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      JUST IN!   04/24/2018

      HOW TO: 4-STROKE PISTON REPLACEMENT DONE RIGHT!

dennistruckdriver

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About dennistruckdriver

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    Missouri
  1. So sue me! Let's just agree to disagree on our philosophy in tuning. I didn't mean to step on your toes. Let's just not respond or reply to any thing that each other might post. My system has been developed during my 37+ years of riding and racing, and it works for me. Your system seems to work for you. I have built some mighty damn fast motorcycles, I'm sure you have too. This is a forum in which anybody can say whatever they want to say, and I have said all I am going to say to you. Matter of fact you can keep all these knuckleheads to yourself if they are not smart enough to diagnose their own problems with a little guidance. I've got all I can do to help those who are willing to listen. Bye! P.S. I've got a fancy shirt and fancy sunglasses too!
  2. Geez! I didn't mean to make anybody mad! I only meant to suggest that when problems arise with your jetting as with anything, go back to the beginning and start over. By the way I am SOOO impressed with 'yur big wurds'. Don't be so sensitive! Most guys having problems don' know as much as you may know. My advice was meant for the average guy. You obviously know more than the average guy. The information you have including all the technical lingo was perhaps learned by experience, which is how I learned what I know. I never said to KEEP a bike stock, I recommend when having trouble to go back to stock and work your way up a LITTLE AT A TIME! I didn't mean to impugn your knowledge. Have a day.
  3. Did the bike run okay before? Was it not fast enough for you? If not you are some kind of freakin' superhero! I reiterate; when in doubt, GO BACK TO STOCK! These new four-strokes are not like the old TT500s of the '70s! They are rocketships from the factory! If it ran okay before, then the solution would seem simple to me. Sure, IF you get it running right, it may be twice as fast as my stock 426, but right now, sounds like it ain't! All kidding aside, it sounds to me like you tried to modify too much at one time. You may have to backtrack and undo as many mods as you can and take one step at a time. Good Luck Dennis
  4. Call Larry at Donelson Cycles in St. Louis MO at 3148491830. Tell him 'Goat' said to call. He's built dozens of those stinkin', smokin' buzzbombs. Try a new YF-Z 450, and all your wildest dreams will come true. (Vote for Pedro!) Good Luck, Dennis
  5. I just joined this group out of curiosity, and am amazed by the number of guys having jetting problems! I am on my third Yamaha four-stroke now and have had no jetting problems. The solution is very careful consideration of perceived problems, and judicious application of common sense, something I noticed was in short supply with most four-stroke 'jetting' problems brought to me by my customers when I worked as a parts man in a Yamaha shop. Every problem is not solved by a main jet change, a new pipe, or a jetting kit. If these bikes are left stone stock, and jetted properly, they are rocketships! I can't tell you how many guys I do not even know that think I am some kind of wizard because I made a simple 1/4 turn adjustment in their fuel screw or recommended a simple jetting change, or told them to use a little bit of race gas in their tank. Guys, this is not hard! Don't over-analyze your problems, and don't worry over EVERY little burp or fart your bike makes. The simplest solutions are usually the cheapest and the best, and you don't have to try to outsmart Yamaha's university-educated engineers! When brute force and sheer ignorance doesn't work, try common sense and the owner's manual. Go back to stock, and work forward in small increments from there. Document your changes, and note what effects were noticed. When in doubt, GO BACK TO STOCK! Got it? Dennis
  6. I had a 1999 WR400F that I harescrambled, and motocrossed. I installed a stock YZ muffler, YZ spec jetting, and opened up the airbox as much as possible, by removing the stupid top lid. With these simple (cheap) mods, a friend of mine who had never ridden a four-stroke before was able to clear the doubles on the motocross section of a team hare scrambles we entered and finished 3rd in class, 9th overall at Lincoln Trail Motorsports in Casey, IL. He then bought his own four-stroke the next year when the 426 came out. Try the simple stuff, first. Usually, these bikes will respond to very changes in pilot jet and fuel screw adjustments. Good Luck, Dennis
  7. Hey, grips; I have a 2000 426 also. I have had it since new, and it is stock as a rock. I had noticed it starting to snap and pop when cold, and when decelerating hard. I thought maybe the valves were getting tight, so I checked them, and they were still within spec. (even after 5 years, and being ridden by some fast guys such as Pedro Gonzales, and Scott Meyers). I then thought that perhaps the carb was getting a little gummed up, since I hadn't ridden it much in the last 2 or 3 years, because of various distractions, including a broken wrist. I had to diagnose a sticking throttle grip, so, off came the throttle handle assembly, the cable, and the carb. Since I had all this off, I replaced the cable assembly, and that was not the problem. So I took the carb apart to check for wear and found no problems there. While I had it apart, I replaced the stock 42 pilot jet with a 45. Finally, I found the throttle action problem was caused by an aftermarket throttle grip tube that was rubbing a little bit. Well, after putting everything back together, and starting it and then readjusting the fuel screw back to stock, the bike starts and runs better than it ever has! Try a 45 pilot, set the fuel screw to the stock setting, and then, start it, let it warm up, and fine tune the fuel screw. Now all this is assuming the basics, like a fresh, clean airfilter, an engine with no excessive wear in the piston and rings, and valves in spec. Good Luck