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Thread: Atc 350x rebuild. Help and suggestions

  1. #1
    Join Date
    Feb 2017
    Location
    Corona CA
    --
    743

    Atc 350x rebuild. Help and suggestions

    So I had an appendicitis a few weeks ago. Iím fine. Due to the nature of what I do for a living Iím out for 7 weeks. Fortunately I live in California and have state disability so money wise Iím ok and had some savings. Iíve got time , money and an original 1985 piston in my 350x. Letís get started.
    I already have a 400ex carb and full exhaust I like. My plan is cam shaft from WEB and a wiseco piston.
    Anyone prefer a grind? I was leaning to the more aggressive 213 grind? Feel like these bikes have plenty of bottom and could use the top to help.
    Pistons? Iím gonna go with a wiseco, anyone on compression ? 10.25 or 12. Aware if I go to 12 Iíll probably be stuck on race gas with an aggressive cam. Is it a huge power difference?
    Final and bigger question is bore vs Hone? My bike ran and had good compression. Less than 5% difference than oem specs. Cylinder wall looks fine. I feel like I could order a oem size wiseco and save some money ? Thoughts ? And can I hone this myself ? Anyone suggest a good tool? Iím not a machinist but I am an ok mechanic. Or pay race tech to hone it for me ? Thanks guy and wish me luck !!


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  2. #2
    Ranvier is offline At The Back Of The Pack Arm chair racerAt the back of the pack
    Join Date
    Sep 2016
    Location
    Phoenix, AZ
    --
    305
    I recently bought a powroll 430 with cam and 12:1 piston. I haven’t had time to install it yet.

  3. #3
    Join Date
    Jul 2005
    Location
    Manheim PA 17545
    --
    4,962
    im not a fan of a heavier piston. You can get the same power and more reliablilty from a decked head porting and 5 angle valve grind. Your power is in the head more so then a domed piston. 12:1 should not require race gas. I had 13.5:1 compression in a raptor motor which only startes at 9:1 I ran 93 corn gas. I just prefere a ligth OEM piston and pulling the power out of the head...crank does not know the differance.
    2002 Blaster
    1983 tri moto 200
    2015 Rancher 420 dct eps irs

  4. #4
    Join Date
    Jun 2009
    Location
    Leander TX
    --
    2,218
    When I re-ringed my 86, it already ad a 10.25:1 piston in it. Fresh Wiseco rings and a dingle-ball hone.
    I also lapped the valves.

    Stock cam, EX carb, XR400 head with stock muffler.
    I only took it on one trip before selling so I can't speak to the longevity.

    I really liked the way it ran compared to my completely stock 85. Just crisper and a little faster. No smoke. Really ran better than I expected. I should do the same mods to my 85.

    I liked the stock cam because it was easier - no hardened rockers, no valve spring upgrades, etc.

    No race gas because I don't want to deal with it.

    The right thing to to is have a machine shop rebuild the head and check out the cylinder for you and decide what to to from there.
    And put a new timing chain in it.

    I'd sell you the hone for 1/2 price of new plus shipping if interested if you decide to go that route.

  5. #5
    Join Date
    Feb 2017
    Location
    Corona CA
    --
    743
    I dropped all my parts this week. Web for the cam. Went with the 213 grind. Seems most logical.
    Race tech is boring my cylinder and I went with a .5 over wiseco with the 12 to 1 compression. Race tech is looking at my head, gonna make a decision on porting. Might do it depends on how much they want. Also doing a new clutch with his springs. Not expecting this have 60 horsepower just maybe upper 30s. Seems reasonable. Thanks for the info guys.


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  6. #6
    Join Date
    Feb 2017
    Location
    Corona CA
    --
    743
    Quote Originally Posted by oldskool83 View Post
    im not a fan of a heavier piston. You can get the same power and more reliablilty from a decked head porting and 5 angle valve grind. Your power is in the head more so then a domed piston. 12:1 should not require race gas. I had 13.5:1 compression in a raptor motor which only startes at 9:1 I ran 93 corn gas. I just prefere a ligth OEM piston and pulling the power out of the head...crank does not know the differance.
    When you ported the head did you lose bottom end or reliability? How much will it run me appox?? Iím better off on 350x funds than I anticipated. I might do both. Trying to get the best bang for my buck since Iíll hopefully never do this again.


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  7. #7
    Join Date
    Jul 2005
    Location
    Manheim PA 17545
    --
    4,962
    I put $2200 into my motor and had 60hp...it was a torque monster and reved put like a 450. Guys a 450a road it abs said holly crap. I climbed everything from a dead stop. Brad from kb5ndustries did my motor. He does services a national race team...

    His head deck was 75 bucks. I added 5 new OEM valves with a 5 angle grind and his porting. I lost no reliability and it's the strongest bike I ever had. Head holds alot of hp. I was limited by carbs and if I wanted over 6php I need 39mm carbs...I'd feel power loss in 3rd on hills over 400ft. Walls at the tops were no issues with the right rubber on silt hills with 50-60% grade. My accident I july 2018 limited me from using the bike right so I left it go...now I'm good and looking for another ignore to do up for hills, flat riding is boring me.

