentioned, the carb cleaner through the opening and the stuck plates maybe...
    I really would love not to have to split the case. Can i upload a video on this forum?

    Thanks
     
  10. Franz

    Franz Well-Known Member

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    You can create a YouTube video and post the link on the forum, that will work.
     
  11. swingmanu

    swingmanu Member

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    Here it is :
    So it cranks for a little bit and then spins...
     
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  12. k-moe

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

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    I'd think that stuck clutch plates are the likely culprit. They are certanly easier to remedy than rebuilding the starter clutch.
     
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  13. swingmanu

    swingmanu Member

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    Thanks k-moe, I've tried it all now. Brake cleaner in there, pulling the clutch lever, rolling the bike back and forth. The brake cleaner helped a bit. It stayed engaged better but still slipped eventually...

    As I have pulled everything else in the bike I can't get it started and running warm to do another oil change. I'm gonna try still to do a cold oil drain (all night and pull new oil tomorrow) basic mineral jaso (cheap)

    And try it again.

    When the battery is fresh it slips out even easier.
     
  14. k-moe

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

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    In that case it's likely in need of a starter clutch rebuild. Keep in mind that it's apretty easy bike to bump-start, so you can put the teardown off for a long while if you want to.
     
  15. PJC750

    PJC750 Member

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    Have same problem, especially after a short ride(engine oil is toasty) AND turn off bike. Try restarting 5 min later and she plays the boxorocs thing. So, I started (ahem) with the starter rebuild kit...heck whats 30 bucks. My starter is Now up to snuff...ck that box.
    A FRESH STRONG battery turns it over right away...yesss! Yes I also bucked up and git me a new LiPo battery with 400 cold cr amps. ( Yes, came a month later, was $107, and the poles are swapped(annoying) but aint 10lbs ; ] !
    To Kmoe's point, I do have to install new clutch friction pads, so I can eliminate that sticky possibility too. The last thing I will do is make sure nothing is draining my battery while she is sleeping, and the charging system is doing it's job while running.
    Fresh strong battery...priceless.
    81 xj750
     
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  16. Jetfixer

    Jetfixer Well-Known Member

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    My two cents , I have now did two starter clutch replacements , my findings one had a roller with a flat spot and both the springs were shorter than the new springs . My thought the old springs after 30 plus years of wear and tear , loose their tension hence so the rollers slip .The rebuild kit I used has a heavier spring and had new rollers and the new cups has an oil hole in the bottom ( the original is lacking the oil hole) . I learned the hard way when you split case DO NOT turn the crank over with the cam tensioner out ( you can skip cam timing) . After removing engine from the frame , I can split case in about an hour , I know Kmoe has done deed as well but these are just my findings . My original engine to the bike the starter clutch slipped when engine was hot , tried oil change , heavier weight oil , tried Seafoam in the oil , I replaced the clutch as well , rebuilt the starter, the carbs were taken to church as well . I bought another engine , this engine had 38k on it ,but had 150 psi on all four cylinders, I got two years out of last summer it started slipping and got to the point would slip even cold. This engine was spotless inside when I tore it down , the other engine has low compression with two cylinder at 90 psi ,one at 140 psi and one at 150 psi , I'm hoping I did not kiss a piston with the valve when I skipped timing . Lesson learned maybe in the spring I will do a leak down test to see if it is piston rings or the valve. Anyway this is my starter clutch experience.
     
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  17. PJC750

    PJC750 Member

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  18. PJC750

    PJC750 Member

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    This new LiPo battery, bangs that starter out and she turns over in one press of a button.
    But, because its cold now and I can't ride, I cant test what happens after she is warmed up. (You know...ride 20 min, turn off for 5 min, then try to restart.....to see if the "b-o-r" (Box-o-rocks) noise comes back.
    My guess is, over time that spring weakens.
    I have seen some youtube vids where guys discuss removing the spring. Their reasoning is, the spring prohibits full gear tooth contact. Not sure if that is true.
     
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  19. k-moe

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

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    The springs are what make the starter clutch work properly. The starter gears on an XJ are always in full contact with one another (which is why there is a starter clutch). I have no idea what bike those Youtube guys are refrencing, but it isn't an XJ.
     
    Last edited: Dec 22, 2021
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  20. Jetfixer

    Jetfixer Well-Known Member

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    When it starts slipping it us time to roll up your sleeves and split the case and replace the springs and rollers . A good set of torx bits ( the type you put on a ratchet) and another set of Allen sockets . See my thread on The dreaded starter clutch I have pictures .
     

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