4 valve head vs 2 valve

[storminnorman07]

i have been pondering this for a while now so i figured i would see what everyone else things about it. ok heres whats on my mind i have a dohc 124 take motor that pulls a 18.6hp with 8.8ft/lbs of torque then on the other hand you have finchs 2 valve 153cc with 19+ hp with over 10ft/lbs of torque. every where i read just about everyone claims a 4 valve head will out perform a 2 valve modded or stock. finch has my 4 valve head right now and he tells me it won't ever beat his 2 valve setup. can someone explain to me why this is cause i'm starting to think i might of messed up going to 4 valve route.

[PlanetMinis.com]

[ibmike13]

one reason is the intake ports need to be srunk on those DOHC heads not ported so epoxy away.

[ghostryder]

18.6 aint nothing to sneeze at

[TRT]

But the tourque numbers are low in comparrison.



The daytona 4 valve seems to be winning all the big races this season.....

Troy

[trailpimp33]

The way that I understand it is 4v heads make more power higher in the RPM range. The 2v heads can make power lower in the RPM range, so the curve may be more desirable making the 2v more ridable. Like stated above though, 18.6 is nothing to sneeze at and 8.8 for torque is not bad either. I would say with all that power the only thing you may need is better suspension, and hone your skills!!!

Oh and the dyno I read of the 153 said 17hp not 19hp with 10lbs. so your 124 already makes more power.

[slowracer]

The 153 has got about 6 or 7 millimeters bigger stroke compared to your 124,And that makes a huge difference right there.You will notice a increase of botom end by advancing the cams and ignition.I frogot to tell you the pistons are done so I'll pm you my brothers # so you can pick one up.

[Kurlon]

A 4v head can flow FAR more than a 2v head built for the same bore size. Take a look at just about any motorsport series where there is a displacement cap on the motor... they all move to multivalve setups to wring more power out of the motor.



Look at the numbers you listed, a 54 x 54 motor putting down 8.8 ft/lbs compared to a 59 x 57.5 (I think, don't recall the exact bore) motor that put down 10 ft/lbs of torque... The head had to have extensive rework to put down those numbers. If there was a version of the Daytona 4v head sized for the large import bores... heh... NO CONTEST. : )

[JJW Designs]

Crud, 18.6? That's nothing to sneeze at. I have a 138 2 valve setup that puts out 18.6, and I was told that's it, that's all you're getting out of a Honda 2 valve engine. I'd imagine a 4 valve setup could flow better, but from the dyno's I've seen, a stock Take 124 DOHC only puts out about 15.8-16.2 HP.



Which means you must have had some work done to yours?



I'd like to know which is more reliable. My engine has about a 15 hour engine life. Which, uh, sucks.



My vote is still on a 2 valve setup...

[ibmike13]

A 4v head can flow FAR more than a 2v head built for the same bore size. Take a look at just about any motorsport series where there is a displacement cap on the motor... they all move to multivalve setups to wring more power out of the motor.



Look at the numbers you listed, a 54 x 54 motor putting down 8.8 ft/lbs compared to a 59 x 57.5 (I think, don't recall the exact bore) motor that put down 10 ft/lbs of torque... The head had to have extensive rework to put down those numbers. If there was a version of the Daytona 4v head sized for the large import bores... heh... NO CONTEST. : )

there is! you CAN put the DOHC heads on a Honda Nice motor all the way up to 176cc ive seen um pump out 22+hp and unbievable torque! now with that being true that means it should fit onto the GPX sence its a nice copy.

[ibmike13]

The 153 has got about 6 or 7 millimeters bigger stroke compared to your 124,And that makes a huge difference right there.You will notice a increase of botom end by advancing the cams and ignition.I frogot to tell you the pistons are done so I'll pm you my brothers # so you can pick one up.

Pistons done? what do you got going on?

[RcWannabe]

[quote name='ibmike13']there is! you CAN put the DOHC heads on a Honda Nice motor all the way up to 176cc ive seen um pump out 22+hp and unbievable torque! now with that being true that means it should fit onto the GPX sence its a nice copy.[/QUOTE



They cant be using a crf50 DOHC head because it has different stud spacing they are doing this in europe and they may have some other DOHC head available.

[fatcaaat]

[quote name='ibmike13']there is! you CAN put the DOHC heads on a Honda Nice motor all the way up to 176cc ive seen um pump out 22+hp and unbievable torque! now with that being true that means it should fit onto the GPX sence its a nice copy.[/QUOTE



They cant be using a crf50 DOHC head because it has different stud spacing they are doing this in europe and they may have some other DOHC head available.

Wrong. Honda Nice has same stud spacing as CRF50. Those Lifan 120's and GPX are not direct copies of the Nice.

[reynolds_brad]

Fatcat is correct, I installed a ported nice head on my CRF and had the heads side by. the stud spacing between the nice and CRF motors is the same. The cylinder length is longer on the nice though. that is what allows the longer stroke options.

[slowracer]

Pistons done? what do you got going on?

We had custom high compression pistons made for the takegawa dohc.the stock set up is only 10 to 1

[storminnorman07]

wow thats what i like to see alot of different opinions. i am not having problems winning races so far all the races i raced i either won or top 3 so i'm not hurting for horsepower i'm just a horsepower freak the more power i have the happier i am. i'm really just looking to broaden the powerband of it a lil and raise my torque numbers.

ibmike- i looked into that velocity porting thats not going to get what i'm trying to get out of it



pitbikeguy- yes its been ported but thats it i'm running a 26mm carb which from dynos i seen from cycle by putting a 28mm on there i should gain .5 to maybe a 1 hp in the mid and top. like slow racer said the compression on these 4 valves are way low 10.1 maybe 11.1. piston life on mine i have over 60 hours and piston and rings still looked good valves on the other hand the stock valves suck a$$ you'll prolly get about 20 hours out of them if you ride the bike high in the R's like i do.



i dont know i have some ideas of how to get what i'm looking for. i wanna put a over square bore on it but i don't know where i can locate a bigger piston cause from what i read 4 valves head respond better to over square bores. if not i'm going to stroke it i know where i can find a stroker pin. if any one knows where i can find a bigger piston setup for this please let me know

[slowracer]

Storm,

to bad you dont have a daytona my next project is going to be 57 mill pistons for the daytona Dohc.Pax will stroke your crank and shrink your rod(so you maintain the same deck)for 300

[storminnorman07]

slowracer that bad thing is thats what i orginally wanted to get was the daytona. at the time bbr, two brothers, classic, and crower all said the daytonas werent as good of a motor as the take that i would be making a big mistake. now i'm pi$$ed off cause now they are all like yeah we missinformed you the daytona is better etc.. where you getting the 57mill piston at?? and you wouldn't happen to have paxs number would you?

[slowracer]

slowracer that bad thing is thats what i orginally wanted to get was the daytona. at the time bbr, two brothers, classic, and crower all said the daytonas werent as good of a motor as the take that i would be making a big mistake. now i'm pi$$ed off cause now they are all like yeah we missinformed you the daytona is better etc.. where you getting the 57mill piston at?? and you wouldn't happen to have paxs number would you?

I'm having them made just like the one for your motor.

Pax (81 897-0373

[HACKMUNCH]

You Can Not Compare 124cc Engine To A 153cc, 2 Different Slices Of Bread.

[cyclerider57]

Not only two different slices... ones from a totally different loaf of bread.