Eric, case-reed questions

[Rider 007]

Eric,
this year before Honda released the 02 CR250 I heard & read all the musings of how doubtful it was that they could get the broad spread of power out of it like the 95-96 engines due to the case-reed design. Then the mag tests come out and they start with the "see, I told you so", and blame it on the case-reed engine design. A friend has one and agrees that it isn't what the older CR's were in the engine department.
My question is, if the case-reed engine is supposedly an inherently high rpm design and is to blame for the CR's engine shortcomings, how does KTM manage to put out such broad, massive power according to all the owners I hear from, using a case-reed?
Have you spent enough time in the 02 CR jug to see what the deal is that makes it so sleepy compared to the KTM?
I'm curious to know if you think, or know by now, if it can be made like the old 96 motors. It seems the rest of the pieces are there to be the king of the hill, it just needs the juice.
Thoughts, ideas, specific recommendations?

Thanks in advance.

 

[spanky250]

This was discussed in another thread:

Originally posted by EricGorr
I've been talking with Pete Payne and Wes Gilbert on the CR250. I think that the transfers are too high (advanced timing, long duration) and the exhaust port is too low (long effective stroke but retarded timing and not enough duration).
Wes has some interesting observations on the exhaust valves and how they fit up into the port. He's specced out the blowdown timing (distance from when the exhaust opening to transfer opening) and found it to be suspect at low rpm. Pete and I talked about adjusting the front cable so the exhaust valve doesn't close as far.
Lets remember that this engine has roots as a dual sport bike in Japan and Europe. In recent years it has had a motorized exhaust valve meaning that it goes through an open and closed cycle every revolution, in order to facilitate activated radical combustion.
Having an exhaust valve close very far like this could influence emmisions and noise too.
I've tried some different porting so far. The first iteration was to turndown the cylinder base 1mm and raise the exhaust port 1.5mm, and recut the head accordingly. The rider, a DRN member in Colorado said that made a difference but the jetting was where he found the most beneficial gains for the high altitude.
I'm also looking into some billet parts with AJ from Service Honda, in particular the pulley diameter and the butterfly shape and orientation on the exhaust valve servo motor.
One things for sure, its all new and the polishing kings are going to be in trouble :p

 

[Rider 007]

Thanks Spanky, obviously I didn't find that on my original search.
So, has any progress been made on this yet or is everyone still searching for the grail?
I'm very impressed with the 02 CR as far as the rest of the bike, but don't want to drop the cash if the engine can never be what I'd like. I had a 95 and had Eric do the cylinder on it and would like the same performance in the 02 if possible.

 

[HiG4s]

125 Husqvarnas make pretty fair low end for a 125, and have the intake in the case not the cylinder. I hadn't really thought about it until some one on an RM250 mentioned to me my bike seemed to have lots of low end for a case reed engine.

 

[cr-man]

The 02 CR250 also has a very weird reed cage design that I'm kind of surprised nobody's mentioned not sure if it's good or bad just different. Eric does cometic make a base gasket that will drop the cylinder? I'm going to mess with the exhaust valve and see how that works my bike runs pretty rough up to 1/3 throttle I have a leaner needle on order. If I can get this low-end cleaned-up and keep the mid and top I'll be in good shape.:)

 

[EricGorr]

Thanks Spanky for bringing back that post on crankcases. You're better at this editing thing than I!

CR Man, I haven't seen the reed valve yet. Service Honda sent me an engine without the reed to take some measurements from. The cometic gaskets are only .010 inch thinner than stock. I figure the transfers have to be lowered .040 inch.
The other day we discussed making adjustments to the cable for the full closed position of the valve. If you get a chance to try that please let us know how it works. :)

 

[cr-man]

Hey Eric,
The reed valve is a funny shape like two different angles for the reeds and the divider is positioned more to the bottom instead of in the middle (more space in the reed cage for the top reed). The reeds are set-up kind of like the reeds RCE sells with stiffener reeds on top.
Eric I played with the exhaust valve cables for a couple hours today without much luck no matter how I adjusted them they still closed. I have the carb off waiting for the leaner needle to come in, so I did not run the engine to see how it was working I was just moving it by hand. I will give you a call to ask you some questions I have about it. Some of them are pretty good for DRN members though How about the servo motor does it have to move all the way through it's range of motion? If it doesn't wouldn't be easier to just make a bushing and put it on the stop pin? Also when you adjust the cables they seem to pull on the servo motor rather than one side loosing up. You are right about the exhaust valves closing pretty far making the exhaust port very small in the closed position. I must be one of the weird ones though because I love the kind of power this bike makes just grab the throttle when you need more and it rips, but I would like to get rid of the funky running up 1/3 throttle. All of the magazines are running some funky jetting that would make my bike un-ridable they actually are richening them were mine runs rich and there at sea level I don't understand it:scream: . I'll be talking to you Eric:)

 

[spanky250]

It sounds to me like your bike might be a candidate for a leaner slide. The bottom 1/3 of thottle is exactly where a leaner slide will benefit you.

 

[marcusgunby]

Heres some interesting Cr250 tuning info -a well known Uk based Honda team spent a whole day testing a euro made pipe-after trying 6 different pipes on 6 newbikes(too show how professional the set up is) they ended up at the end of the day saying how well one pipe worked -the pipe was 02 Cr250 std.

 

[cr-man]

Spanky I talked to Eric about a Leaner slide and that's how we got on the Discussion of the power-valve dropping so low in the cylinder he said that I should try that before trying the slide.
Marcus that's good to know. Do you know which pipes they tried and why they didn't like them? I'm interested in the Doma pipe. What did they find out in their testing of the 250?

 

[Rider 007]

CR-man,
I assume you own the CR that Eric was referring to in his post as having modified. If so, when you say you love the power on it, are you referring to pre or post modification? How is the power different now? And was the jetting rich up to 1/3 throttle before the mods?
If you haven't modified it, then .... nevermind! :confused:

Thanks!

 

[cr-man]

Rider 007 - I am not the guy that Eric did the cylinder for I had just called Eric about whether I needed to try a leaner slide and that's when he told me to try and adjust the powervalve. I like the way it runs stock except for the low-end is not very crisp at all. I'll get it working though.:) Rider 007 are you having problems with yours? I live in PA the guy that Eric did work for is in CO. I believe.

 

[Rider 007]

CR-man,
I don't currently own the 02 CR250, but considering it. That's why I was looking for some feedback on the new engine. I had a 95 that Eric did and I liked the broad, smooth power (not like my WR4F, mind you) that it had and want to make sure I'll be able to get it to run the way I want before I drop all the money on one. I'm trying to arrange a ride on my buddy's 02, but it's been difficult with my travelling and him across the state. One ride would be worth a bunch of word-of-mouth reports, you know?
However, the input of people like you and tuners like Eric will also help shape my decision, one way or the other.
Thanks for the info and I'm sure alot of other people find it helpful, too!

Take care
:)

 

[cr-man]

I also had a 95 CR250 Eric did for me and it had a nice tourqey powerband. I did not like my 95 because of the forks they felt like they flexed a lot to me. The 02 is way faster to me, but not as tourqey as the 95. One thing to keep in mind about the case reed is that you don't have the long cut-outs in the cylinder for the reed induction and that should pro-long piston life. I like it! It is not perfect, but no bike is.