70cc valve size questions

[oscarmayer]

I'm building a racing 70cc setup. The rule state i have to keep it 70cc. meaning no boring/stroking. I found a palce that sells lots of race stuff for a 70cc. they have a race head that is what they call a big valve head.

http://www.tboltusa.com/store/trail-bike-race-head-kit-for-88cc-fits-crf50-p-45.html?osCsid=9d3c68ab0705af3563b7bdad62aa68b1

it's 25mm intake and 22mm exhaust and the ports are bigger as well as the valve angle changed slightly. it was designed for a 88cc bigbore setup or bigger, but the guy said it woudl work on a 70. My question is what is the stock honda valve sizes? are they close to that size?
should I get this eace setup? I'm going to buy a race piston and alloy cyclinder from the guy for sure. I need a 15:1 compresion setup if he can get it to me, but anything over 12:1 will work for now. We'll use cb16 airated race fuel (130 octaine rated if we have too.) but expect if we get it to like 13:1 100-110 octaine will work fine.

later we will be designing a compelte EFI or electronic fuel injection system for this setup as well. So YES upgrade just will be offered which means you guys can convert to EFI!!!!

anyway, what are your thoughts. I'm going to be purchasing parts next week.

[Thorpe]

SCHWING!!! A fuely 70! :drool::drool:

[oscarmayer]

let me rephrase this, the efi kit will will be available for ANY size chinese ATV/scooter/pitbike engine size this manufacturer sells. So the 200x can be EFIed and so can the 350x.

[Thorpe]

So could my BR!!!???? SCHWING!!!!

[Yamada]

I'm building a racing 70cc setup. The rule state i have to keep it 70cc. meaning no boring/stroking. I found a palce that sells lots of race stuff for a 70cc. they have a race head that is what they call a big valve head.

http://www.tboltusa.com/store/trail-bike-race-head-kit-for-88cc-fits-crf50-p-45.html?osCsid=9d3c68ab0705af3563b7bdad62aa68b1

it's 25mm intake and 22mm exhaust and the ports are bigger as well as the valve angle changed slightly. it was designed for a 88cc bigbore setup or bigger, but the guy said it woudl work on a 70. My question is what is the stock honda valve sizes? are they close to that size?
should I get this eace setup? I'm going to buy a race piston and alloy cyclinder from the guy for sure. I need a 15:1 compresion setup if he can get it to me, but anything over 12:1 will work for now. We'll use cb16 airated race fuel (130 octaine rated if we have too.) but expect if we get it to like 13:1 100-110 octaine will work fine.

later we will be designing a compelte EFI or electronic fuel injection system for this setup as well. So YES upgrade just will be offered which means you guys can convert to EFI!!!!

anyway, what are your thoughts. I'm going to be purchasing parts next week.

Do you use an atc-70 engine? Because they are 72cc...

[oscarmayer]

the rules he ride in only allow up to a 70cc 4-stroke or a 50cc 2-stroke. the sad thing is the power of the 2 do NOT compair. those are factory build race bikes and engines. DRR is one of them and APEXI is another. the onyl chance I have is if they next year change the rules to make it more fair and let me run a 90cc in the class. even iwth about $1200 in motor work and efi systems, we will only get about 10-11 hp. thyse 2 strokers are running 13 or so HP @11k and can rev to 14k-15k.