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Thread: 350x top end rebuild need help please!

  1. #1
    Join Date
    May 2005
    Location
    Michigan
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    Question 350x top end rebuild need help please!

    Hey guys, rebuilding a 86 350x motor. I need the tq specs for the head, and a rundown on how to time it correctly. There are 8 and 10 and 14mm bolts, I am assuming differend tq specs for each. Can someone with a manual tell me what they are? I guess more importantly though I need to know how to retime it properly. I don't know if this makes a difference, but I have the 12:1 40 over wisco piston. I am getting the rest of the parts tomorrow (tusday) and want to get the motor back together tuesday night. Thanks.
    83 Honda ATC250r
    87 TRX 250x with ATC 350x motor
    98 Polaris Trail Blazer 250
    89 Kawasaki KLR 250
    99 Yamaha WR400F

  2. #2
    Join Date
    Oct 2004
    Location
    Opelousas, Louisiana
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    1,337
    a manual would answer alot of questions and help you out big time.
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  3. #3
    Join Date
    Jul 2005
    Location
    Richland WA
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    808
    If you cant find a manual, search the internet for screw and bolt torque charts, I know they are out there - if you cant find them, I have them in an engineering book somewhere. The compression does not govern the bolt torque, thats a static torque reading although high compression does increase the torque when the fuel goes boom. I might reduce it a pound or two with a high comp motor.

    The most important thing is to cross tighten the screws to prevent head warpage.

  4. #4
    atckowalski is offline Formerly "aaakowalski" Arm chair racerJust too addicted
    Join Date
    Nov 2002
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    Northern Mi.
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    516
    I have a manual and just reassebled my 350x but it is at camp but I can post later tonight if nobody else does.I could go by memory if I had one To time it correctly you should first,bring piston to top dead center (tdc) Do this by lining up the (T) mark on the flywheel in the small window on the left side case.Now insert your cam (lobes down!) followed by the cam sprocket with the bolt hole with the small mark next to it up(it looks simillar to a mark left by a center punch) This can be very tight so take your time and don't worry if it is.insert the bolt and tighten then rotate the motor until the other bolt hole comes around and insert cam sprocket bolt 2.( I think it is 12lb tg)After that check the back side of the cam sprocket to see if there is a straight line on each side at 9 oclock and 3 oclock and check your timing window again to make sure eveything is lined up.At this point it might be a good idea to grab the front of the motor and try to slowly turn it over while looking down in the motor to see if the piston clears the valves.If everything looks good the timing should be set correctly, if you hear alot of noise coming from the top of the motor it is just the cam chain, the noise will disappear when you install the cam chain tensioner. I will try rto post the rest of the setting later.
    1985 Ytm 225 dr (Black and gold)
    1984 Kxt 250 A1 Tecate
    1981 KLT200a1
    1983 Yt 175
    1985 Atc 350x
    1983 Klt 200 C
    1985Ytz250 Tri z

  5. #5
    Join Date
    Feb 2004
    Location
    Tionesta, PA
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    A quick word of advice - if you are rebuilding a 350X topend, and especially putting in a higher compression piston, rebuild the bottom end too. If you don't you have a really good chance of scattering the bottom end. Just think about it.
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  6. #6
    atckowalski is offline Formerly "aaakowalski" Arm chair racerJust too addicted
    Join Date
    Nov 2002
    Location
    Northern Mi.
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    516
    Here are the torque setting for the cylinder head'
    Install the 2 bolts and 4 nuts in this sequence in 2 or 3 steps.(Don't tighten them all at once)
    cap nut; 3.5-4.5 kg, 25-32 ft lb (there are 2 of these)
    bolt; 3.5-4.5kg, 25-32 ft lb (there are 2 of these)
    sequence is
    1 bolt on intake side
    then as you work your way clockwise 3, 5, 2, 4, 6
    3 being in the 2 o'clock position (nut)
    5 being in the 4 o'clock position(nut)
    2 being in the 6 o'clock position (Bolt)
    4 being in the 8 o'clock position (nut)
    6 being in the 11 o'clock position (nut)


    Then
    Tighten the cylinder head cover bolts in a crisscross pattern in 2 to 3 steps starting with the center bolt.There are 14 bolts
    7 mm bolts (10mm socket) 1.3-1.7 kg 9-12 ft lb
    6mm bolts (8mm socket) 0.8-1.2 kg 6-9 ft lb
    Again you will want to make sure that everything is right in the motor before you put it back in the frame.Good Luck!!
    1985 Ytm 225 dr (Black and gold)
    1984 Kxt 250 A1 Tecate
    1981 KLT200a1
    1983 Yt 175
    1985 Atc 350x
    1983 Klt 200 C
    1985Ytz250 Tri z

  7. #7
    Join Date
    Jan 2005
    Location
    RI
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    hope these help...let me know if you need others...

  8. #8
    Join Date
    May 2005
    Location
    Michigan
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    15
    Thats perfect! Thanks guys...
    83 Honda ATC250r
    87 TRX 250x with ATC 350x motor
    98 Polaris Trail Blazer 250
    89 Kawasaki KLR 250
    99 Yamaha WR400F

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