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  1. jaguar

    Porting by Computer

    Rule #1: There’s more or less a set amount of power available for you to manipulate. If you port for high RPM power then your low/mid-range power will suffer. You are robbing Peter to pay Paul. Rule #2: You are pretty much stuck with the porting arrangement the factory put in your cylinder...
  2. jaguar

    balance a 2 stroke motor

    I know this is an old post but I want to add to it. Yes a balanced 2 stroke is smooth only around its resonant RPM which should probably be around its peak power RPM. Yes you can use a fancy trial and error method but I prefer to measure/weigh all the parts and enter them into an inexpensive...
  3. jaguar

    free 2 stroke calculators

    I forgot to mention that the piston velocity is pretty much independent of the conrod length. There's a calculator on the internet that shows about a .5% difference in speed for a 10% difference in conrod length (from 2x the stroke to 2.2x the stroke).
  4. jaguar

    free 2 stroke calculators

    Notes on my free spreadsheet of mini 2 stroke calculators Some of these calculators have never been available till now although engineering types have always been able to figure this stuff out. Maximum Average Piston Velocity Calculator The average (mean) piston velocity is what most...
  5. jaguar


    probably the crank seals need replacement
  6. jaguar

    Spark problems 1990 suzuki 250 RMX any help welcome

    here's my page on troubleshooting: Troubleshooting the Ignition System
  7. jaguar

    Help My bike won't start - KDX 250

    On old bikes you should always put soapy water on the left crank seal, take the spark plug out, and crank the engine over while looking for bubbles to form at the seal. Those bubbles indicate you are losing compression at the seal. Also backfire-like noise can be caused by a blown head gasket.
  8. jaguar

    Carb Sizing Help

    When looking at what carb sizes manufacturers usually put on their bikes and the resultant air velocity at max RPM I came up with this chart and then the Excel spreadsheet that calculates your carb air velocity and where in the range of enduro to motocross it falls within. What is curious is how...
  9. jaguar

    Help E series ignition on C Series KDX

    Using the complete system should work if it fits and if the location of the flywheel on the crankshaft is the same.
  10. jaguar

    Jet Size vs Gas Flow Rate

    I also bought a Mikuni needle jet and tested the flow rate through it with the needle at different locations in it. At "closed throttle" with the fattest part of the needle at the needle jet (allowing the most minimal space) there was still some flow. That means the needle width in relation to...
  11. jaguar

    Jet Size vs Gas Flow Rate

    I've read that there are significant differences between the different brands of jets due to the entry and exit angles for their holes. But when I tested a bunch of main and idle jets for flow rate they all basically were the same, with the flow rate only depending on the hole size (the area to...
  12. jaguar

    OEM Keihin needle specs

    If your bike has any of these needles and you want to try an aftermarket needle now you have some point of comparison because no where else have these specs been presented other than in the JD Jetting Spreadsheet (no longer sold). These needle specs are programmed into my jetting calculator. Go...
  13. jaguar

    About Carb Jetting

    What I’ve Learned Different About Carb Jetting 1. the main jet affects the idle mixture because some fuel is pulled up past the space between the needle shaft and the needle jet, and the main jet although its flow area is bigger, still does affect the flow past the needle at that setting. 2...
  14. jaguar

    My cr500 is still hard to start! please help

    read my reply above. One symptom of this is if you can start it by letting it roll fast down a hil and then dump the clutch and it starts but once you let the RPM drop down then it dies
  15. jaguar

    Free Jetting for Weather Calculator

    is my video on how to use the Jetting for Weather Calculator and where to download it from. Just in time for seasonal changes. :-)
  16. jaguar

    2012 KDX200

    "Service Honda is the owner of the trademark 'AF500, and produced the CR500AF and other two-stroke dirt bikes for many years. Unfortunatly because of the limited availability of two-stroke engines, and other parts used in the construction of the bikes these bikes are no longer being produced...
  17. jaguar

    Top Ten Worst Dirt Bikes of All Time

    the article is now at Ten Worst Dirt Bikes of All Time:
  18. jaguar

    True Results of Jetting Changes

    You can remove the ethanol yourself (please no chemical soup mix!): How To Remove Alcohol From Gasoline or look up where to buy ethanol free gas in your area: Ethanol-free gas stations in the U.S. and Canada
  19. jaguar

    True Results of Jetting Changes

    It is advised to stay away from ethanol laced gasoline but if you have to use it then you have to jet richer for ethanol. I was using ethanol gas unknowingly on a bike with the old style seals that arent ethanol-proof and soon enough I had to split the cases to replace the seals.
  20. jaguar

    True Results of Jetting Changes

    Move the nedle clip up and try it. then move it down and try it. You can go as thin as 50:1 on that Silkolene.
  21. jaguar

    True Results of Jetting Changes

    dump it! off idle is the domain of the carb slide and the clip position.
  22. jaguar

    True Results of Jetting Changes

    Well my full write-up on jetting is at Needle Selection Reducing the main jet size also affects mid throttle jetting as you can see on my graphic above. If you feel the mid throttle jetting is still a bit rich then you can lower the needle although the right way to do it is to buy a needle with...
  23. jaguar

    True Results of Jetting Changes

    OK if I make a +/- 3.5% change (from 140 to 150) on the main jet then it shows a 3% change at idle and a 9% change at WOT.
  24. jaguar

    True Results of Jetting Changes

    I'm pretty sure that every other graphic you have seen showing the amount of jetting effect each adjustable part has was only some persons idea coming from their own experience, not from a computerized jetting calculator. And none of it was "specific", only generalized. This graphic comes from...
  25. jaguar

    What happened to the place?

    It is going to do the opposite of "snap back" since China is now stopping food imports from USA in the current trade war