What carb to use with the big bore kit?

Discussion in 'Engine Mods and Swaps' started by turbowrenchhead, Sep 9, 2011.

  1. turbowrenchhead

    turbowrenchhead New Member

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    I have decided to go with a 240 big bore kit from ken. I just have to wait till have some funds to purchase it. In the mean time what carb can you use for the set up. I'm looking for something more affordable rather then extravagant. Are there any other machines that will cross over? I took a look on ebay for 36mm carb, there are so many that I wouldn't know which one to get. Can you eliminate the carb switch? What is the purpose of the carb switch?
     
  2. cole454

    cole454 Member

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    A 34pj should work well and be cheap. Can find them for 60-80 on ebay.
    The best would be a 35-36 PWK.
     
  3. turbowrenchhead

    turbowrenchhead New Member

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    What do the letters stand for?
     
  4. sicivicdude

    sicivicdude Member

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    If you ask your builder his opinion he'll tell you a Mikuni TM series carb in the 33-38mm size range. Also depends on the pipe choice, airbox setup, riding style, and choice of durability LOL.

    Bigger is better for top end power, smaller is better for torque. TOO large and there will be periods of low velocity through the carburetor throat where the vacuum signal won't be strong enough to pull fuel from the float bowl and that could cause fuel/oil starvation. TOO small a carb, and you'll be limiting your top end HP by not being to flow enough air into the engine.
     
  5. sicivicdude

    sicivicdude Member

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    They're "series" denominations.

    Keihin starts a lot of their carburetors off with "P" and then adds letters so you can tell their different carb designs apart....

    The PE carbs are 4 stroke smaller bore and much older design. PJ carbs are two stroke medium bore carbs, an older design that uses the choke knob as the idle adjustment, PWK is a more modern design "d" slide two stroke carb with a dedicated idle control circuit. PWK's are *generally* regarded as the benchmark carburetors for 2 strokes. Keihin has introduced a newer carb, the PWM which is supposed to have a little crisper throttle response and better top end power because of a shorter venturi.

    Mikuni has their own series of carburetors with their own numbering/lettering system. The stock blaster carb is a VM26 round slide
     
  6. turbowrenchhead

    turbowrenchhead New Member

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    I will probably use the stock airbox setup, due to the amount of water and mud that was on the trails. If there is just a unifilter hanging out there its going to get wet and muddy. As for a pipe I haven't even looked. I will probably use the stock one till I find a deal on a aftermarket. can one replace the rear section of the pipe?
    My riding style is usually full throttle or all brake. I like to ripe up the trails.
     
  7. sicivicdude

    sicivicdude Member

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    Don't take this the wrong way.... build your stock engine (porting) and put a decent pipe on it first before going with a BBK. If you go straight to the BBK with a stock pipe and airbox not only will the BBK disappoint it could actually be bad for its health.

    Corking up a big bore kit with a stock pipe and airbox is a poor idea.
     
  8. turbowrenchhead

    turbowrenchhead New Member

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  9. turbowrenchhead

    turbowrenchhead New Member

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    So what are my choices for a pipe and air box on a budget? The trails have a 96 db limit as well.
    My piston is melted with a broken skirt. So if I am going to rebuild I'm going to go with a bigger bore. The stock setup did not suffice.
     
  10. sicivicdude

    sicivicdude Member

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    1, or 4 if you can. They are PWK carbs, the CR250 quadvent is an Air Stryker carb.

    The stock piston melted because of an airleak or other jetting problem. Of course the stock setup didn't suffice with a stock pipe and airbox setup. Port the top end you have, get a good pipe (fmf, procircuit, dynoport, pual turner, F7, hell any aftermarket pipe), remove the airbox lid and rejet. Thing will sh*t and git like that.

    Once you get tired of the "regular" power a blaster has THEN stroke it and go with a big bore kit. A big bore kit without the supporting upgrades will disappoint you.... all you're adding is 40cc's of displacement.
     
  11. turbowrenchhead

    turbowrenchhead New Member

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    Last edited by a moderator: Sep 25, 2014
  12. sicivicdude

    sicivicdude Member

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    No, you need to replace the headpipe and silencer as a package deal.

    Look up "tuned expansion chamber" for a better idea of how it works and why the stock one stinks and the aftermarket ones are a WHOLE lot better.
     
  13. turbowrenchhead

    turbowrenchhead New Member

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  14. Clay250

    Clay250 New Member

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    I have 02 blaster with vitos big bore kit and full fmf exhaust vforce 4 reeds open air box what carb should i use 34mm or 35mm
     

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