more midrange on 2007 yz 250

i need more midrange power on my 2007 yz 250 which i ride in enduros,the bike is well sorted and is fitted with std exhaust with fmf powercore 2 silencer9oz gytr flywheel, 14x48 gearing,powerblade,boyesen radvalve and the std ports have been cleaned up and head shaved down to 050 clearence,i run 32.1 motul 800 with shell v power petrol. after rideing the 265 of brms which has more midrange than the extra 15ccs he has i now need some help to pep my midrange up. has anybody also tried a quicker action throttle on their yz 250 . philip coley

You've done quite a bit already, maybe it's time to bore it out? Get more low and mid

ditch the boyseen.

i need more midrange power on my 2007 yz 250 which i ride in enduros,the bike is well sorted and is fitted with std exhaust with fmf powercore 2 silencer9oz gytr flywheel, 14x48 gearing,powerblade,boyesen radvalve and the std ports have been cleaned up and head shaved down to 050 clearence,i run 32.1 motul 800 with shell v power petrol. after rideing the 265 of brms which has more midrange than the extra 15ccs he has i now need some help to pep my midrange up. has anybody also tried a quicker action throttle on their yz 250 . philip coley

I can help u. Tell me what you low and top is like as well.

Check your timing, if you already have tell me what it's at. Tell me your jetting specs and elevation and temps. Could be your needle.

14x48=3.42 final

Im at 13x48=3.69 final which I like alot for the woods. Mostly depends how much you top out in 2nd going up hill climbs or if you use 3rd gear more..

If you have room in your budget getting your carb modded and your squish done a bit lower and the right jetting will make you bike feel like a 285. But for starters, ditch the flywheel, it's unessesary and is hurting your goal, I'm sure of it.

You've done quite a bit already, maybe it's time to bore it out? Get more low and mid

I dont think so at this point.

ditch the boyseen.

May be, but since he has the 07 he will have the updated one..i or j I cant remember.

hollywood my bike has good low and top end power, and i set my timing at std with a good dial gauge. my carb has 185 main,45 pilot,n3ew needle clip 4 airscrew 2 turns out ( european spec yz ) twinair filter, elevation up to 2000 above sea level. the boyesen radvalve took some time to jet in but i can just potter along and then crack open and the bike just pulls nice and smooth right up till flat out. many thanks philip

HGS:excuseme:

HGS:excuseme:

Mate that's the loudest pipe I've EVER heard.

Even in Thailand the local constabulary have to be avoided with that pipe.

Works like a charm though, very impressive.

hollywood my bike has good low and top end power, and i set my timing at std with a good dial gauge. my carb has 185 main,45 pilot,n3ew needle clip 4 airscrew 2 turns out ( european spec yz ) twinair filter, elevation up to 2000 above sea level. the boyesen radvalve took some time to jet in but i can just potter along and then crack open and the bike just pulls nice and smooth right up till flat out. many thanks philip

Ditch the boyseen!!!

I'm not just saying that to say it...

Any typically, at your elevation, and with a boyseen, the main can be down to about a 170-2 at about 60-70 degrees on decent gas mixed around 30:1

But that still won't help your issue!

I feel the PC pipe damn good mid to top as well.

Mate that's the loudest pipe I've EVER heard.

Even in Thailand the local constabulary have to be avoided with that pipe.

Works like a charm though, very impressive.

Definately has a sound all of it's own:thumbsup:

or you could simply send your cylinder and head to Eric Gorr and ask for a 295 set up for pump gas......take your choice of which kit (mx or enduro)

I've always been disappointed with a YZ250/Boyesen combo. I'm more of a V-Force guy. While I would always describe Boyesen as producing a "change" while I would describe the V-Force as producing a general improvement.

I feel the same way about pipes. Some, like the Boyesen reed, seem to attempt to focus some more power on the top end at the cost of softening the power else where. While others attempt to produce an overall effect.

If you're looking for low mids you might want to try a Gnarly pipe. But be careful what you ask for, because you just might get it.

hollywood my bike has good low and top end power, and i set my timing at std with a good dial gauge. my carb has 185 main,45 pilot,n3ew needle clip 4 airscrew 2 turns out ( european spec yz ) twinair filter, elevation up to 2000 above sea level. the boyesen radvalve took some time to jet in but i can just potter along and then crack open and the bike just pulls nice and smooth right up till flat out. many thanks philip

I think I see the problem, jetting. The EW needle has gotta go and your main is rich as well. At your elevation I'm not sure if your safe to go lower than the EJ needle but it would be a start. I bet if you go to an EJ clip 2-3 and drop that 185 way down you will see drastic improvements. Harris below thinks you can go to 170-2 but I wouldnt just drop to that right off the bat, I would start from 178 and work you way down and keep an eye on your plug each step. It sounds annoying but you can easily get it strait in a few hours along with the needle. Also with your power hole in the mid of you power band, after you test the bike with the jetting dialed in, follow Harris's advice and swap out the boysen to see what happends.

Ditch the boyseen!!!

I'm not just saying that to say it...

Any typically, at your elevation, and with a boyseen, the main can be down to about a 170-2 at about 60-70 degrees on decent gas mixed around 30:1

But that still won't help your issue!

I feel the PC pipe damn good mid to top as well.

Ya cant go wrong with the PC pipe. But getting his jetting set right should yeald more power than the PC pipe at this point with how rich he is.

