Home Forums 250 Superkarts All Things CR250

This topic contains 33 replies, has 11 voices, and was last updated by  Stephen gleason 4 months, 1 week ago.

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  • #5135

    Ian Harrison
    Participant

    Hi Guys

    I’m not sure if this is the best way, but click on this link to go to the “All Things CR250″ topic in the Cassic EKN Form.

    http://eknclassic.com/viewtopic.php?t=66607

    This was started in Jan 2009 by my good Superkarting friend, Erik Frank. Since then it had 400 replies and 124,000 views!! I can’t even beging to imagine the hours that I and others have spent researching and posting good and valuable information.

    Hopefully anyone can access all that information for years to come and perhaps that thread can continue in this topic on the new forum.

    Best Regards

    Ian :-)

     

    #5181

    Roger Miller
    Participant

    would propose that we have a sticky topic for this, and maybe a couple of other historical links in the same place.

     

    #6724

    John Benson
    Participant

    Hi Ian ,

    just wondering if any more work had been done with  the HPI box and ’02 stator flywheel?

    #6835

    Ian Harrison
    Participant

    Hi John

    You can forget running an HPI box with an ’02-’07 stator.

    We have developed a fantastic basic programmable ignition with Zeeltronic that works with the ’02-’07 generator (ignition only, no powerjet, powervalve or quickshift). This is designed around our UK regs.

    Prices are:

    New ’02-’07 Generator (if required) – £200.00

    New Rectifier Regulator (if required) – £40.00

    New Coil (uses standard Honda CR250) – £39.00

    Programmable box programmed with 2 Viper Curves - £245.00

    Bespoke Wiring Harness – £40.00

    Best Regards

    Ian

    #8420

    Stephen gleason
    Participant

    <span style=”background-color: rgba(255, 255, 255, 0);”>Hello Ian

    I have had a chance to use a Dyno
    To test my cr250 based engine after getting a good baseline. I put carb (38mm mikuni )on flow bench got a baseline. Then taper bored and worked the bell area. To a 20% increase .
    Re installed on engine and. Reran  the pulls. And the graph layed right over the first runs
    So next I put a 44mm on just to see.  And it did same!!!
    Now I’m confused  (I have V force reeds).  Is that the limit of motor or is there a restriction I need to be looking for?   Any ideas
    Thanks in advance
    Stephen Gleason
    Sent from my iPad</span>

    #8431

    Ian Harrison
    Participant

    Hi Stephen

    Sounds like you engine can pull all the air it can swallow through a 38mm venturi

    On our fully race tuned CR250′s we find the optimum size to be 41.5mm. However, a 38mm will give exactly the same power up to about 9,500 rpm. It’s only really the last 1,000rpm from 10,500 to 11,500 were you begin to see an appreciable difference of about 2 Hp at say 11,200 rpm. Of course if your engine is in a lesser state of tune and doesn’t pull those kind of revs or the power drops off after 9,500 rpm, then your wasting you time, effort and money. Can you post up a dyno graph for us to see?

    Best Regards

    Ian :-)

    #8438

    Stephen gleason
    Participant

    <span style=”background-color: rgba(255, 255, 255, 0);”>Pic

    Sent from my Verizon Wireless 4G LTE Smartphone

    </span>

    #8439

    Stephen gleason
    Participant

    Try again

     

     

    <span style=”background-color: rgba(255, 255, 255, 0);”>Pic

    Sent from my Verizon Wireless 4G LTE Smartphone

    </span>

    #8440

    Stephen gleason
    Participant

    Sent to your email

    #8457

    Ian Harrison
    Participant

    OK Stephen,

    I’ll pick your e-mail up at work tomorrow.

    I’ll try one of mine to see if it works. Could do with preview on here!!

    OK, if your on photobucket you have to click on the “insert image” icon in the EKN message box and copy and paste (only requires a left click to copy) the “direct” link from photobucket.

    Shame the window is now so narrow. Much prefer the old version EKN forum!!

    #8535

    Ian Harrison
    Participant

    Hi All

    Here are Stephen’s dyno plotting points. That’s a very generous dyno. No 250 single 2-stroke race engine ever made 37 FtLb of torque at 9,000 rpm. . . . . I’d guess about 15-20% over the top.  Most likely be around 55 Hp at peak and around 29Ft Lb of torque. Anyway, as long as you always use the same dyno you can at least make valid comparisons as you make any improvements:

    Best Regards

    Ian :-)

    #13280

    StockMoto Joel
    Participant

    I have a spare CR250 Engine (believe it is a 2001 – 2003?) for sale (used) .. $950, email or PM me if you are interested.  Thanks, Joel

     

    #13312

    Ian Harrison
    Participant

    Hi Joel

    The 2001 is a “jug read” motor (reed block on the cylinder)

    The 2002 and 2003 are “case reed” (read block on the crankcase).

