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Thread: 88cc big bore questions

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    corner27 is offline 50cc
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    88cc big bore questions

    I recently bought a CT70K4. I have the top end of the engine apart and the piston/cylinder don't look the best. I could probably get away with using them, but my thoughts were IF I'm going to repalce them, I might as well upgrade to the 88cc kit.
    My question is, will I have to upgrade the carb and exhuast as well, or can I get away with stock? If I need to upgrade those as well, I might just end up sticking all stock.

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    OLD CT's Avatar
    OLD CT is offline 120cc
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    Depends on how much 10 mph is worth to you.I figure 73 bucks worth of parts will make it happen.You could rejet your stock carb or buy a 28 dollar aftermarket carb and use your stock exhaust.Hi volume oil pump,re-jet,counter sprocket.$200 all in 88 kit included before head work.The head done right is where it adds up quick,and needs to be rebuilt either way.
    Last edited by OLD CT; 05-19-2013 at 06:52 AM.
    I fart alot because it's the only gas i can afford...

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    lukelaw1 is offline 120cc
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    Quote Originally Posted by OLD CT View Post
    Depends on how much 10 mph is worth to you.I figure 73 bucks worth of parts will make it happen.You could rejet your stock carb or buy a 28 dollar aftermarket carb and use your stock exhaust.Hi volume oil pump,re-jet,counter sprocket.$200 all in 88 kit included before head work.The head done right is where it adds up quick,and needs to be rebuilt either way.
    I have recently put the similar setup on one of my bikes. rebuilt head, 88cc big bore kit, hi volume oil pump, stock exhaust with baffle removed, stock carb not re jetted, What size main jet should be used with a stock carb on this setup???? What will happen if the stock carb isn't re-jetted???? and what size counter sprocket???? I only started the bike for a little while to make sure oil was pumping up to the head and haven't broke it in yet.
    Last edited by lukelaw1; 05-19-2013 at 01:21 PM. Reason: added info

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    OLD CT's Avatar
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    Only you know what year bike and what jets you have.Different years=different parts.See the gearing questions posted today. Check the color of your plug to determine jetting.free flow air filter?stock air box?Either way,you have some tuning work that only you can do.When i went 88 i didn't use a stock carb.No one size fits all here.
    Last edited by OLD CT; 05-19-2013 at 01:42 PM.
    I fart alot because it's the only gas i can afford...

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    lukelaw1 is offline 120cc
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    Quote Originally Posted by OLD CT View Post
    Only you know what year bike and what jets you have.Different years=different parts.See the gearing questions posted today. Check the color of your plug to determine jetting.free flow air filter?stock air box?Either way,you have some tuning work that only you can do.When i went 88 i didn't use a stock carb.No one size fits all here.
    thanks old ct. what carb did you do with on your 88 big bore setup? and where can i get the same cab setup?

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    OLD CT's Avatar
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    Even the head and type of cam matters with jetting,a race head will need more jetting.Fuel quality matters also.Way back in 2006 when joined here,i had my 88 on the road with a sl70 hot cam it ran fine with a pz19 with the factory jets and a free flow filter,pre ethonol era.I no longer run the 88 it's bagged on the shelf.Now in 2013 with a full race cam,even a pz19 needs more jetting.Different scenarios=different jetting.Usually one jet size up on the main with a stock carb or hot cam may just do the trick.Try working with your stock carb first.
    Last edited by OLD CT; 05-19-2013 at 03:03 PM.
    I fart alot because it's the only gas i can afford...

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    lukelaw1 is offline 120cc
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    the bike is a 72 k1 with hi volume oil pump TB parts, free flow air filter dr atv, stock intake tube, stock head with hot cam CHP and hd valve springs CHP, carb is a 533a with 58 main jet and 35 slow jet, cylinder and piston are 88cc big bore from dr atv, fuel will be 87 or higher octane no ethanol.

    one size up would put me at a 60?

    I have some spare carbs laying around ie HT7A with a #60 main jet and a couple AT7B with a #65 main jet if i were to swap out the main jet which one should i try first before buying the one i need?
    Last edited by lukelaw1; 05-19-2013 at 03:31 PM.

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    OLD CT's Avatar
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    60 would be the next step.Try the 60.
    I fart alot because it's the only gas i can afford...

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    lukelaw1 is offline 120cc
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    Quote Originally Posted by OLD CT View Post
    60 would be the next step.Try the 60.
    Thanks a million old ct greatly appreciated!!!

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    OLD CT's Avatar
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    Let us know how it runs,findings.rapid oil changes in the beginning to get rid of the stardust.And retorque the head.
    I fart alot because it's the only gas i can afford...

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