best mx dune pakage

[mxduner]

what does anybody think is the best engine pipe setup for dunes and mx?

[wilkin250r]

They're generally opposite realms.

Sand doesn't have any traction, no matter what you do, so dune porting tends to be a little more radical, mid-high revs. You don't care about wheelspin, you want max horsepower. Traction is really important to MX, getting speed out of the corners, so porting tends to be more low-midrange to keep wheelspin to a minimum.

The suspension needs are also at odds. Dune porting tends to be softer, to soak up little bumps at high speed. MX is the opposite, you need stiff suspension for landing big air and handling big whoops.

These aren't hard, fast rules. Just general. My advise would be to build an engine/suspension package for whichever is most important, and then live with it when you're in the other arena. Since dune riding is strictly recreational, no serious competition, I imagine you'll be ripping the bowls with a midrange porting package.

[mxduner]

thanx for the post, I'm kinda favoring low to mid power, my 250r that i just got has a paul turner 89 rase pipe and the porting looks pretty wild (no initials) past owner did not know anything about that, kool head and a 38 tmx on it. The jetting is off a bit bore at 66.5 and fresh 210psi.At waynoka i got beat at midrange by 450r's with power up kits.anyways do i powervalve or not pvalve is the question? just got a trx6 pipe but i have not had time to install it, thanx

[TheFontMaster]

For your powervalve question, if you are riding mainly dunes you don't need it. Powervalves help the low end power, which as Wilkin has already stated you don't need in dunes. For MX I would say get the powervalve. Some people say that once you get to the bigger bore top ends, 310+ that they make enough bottom end power that you don't need a powervalve. I would still go with the powervalve no mater what the size.

[wilkin250r]

If you are looking to build a bridge between two opposite worlds, then I would definitely recommend a powervalve.

A powervalve raises and lowers the exhaust port. When it's lower, at low RPMs, it gives you more compression, which gives you more torque. This is ideal for low-RPM operation. If you were to examine the differences between low-end and a high-rev port jobs, you would see a much lower exaust port height on the low-end porting.

As RPMs rise, so does the powervalve. This allows the engine to breath better, and is ideal for high-rev operation.

In a nutshell, the powervalve will give you a smooth powerband (which helps eliminate wheelspin and improve traction, ideal for MX). It gives you all the top-end power without that light-switch powerband that high-rev port jobs are known for. It also gives you much better low-end power that high-rev port jobs are lacking.

If you were only looking to ride the dunes, I would say a powervalve is almost useless. If you were only racing MX, a powervalve would certainly be beneficial. However, since you are trying to do BOTH, I would say a powervalve is the direction you probably want to go. It gives you the best of both worlds, good top-end power to scream through the bowls, but still has the low-end power and smooth powerband that high-rev port jobs are lacking, and those things are necessary for traction and MX.

[PYF]

Originally posted by wilkin250r
If you are looking to build a bridge between two opposite worlds, then I would definitely recommend a powervalve.

A powervalve raises and lowers the exhaust port. When it's lower, at low RPMs, it gives you more compression, which gives you more torque. This is ideal for low-RPM operation. If you were to examine the differences between low-end and a high-rev port jobs, you would see a much lower exaust port height on the low-end porting.

As RPMs rise, so does the powervalve. This allows the engine to breath better, and is ideal for high-rev operation.

In a nutshell, the powervalve will give you a smooth powerband (which helps eliminate wheelspin and improve traction, ideal for MX). It gives you all the top-end power without that light-switch powerband that high-rev port jobs are known for. It also gives you much better low-end power that high-rev port jobs are lacking.

If you were only looking to ride the dunes, I would say a powervalve is almost useless. If you were only racing MX, a powervalve would certainly be beneficial. However, since you are trying to do BOTH, I would say a powervalve is the direction you probably want to go. It gives you the best of both worlds, good top-end power to scream through the bowls, but still has the low-end power and smooth powerband that high-rev port jobs are lacking, and those things are necessary for traction and MX.

Awesome Information Wilkin...I must say I'm really surprised by your knowledge...

[mxduner]

thanx for the great posts! I'm thinking on the 265pv to stik with ama rules but i don't rase too often that it's too important, is there that big of a differene between 265s and say a 310 or so as far as prise and power? i ride dunes 1 or 2 times a year and ride traks a handful of days a year i'm gonna get the p.v. for sure seems i'm a suker for low end power

[mxduner]

and btw engine builders????

[fireburns99]

Originally posted by mxduner
thanx for the great posts! I'm thinking on the 265pv to stik with ama rules but i don't rase too often that it's too important, is there that big of a differene between 265s and say a 310 or so as far as prise and power? i ride dunes 1 or 2 times a year and ride traks a handful of days a year i'm gonna get the p.v. for sure seems i'm a suker for low end power

First of all, its not rase, its race, and prise, is spelled price. I'm sorry i'm picky about grammar.

A well built 265 pv will hang with most 310. It just seems that the 265 had more R&D behind it. I'm not familiar with many engine builders, but for porting etc, i've heard good things about neil, at c-leigh.

[mxduner]

I apologize fireburn99 my (see) letter just (K)rapped on my keyboard and i'd rather spend money on my R seems i'm going to st. anthony in 2 weeks.Anyways i'm not familiar with,hee hee, see leigh kan you fill me in I just bought this r and i've been out of the quad loop for a few years,thanx!

[BLACKeR]

I apologize fireburn99 my (see) letter just (K)rapped on my keyboard and i'd rather spend money on my R seems i'm going to st. anthony in 2 weeks.Anyways i'm not familiar with,hee hee, see leigh kan you fill me in I just bought this r and i've been out of the quad loop for a few years,thanx!

LMAO how do you tell someone your (C) doesnt work when you dont have a (C) on your keyboard. i had to read that post a couple times before it made any sence...

[fireburns99]

his name is C-LEIGH RACING and hes a member on these forums, so i would get in touch with him. I'm sure that he could point you down the right direction.

[zedicus00]

neil at c-leigh racing has been TERRIBLY busy here latly. hopefully he doesnt get burnt out like rick at macdizzy did and like eric gorr went through a while back. anyways in case he doesnt answer yur pm right away just no hes been working his tail to the bone rebuilding engines from forum members here and on other forums....

[mxduner]

how does he fair to big names like esr lrd and does he build power valve motors?

[707trx250r]

Neil will build any motor you have the funds for. His work is far better than esr or any big builder. Neil will be doing a pro-x 330 for me at the end of summer.

later
Adam

[wilkin250r]

I don't know how much flexibility Neil will have with a powervalve motor. The powervalve makes it extremely difficult to modify the exhaust port. If the exhaust port is fixed, than the transfers are extremely limited in their adjustability.

As such, I don't know if Neil will be able to put together a significantly better package than another company.