Trail ReportsTech ArticlesVideo GalleryHOME

Jan 3, 2010

Top End Rebuild And VForce3 Reed Upgrade, 2001 CR250.

It was time for another fresh top end on my bike. I'm taking the opportunity to do check the health of the bike in other areas as well. The Boyesen reeds have done a fairly good job on the intake side of things, but they've lived their life and it's time to try something else for a while. I decided to try V-Force reeds. They are a bit pricey compared to stock reeds and/or most Boyesen options, but they are less than the Boyesen Rad Valve. They have a unique dual V shape with twice the reed tip surface for better response and better reed life. They also have a snap apart design and use the same reeds top and bottom for easy replacement. The composition of the reeds themselves consist of carbon fiber and allow the reed stops to be unused. Compared to the stock reed cage, it's obvious to see the difference. Although I had been using the stock reed cage, the reeds are Boyesen dual stage reeds that use a stiff inner partial reed and a softer outer reed. The dual stage reed offer a good low end, but seem to allow too much reed flutter and inconsistency at higher rpms.





On a few models(mine included) the rubber needs to be trimmed from the stock intake boot in order to fit the design of the V-Force 3 reed cage. The instructions a are really clear on how to do this and it's not a big deal, but going back to stock will be more difficult for sure. Make sure to pay attention when lining up the intake boot with the reed cage, there is a top and bottom. The hole is offset, and will be partially blocked if turned upside down.

After measuring the cylinder, I determined that it was still in good enough shape to not require any work. To measure the cylinder first determine the specifications. On a 2001 Cr250 it should measure between 2.6141 and 2.6144 with the service limit being 2.615. The cylinder should be measured in a number of locations along the cylinder on both x and y axis. My lowest measurement was 2.6143 and my highest was 2.6148 so it was within the service limits.




Removing the top end is very basic. Remove the cylinder, then the old piston and re-install the new piston. Make sure you get the top gasket installed the right way(as shown) and the piston the right direction. Some have arrows that will point forward, this one did not, so make sure the cut out in the piston goes towards the back as shown. It's best to take note of how the old stuff comes out to make this process easier.



Below is a shot of the nifty V-Force 3 Reed logo on the side of the reed cage, hey at least you see this much, the piston never gets seen. Hopefully they will do their job as required. This was an easy job and an even easier upgrade to the V-Force 3 reeds. Next up is the rear shock.

5 comments:

  1. loved the pictures of the kids up above, oh waith a minute that was pictures of motors up above, my mistake...the putz

    ReplyDelete
  2. Awesome! Looks like a chore!

    ReplyDelete
  3. Yea for sure. I think I got past the hardest part tonight..taking the rear shock apart. Now all I gotta do is fill it with fresh oil and get the bladder charged with nitrogen and I'll be all but done with my 2 biggest projects.

    ReplyDelete
  4. it all looks easy did youhave to do anything in order to the barrel concerning the power valve as ou have said nothing about it and that is my area of concern

    ReplyDelete
  5. also can you tell us anything about how the bike ran after th new reeds were fitted were there any major improveents?

    ReplyDelete