Recent content by cujet

  1. Crank Balancing, the right way

    For those who don't know, a single cylinder engine has reciprocating mass, in the piston+rings, pin and rod. We could add an equivalent balance weight at 180 degrees to the crankpin. A 100% balance factor. But what happens is that weight has little to oppose it, when the crankpin is at the 90...
  2. Motorcycle Myth # 5 - You need big ports to make big horsepower

    Hard to believe (sarc) but I did install the Challenger K+N filter and a Powerflow tuned exhaust and GAMI injectors. My plane has a constant speed prop, so it's always adjusting pitch for conditions. The mods helped a good bit. It's a 2800 pound airplane with 200 HP, so not exactly overpowered...
  3. Motorcycle Myth #4 – Unleaded fuels make less power

    Possibly of interest, Swift, GAMI and Shell have all worked on unleaded Avgas. If they pull it off, it will be a significant accomplishment, due to aviation requirements. Swift has been able to meet and/or exceed the octane of 100LL using a blend of 80/20 Trimethylbenzine and isopentane. I was...
  4. Motorcycle Myth # 5 - You need big ports to make big horsepower

    Always of interest. It may be interesting to note that my lowly airplane (177RG) has a 200HP 4 cylinder Lycoming engine with 5.125 inch pistons. Yet the intake pipes are 1.5 inch steel tubes with an inside dia slightly smaller than that . Sure, it's no high RPM monster, with a 2700 (3300 in...
  5. My 380EXC jetting/carb blubbering situation + partial solution

    While I like my 380, it has some glaring faults. First, the close ratio 5 speed is not good enough. The bike's top speed is 75MPH and first gear is WAY too tall. That's annoying. Second, the 380 engine really is down on torque, down below the powervalve opening RPM. It's far from being a...
  6. What coolant to use in KTM 450 EXC?

    In general, conventional antifreeze (ethylene glycol) without silicates is fine for motorcycle use. It's the silicates that cause rapid pump seal wear. I simply go to my local auto parts store and pick up a gallon of Prestone extended life, as it's silicate free. I then mix it with Reverse...
  7. Ultimate Woods Bike

    People are generally in agreement. The 300EXC is one excellent dirt bike. Light, easy to ride, responsive and so on. All of it is true. As for it being the ultimate woods bike, that's largely a matter of personal opinion. It has a fairly tight 5 speed trans and I find that I'd like a 300EXC...
  8. My 380EXC jetting/carb blubbering situation + partial solution

    I'm currently riding a 2001 KTM 380EXC with a tag and taller gearing. It's set up so RPM and MPH are nearly married. The problem with the bike has been the awful blubbering situation at part throttle, lower RPM. Such as when cruising down a firetrail at 30-35MPH in Ocala Natl Forest. It's...
  9. PDS shock, KTM 380EXC, 2001 ?? Jeremy??

    Ok, thanks for the response. I'll check out the website. Do you sell a DIY "kit"?
  10. 2003 yz250 shock recharge

    Try putting air in it. If it holds air pressure and no oil comes out, the bladder is probably fine. Air is not the proper thing to service with, but it's a great troubleshooting tool.
  11. Older bikes as fast as the new bikes ?

    Just an FYI, the Honda CR125 based shifter Kart engines dyno (at the wheels) at just over 50HP. A typical one has the power valves removed, otherwise stock internals, stock porting, stock piston and head. The key is the pipe and carb. And, many of those engines are quite old.
  12. Money No Object!! Best Trail Bike is.....??

    I know this is a bit late, and lord knows I'm not a huge KTM fan (at least not the one I own). But the 350XC-F seems to be a wonderful woods machine.
  13. PDS shock, KTM 380EXC, 2001 ?? Jeremy??

    My latest gem, a "vintage" 2001 KTM 380EXC is a PDS. (it has a tag, so that's why I own it). I'm not in love with the bike, but it's mine. I'm not happy with the shock, or the forks for that matter. They start out quite harsh feeling, but blow completely through the stroke on anything bigger...
  14. Ethanol Fuel

    Certainly, the turbo guys love E85. It's high octane works well in turbocharged, high boost engines.
  15. Help needed with my IT400

    Ahh, very good. The IT's had very mild exhaust port tuning. If you want a bit more top end, (and you have a stock cylinder), you can raise the exhaust port 2 to 3mm and widen it 5mm (at the top only if you want good piston support). The transfer port timing is enough. What ever you do, don't go...