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Thread: 350X 400EX Transplant Build!

  1. #1
    Join Date
    Mar 2010
    Location
    Freedom Township, MI
    --
    641

    350X 400EX Transplant Build!

    Iíve been wanting to put a 400ex engine in a 350x for a few years now. When I originally starting searching I couldnít find anyone who had actually completed the project; just speculation or in some cases abandoned projects. Then came along ďTop Notch 350xĒ who was actually successful in the idea. Whilst he didnít write a long detailed build of it, he did post some really important details and so thus far I believe heís the only one to actually go through with it.

    The bones of the project:
    I originally bought this 350x back in 2011. The frame was trashed so I bought a pristine 86 frame from someone here on the boards. I actually ended up selling and rebuying this same 350x twice. Itís not going to be sold again, itís a solid foundation for what I want to do. Hereís what it looked like the day I brought it home (with the bad frame):




    This is what it looked like before I started tearing it apart:


    Part of the reason I havenít started until now was because I was waiting for the right deal to come along for a 400ex. Ebay has engines priced for what I can get a whole quad for which if I bought the quad I would also get the carb, electronics, exhaust, etc. So it didnít make sense to buy just the engine. I found plenty of good deals on first gen 400exís but I wasnít going to do it unless it had reverse too so I needed a 2005 and up. Finally the right deal came along-I traded another 350x I had for a 2006 400ex with first gen plastics. This thing was hideous and was obviously ridden hard but the engine ran good and thatís all I really cared about.





    I had quite the time getting this engine out as the swingarm bolt was seized to the bushings. Had to cut it out.


    Got the engine out and traded the roller for a kx80 project which I then sold on craigslist. So overall I did much better than buying just the engine online, plus this way I could hear it run.


    And hereís the engine sitting in the X for the first time. Only the bottom bolt is holding it.


    Current Trikes:
    85 350x
    P3 (x2)

    Quads:
    2003 Polaris Predator 500
    1988 Yamaha Warrior
    2003 Polaris Predator 90

    Previous Trikes:
    84 Honda 110 (parts)
    85 Honda 110
    85 Honda 200x
    87 Honda 200x
    85 Honda 250sx
    KX 80 Trike conversion

    Gone and missed:

  2. #2
    Join Date
    Aug 2014
    Location
    South Louisiana
    --
    1,915
    Looks good. Do you plan on modding the swingarm so the bolt goes through the motor. It's probably your best shot to make everything fit tightly. Just remember to measure twice and cut once...
    "Roll on 3"

    RIP Ol' Deuce

    "Long Live the ATC"
    Building: ATCr125x
    Riding: ATC200sx
    "I am not a mechanic, mechanics get paid for this. I do it because I enjoy it."

  3. #3
    Join Date
    Mar 2010
    Location
    Freedom Township, MI
    --
    641
    Quote Originally Posted by Jmoozy27 View Post
    Looks good. Do you plan on modding the swingarm so the bolt goes through the motor. It's probably your best shot to make everything fit tightly. Just remember to measure twice and cut once...
    Nope. I actually used the mount right below the swing arm mount. I'm further than what's in the above post. I have more pics but it's hard to post from my phone. More to come tomorrow.
    Current Trikes:
    85 350x
    P3 (x2)

    Quads:
    2003 Polaris Predator 500
    1988 Yamaha Warrior
    2003 Polaris Predator 90

    Previous Trikes:
    84 Honda 110 (parts)
    85 Honda 110
    85 Honda 200x
    87 Honda 200x
    85 Honda 250sx
    KX 80 Trike conversion

    Gone and missed:

  4. #4
    Join Date
    Feb 2010
    Location
    Blossvale NY
    --
    4,542
    This build has my interest. As much as I love the 350x, it's hard to deny the plethora of aftermarket support for mods with the 400 mill! Plus there's the issue with worn cam journals making paperweights out of 350 heads and the fact that there are less good 350 heads out there as time goes on makes this problem get steadily worse as time passes.