And to the others in this thread and in general;

Just because someone says they need more power, the blanket statement of just go over bore gets thrown around here too much. Seek to understand the users setup first before rushing to conclusions. Over bore is not the cure for every power problem. Even the statement of has good low, weak mid and good top. That tells me right away that there is a clearly a setup issue and a over bore is not the cure....:excuseme:

hollywood my bike has good low and top end power, and i set my timing at std with a good dial gauge. my carb has 185 main,45 pilot,n3ew needle clip 4 airscrew 2 turns out ( european spec yz ) twinair filter, elevation up to 2000 above sea level. the boyesen radvalve took some time to jet in but i can just potter along and then crack open and the bike just pulls nice and smooth right up till flat out. many thanks philip

I am in SoCal at 1500 feet and 60F. 180 main and 48 PJ is too rich. 185 must be spewing spooge.

The pc pipe does offer more upper midrange, well...maybe midrange as well. I woudl love to see a dyno chart as I feel some of this gain is because the low end power is down on the pc pipe.

I also agree with the reed assemblies. I think the stocker has to be put back in for a baselin measurement. I have the v force in mine mow and it for sure smooths out the low end. If it gives any midrange improvement, I would be surprised. Keep in mind Yamaha worked for years to perfect this motor. Dont be surprised if bolt on's dont do much.

most of the replys to this thread defy logic and show lack of real knowledge of the 2007yz 250, the boyesen radvalve is known to out perform the v force,and inturn the v force also out performs the std reedvalve,the boyesen is known as harder to jet than the v force.the std reedvalve is a bad design and has been the same for many years. my bike does not have much spooge and the idiots that think droping to a main 170/172/174/176 from a 185 no nothing about jetting, thats a 1 step down at a time and do a plug chop. my bike does not have a weak midrange i just wanted to pep it up as thats a important area in enduro rideing. on a exhaust pipe theme it looks like dep,hgs and gytr are the only companys that have updated their pipes since the alloy frame was introduced in 2005. come on you experts how do i get more midrange.stop laughing brm. philip

hollywood can you define your comment about ditching the 9oz flywheel to help pep up my midrange also what squish would you choose for enduro work and what carb mod do you refer to. philip

Wow someones grumpy, considering Harrperf builds bikes i consider him quite knowledgeable, you're asking for advice then calling people names for for giving advice. The v-farce did not do a damn thing to my bike back to back against the stocker so the stocker is back in mine, every debate i have seen about the boyesen is you end up going leaner across the board because of the improved intake trac. that jetting seems way rich, like Hollywood said but i'm done hear have a nice day

most of the replys to this thread defy logic and show lack of real knowledge of the 2007yz 250, the boyesen radvalve is known to out perform the v force,and inturn the v force also out performs the std reedvalve,the boyesen is known as harder to jet than the v force.the std reedvalve is a bad design and has been the same for many years. my bike does not have much spooge and the idiots that think droping to a main 170/172/174/176 from a 185 no nothing about jetting, thats a 1 step down at a time and do a plug chop. my bike does not have a weak midrange i just wanted to pep it up as thats a important area in enduro rideing. on a exhaust pipe theme it looks like dep,hgs and gytr are the only companys that have updated their pipes since the alloy frame was introduced in 2005. come on you experts how do i get more midrange.stop laughing brm. philip

He didn't say that there was anything wrong with his bike. He rode his buddies 265 and decided to " keep up with the Jones". The Rad valve is doing what it was designed to do...good response with a smooth transition throughout the range. This is how you ride fast and win races. Racers above the beginner level know this through experience. He can modify his head or carb or change his pipe. This may or may not work well. Sometimes doing all of this results in less performance than stock which, in the case of a YZ250, is very good to start with. If the 265 he rode had a decent porting job such as Eric Gorr's and a number of others, he will be hard pressed to out perform it with a 250. He'll be spending money without that much "bang for the buck". To get a huge jump in power there's no substitute for a big bore. Currently, the EG295 kits are probably the best buy on the market. These motors rip, especially the MX version. This one will put his buddies 265 to shame. He will have "kept up with the Jones".......

It's easy to get grumpy while chasing the jones's.

most of the replys to this thread defy logic and show lack of real knowledge of the 2007yz 250, the boyesen radvalve is known to out perform the v force,and inturn the v force also out performs the std reedvalve,the boyesen is known as harder to jet than the v force.the std reedvalve is a bad design and has been the same for many years.

harperf has done more tests with this than anyone else on this board, including dyno time and with riders far more capable than the rest of us. I trust his findings.

my bike does not have much spooge and the idiots that think droping to a main 170/172/174/176 from a 185 no nothing about jetting, thats a 1 step down at a time and do a plug chop.

I'm going to go with the others here and say that your setup is RICH. I lived in AZ and spent most my time between 2000-4000 ft, usually ran a 168 or 172 main depending on temp. I'm now riding around 300 ft and a 178 main is a bit rich at 60-75F. Need to swap in my 175.

my bike does not have a weak midrange i just wanted to pep it up as thats a important area in enduro rideing. on a exhaust pipe theme it looks like dep,hgs and gytr are the only companys that have updated their pipes since the alloy frame was introduced in 2005. come on you experts how do i get more midrange.stop laughing brm. philip

Not all the pipes needed updating because many had enough clearance for the aluminum frame already. Engine porting changes have been nill from the steel to aluminum frames.

A FMF Gnarly might help you get some of that mid you are looking for, at the expense of over-rev. I bought my bike with a Fatty on it, which many say performs close to stock. I swapped a Gnarly on and noticed the power started earlier, had a noticable hit in the middle, then signed off sooner (still plenty of power up top for me, a quick B offroader).

I'd also try riding without the flywheel weight. I ended up ditching mine after going back and forth with it many, many times. With it I always felt like I needed a bit of clutch to get out of the corners, because the bike didn't want to pick up revs and get up in the power fast enough. Without the flywheel weight it has much better throttle response and feels more powerful coming out of the corners. I was running 15/51 gearing during this (basically the same as 14/48 you have).

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now