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Thread: Gx240/gx270

  1. #1
    Join Date
    Oct 2013
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    290

    Gx240/gx270

    Not karting related.
    Sorry guys, but often I find the best ideas come from racing.
    I never built a clone bigger than a 208.

    What are the stock parts solutions for the intermediate clones?
    I am looking for some ways to boost compression and improve VE on these for a natural gas conversion project I am working on but I don't want to do anything that will adversely effect the reliability of these clones.
    Application Natural gas fuel conversion 3600rpm generator prime mover.

    I see ARC has a rod that's probably a good idea to use for improved oiling.
    What else do you fellows think?
    Thanks in advance for advice

  2. #2
    Join Date
    Oct 2013
    Posts
    290
    Gentle poke at you fellows.
    I am doing something outside the envelope and speed parts are outside the envelope.
    Come on, any thoughts on building a natural gas engine?

  3. #3
    Join Date
    Oct 2013
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    3,610
    As most won't have NG experience, I will say any and all mods will benefit the same with any fuel, once you have the system to provide the correct amount of fuel. A generator will tie your hands as far as exhaust goes, and because you are limited by exhaust that will tie your hands on the intake. I would definately bump the compression give a small timing increase, run quality oil and not worry about the rod.

  4. #4
    Join Date
    Oct 2013
    Posts
    290
    I do appreciate the reply kart43

    I know not too many natural gas powered karts, but engines follow rules and I have a low cal high octane fuel. ( 130 they say but lets assume for reliability I do not exceed 10:1 and perhaps add some timing )
    I need compression and improved flow at 3600 rpm

    What have we got for head options and pistons?
    I don't have an engine yet but looking in the parts pictures it would appear the 240 piston is a flat top ( as seen in Sneaks builds from way back )
    This leads me to think the head is the same for both and the 270 is a larger dished.
    I might have to mill the head, unless there is a flat top available for the 270 ( does anyone know ? ).

    Kohler K181 is 18 cubic inches 305cc rated at 8 hp on gasoline 3600 rpm. ( less on natural gas so this engine was larger than the Gen head required for gasoline by maybe 25%, and a flat head with low compression ).
    Hard to say dealing with stuff this old, the gen head may have been de rated to match the weaker NG engine.
    I will not know until I strip and test things to find out specifics but I will error in the side of caution and say I need 8 hp.
    A GX200 could probably do it with little more than some simple mods.
    Bigger though is probably better to pull sustained loads so the range should be a 240 or 270 ( leaning towards a 270 )

    Have not even gotten into taper issues adapting the US made generator to the Jap crank ( both appear to use a standard SAE taper )

    Maybe these are questions I should put to tractor pulling guys that use the K range engines?
    Any imput is appreciated though thank you in advance

  5. #5
    Join Date
    Jul 2015
    Location
    Byron, Ga.
    Posts
    137
    Quote Originally Posted by WinstonSmith View Post
    I do appreciate the reply kart43

    I know not too many natural gas powered karts, but engines follow rules and I have a low cal high octane fuel. ( 130 they say but lets assume for reliability I do not exceed 10:1 and perhaps add some timing )
    I need compression and improved flow at 3600 rpm

    What have we got for head options and pistons?
    I don't have an engine yet but looking in the parts pictures it would appear the 240 piston is a flat top ( as seen in Sneaks builds from way back )
    This leads me to think the head is the same for both and the 270 is a larger dished.
    I might have to mill the head, unless there is a flat top available for the 270 ( does anyone know ? ).

    Kohler K181 is 18 cubic inches 305cc rated at 8 hp on gasoline 3600 rpm. ( less on natural gas so this engine was larger than the Gen head required for gasoline by maybe 25%, and a flat head with low compression ).
    Hard to say dealing with stuff this old, the gen head may have been de rated to match the weaker NG engine.
    I will not know until I strip and test things to find out specifics but I will error in the side of caution and say I need 8 hp.
    A GX200 could probably do it with little more than some simple mods.
    Bigger though is probably better to pull sustained loads so the range should be a 240 or 270 ( leaning towards a 270 )

    Have not even gotten into taper issues adapting the US made generator to the Jap crank ( both appear to use a standard SAE taper )

    Maybe these are questions I should put to tractor pulling guys that use the K range engines?
    Any imput is appreciated though thank you in advance
    Mill the head around .060 - .070" , port it well, go bigger on the intake valve, get a flat top piston, kick the ign. timing up to around 29 to 31 BTDC. also play with a longer exh. header and larger muffler. and yes the ARC rod has much better oiling and replacement inserts for wear up to .010" undersize.

  6. #6
    Join Date
    Oct 2013
    Posts
    3,610
    I can't see the exhaust header and muffler being a viable modification for a stationary generator, this build should be all reliability and low end torque.

  7. #7
    Join Date
    Sep 2018
    Location
    Boston ma
    Posts
    20
    how is the carb setup on the natural gas ? ..I know if you can optimize your air fuel ratio you will make efficient power ...I don't know what the ratio is with natural gas or how the carb meters it ...but if it's as close to perfect as you can get it , it will help !

  8. #8
    Join Date
    Sep 2018
    Location
    Boston ma
    Posts
    20
    The most important part of the engine is the intake valve and seat ...especially 1/4" before and after the seat ...if you optimize flow thru the seat you will increase low lift flow helping efficiency .. make the transitions smooth,even with each other and nice angles on seat and valve will help any engine ! Wether you want fuel efficiency or power ..

  9. #9
    Join Date
    Sep 2018
    Location
    Boston ma
    Posts
    20
    Ps...I have some info on big block engine building on my you tube channel...Paul's karts...you should find all kinds of info on intake flow,head porting,cam timing and selection,valves ,seats,carbs,best sizes,ratios,velocitys,efficiencys.. etc ...on the page ...! hope it helps ..

  10. #10
    Join Date
    Oct 2013
    Posts
    290
    Late getting back to this.

    So there is a flat top piston for the GX270 seems the 240 already a has one (and compression comes from milling on that engine).
    I read all the replies and thank everyone for thier input and I will post what I end up doing.
    Likely compression increase and more timing on a GX240 looking for small improvements in VE to compensate for lower BTU content of fuel ( but higher octane )

    Engine will only turn 3600 rpm as designed.
    Maybe a better scavenging exhaust and free flowing intake will help a little.

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