    Reverse, just cool.

    What's your plan for the battery??
    Trikes:
    '85 ATC 350R
    '85 ATC 250R
    '86 ATC 350X
    '85 ATC 350X
    '84 ATC 200ES Big Red
    '84 ATC 125M
    '85 ATC 110
    '85 ATC 70/110

    If you have bought from me or sold to me, please leave me feedback here>>> http://www.3wheelerworld.com/showthr...+RIDE-RED+250r

  5. #5
    Join Date
    Oct 2013
    Location
    Wherever I May Roam
    --
    3,757
    Joe, are you aware that the trx350 heads 86-89 are a direct replacement?

    Unless I'm making that up, like the rest of my stories.

    Yep all I can think is 440x.

  6. #6
    Join Date
    Jan 2015
    Location
    LaGrange, OH
    --
    253
    Wow definitely going to be following this build! I've been wanting to do one of these too with my 350 roller.

  7. #7
    Join Date
    Mar 2010
    Location
    Freedom Township, MI
    --
    641
    I'm planning to use a really small motorcycle battery. There are some that are the size of a multi meter. I'll figure out somewhere to mount it. Probably in place of or on the opposite side of the tool box.
    Current Trikes:
    85 350x
    P3 (x2)

    Quads:
    2003 Polaris Predator 500
    1988 Yamaha Warrior
    2003 Polaris Predator 90

    Previous Trikes:
    84 Honda 110 (parts)
    85 Honda 110
    85 Honda 200x
    87 Honda 200x
    85 Honda 250sx
    KX 80 Trike conversion

    Gone and missed:

  8. #8
    dman10's Avatar
    dman10 is offline At The Back Of The Pack Arm chair racerAt the back of the pack
    Join Date
    Jul 2013
    Location
    Elgin, TX
    --
    402
    Keeping tabs on this one. Got a 350x frame here that needs a heart
    Quote Originally Posted by tri again View Post
    Cool stuff seems to happen when I'm sleeping.
    Nice to know things happen without me.

  9. #9
    Join Date
    Feb 2010
    Location
    Blossvale NY
    --
    4,542
    Quote Originally Posted by DohcBikes View Post
    Joe, are you aware that the trx350 heads 86-89 are a direct replacement?

    Unless I'm making that up, like the rest of my stories.

    Yep all I can think is 440x.
    Yes Sir I am aware. But are there many of those still out there these days?
    Trikes:
    '85 ATC 350R
    '85 ATC 250R
    '86 ATC 350X
    '85 ATC 350X
    '84 ATC 200ES Big Red
    '84 ATC 125M
    '85 ATC 110
    '85 ATC 70/110

    If you have bought from me or sold to me, please leave me feedback here>>> http://www.3wheelerworld.com/showthr...+RIDE-RED+250r

  10. #10
    Join Date
    Oct 2013
    Location
    Wherever I May Roam
    --
    3,757
    Well I guess I didn't make it up. How unlike me to be honest.

    http://m.ebay.com/sch/i.html?_nkw=Tr...+cylinder+head

    Be sure to spot the 4 valve heads.

    Here's a nice one. http://m.ebay.com/itm/86-89-Honda-Fo...EAAOSwvU5XM4sU

    Even have fresh rebuilt listed there somewhere.

    Seems pertinent to the thread. Carry on.

