Planet Minis

tcr0148

I was wondering what was the base/average CFM with the TB V2 head v.s the CFM for the yx 160 head in stock form or lightly ported?

Blackwoodz

I have never heard anyone using a flowbench on these heads here. I would like to know myself.

Matified

the secret of the v2 vs stock is really not as much the valve size and or port size and it is the fact that it has a roller cam v2 profile that is virtually square compared to the little triangled shap of the flat tappet cam of the YX, that is where the big power gains are.
the v2 pops the valve open , holds it there and pops it shut, the yx gradually opens and peaks then gradually closes the valves.

basically alot ,more in and out, sure porting will help, but with both ported similar, the V2 (+R) will aways outshine the YX.

Blackwoodz

which equals more duration......opening sooner....closing later all at a faster rate.
Just another reason until that 4V head is made into a roller rocker the V2 will out perform it.

T719mx

I want to put one on my yx 160. What will it give me?? More top end??

Kurlon

Yeah, but multivalve setups flow more at initial lift... so that 4v head may be able to beat the V2's longer peak lift duration by better flow when not at peak lift.

firepower354

If the port shape wasn't poop, and the valves shrouded to reduce their theoretical low-lift curtain area advantage

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T Bolt USA

3-4 hp over stock , v2 rips
let me know if we can help

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firepower354

You'll go faster due to a lighter wallet, with a 4V, unless porting is done, and done right. I'm digging in to one next week, and will get some measurements and info before & after. It's clear already, that along with the valves needing unshrouded, the valve job needs work. That's a major key to low-lift flow. I'll try 3 and 5 angle setups, and maybe even the full-radius cutter we use on the big stuff.
My flowbench still isn't finished...

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FirepowerMinis.com
Custom FPM parts and engines.
Parts and service for all makes.
Honda Trail Bikes parts and accessories.
Pitster/Piranha/Thumpstar bikes, parts, engines and accessories.

Blackwoodz

sounds good on paper...why not prove it in a real life flowbench dyno run. OBTW with the 4v unless you grind your own cams not alot of options right now.

If you need anything tcr0148 check out www.firepowerminis.com for all your high performance parts.

tcr0148

The bottom line is that the TB V2 head's dynamics (chamber shape, roller rockers, piston shape) is much more efficient, right? And what I mean by efficient, is that the V2 will come closer to maximizing the YX160's horsepower and torque potential .......given that the air to fuel is equally met.

PM already sent to Terry on behalf of the 192cc w/full skirt

Blackwoodz

IMO....there is potential for the YX 4V head yes but it will take work to get it on par with the stock out of the box TB V2. Maybe this time next year the roller rocker V4 from TB will be all the rage..

tcr0148

I think for obvious reason that a head with 4 valves would flow alot more "efficient" air. With this being said, won't the massive increase in valve area (the extra valves) reduce the port velocity drastically in the chamber.......which will then decrease low end torque and horsepower?????? I'm guessing that is why there are DOHC in most 4 valve applications. In other words we are making do with the technology that we have thus far and V2 is where its at for NOW at least

Kurlon

I think I can do the combustion chamber work, and I've got access to a dyno... I'm lacking base engines, cash and time though. :P I know nada on porting, will need help there too. So, all I've got at the moment is paper comparisons.

Paxracing

I will try to flow one for you next week.

teflonmats

here you go.
measured at 28"

yx head.
lift in out
2mm 30 26 cfm
4 60 53
6 69 54
7 70 54
8 73 ...
9 73(staling)

tb head
2mm 31 32cfm
3 46 47
4 63 57
5 64 64
6 92 70
7 94 72
8 96 74
9 99 75


mats

schofell84

wow. huge differences in high lift.

same cam? or just same lift?

teflonmats

there are a big differense in porting and porting so cant realy just put in some
numbers..
depending on what has been done.

mats

teflonmats

just lift.

mats

schofell84

so basically theres no point in running a cam with over .250" lift in a stock yx head? duration is key from what i'm seeing.