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Thread: 85 honda350x big bore questions?

  1. #1
    Join Date
    Sep 2018
    Location
    Arizona
    --
    4

    85 honda350x big bore questions?

    I have a stock 85 Honda 350x. I am looking at the kustom kraft big bore kits.They say bolt it on an break it in...I am new to the big bore options etc.. I know just some of what I have read on old posts. Bigger carb.. 400ex...crf 450...Pipe the bike what do you think is a good recommended place of start...over size clutch springs...where do you get them ? What brand etc..? I believe anything over 12:1 ratio must run high octane fuel. ..For the most I think that would be a good starting point. ..Anything about it would be greatly appreciated!

  2. #2
    Join Date
    Feb 2017
    Location
    Corona CA
    --
    675
    Keep on mind scooter , with any of the big bore kits over 426 you have to split the cases and bore them as well. With the 452 kit from KK youíll need to have some one port the head and for best results get bigger valves in there. Look at Fourstroketech.net Mickey has a 500 kit and lists all the hinge he does to make it breath. Valves porting 450r carb etc. gets real expensive real fast. Personally if I had just bought my 350 Iíd go with the HRE header( uses a 450r can OEM or aftermarket) a 400ex carb a 12 to 1 wiseco (pump gas ) and a semi mild cam from Webb (with stiffer springs) then go to racetech and get your suspension done. You could have some mild porting done for the new flow give an extra bump. Clutch isnít necessary unless you need one honestly. Hope that helps.


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  3. #3
    Join Date
    Mar 2010
    Location
    Slidell, LA
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    4,381
    Where are you finding a 12:1 pump gas piston?
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  4. #4
    Join Date
    Feb 2017
    Location
    Corona CA
    --
    675
    Quote Originally Posted by yaegerb View Post
    Where are you finding a 12:1 pump gas piston?
    Wiseco says properly jetted 91-93 octane is fine. Hell the new Kawasaki 450 has 13.9 to 1 compression from the factory and it recommends 92. Dunlap sells 11.5 to 1 pistons he swears run on pump for almost every bike he works on. I have an 11 to 1 in my 400 and I run 91 all the time. You do have to bump a main jet size up one typically.


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  5. #5
    Join Date
    Mar 2010
    Location
    Slidell, LA
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    4,381
    Quote Originally Posted by Shawn Powell View Post
    Wiseco says properly jetted 91-93 octane is fine. Hell the new Kawasaki 450 has 13.9 to 1 compression from the factory and it recommends 92. Dunlap sells 11.5 to 1 pistons he swears run on pump for almost every bike he works on. I have an 11 to 1 in my 400 and I run 91 all the time. You do have to bump a main jet size up one typically.


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    Have you ever performed a UCCR is a Kawasaki 450 or see where the squish is at? The compression of a piston is only half the story. I wouldn’t be recommending a 12:1 compression piston to guys if you don’t know what the squish or uccr is on their particular motor. 11:1 in your 350x on 91...sure it’s borderline. To the OP....running 12:1 in your 350x all things being equal, I would recommend a lower octane race fuel to be safe or run a 11:1 all day on 93.
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  6. #6
    Join Date
    May 2015
    Location
    San Diego, CA
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    1,162
    Quote Originally Posted by Shawn Powell View Post
    Hell the new Kawasaki 450 has 13.9 to 1 compression from the factory and it recommends 92.
    Isn't that crazy?

    Uncorrected test or not it's impressive what modern digitally controlled machines can do. My old 86 GSXR1100 was very close to 10.1 and that was close to the acceptable maximum of its day. Now the new 1000 are like 12.5.1...on pump and will even adjust for lower grade fuels. The only way to get 170HP and be EPA/DOT compliant and have a motor well mannered, reliable, good temperament, outstanding performance and be 12.5. 1 and run on ARCO pump gas is to be computer controlled.......everything the 350X isnt.

  7. #7
    Join Date
    Feb 2017
    Location
    Corona CA
    --
    675

    85 honda350x big bore questions?

    When I asked wiseco I specifically asked about there 82mm piston for the 350x and there answer was premium fresh pump is fine. When I get mine installed Iíll keep everyone posted I guess. I feel like I just started an oil thread. Sorry.


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    Last edited by Shawn Powell; 09-21-2018 at 04:28 PM.

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