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About James_Dean

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  1. These are good points to consider after reading the pages of comments up to this page. The improvements from bottom to top are significant after having both the Mikuni and Keihin-STIC compared, from Mikuni at 38.52HP to Keihin-STIC 40.05HP The 1/4 throttle comparison to a 250 4-stroke isn't any surprise, as the 4-strokes always have declining torque at low throttle with increasing RPMs. --Which is why we feel the 4-strokes keep traction and 2-strokes spin wild in slippery conditions. Thanks for sharing the results!
  2. James_Dean

    RK Tek performance head vs Slavens S3 vs cut stock heads

    Same results here. The lab dyno matches REAL WORLD power improvements on the butt dyno. Saying that the power on a MEASURED device isn't a valid test is denying the simple physics. The results were consistent with riding in EVERY case. The measured dyno improvements can be felt with more torque climbing hills, accelerating out of corners, and riding a gear higher. These effects were experienced in all four cases with the bikes that showed improvement on the dyno. The 250SX heads and 300SXS heads from KTM make easy off-the-shelf improvements when riding. The other heads sent out for machining cost $60 plus shipping, for similar increases in torque climbing hills, lugging the motor and pulling, and made better running machines overall. Premium pump fuel was used in the bikes, so no race fuel required. None of this is suggesting the other aftermarket heads from VHM, S3, or RKTek aren't adding performance. The question remains ENTIRELY SUBJECTIVE from one rider to the next whether the performance differences are worth the cost, and the degree of difference. Performance mods are addictive. If you spend $60 to $100 and find an improvement, there is a good chance you will spend much more for something that looks pretty, whether further gains are there or not.
  3. James_Dean

    Define “loading up” in no nonsense terms

    colotaco: Loading up includes the misfiring of your 2-stroke motor with excessive smoke from extra fuel that accumulated in the lower engine area, and it usually clears out and runs smooth when you rev the motor and run it at higher rpms. When you ride very slow, the 2-stroke motors are most likely to load-up from RICH JETTING. Consider riding a very slow trail where your motor begins to run rough and smoke, and then reaching a more open area where you can ride faster, the motor runs rough and leaves a smoke trail behind for a few seconds as it cleans out, because it was loaded up. Try starting your bike with cold motor, LEAVE THE CHOKE ON, and ride it around for a few minutes with the choke on. The bike will become very loaded up, misfiring, and leave an excessive smoke trail.
  4. James_Dean

    RK Tek performance head vs Slavens S3 vs cut stock heads

    Maybe a few dyno graphs will be of value, considering the lengthy discussion that readers (like myself) have taken the time to spend on the dialogue... The KTM 250SX and 300SXS Heads are a good value over stock KTM XCW and XC heads. The 2017-18 300SXS head is available for under $80, as well as sending a standard head out for 0.5mm to 1.0mm machining. Take a compression check and compare any head before and after you install it to take some degree of measure before and after. The compression should be higher than stock for the XC/XCW 250 and 300, and results consistently show improvements in the 10-20% range on a dyno thru most of the rpm range. See torque curves below. Why show torque and not simply horsepower curves? -Because the improvement is mostly noticed from the bottom-end, and thru the mid-range where torque curves display the percentage improvement best. The torque below 4000rpm on carbureted bikes should be ignored, because the throttle is still being rolled open in that range, but the 2018 TPI (injected) motor EASILY takes full throttle from 2000-3000rpm. Whether simply installing the KTM 250SX head or standard 300SXS head, a good measured improvement is there. If the head is machined, then even more torque and power is found.
  5. KTM Owners- • KTM gas caps are hard to open, especially in cold weather. Here is the best fix I’ve seen, and it keeps the locking feature working. • After modifying, the filler cap removal takes less than half pressure from the thumb tab and saves frustration. • Orient the long leg towards the thumb tab, after cutting ONLY 2 of the legs shorter as shown. • Make sure to reinstall the same side of the locking part upwards, just as it was removed. • This modification also works on the “new” 2013-2014 KTM gas caps too. You might still want to put a little grease on the rubber seal, but the critical problem is solved. --After disassembling the gas cap, cut 2 of the legs of the locking piece so they are just short of extending outside of the housing --Orient the long leg towards the thumb tab when reinstalling the parts. --The problem with the original design is that it uses leverage to push down on the inner plastic ring, but the downward force is nearest to the end of the thumb tab, opening the nearest tang more than the other 2. In colder conditions (and sometimes warm too), the plastic is too stiff and is hard to deform, making removal nearly impossible.
  6. Make sure the fuel screw is installed with all the parts, including the Spring, washer, and little O-ring on the tip. You MUST have all the parts, and make sure the passages are clean, or you may have a poor idle mixture and inconsistent results.
  7. Dirt Rider Magazine has an article in the March issue about tuning the Power-Valve on the KTM 250 and 300 models (pages 84-85). The titles on the 2nd page are backwards, where INWARDS is actually OUTWARDS, and OUTWARDS is INWARDS. The text is describing dyno curves, and there are several torque curves that show the effect of turning the external PV dolly screw inwards and outwards. I wish I could have reviewed the article before it went to print, but Murphy's Law is still in effect... Turning the dolly screw OUTWARDS from a max-torque setting while using the Red spring lowers torque near 4000-6000rpm- Turning the dolly screw INWARDS from an ideal setting lowers the peak torque, near 6000-8000rpm-
  8. James_Dean

    Help with what needle

    A DEJ needle is nearly identical to your DDJ, but 1 1/2 clip positions leaner. You would want to use the DEJ in clip position #3 from the top as an estimate.
  9. The jetting still may be too rich, so try a leaner clip position. A JDJetting kit, or a Keihin 38mm Air Striker carb replacement are popular changes that can transform the bike too.
  10. Try running the JD Red marked needle in the 3rd from top clip position, and then the 2nd if needed, to lean the jetting overall.
  11. With the hose blocked and a #100 pilot air jet, your pilot jet should be near a #45 or #48 because this is an older version FCR carburetor. The '98-99 YZ400 with the same carburetor ran a #45/#100 PAJ, and the KTM 400/520 ran a #48/#100 PAJ combination using the same carburetor. If you had a #60 PAJ, then you should have the air-cut (octopus) hoses installed, or else the passage blocked off, where the pilot jet drops MUCH lower in size. This is because the #60 pilot air jet is feeding air to the pilot jet, instead of the #100. You shouldn't have the hose routed as you've pictured it, which is basically removing the pilot air jet, with the air bypassing the jet. Newer FCR-MX carburetors will more often use a #42 pilot jet, but these are 2 different types of pilot jets. See below, where the FCR-MX pilot jet is on the right.
  12. This has been too long, but what size is your pilot air jet? Are you bypassing the pilot air jet by using the short (new) hose on the side of the carb? Try blocking off the short hose on the side and see what it does to your idle mixture.
  13. 4-stroke FCR carburetors- 2-stroke PWK carburetors-
  14. James_Dean

    FCR AC pump squirt nozzle

    Tucker, You emailed me, but your return email did not work. Yes, we have a replacement nozzle for the FCR carburetor. It's called a "Dual Spray" and significantly improves the response, reduces bogging (eliminates it really), and includes the mid-body gaskets, leak jets, and wire to wrap around the linkage. If anyone needs to replace the mid-body gaskets, then adding the new nozzle is worth the few extra dollars and the few minutes to replace the part. Look for the part on our website. Thanks, James