  11. #11
    Join Date
    Aug 2008
    Location
    devore,ca
    --
    1,006
    What are the advantages you are looking for over the 350x motor ?. I have thought of this conversion off and on through the years and ended up talking myself out of it many times. The only real advantage I came up with was the electric start. I think the ex motor was only about a 1 hp gain ( may be very wrong on this) and the big problem I had with it was having to find somewhere to mount a oil tank. Maybe engine parts are more available ?.
    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

  12. #12
    Join Date
    Mar 2010
    Location
    Freedom Township, MI
    --
    641
    Quote Originally Posted by BOB MARLIN View Post
    What are the advantages you are looking for over the 350x motor ?. I have thought of this conversion off and on through the years and ended up talking myself out of it many times. The only real advantage I came up with was the electric start. I think the ex motor was only about a 1 hp gain ( may be very wrong on this) and the big problem I had with it was having to find somewhere to mount a oil tank. Maybe engine parts are more available ?.
    The advantages for me are as follows:
    -Electric start
    -Reverse
    -Lighter engine (don't know the exact numbers but I do believe it's lighter)
    -More aftermarket support/parts availability

    Other than that I don't know what to tell ya. It's something that I've wanted to do for a while. The overall idea is to end up with a more modernized 350x. A 450 hybrid would be cool but a bit out of reach for me plus I really like the 350x so a modernized version of it really appeals to me.
    Current Trikes:
    85 350x
    P3 (x2)

    Quads:
    2003 Polaris Predator 500
    1988 Yamaha Warrior
    2003 Polaris Predator 90

    Previous Trikes:
    84 Honda 110 (parts)
    85 Honda 110
    85 Honda 200x
    87 Honda 200x
    85 Honda 250sx
    KX 80 Trike conversion

    Gone and missed:

  13. #13
    Join Date
    Mar 2010
    Location
    Freedom Township, MI
    --
    641
    Motor Mounts. The only mount that lines up is the bottom 220mm long bolt. The spacers don't work but at least you can get the bottom bolt through so that the rest of them can be worked. on. I decided to start with the front mount since it was the easiest to access for measuring purposes. I measured and designed the mount in CAD and than cut the design out with a laser. The mounts are made of 5mm thick stainless steel! Plenty of strength here:


    Here's the first mock up of the front mount:


    I went ahead and upgraded all of the bolts to M10's. The front mount previously were M8's but the sleeve was big enough for an M10 so and M10 is what it got. I wasn't happy with the way the mount contacted the engine block so later I went and trimmed the design and recut the front 2 mounts on the laser.
    Current Trikes:
    85 350x
    P3 (x2)

    Quads:
    2003 Polaris Predator 500
    1988 Yamaha Warrior
    2003 Polaris Predator 90

    Previous Trikes:
    84 Honda 110 (parts)
    85 Honda 110
    85 Honda 200x
    87 Honda 200x
    85 Honda 250sx
    KX 80 Trike conversion

    Gone and missed:

  14. #14
    Join Date
    Mar 2010
    Location
    Freedom Township, MI
    --
    641
    Next I decide to tackle the upper mount. For this I first had to replace the rocker cover as I didn't notice the mount was broken when I bought the quad.



    Ended up getting a good deal on a cover off of someone on Facebook. While waiting for the head to come I decided to go ahead and see where the engine needed to sit to line up with the sprocket, carb, etc. Center of the mounts seemed to be where everything lined up well:



    Chain is just laying in this picture, that's why the bottom looks tweaked.



    Exhaust doesn't really fit without a fight. The end of it will need to have the angle reduced in order to work properly.

    Current Trikes:
    85 350x
    P3 (x2)

    Quads:
    2003 Polaris Predator 500
    1988 Yamaha Warrior
    2003 Polaris Predator 90

    Previous Trikes:
    84 Honda 110 (parts)
    85 Honda 110
    85 Honda 200x
    87 Honda 200x
    85 Honda 250sx
    KX 80 Trike conversion

    Gone and missed:

  15. #15
    Join Date
    Aug 2014
    Location
    South Louisiana
    --
    1,915
    Those mount plates look badazz. It sure beats a cut off wheel and shaping with a bench grinder for hours.
    "Roll on 3"

    RIP Ol' Deuce

    "Long Live the ATC"
    Building: ATCr125x
    Riding: ATC200sx
    "I am not a mechanic, mechanics get paid for this. I do it because I enjoy it."

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