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Yeah they took off .020”
I had to squeeze that out of them (or it’s very possible it’s just that hard to talk to someone with any engine knowledge there)
I’m currently putting the PC set up on. Mitch said the squish being 1.1-1.3mm is ideal. I’m right at 1.1mm with the oem 04 base. There isn’t much I can do without stacking gaskets (not a fan of), so hopefully it’s good. 1.1mm seems closer to 125 numbers. Will give an update shortly.
I also matched the pc exhaust flange to the cylinder, it was pretty far off on both sides, I’d say 2-3mm. I also put a 05-07 reed boot, there is a very noticeable difference in looks compared to the 04. The 05-07 looks like it will flow much better
Excited to see what you think of the PC cylinder. I had my 2002 done by them. It was too much for my C class skills. Bike ran amazingly well on VP C12. PC's jetting recommendations were spot on. Never ridden a more clean, crisp two stroke as that bike.
Lowering the base of the cylinders on the cr250, actually has the opposite effect. It bumps up the lowend and lessens the hit a little into the mid.
Did PC fill in the J-hooks ? which bumps up the lowend a little more and smooths the hit into the mid even more.
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They didn’t fill the j hooks. The work done was pretty minimal minus the exhaust port and milling the cylinder base.
I broke it in and it’s really crisp down low into the mid. Im going to go down a size on the main to see if it will pull harder up top. I feel like I’m a bit rich with the 440 main. I was running a 430 with the pr2 setup, just wanted to be safe on the break in
Edit. This is with f&l sp3 oxygenated
Ended up going with the 440 main, 32.5 pilot, stock needle second clip.
i really like the power down low, but it doesn’t quite pull up top how I was hoping. I may end up trying a .012 and .015 stacked to get a squish of .050 to see if that helps with the over rev. Current squish may be a little tight at .043
If you’re using the stock 04’ needle, 6CHY12-82, which I’m not a fan of, that main,440, looks really big. I would expect it to be around a 400. The pilot looks close.
do you know how much they took out of the bowl ? I’m assuming you asked to use pump fuel, in order to cut down on the detonation. The squish isn’t off enough to be concerned about, unless it’s causing detonation.
They specd it for mrx02. With 110 or c12 I’d likely be around a 410. With the oxygenated fuel, the 440 seems to be good, maybe slightly on the rich side. It’s still been around 60 degrees out here.
I’m willing to try another needle, I think you have recommended the 05-07 needle to me before?
the bike had a ton of over rev with the pr2 cylinder and head, but really lacked down low compared to the pc setup
jetting was on the rich side, yesterday and today I made a couple changes and the bike rips even better. Moved the needle down one position and ended up with a 420 main like digger suggested
Overall I’m pretty stoked on the power
Also, does anyone have any oem needles available? I can’t seem to find any. It’s going to be really hot here soon so I’ll most likely need a leaner needle than the stock 82
Like Mitch said, your squish is fine. .042"-.045" is very safe on race gas. Their shop bikes are probably about .038". More than likely they took the .020" off the base and raised the exhaust the same, to increase blow down for top end. Very typical porting from PC. If you told them you were going to run race gas, they probably have the compression toward the high side, too.
Personally, I have never really seen a PC 250+ production pipe that I would say had a lot of over-rev. Add in some higher compression and it's really just not a good recipe for great over-rev.
After the jetting changes, it seems to pull better up top. Not quite the over rev I had with the previous cylinder, but the pc setup is better everywhere else. I have oem pipe and a fatty I haven’t tried yet. I’m sure the r304 doesn’t help with top end, but Tom Morgan and pr2 recommended it
Absolutely lots of great feedback here as always. Honda case reed motors like fuel as do most of that design A lot of users say to lean these out and its exactly the opposite. I think Digger is on track with the needle to start with.. I would be substantially larger on the main based on fuel selection, and clean up the the throttle response with a straight rate needle of some profile. I also am not a fan of any clip position other than the middle, otherwise get another needle.. Also, when solving any jetting equation like most moves, one change at a time with a test to control variables.
Pick one fuel and it stick with it, find a setting and test it.
Yes, a longer silencer will help the top side, but you'll most likely lose the "better everywhere else" you like. Pretty much the same if you back off the compression, too. But the two together might boost the mid up power enough to make a worthwhile trade. Something you'll just have to test and see if it suites you, or just forget and be happy with what you got.
Honestly I’m pretty happy with it as is. It’s more rideable than I was thinking it was going to be and the power is there. I planned on getting a couple more cylinder/heads down from other tuners, but I don’t think it will be necessary
Have you been riding the bike quite a lot?
I know it’s still the off season for off-road so probably no racing.
I saw on Jwack thread that you changed graphics and also get PC clamps!
