47cc 2 piece head kit - Pocket Bike Forum - Mini Bikes
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post #1 of 285 (permalink) Old 09-01-2018 Thread Starter
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47cc 2 piece head kit

Hey guys I'm just curious, with a 40mm bore 2 piece kit, If I have the cylinder and dome cap, will a 49cc head kit work to hold the smaller dome cap?
For example an ada 40mm billet cap with a 4 piece wing kit holding the dome down, or are the head sizing different't for the smaller cap and require a smaller head ?cover because that technically all the billet heads really do well that and cooling.

Basically are the domes between the big bore kit, and smaller ada kits differ much?

Thanks. Basically I have a found a 47cc or 40mm cylinder kit for a 2 piece head, and there are domes available, just not the head portion to clamp it down, so my question is are the ada heads the same size as the chinese big bore heads?
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I have two 44 mm caps and two domes and they won't interchange they don't really fallow any true manufacturing tolerances

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Re: 47cc 2 piece head kit

Can't interchange ADA and China caps, you might be able to mod one too fit but not sure you can. I have a new 2 piece ADA round alum allow head w/ 40mm compression cap and 40mm cyld, also have a 10mm full circle crank to fit the 10mm / 40mm piston & a engine it is supposed to fit on. I might sell all or part of them.

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post #4 of 285 (permalink) Old 09-01-2018 Thread Starter
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Re: 47cc 2 piece head kit

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Originally Posted by MrKitty View Post
I have two 44 mm caps and two domes and they won't interchange they don't really fallow any true manufacturing tolerances
Didn't think so, thought I'd ask I don't need one just was curious really.
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post #5 of 285 (permalink) Old 09-01-2018 Thread Starter
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Re: 47cc 2 piece head kit

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Originally Posted by EPR View Post
Can't interchange ADA and China caps, you might be able to mod one too fit but not sure you can. I have a new 2 piece ADA round alum allow head w/ 40mm compression cap and 40mm cyld, also have a 10mm full circle crank to fit the 10mm / 40mm piston & a engine it is supposed to fit on. I might sell all or part of them.
Thanks, I was just more curious than anything.
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post #6 of 285 (permalink) Old 09-01-2018 Thread Starter
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Re: 47cc 2 piece head kit

I screwed up tonight with my cylinder I was touching some thing up basically just cleaning stuff up, and I put it in a vice, and I made a mistake and it pushed in the boost port as the skirt but how it pushed in I got lucky and it cracked straight across and didn't wreck the cylinder. Should still work let me know.
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slap it together and see if the piston runs up and down ok then start it up what do you have to lose 🙂

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Re: 47cc 2 piece head kit

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slap it together and see if the piston runs up and down ok then start it up what do you have to lose 🙂
The piston will run fine the only thing I was slightly worried about was the head sealing but I think it will be alright. I've seen a couple heads where they cut the skirt out on purpose where the boost port is.
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it will seal just use a thin coat of yamabond

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post #10 of 285 (permalink) Old 09-02-2018 Thread Starter
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Re: 47cc 2 piece head kit

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it will seal just use a thin coat of yamabond
Ya that's what I'm thinking putting some sealant in that spot just in case.
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I don't even wast my time with a gasket I just yamabond the thing together JB Weld is another option but then you need a plumbing torch to get it apart I learned this trick from CAM2

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post #12 of 285 (permalink) Old 09-02-2018 Thread Starter
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Re: 47cc 2 piece head kit

I milled the top of the jug down to get the squish I wanted, so I didn't change any of the port timings. I'm going to try the no gasket on my other motor hopefully 100 octane is enough lol
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I have trouble starting mine I have to hold it down with my knee and use a leather glove most of the time I will pray to the starter rope LOL then vroom 🙂 I never use a base gasket and I fix the timming with home made rocket keys.
I don't understand why people insist on using the base gasket that makes absolutely no sense to me unless the squish is too tight and you don't have a choice
Maybe I have been in the hobby too long and I'm just stuck in the old school ways but it's to my understanding the sooner all the ports get closed off and the Piston starts making compression and the more travel that piston has to make that compression the more potential horsepower the engine can make.
hummmmm idk...