    I had so much bottom end it had to be thrown away with a stage 2 cam and springs. What it needed was a plus 6 swinger cuz plus 4.5 was still making ne wheelie up hills. trail riding it I only could use 2nd gear. I never shifted. It felt like a very healthy yz426f if you ever read one youd know what I mean, just double its torque basickly.
    Last edited by oldskool83; 10-19-2019 at 09:08 PM.
    2002 Blaster
    1983 tri moto 200
    2015 Rancher 420 dct eps irs

  8. #8
    Join Date
    Mar 2010
    Location
    Slidell, LA
    --
    4,585
    Quote Originally Posted by oldskool83 View Post
    im not a fan of a heavier piston. You can get the same power and more reliablilty from a decked head porting and 5 angle valve grind. Your power is in the head more so then a domed piston. 12:1 should not require race gas. I had 13.5:1 compression in a raptor motor which only startes at 9:1 I ran 93 corn gas. I just prefere a ligth OEM piston and pulling the power out of the head...crank does not know the differance.
    This is interesting. Can you explain why you wouldn’t run race gas in a 12:1 setup?
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  9. #9
    Join Date
    Feb 2017
    Location
    Corona CA
    --
    743
    Quote Originally Posted by yaegerb View Post
    This is interesting. Can you explain why you wouldnít run race gas in a 12:1 setup?
    Iím not saying you couldnít or maybe I wonít even need to but, wiseco when asked about this exact piston said it would be fine on fresh 91 octane. Kevin at race tech agreed and showed me some stats on 450s , 15.5 to 1 on 91 octane. Of course these are water cooled more efficient heads but none the less. I have an 11 to 1 in my 400ex runs on 91 perfect. Dunlap says his 11.5 to 1 run on pump as well. The only thing everyone has agreed on if your getting it too hot it could detonate, but Iíve never gotten my 350 that warm. If your running say 100 octane and not using it your just losing power and wasting money.


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  10. #10
    Join Date
    Feb 2017
    Location
    Corona CA
    --
    743
    Quote Originally Posted by oldskool83 View Post
    I put $2200 into my motor and had 60hp...it was a torque monster and reved put like a 450. Guys a 450a road it abs said holly crap. I climbed everything from a dead stop. Brad from kb5ndustries did my motor. He does services a national race team...

    His head deck was 75 bucks. I added 5 new OEM valves with a 5 angle grind and his porting. I lost no reliability and it's the strongest bike I ever had. Head holds alot of hp. I was limited by carbs and if I wanted over 6php I need 39mm carbs...I'd feel power loss in 3rd on hills over 400ft. Walls at the tops were no issues with the right rubber on silt hills with 50-60% grade. My accident I july 2018 limited me from using the bike right so I left it go...now I'm good and looking for another ignore to do up for hills, flat riding is boring me.

    I had so much bottom end it had to be thrown away with a stage 2 cam and springs. What it needed was a plus 6 swinger cuz plus 4.5 was still making ne wheelie up hills. trail riding it I only could use 2nd gear. I never shifted. It felt like a very healthy yz426f if you ever read one youd know what I mean, just double its torque basickly.
    Yeah thatís more than I want /need and am willing to spend. But I would like to break into the 40hp range. Make it feel like my mild 400ex. Iíll talk to my guy on Monday see what he thinks. Thanks.


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  11. #11
    Join Date
    Mar 2010
    Location
    Slidell, LA
    --
    4,585
    Quote Originally Posted by Shawn Powell View Post
    I’m not saying you couldn’t or maybe I won’t even need to but, wiseco when asked about this exact piston said it would be fine on fresh 91 octane. Kevin at race tech agreed and showed me some stats on 450s , 15.5 to 1 on 91 octane. Of course these are water cooled more efficient heads but none the less. I have an 11 to 1 in my 400ex runs on 91 perfect. Dunlap says his 11.5 to 1 run on pump as well. The only thing everyone has agreed on if your getting it too hot it could detonate, but I’ve never gotten my 350 that warm. If your running say 100 octane and not using it your just losing power and wasting money.


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    I wasn’t referring to your post.
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  12. #12
    Join Date
    Feb 2017
    Location
    Corona CA
    --
    743
    For anyone listening I went ahead and gave Andrew at race tech the ok to do a 5 angle valve job and port my head. Everything Iíve read and heard is you can get a lot of power from these. Heís pretty confident he can do it and has some very good documented result on similar bikes.(400ex xr600/650)
    So between that a 12-1 wiseco and my 213 cam from web and my existing exhaust and 38mm carb I should hopefully be running pretty strong. Anyone have a guess on horsepower numbers? Iím hoping high 30s. Low 40s really but I just feel thatís being delusional.


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  13. #13
    Join Date
    Jul 2005
    Location
    Manheim PA 17545
    --
    4,962
    send motor over to brad...he has 4 or 5 locations in the USA.
    2002 Blaster
    1983 tri moto 200
    2015 Rancher 420 dct eps irs

  14. #14
    Join Date
    Sep 2010
    Location
    NEPA
    --
    7,032
    I think you will be very happy with your results. There will still be some left on the table, but doubt you will ever want it.
    Please help those who cannot help themselves.

    ALWAYS buying Museum quality machines,3 and 4 wheels. And any and ALL ,NOS parts,EVERY brand.

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  15. #15
    Join Date
    Feb 2017
    Location
    Corona CA
    --
    743
    Quote Originally Posted by atc007 View Post
    I think you will be very happy with your results. There will still be some left on the table, but doubt you will ever want it.
    Yeah for sure. I didnít wanna spend 4500 bucks for a big bore with machined in valves and get all crazy for 1985 suspension to not work right. At that point I would have sold mine and bought a 450 conversion.Thanks.


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