I’ve put quite a bit of time on it in the desert out here and it’s really good all around. I spent countless hours with jetting (even ran a keihin for a few minutes) and the mikuni is dialed. I ended up cutting the slide on it and that pretty much fixed any issues I had. The bike absolutely rips.
lately I’ve been taking it to Glen Helen and my suspension is way too soft there. It’s a head scratcher because I hit stuff way harder and faster in the desert, but I’m like a fish out of water on a mx track right now. I picked up an extra set of suspension I’ll have Graeme setup for mx.
Yeah I got rid of the rg3s and put on the pc clamps. I like them so far. I also picked up another set of shroud graphics
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Why didn’t you stick with the Keihin? How did it feel compared to the Mikuni? Were you able to get more Top with the jetting? I know that’s what you were looking for with the PC cylinder.
Did you try the PR2 cylinder again? That one might be nice for the desert even if you don’t have much bottom.
That bike must be fun wide open up the hills! Haha But down the big hill with your suspensions that might shake you up 😳
I tried a good base setting for the keihin, it was a bit on the rich side so I went to make some adjustments and realized I don’t have room to rotate the carb to get to the main/pilot . It’s too damn hot in my garage for all of that, so I threw the mikuni back on lol. It screams up top.
I don’t see me getting the pr2 cylinder replated and ever running it, the pc setup makes more down low and I believe it matches it up top now.
Ah that’s sucks if you have to move the subframe to take off the carb, I guess at home its okay (even though in summer it’s too damn hot 😂) but doing adjustments in the desert or GlenHelen it’s too much! Haha
It would off been nice to ride that bike stock and see how it feels compared to the PC engine.
is the PC engine still smooth enough that it doesn’t wear you out so much? Or it hits quite hard?
250 2 stroke can get tiring quickly when it gets rough.
It was pretty damn hard to ride on hard pack Rocky stuff out here, hits very hard. I’m running a 13oz fww and it helped a ton. I like pretty much everything about the power, even on the track 13/48 gearing felt good
Maybe you could try 14/51 to tame it down a bit, mostly when it’s hardpack and it hits too much it’s not so fun.
since you ride desert a lot that would actually be a good gearing probably? I’m sure it has enough bottom to take it right?
That’s how I remember my 2002 PC CR250. Sooo much power. Had a bad get off in 4th gear on some hard pack rollers. Back end came out and that was that.
Yeah the mid transition was pretty damn sketchy for a bit. A 10oz ffw did absolutely nothing, the 13oz seemed to smooth it out a bit and made me not want to sell the bike anymore lol
I’ve considered 14/51 which will be near identical to the 13/48 I’m running. The bike tops out around 82mph so it’s a good mix for desert and Glen Helen for me. I really like 3rd with this gearing. It pulls forever and was actually making time on 450s up the hills at gh
Hey Zack - Good to hear you got the PC cyl & head mods working good. It's a shame Honda didn't put the R&D to develop the case reed engine further & left a diamond in the rough. Off the showroom floor the engine got bad reviews from most of the mx mags at the time. One of the biggest issues is a sensitive carb that came overly rich off the showroom floor. Once the jetting is sorted out with good gas it will run very good.
As you found out the CR case reed engine can go to the next level. It comes alive with just cyl & head mods with some good engine specs from reputable tuners. I've been fortunate to have owned & ridden a few fast 250 2-strokes in 4+ decades. What I found out is the 02-07 CR makes an extra 5-7 hp over the traditional cyl with the reed intake. Like you I've passed & pulled a few 450's on some straights. The rider will sometimes come over to where I'm parked afterwards & ask, if I'm running an older CR engine with a bigger bore. They always seem stumped when I point at the CR electronic valve & let them know it's a standard 250 engine.
Most have commented that they heard or read the case reed engine was a dog. It puts a smile & I get a chuckle off that..
Hey ray. I completely agree, the modded engine is insane. I’ve built a couple modded 250s recently and they don’t compare to the case reed. The closest I’ve ridden was a stock 22 250sx the other day. Very similar power characteristics to my cr, surprisingly my bike had slightly more bottom and obviously more top and over rev.
I got in a heated argument about the 01 vs the case reed on Facebook. This hick kid swore his 01 with the head sanded down is faster lol
A good friend of mine who passed was a pro rider who had a 96 & 01 CR250r's that were done up. I had a 01 as well that had mods, but the 02-07 would pull the 01's. He had read the mags & was talking smack about the new case reed design. I actually dispelled the myth after we put that theory to the test. He was stumped as well & I never heard another peep from him. The funny thing was he tried to buy the bike from me several times before he passed.
To this day I still hear the negative talk especially on social media. The mx mags definitely had an impact on that IMHO..
Yeah there are a bunch of people that swear the 02-07 is useless because the magazines and jetting issues. Oh and incorrect powervalve adjustments
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