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Thread: Top end rattle help

  1. #1
    Join Date
    Dec 2009
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    Top end rattle help

    I have a 350 Rancher with a new crank, new NICHE cylinder with new piston/,pin and rings,Tight timing chain.. I can't figure out what this rattle is.. the valves are tight... I'm leaning towards the Cheap Niche cylinder that has play but it's brand new maybe piston slap?

  2. #2
    Join Date
    Jul 2009
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    Are you positive it’s not timing chain slop ?
    Only way to tell is by pulling the back cover off .
    Also the auto timing chain tensioners do fail .
    I’ve installed a lot or those Niche rancher cylinders with no issues at all , definitely don’t use their pistons though .
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  3. #3
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  4. #4
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    I split the cases and has a New timing chain, it was tight when I assembled it

  5. #5
    Join Date
    Aug 2016
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    I may be way off base here, not sure what yr your rancher is but didn't the earlier models have a decompression lever system? If yours does it sounds to me like the decomp part in the head is clacking against a rocker. Your cable too tight? If you have one. Thats all i got.... good luck

    shep

  6. #6
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    Quote Originally Posted by Shep1970 View Post
    I may be way off base here, not sure what yr your rancher is but didn't the earlier models have a decompression lever system? If yours does it sounds to me like the decomp part in the head is clacking against a rocker. Your cable too tight? If you have one. Thats all i got.... good luck

    shep
    thanks for your reply, unfortunately this model does not have a compression release

  7. #7
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    Dec 2009
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    illinois
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    It really has me stumped and it's the same sound before I rebuilt it! What's strange is I replaced the old crankshaft because the rod had wrist pin play so I was certain that was the issue.

  8. #8
    Join Date
    Aug 2016
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    East of Worcester ma
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    Lurking around the web- it seems some 350 ranchers have valve seat issues- again i have no idea if this is your problem but over the last hour i must of read 10 different posts about loose valve seats or failing altogether. I'd imagine though if u had it apart you'd of noticed something. Just an example-
    https://www.hondaatvforums.net/threa...ve-seat.99594/

    shep

  9. #9
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    Dec 2009
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    Think I have an idea, it could be worn rocker arm shaft

  10. #10
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    Jul 2009
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    The cam followers / caps , push rods and rockers when worn can make that rattle noise . Basically their excessively loose during the rotation of the camshaft even though their at spec at top dead center . I’ve seen the followers cuped were the camshaft pushes on them as well .

    Another thing to check is the tappet adjustment screw , sometimes they get worn on an angle were they touch the valve and make it impossible to get a good adjustment .

    The camshaft does have a decompression mechanism built into it and if stuck open or worn can cause the that rattle as well .
    Last edited by shortline10; 02-01-2021 at 07:21 AM.
    78 atc 90/180cc Dickson Full Suspension
    76 ATC90/180cc Nicholson
    77 atc 90 Dickson Full Suspension
    84 KLT 110/123cc Powroll Racer from 80s
    87 atc 125m stock
    84 atc 200x Curtis Sparks
    84 atc 200x Powroll My race bike from 80's
    83 atc70/108cc Powroll blue Xmas Special
    81 atc185s HP-ATC full suspension

    Performance Shop is Open PM me for Service

    My Feedback http://www.3wheelerworld.com/showthr...ck+shortline10

  11. #11
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    illinois
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    It wasn't the rockers, it must be a defective NICHE cylinder/piston kit. First time I used this after market brand, I've bought others without any issues. I will tear it back down Sunday

  12. #12
    Join Date
    Jul 2009
    Location
    South Florida
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    I’ve run into this several times with the 350/450 models
    It usually ends up bending a valve or loss of compression .


    Quote Originally Posted by Shep1970 View Post
    Lurking around the web- it seems some 350 ranchers have valve seat issues- again i have no idea if this is your problem but over the last hour i must of read 10 different posts about loose valve seats or failing altogether. I'd imagine though if u had it apart you'd of noticed something. Just an example-
    https://www.hondaatvforums.net/threa...ve-seat.99594/

    shep
    78 atc 90/180cc Dickson Full Suspension
    76 ATC90/180cc Nicholson
    77 atc 90 Dickson Full Suspension
    84 KLT 110/123cc Powroll Racer from 80s
    87 atc 125m stock
    84 atc 200x Curtis Sparks
    84 atc 200x Powroll My race bike from 80's
    83 atc70/108cc Powroll blue Xmas Special
    81 atc185s HP-ATC full suspension

    Performance Shop is Open PM me for Service

    My Feedback http://www.3wheelerworld.com/showthr...ck+shortline10

  13. #13
    Join Date
    Dec 2009
    Location
    illinois
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    1,763
    Figured it out.. it was DEFINITELY the NICHE cylinder kit.. the bores are out of spec. It sounded fine at Idle but when I give it gas it would rattle. Clearance between the cylinder wall and the piston was .005 . The seller on eBay sent me another and it sounded exactly the same, similar clearance also. So I installed a different brand I normally use and it sounded perfect.. nothing better than OEM but I'm staying away from this NICHE brand!
    Attached Images Attached Images

  14. #14
    Join Date
    Jul 2009
    Location
    South Florida
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    So do you know if the bore was to big or the piston was made to small ?
    Like I said earlier I use their cylinders all the time but never use their pistons .
    I have two niche rancher 350 cylinders in stock , I use prox pistons with them and never had that problem .
    78 atc 90/180cc Dickson Full Suspension
    76 ATC90/180cc Nicholson
    77 atc 90 Dickson Full Suspension
    84 KLT 110/123cc Powroll Racer from 80s
    87 atc 125m stock
    84 atc 200x Curtis Sparks
    84 atc 200x Powroll My race bike from 80's
    83 atc70/108cc Powroll blue Xmas Special
    81 atc185s HP-ATC full suspension

    Performance Shop is Open PM me for Service

    My Feedback http://www.3wheelerworld.com/showthr...ck+shortline10

  15. #15
    Join Date
    Dec 2009
    Location
    illinois
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    1,763
    Quote Originally Posted by shortline10 View Post
    So do you know if the bore was to big or the piston was made to small ?
    Like I said earlier I use their cylinders all the time but never use their pistons .
    I have two niche rancher 350 cylinders in stock , I use prox pistons with them and never had that problem .
    Yup.. I used a different aftermarket piston in the NICHE cylinder and it sounds great. It's the pistons that comes with the NICHE kits they sell on eBay.... So the cylinders are fine, the pistons have too much clearance

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