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4 valve head vs 2 valve

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#21 ·
storminnorman07 said:
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.
Click to expand...




you should atleast be fair an tell them i'm doing a 2 valve head for you too, it's not like i wasn't going to prove which is better.:D
 
Discussion starter · #22 ·
i'm not out to prove which is better as far as dyno goes i just wanna find a motor that fits my high revving riding style with tons of power and torque. and i was just curious why it is your 2 valve head is out performaning my 4 valve. which finch is right i should of mentioned that he is putting together for me a 140 cc kit with his fully tricked out 2 valve head.
 
Discussion starter · #23 ·
hack and cycle i figured it was 2 different slices of bread i was just wanting to make sure i was figuring right. has any one done a dohc with that kind of cc's not well i heard if you put it on a nice motor is makes 20+ hp?
 
#24 ·
Putting a Daytona DOHC head on a big bore/stroke import isn't the same as putting a reworked Lifan head on a big bore/stroke import. The Lifan head is getting bigger valves jammed in, and can because of the larger bore, while the DOHC is likely running the same valving or comparatively close to the same valving as stock, where it was made to work on a smaller bore. That's kinda like comparing a bored and stroked supercharged V8 to a ported NA 4 banger and declaring the V8 the winner.



When you deal with a set bore size and build the biggest head you can for that bore, you can get more flow and power with a 4v setup than you can a 2v. Look at the 124cc Honda motors, with a 54mm bore cap, and 2v and 4v heads available for that setup, the DOHC 4v has the most potential.



Finch is able to get more HP right now with a 2v setup because he's not restricted to 52.4mm or 54mm bore sizes. He can jam larger valves in that result in the head requiring a larger bore for clearance, and just build the motor with the required bore for it to fit. If you built a 4v head to take advantage of the larger bore, you'd see even bigger numbers posted. Unless the import motors really take off, I don't think you'll see one from Tak/Daytona/etc or any of the import makers. The import brands have pretty much standardized on 52.4mm bore, so what ever they produce for a 4v head will be choked accordingly to fit that limit. Unless someone produces their own head, we'll never get a fair comparison past Honda 54mm bore setups.
 
#26 ·
okay. let's stop talking about my stuff and my builds for a moment and see if anyone can explain or show some kind of proof why it is that the +r heads make as much, if not more hp than any of the 4 valve setups that are out at the moment on their given engine displacement. that gives you a chance to try to show where you are coming up with the 4 valve will destroy a 2 valve scenario. the 4 valve has to work at a higher rpm to get it's flow rates, regardless of what most think. i wears itself out. the 2 valve motor comes on stronger, lower, and will start pulling bike lengths on the 4 valve in every corner. even if it doesn't make as much peak hp, you are still going to have a hard time outrunning it. this was written as a statement of opinion. if you do not believe what i do, sorry.
 
#27 ·
I'd like to see a CRF/XR 50 engine crank out 20+ HP.... I really would. But so far I haven't seen it done.....



Anyhoo, Finch, I'm going to have to talk to you about an engine. If you can really crank that many ponies out of a bike, for okay prices and have it be reliable, I gotta try it. I have a $7000 engine that lasts like 12-14 hours apparently (valves, which when they go out, they take the rest of the engine with them).



I lost my sponsorship so I don't care where I get my engines now. Hope you're around Monday...
 
#29 ·
rkfinch23 said:
okay. let's stop talking about my stuff and my builds for a moment and see if anyone can explain or show some kind of proof why it is that the +r heads make as much, if not more hp than any of the 4 valve setups that are out at the moment on their given engine displacement. that gives you a chance to try to show where you are coming up with the 4 valve will destroy a 2 valve scenario. the 4 valve has to work at a higher rpm to get it's flow rates, regardless of what most think. i wears itself out. the 2 valve motor comes on stronger, lower, and will start pulling bike lengths on the 4 valve in every corner. even if it doesn't make as much peak hp, you are still going to have a hard time outrunning it. this was written as a statement of opinion. if you do not believe what i do, sorry.
Click to expand...


I'm not saying one way or the other but...



You want people that think 4 valve setups work better to show proof that a +R head makes the same power?



Which form of racing are you talking about? Last I looked there wasn't a single 2 valve engine competing in motocross or supercross and doing anything work talkin about. Last year at all the short track nationals I went to it was the 4 valvers dominating. The only reason the 2 valvers dominate on the national miles is because there aren't any other bikes produced for that class. Heck in this aspect of racing... mini bike... look at most of the pro's at the mini moto. I don't see an SE pulling any of the DOHC engines off the starting line.
 
