Jump to content
Sign in to follow this  

2002-2007 CR250 case reed engine

Recommended Posts

For those of you with experience with the case reed engine, what mods work best on it? Some guys advocate putting the Keihin carb on, some say that the crankcase volume is excessive, some say the squish band needs to be set--- what works?

Share this post


Link to post
Share on other sites

Some guys advocate putting the Keihin carb on, some say that the crankcase volume is excessive, some say the squish band needs to be set--- what works? YES, no and YES

Share this post


Link to post
Share on other sites

Short of serious porting work, I would go with a set of V-Force reeds and call it good. SST pipes are ok but you've got to run at least 50/50 race fuel, the motor is already borderline with 91 octane in stock trim. The Keihin/Mikuni thing stems from people being more experienced with the Keihin so the Keihins are easier to get tuned right but the Mikunis are just as good, if you can tune them. It's a solid motor and there just isn't much that it needs done.

Share this post


Link to post
Share on other sites
Short of serious porting work, I would go with a set of V-Force reeds and call it good. SST pipes are ok but you've got to run at least 50/50 race fuel, the motor is already borderline with 91 octane in stock trim. The Keihin/Mikuni thing stems from people being more experienced with the Keihin so the Keihins are easier to get tuned right but the Mikunis are just as good, if you can tune them. It's a solid motor and there just isn't much that it needs done.

I have an '02 and run a stock expansion chamber, 30mm cut off the length of the stock silencer. A 5mm spacer under the exhaust flange on the cylinder, a V force 3 reed block, 13/50 tooth gearing and I think I have the jetting right with the stock carb. After all this I'm happy but I think I'm just too used to it until a friend with his '06 commented on how responsive and strong it pulled from low revs. Getting the jetting right was the most satisfying and cheapest.

Share this post


Link to post
Share on other sites

ive done some research on this as i have a 03 it seems that the squish height is often excessive especially on the 02 to 04 models and that fixing it will smoother,cleaner, and make it easier to tune but as 1987cr250r said "the motor is already borderline with 91 octane in stock trim." if you reduse the squish and don't want to run race gas then make sure to have the head work done to maintain the stock compression.

the stock carb is tuned poorly from the factory and can be tricky to get tuned right. Many people swear by the jd jetting kit and claim huge improvements

i plan on both these mods just to make my bike run smoother.

as for the crank case volume being to large i've read that and also that the porting specs are less than optimal but i would leave that kind of work up to the discretion of an engine builder with lots of experience with these particular motors

Share this post


Link to post
Share on other sites

Great info, and thanks for your help.

Share this post


Link to post
Share on other sites

The case reed motor needs just a little tweeking to get it to run really good. As some have commented the jetting is crucial it comes way to rich w/ factory specs. The 2nd thing is the 02-03 came with a 48t (49t 04-07) rear sprocket. By adding a couple of teeth to a 50t it will add some snap on the lowend. The 3rd thing is by adding an aftermarket reed cage like a vforce or boyesen helps the overall powerband. These mods alone are a great improvement over the stock settings. The motor will really benefit from cyl. porting & head work, It's like waking up a sleeping giant.

Share this post


Link to post
Share on other sites

How about the RC valve cable adjustment? The cables are rumored to need constant attention. Keep in mind that I'm on a late model YZ250 which only needs a small amount of jetting to run fantastic. However I have always liked the Honda overall design, quality of components, durability, and fit and finish.

With reference to the V-Force, I tried them on the YZ and actually took them off in favor of the stock carbon fiber reeds. IMO, the V-Force did very, very little for the YZ. It's surprising that they are recommended for the case reed CR.

Please keep the comments coming, as they are valued from people who have actual experience with getting this engine to roar.

Share this post


Link to post
Share on other sites
"These mods alone are a great improvement over the stock settings. The motor will really benefit from cyl. porting & head work, It's like waking up a sleeping giant."

How does the modified CR case reed engine compare to a late model YZ? Has anyone had the chance to ride both and compare?

Share this post


Link to post
Share on other sites

"The 2nd thing is the 02-03 came with a 48t (49t 04-07) rear sprocket. By adding a couple of teeth to a 50t it will add some snap on the lowend." I never bought into this one. I run a 14/50 gear and built enough motor to pull it. PWK, 205 psi, porting, dep pipe, rad valve and 265cc are what it took to get it done.

Share this post


Link to post
Share on other sites
How does the modified CR case reed engine compare to a late model YZ? Has anyone had the chance to ride both and compare?

I use to own 02 & 04 YZ250's. From what I have read it's basically the same design motor from 02-09. IMHO I think the YZ motor is over rated. The 04 model YZ had some port work done by the same tuner that my 03 CR250 has. From my experiance, YZ vs. CR have a similar lowend response & in the midrange is where the CR comes on strong over the YZ. The topend & overrev, there is no comparison the CR keeps pulling hard & kept reving over the YZ. The YZ felt like it signed off to quick compared to the CR. They are both good bikes & motors. I picked the CR it just suited my type of riding & style (MX).

Share this post


Link to post
Share on other sites

They dyno says, 02 CR makes more bottom end, mid and same peak power as 01 YZ. The 01 YZ has more overrev.

Share this post


Link to post
Share on other sites

With reference to the V-Force, I tried them on the YZ and actually took them off in favor of the stock carbon fiber reeds. IMO, the V-Force did very, very little for the YZ. It's surprising that they are recommended for the case reed CR.

Team Honda ran them on RC's 02-03 factory CR250's. When I had them on the YZ It was recomended by a factory tuner that the stock unit was better.

Share this post


Link to post
Share on other sites
They dyno says, 02 CR makes more bottom end, mid and same peak power as 01 YZ. The 01 YZ has more overrev.

Keep in mind these are both modified units not stock.

Share this post


Link to post
Share on other sites

Both bikes in the dyno sheet I saw had aftermarket pipes but were otherwise stock.

Share this post


Link to post
Share on other sites
Short of serious porting work, I would go with a set of V-Force reeds and call it good. SST pipes are ok but you've got to run at least 50/50 race fuel, the motor is already borderline with 91 octane in stock trim. The Keihin/Mikuni thing stems from people being more experienced with the Keihin so the Keihins are easier to get tuned right but the Mikunis are just as good, if you can tune them. It's a solid motor and there just isn't much that it needs done.

I think the Mikuni is just more sensitive to elevation/temp than the Keihin. I have ran both on my 03 and like the Keihin much better. It has a much broader range with the same jets. Not to say it ran bad with the Mikuni. It has alot to do with what you want to do with the bike... trail ride or pure mx. I think the Mikuni is better suited on the track, and the Keihin on the trail.

Share this post


Link to post
Share on other sites
I think the Mikuni is just more sensitive to elevation/temp than the Keihin. I have ran both on my 03 and like the Keihin much better. It has a much broader range with the same jets. Not to say it ran bad with the Mikuni. It has alot to do with what you want to do with the bike... trail ride or pure mx. I think the Mikuni is better suited on the track, and the Keihin on the trail.

same sentiment I came up with after trying both carbs, both carbs with JD jet kits installed too.

Share this post


Link to post
Share on other sites
When I had them on the YZ It was recomended by a factory tuner that the stock unit was better.

No surprise at all. If I had known this ahead of time, it would have saved me some wasted money.....

Share this post


Link to post
Share on other sites

Interesting thread...

Where should a 2004 CR250 engine go to get ported?

Should it get "squished" as well?

I would like to keep the stock bore and run 91 octane pump gas, and this will be be a XC/H+H/single track offroad motor...

thx

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

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

Reply with:

Sign in to follow this  

×