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post #14 of 285 (permalink) Old 09-02-2018 Thread Starter
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Re: 47cc 2 piece head kit

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I have trouble starting mine I have to hold it down with my knee and use a leather glove most of the time I will pray to the starter rope LOL then vroom 🙂 I never use a base gasket and I fix the timming with home made rocket keys.
I don't understand why people insist on using the base gasket that makes absolutely no sense to me unless the squish is too tight and you don't have a choice
Maybe I have been in the hobby too long and I'm just stuck in the old school ways but it's to my understanding the sooner all the ports get closed off and the Piston starts making compression and the more travel that piston has to make that compression the more potential horsepower the engine can make.
hummmmm idk...
I 100% agree that compression = power but as long as you have enough octane to stop detonation. I just don't feel like putting my nice expensive race fuel in a little 49cc motor. I have some 100 octane to use, my problem is the squish would be so tight like .01" if I take out the base gasket, which is c116 or meth.
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post #15 of 285 (permalink) Old 09-02-2018 Thread Starter
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Re: 47cc 2 piece head kit

One thing I noticed with the split port head it puts the transfers in a weird spot on the piston, and I can't drill boost ports in it because the one side of the transfer port almost runs through the piston pin. I was like well I guess there's no room for those on this motor lol.
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you don't want a anti para mod on a piston with a window you want the effect to charge the boost port you have to be careful you don't over modify these things or there impossible to tune

CAM2s anti para and turbo crank mod 2 big main ports no boost ports are more for high rpm builds

Big wide boost ports fingered cylinders and window pistons are for low RPM high torque builds

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Re: 47cc 2 piece head kit

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Originally Posted by MrKitty View Post
you don't want a anti para mod on a piston with a window you want the effect to charge the boost port you have to be careful you don't over modify these things or there impossible to tune

CAM2s anti para and turbo crank mod 2 big main ports no boost ports are more for high rpm builds

Big wide boost ports fingered cylinders and window pistons are for low RPM high torque builds
If you look at the ADA 15:1 alky headkit they use a 40mm cylinder with no compression releif notch and no extra boost ports piston windows etc...

Kittys right about adding too many anti parachute releifs as the engine wont build up enough velocity with-in the crankcase...Youd get better results super lightening the piston and polishing key components to reduce drag....

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post #18 of 285 (permalink) Old 09-02-2018 Thread Starter
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Re: 47cc 2 piece head kit

I was kinda figuring there was a reason for the transfers lining up so differently. Thanks for the advice guys it's much appreciated I honestly have learned a ton. The new motor has a ton of compression I think it's going to be a b*tch to start lol. I also made some improvements to the old motor, pretty excited in the next week or 2 to see the results.

Quick question for you guys, Cam2 and mr kitty, if I was doing an all out rpm build I would want large transfers and max compression, now my question is do you want a boost port as well? or just run 2 large transfers, lots of compression, and parachute holes?
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Re: 47cc 2 piece head kit

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Originally Posted by TeePee View Post
I was kinda figuring there was a reason for the transfers lining up so differently. Thanks for the advice guys it's much appreciated I honestly have learned a ton. The new motor has a ton of compression I think it's going to be a b*tch to start lol. I also made some improvements to the old motor, pretty excited in the next week or 2 to see the results.

Quick question for you guys, Cam2 and mr kitty, if I was doing an all out rpm build I would want large transfers and max compression, now my question is do you want a boost port as well? or just run 2 large transfers, lots of compression, and parachute holes?
Lightened piston zero windows or holes......transfers that are comservatively enlarged...high compression around 200psi...methanol fuel....

The best mod would be to buy a high chrome 40mm steel sleeve map the ports and cut in proper port windows and press that sleeve it into a 44mm cylinder with the de-compression notch welded shut..........
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Last edited by CAM2; 09-02-2018 at 09:40 PM.
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post #20 of 285 (permalink) Old 09-02-2018 Thread Starter
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Re: 47cc 2 piece head kit

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Originally Posted by CAM2 View Post
Lightened piston zero windows or holes......transfers that are comservatively enlarged...high compression around 200psi...methanol fuel....

The best mod would be to buy a high chrome 40mm steel sleeve map the ports and cut in proper port windows and press that sleeve it into a 44mm cylinder with the de-compression notch welded shut..........
Cool thanks
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