#30 ·
explaining myself better

Can anyone show any dynos for a +R headed 124 and any of the DOHC's? i think if someone can show some dynos, you will see that the 2 valve makes more power down low.



i also don't believe that i EVER said anything about the SE heads. the SE head in no way has a better port than the +R.



i know, cyclerider, that you are building a custom 4 valve head. i hope it works out for you.

for a shop that does an awful lot of 4 valve heads and mulit-thousand dollar work on them, why would you think that i would be pushing the 2 valve head? i think i have seen what a 4 valve head is capable of.
 
Discussion starter · #32 ·
#33 ·
storminnorman07 said:
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.
Click to expand...






We'll I find somehting hard to believe...your current setup makes 18.6hp correct? If what you say is true then you do have the better kit because the Daytona after being totally reworked only has 16hp!



BBR's Quote about Costella's Daytona engine!



Nearly every single componet in BBR race motors is modified in some way. The transmission gears are cryongenically treated, and tranmissions shafts are polished and molybdenum-disulfade coated for smoother shifting. Valves and camshafts are DLC coated for durability. The crank is balanced and the piston is shaved for balance and weight reduction. The piston dome is thermal-ceramic coated and the skirts of the piston is coated with molybdenum disulfade. Even the combustion chamber is thermal coated for better heat transfer.

Valve size , cam grind, and cam timming are modified to meet Costella's particullar riding sytle. The Daytona 4-Valve head provides more potential for performance modifications than any other head on the market. The clutch plates are hard anodized for added durability.

BBR actually fills and reshapes th port floors in the intake and exhaust ports to increase velocity.(This added 2 HP and boosted the rev range). The claimed HP is 16 at 13,200 rpms.

This is an art that could be foreign to most engine builders. Bigger port volume isn't always better says Mike. Everyone talks about huge valves and ports, but usable power is really detemined by the velocity of the intake charge. Moving the same amount of air through smaller ports results in higher velocity, and the higher velocity creates a ram-air affect into the cylinder!
Click to expand...


This is the article from MM isue 4 about costella winning bike/engine...

Troy
 
#34 ·
this debate sucks. 4 valve heads are better up top,2 valve heads are better down low. no matter how good a china engine is people want Japan sh!t. the whole probleme is these Big CC klx engines,well no Honda engine is going to compare to a 180+R so until someone makes a Better HONDA engine,119/124+R,SE,or DOHC,s are going to be what most Honda riders ride. im just not willing to put out $3000+ dollars for someone opinion at least i know my 124+R runs pretty good and there is room for at least a couple more HP.
 
#36 ·
rkfinch23 said:
explaining myself better

Can anyone show any dynos for a +R headed 124 and any of the DOHC's? i think if someone can show some dynos, you will see that the 2 valve makes more power down low.



i also don't believe that i EVER said anything about the SE heads. the SE head in no way has a better port than the +R.



i know, cyclerider, that you are building a custom 4 valve head. i hope it works out for you.

for a shop that does an awful lot of 4 valve heads and mulit-thousand dollar work on them, why would you think that i would be pushing the 2 valve head? i think i have seen what a 4 valve head is capable of.
Click to expand...




I was just using the SE as an example of a 2 valve engine. We also do a lot of work on multi-thousand dollar heads. I'm just saying every form of racing involving corners that I am in the 4 valve heads have been a dominate force. The only 1/2 mile+ oval tracks I've seen a 2 valve engine race a 4 valve engine the 4 also takes it. 2 valve Harley XR 750s are getting stomped by one triump because it has aftermarket 4 valve heads. It just rocks them coming out of the corners all the way down the straightaway. Ask every racer on that track. They will say the same thing. That's all I'm sayin.



As far as dyno numbers, I'm not worried about it. I was using race examples.



I hope it works out for me too. I'm not to worried about numbers. I'll be happy to say I did it, as every part of the process is done by myself.
 
#37 ·
storminnorman07 said:
yeah talked to bbr about it they said there dyno is usuually 3 to 4 hp off from other dynos they only use it for tuneing purposes
Click to expand...


Are they using an old style water dyno?
 
Discussion starter · #38 ·
cycle i am not sure i didnt ask him what dyno they used he told me that the hp is usually 3 to 4 hp behind any other dyno you put it on. he told me as a stock bolt up kit with nothing done on their dyno the daytona pulls 12 to 13 hp at rear wheel
 
#39 ·
Stick a Daytona DOHC had on a 150+CC honda nice motor and pretty much nothing out there that will outperform it, ive seen 22hp and huge torque numbers, so what you willing to send to have the best motor?

money talks BS walks.
 
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