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Thread: 1986 ATC 350X top end questions

  1. #1
    Join Date
    Aug 2006
    Location
    new hampshire
    --
    876

    1986 ATC 350X top end questions

    I sent my head to the machine shop to get checked out. OEM valves are no longer available. Are versah valves a good quality valve?
    Im a parts unlimited dealer and can get a good price on the 12;1 Wiseco piston and the valves. I guess I'm looking for the best set up with out modifying to much. I have the bottom end together with a new rod and bearings. What are you guys using for valves, piston, and cam?
    I have used the search button and its to much to take in.
    Thank you
    shawn
    1983 ATC 200E
    1984 ATC 200S
    1985 ATC 70
    1985 ATC 200S
    1985 ATC 250R
    1986 ATC 350X
    2004 kfx 700 XC
    2006 prarie 700 XC

  2. #2
    Join Date
    Jul 2005
    Location
    Manheim PA 17545
    --
    5,139
    You guys need top stop with the heavy high comp pistons. Flt cut cyclinder base will raise the compression the same but keep weight off the crank bushings/ bearings. 5angkw valve job, porting and a cam will rip your arms off. My guy fly cuts cylinders normally $80...your double that for a heavy piston. I just did another motor. Veshra valves are fine, kibble white is best but most trail riders dont head them.
    1988 Warrior
    2002 Blaster
    2015 Rancher 420 dct eps irs

  3. #3
    Join Date
    Apr 2014
    Location
    Edmond, KS
    --
    1,864
    My 350X with stock compression can be a bear to kick over sometimes. I can't imagine trying to start it with higher compression.

  4. #4
    Join Date
    Aug 2006
    Location
    new hampshire
    --
    876
    I put 11.5:1 piston and a big web cam in my kfx 700 and it turned into a monster. It was also fairly cheap and easy to do. Was a great bang for the buck. I just do not know what works well to gather as far as parts go on the 350. I’m looking for a little more then what a stock 350 puts out which I feel is u dear powered. Was great 35 years ago... so can some one recommend some packages that work well together so I can start shopping. My two and a half year project needs to get finished.
    1983 ATC 200E
    1984 ATC 200S
    1985 ATC 70
    1985 ATC 200S
    1985 ATC 250R
    1986 ATC 350X
    2004 kfx 700 XC
    2006 prarie 700 XC

  5. #5
    Join Date
    Aug 2008
    Location
    devore,ca
    --
    924
    I Run 10.25:1 wiesco pistons in all my 350x's. I don't remember paying all that much for them. I'm not sure if it gives it any more power but it definitely makes it run better. And if the valves are still in decent shape I just clean them and lap them in until they seal nice again.
    YAMAHA 450 HYBRID
    85 350X- RED
    85 350x -BLACK
    86 350x-WHITE (with Goki)
    85 250r
    83 atc 70
    84 atc 70
    84 atc 110
    09 yfz 450
    2006 Arctic Cat Prowler
    RZR XP 900

  6. #6
    Join Date
    Aug 2006
    Location
    new hampshire
    --
    876
    I have ordered seals and valves I’m waiting on those. Where can I get an 11:1 piston? What cam should I be looking at?
    1983 ATC 200E
    1984 ATC 200S
    1985 ATC 70
    1985 ATC 200S
    1985 ATC 250R
    1986 ATC 350X
    2004 kfx 700 XC
    2006 prarie 700 XC

  7. #7
    Join Date
    Oct 2002
    Location
    Northeast
    --
    17,137
    You can't get an 11:1 piston, I have bought 12:1 pistons and turned them down on my lathe so I don't have to run race gas.

    There are complete Wiseco piston kits for 122$ shipped on Ebay. 81 or 81.5mm and 10.25 : 1, you'll be fine with that.

    There's people on FB saying they have an account at Wiseco and they get the best prices, but they want >160$

    Vesrah valves are just fine, porting the head is a great investment.

    You can't buy the timing chain guides anymore, super expensive when found.

    OEM timing chains are discontinued, they have aftermarket cam chains. If you want OEM cam chains, I have a few extras in my stash...
    WHO IS Q?? WWG1WGA!!


    86 ATC200X Flatrack ( I may not be fast but this is one FAST 200X!!

    86 ATC350X Motocross, 86 ATC452X Flatrack!!

    07 Weekend Warrior Toy Hauler

  8. #8
    Join Date
    Aug 2006
    Location
    new hampshire
    --
    876
    Thanks for the offer. I bought a moose cam chain looks to be good quality. I’ve been dicking around collecting parts for this thing since feb of 2018..... the end is near.
    1983 ATC 200E
    1984 ATC 200S
    1985 ATC 70
    1985 ATC 200S
    1985 ATC 250R
    1986 ATC 350X
    2004 kfx 700 XC
    2006 prarie 700 XC

  9. #9
    Join Date
    Aug 2006
    Location
    new hampshire
    --
    876
    I ordered the wiseco 10.25:1 piston where and what should I do for a cam??
    1983 ATC 200E
    1984 ATC 200S
    1985 ATC 70
    1985 ATC 200S
    1985 ATC 250R
    1986 ATC 350X
    2004 kfx 700 XC
    2006 prarie 700 XC

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