v-force reeds and jetting?

[yz250flash]

I am sure there have been a million jetting questions on here but I did a search and didn't find the answer to what I need to know.

How does the v-force system affect jetting. What I mean is if I start with the stock jettings will I need to go leaner or richer or will I need to re-jet at all. (I know jetting is different everywhere but I thought there may be a common action needed; like generally you have to go leaner)

Everything else on the bike is stock.

 

[CR69r]

i put them in my last 2 rhondas ('01, '02 cr250) and did nothin. however my '03 has went berserk with the vforce. it ran waaay too rich. i leaned out the main a couple, and think i have to fiddle with the needle to reach the full potential. if vforce claims to have better airflow, then i shouldn't have had to go leaner!? they also say that the petals only open half the distance compared to stock (but double the petals) so is it possible vforce delevers less air?

 

[bclapham]

although theorys tend to bite you in the arse and all bikes are different, its not uncommon to have to lean a bike with a v-force a few sizes on the pilot circuit

 

[nephron]

Bruce, this post reminds me of the time you and I were talking about Boyeson. Did you read the article on him in RacerX (I believe)? He has apparently designed a gauge to meter rocket fuel levels for NASA--I'm sure you saw the article, but the fuel is so cold at atmospheric pressure that no instrument has yet been developed to measure its level. I would guess it has to do with the temp affecting the continuous resistance readings of a standard fuel level gauge.

Anyway--I think the guy's great, and it seems the design of V-Force reedblocks (as far as I can tell) are primarily a cut and paste design with a main goal of reducing reed valve/intake area and increase downstream signal--not all designs, but the majority. Not that that's bad, but nonetheless not my idea of engineering. I like Boyeson's way of sitting at a dyno all day long and trying different things until he gets it right.

Of course, I could be wrong about this and would like to hear other people's opinions.

 

[jmics19067]

I am inclined to agree with you Nephron, Although my Vforce makes the bike rev freer <real quick to climb rpms> I dont think it produces any more power than my Rad Valve. Team knucklehead, pant seat dyno runs tells me than with the Vforce the bike is easier to "get on the pipe" slight slip of the clutch and my rpms are up there making good power. My Rad valve is a different story though there is no "pipe' to get in into I can just roll the throttle on no clutching needed, I can lug the engine or scream it with no clutch involved. Both are quite different than the stock one in my opinion . the power of the stock one was good in the midrange and I am not sure either aftermarkets truly beat it , but how each feel getting into the power range is quite different.

I choose to run a Vforce on my motox bike and a Rad Valve on my woods bike because that is how I like them to feel. Some day when I truly get chance to test and Rich's old Air/Fuel meter I am going to make a better back to back experiment. Along with FMF and ProCircuit against a stock pipe

I really do like the idea of most manufacturers actually paying<well atleast used to not sure if the copyrights opened up yet> Boyesen to use his port design. Definately tells me the guy knows his stuff about intake designs !!


P.S. neither one delivers less air requiring smaller jets. Both increase the signal at the jet drawing more fuel thru it recquiring a smaller jet. I am pretty sure that is how it works.

 

[bclapham]

Originally posted by bclapham
theorys tend to bite you in the arse

see, i should have just kept quiet! :confused:

there seems to be quite a lot of anechdotal eveidence to say that the v-force is a much better choice than either stock and/or boyesen reed cages on quite a few bikes, and i am sure a few of the dyno cadets will agree and in some cases (03kx125) say the v-force didnt do squat.

all bikes are different and as ever, they can all repsond do the same mods differently. I am sure Mr. Boyesen is a very nice man, but i am sure Mr Tassinari is too. i dont beleive one design is better than the other, but i think Mr. Tassinari has a better instinct for making money! i wonder if they took his v-design and engineered it per every new bike how it would work out?

ps- i need to subscribe to racerX ;)

 

[mxneagle]

Originally posted by nephron
Not that that's bad, but nonetheless not my idea of engineering. I like Boyeson's way of sitting at a dyno all day long and trying different things until he gets it right.

No thats called trial and error not engineering. Engineering is applying scientific principles to solve problems in a calculated manner. Now thats not saying that Mr. B is not a brilliant man.

 

[jmics19067]

I believe Boyeson is an engineer specialized in fluid dynamics <specialized again in intake airflow characteristics of two stroke engines > I am sure his dyno runs are only proof testing different ideas.

This is pure speculation here on the character of the two designers. Boyeson and Tassinari are both redesigning something that ain't broke. So the interpretation of what is better is open up endless possibilties.One taking the route of reducing the unwanted flow issues and the other dealing with the issues another way. I believe as performance pieces they are both effective provided that the way the power presents itself is what you want. In other words they do change the way your bike feels but whether or not you like the change can only be determined by testingthe two against each other for your application.

I do like the attention to detail that Boyeson has in fit and finish compared to Vforce. The 40$ difference between the two is not proportional to the difference in the amount of labor it took to install them with Boyeson winning for my application.

 

[bclapham]

Originally posted by mxneagle
No thats called trial and error not engineering.

after spending the last 8 years of my life doing research in chemistry and drug discovery i can assure you that successful scientific research is 95% trial and error and 5% luck. If we could just apply a theory then there would be no cancer, no aids, no pollution and we could have flown to mars!:)

 

[billtx]

I installed the V-Force on my YZ125.

Went lean one step on the main and needle. Went rich one step (maybe 1.5 when taking into account airscrew adjustments) on the pilot. The V-Force is in the high tension mode.

It appears that the V-Force (in high tension) flows better than stock in the mid to upper ranges and a little worse off the bottom. the low tension mode may have better low end response, have not tried it and don't plan to. Bike runs great the way it is and I would rather ride than mess with it.

Comparing the V-Force to stock, there is more surface area, not less, that is why it flows better. In the high tension mode, it probably takes a little more to open them than stock.

 

[steve125]

The std.&nbsp;reed valve in most late model mxer's is hard to beat. A few exceptions would be the 02cr125 and 02-03 cr250. The std.&nbsp;03 cr125 valve on the other hand is excellent. Ive found in my dyno testing unless&nbsp;the std.&nbsp;valve is really flawed,&nbsp;there will be no real gains and sometimes a slight loss with an aftermarket reed valve. In comparison an aftermarket exhaust will make much more of a change in&nbsp;power output, good or bad,&nbsp;than any aftermarket reed valve ive tested.

 

[bclapham]

steve: if you build an rm next year, stay clear of the v-force- its made mine a jetting nightmare (ie mega rich) and you have to cut the stuffer so you cant swap back. Did you realise that the rm and yz reed cages interchange???