my second build.need advice on tunning

Discussion in 'Introduce Yourself' started by redrider8605, May 4, 2014.

  1. redrider8605

    redrider8605 New Member

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    I started the build with a brand new 26" Motobecane 400HT.The bikes parts spec includes a Longer travel Suntour 100mm fork with adjustable pre-load, competitive race quality 24 Speed Shimano Alivio parts and powerful Tektro disc brakes. Also has double wall rims and sealedsealed bearings. I went through JNMotors.com and got there 66/80cc sms black engine kit. This is a great engine they go through the engine and change the bearings and out a better intake setup on it then give a 3 month warranty with it. I then purchased the 2-stroke HD shifter kit from sickbikeparts.com. this bike turned out beautiful and rides amazing. My last bike was a29er from Wal-Mart and picked up a motor kit locally and after that got stolen I wanted to do this build right. The break in is now complete and I opened up the baffle inside the stock exhaust and drilled one more whole in the cap and put it back together. I then customized the air filter housing to allow more air flow. I then opened up the intake port on the outside of the cylinder head and the intake manifold. I noticed a huge improvement in power.

    I need some advice on tunning issues. The bike came with the nt speed carburetor and the bike is running lean on the top end and I'm having to run it rich on low to mid because I don't have the main jet. I'm thinking of getting a expansion chamber exhaust and the upgraded to the ufo air filter. Are there any better carburetor out there or is thete somewhere i can get a main jet kit? And is it worth spending the money on the new exhaust, air filter, and carburetor? Any advice would greatly be appreciated.
     

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  2. Ronzworld

    Ronzworld Member

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    looks good ... how does it go ?
     
    #2 Ronzworld, May 5, 2014
    Last edited: May 5, 2014
  3. Theon

    Theon New Member

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    Personally I like the speed carb.
    You are better off buying a set of drills than trusting the size of the jets you buy.
    I build my own exhausts, however others claim improvements from of the shelf expansion chambers, I'd go for something better than a 'banana pipe'.
    I got a noticeable improvement from port matching the standard pipe.
    Ditching the slant head is where I'd start.
    Nice bike.
     
  4. redrider8605

    redrider8605 New Member

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    I am running the speed carb and have look into drill bits but I havent had any luck finding smaller drill bits. Where can I go to get micro drill bits? My next step will be to open up the exhaust like you suggested.
     
  5. redrider8605

    redrider8605 New Member

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    So I got my carburetor tuned right finally and runs clean and Smith through the whole rpm range. It just doesn't seem to have enough air flow with this carburetor. I have a different intake manifold matched the ports on the intake and exhaust and opened up the exhaust where it connects to the cylinder. I have read that the cns carb has a bigger opening and it had more fine tuning adjustments on it so here is the issue...........


    I just picked up a used cns carburetor and I just fully I disassembled and cleaned everything and made sure everything was correct. QUESTION? ??? Where should i start out with the settings on this carburetor for the start. Clip position, air screw, and idle screw before I put it on the bike and start it up?
     
  6. Ronzworld

    Ronzworld Member

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    Hello my friend .. for starters I would suggest the needle clip be in the center position , the idle air screw around 1/4 - 3/4 of a turn out from a "gently" closed position and the idle screw you watch the slide through the air cleaner opening and turn it in until the slide starts to move upward , once it starts to move a good guess would be about 1/2 a turn .This should get the motor to start and at least let you get into tuning .
    Good luck !!
    Ron
     
  7. redrider8605

    redrider8605 New Member

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    Thanks Ron really appreciate it. I will finish putting it together and try it out tomorrow and give an update of how she ran.
     

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