    Engine numbers are on a small stainless steel plate riveted onto the crankcase next to where the gearchange shaft goes in.

    The first 2 numbers indicate the year:

     

    63 = 2001

    64 = 2002

    65 = 2003

    Best Regards

    Ian :-)

    #13330

    StockMoto Joel
    Participant

    Thanks Ian.. appreciate it.. will check it out and update the post.

    Joel

    #13392

    Chris Hegar
    Participant

    What gas were you using for testing Ian?

    #13406

    Ian Harrison
    Participant

    Hi Chris

    We have to use 99 Octane unleadead, which is what the dyno runs were done with.

    We have also run MS109 unleaded, which gives great power, but is like a dry-Martini for your engine. Get the jetting wrong and it’ll end in tears!

    I also test on Q16 (for the US market) and Avgas 100LL (for the Aus market).

    With either of the latter fuels you can run much higher compression and ignition advance, without detonation, but I have found the trade-off between bottom-end power and over-rev renders little or no impression in terms of actual lap time.

    Best Regards

    Ian :-)

    #20399

    Larry Dobbs
    Participant

    I have noticed that long track 250 single owners have been ending up on the side of the track too often due to engine failure here in Northern California.  It seems we have been running too lean.  Is there anyone that could go over the basics as to how to establish a baseline for jetting, a good starting point, and what preparation should be done at home so that when you get to the track you are not overwhelmed.  Also, I have noticed that a common sticking point (pun intended) is mid throttle jetting point.  Anyone care to give advice?

    I realize this is too broad but it is off-season and I could use some help.  If we don’t help each other so that we can at least start fininshing some races there won’t be anyone left to race with :)

    #20427

    Ian Harrison
    Participant

    Hi Larry

    Good points and I have your e-mail on the same subject. What you have asked is a very wide ranging subject, which will take a good deal of thought and time to answer in a way that will help everyone. I’ll put my mind to it next week. For the last few months and the next few days 99% of my focus is on completing and achieving registration, in the UK, for our new Viper SK250S (250cc single cylinder) Superkart motor.

    #20430

    John Benson
    Participant

    Larry ,get someone to hack Anthonys computer for his jetting program!

    #20621

    Tony
    Participant

    Hey John – I don’t have a jetting program, it is all stored upstairs in the old grey matter – for a starting point anyway!! Then tuning to the track by how it feels, looks and sounds on the day right – yeah right!!

    What is going on with your program – have you sold your PVP and heading to the 125 class still or are you going to stay with the lads and get your finger out :)!!?? Just kidding – I think your kart is working pretty good, just needs a few tweaks and you are right there!!

     

     

    #20629

    John Benson
    Participant

    Hi Anthony

    If you don’t have a program on your lap top, what were you looking at all day at Sears while the rest of us were thrashing? :) Yes I’m staying with the 250, and getting a 125 for practice! Larry ,all I know about the Dellorto is there’s to many things to change for my pee brain. I like my Mikuni ,once I got the float level set it’s been good. I know you have a 257 which is a higher level race engine ( I am hoping the club will allow some rule changes so the CR guy’s can compete on a level playing field,that EVO barrel above would be a nice start) so not sure how it would work for you.

    #20631

    Tony
    Participant

    John – I was looking at my data, checking RPM, EGT etc. trying to dial her in!

    I know what you mean about the Dellorto carb – I have a few of them, I found them pretty complicated, however I think once you have figured it out it is a very tune-able carb; Ian knows how to tune them – that said I think he has switched to the TMXX carb.

    And talking about engines – there is nothing wrong with your Honda – I had nothing for you – my speed is in my karts handling – when I came upon you exiting the carousel your engine pulled a couple of lengths on me very easily – get that kart dialed and you are right there my friend!!

    #20664

    Larry Dobbs
    Participant

    My idea is to let the European’s beta test the new barrels this year before we make any rule changes here, and that’s because they have more participants than grid spots and can afford to make a mistake, whereas we have just enough participants to break even on paying for the event, so we can’t afford to alienate any of our participants.

    #20757

    Andy Kiker
    Participant

    I have never found the 250 single to be very jet sensitive. once you have a good setup and it is not blubbering and exhaust temps are not to high leave it alone. Unlike a 125 you do not have to be right on the verge of detonation for it to be fast. I run the same jet almost all the time unless there is extreme air changes or you go to Miller in Utah.

    #20760

    Larry Dobbs
    Participant

    Andy, please tell us what carb, pipe and ignition you were using.  Tell us what piston and piston-cylinder wall clearance, head volume, and reeds.  How often do you need to change the top end and then the crank?  Thanks in advance :)

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