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About cwtoyota

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    TT Gold Member

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    Motocross, Manufacturing

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  1. Thank you! That information will be a big help.
  2. Thanks, I have the right tools to measure a thread, but I don't have a set of forks disassembled to take the measurements.
  3. Thanks, that's good to know. Hopefully someone knows the the thread info, I'm trying to help a buddy swap some things around on his 450.
  4. Do any of you fellas know the thread diameter (major) and thread pitch for the lower tubes on the 48mm WP AER-48 Forks? Do the lugs come off of the tubes without too much trouble? I am specifically interested in the AER-48 that was used on the 2017 Husqvarna two-strokes and the current 2018.5 Rockstar Edition 450. Thanks!
  5. If you compare the shift forks and their guide rods in the YZ250 to just about any other bike, you'll see a major difference in the way they are designed (I suggest you use the 2014+ YZ450F parts diagram vs the YZ250 parts diagram). That's the main problem with this YZ250 transmission in my opinion. The solution I've come up with is to modify the cases and create a new set of shift forks which have a more conventional design layout. My 2002 bike has half of that, using stock YZ forks which slide on fixed guide rods. Unfortunately the stock forks are not wide enough to be stable in this configuration, so I've come up with the billet fork design mentioned & pictured above. I have a little more work to do on the other two shift forks, then these need to be heat treated and tested in a bike. It's a little way off before I can say for sure if these improve the shifting quality, durability and are safe. I am also thinking about grinding a few custom carbide cutters so that I can under-cut the dogs on transmission gears too. That would allow any combination of the three different upgrades: Shift forks, under-cut dogs, 450F gearset (4 dogs per gear instead of 3) I'll update this thread when I have some actual positive results from the prototype forks.
  6. Sorry to leave you hanging on a reply, I didn't get an e-mail this time. Don't wait on me for the forks while you have your cases split this time, but I'll send you a PM about the forks.
  7. Yes. I haven't been on TT in a while, but I got an e-mail since you quoted my post. About a year ago, I installed that 2007 YZ450F transmission in my 2002 YZ250. I used a spare set of cases and made some modifications to them. I also used different bearings on the left side of each shaft. Modifications to the shafts and gears from the four stroke were still necessary to fit in the cases. I ran that setup last year with new 250cc cylinder and some SSS forks on my old 2002 bike. I have about 30 hours on the gearbox. (mostly racing 30+A and 25+A classes). The 450F gearbox feels a lot more reliable than the original setup. I think a big part of that comes from having four dogs on each gear. I have found that the shift fork design is one of the major problems with the YZ250 gearbox. The poor design causes the gears to fail more often than the more conventional style of shift fork. My upgrade to the beefy YZ450F gears helps, but the shifting is still a little vague and it's easy to find false neutrals around 3rd gear. The real solution to that problem requires custom shift forks and a little bit of machine work on the cases. So to cure the problem I have started making a few sets of new shift forks from 4340 billet which will run on solid tool-steel guide-rods. Two photos are attached with the center shift fork and the main-shaft + gears from a 2006 YZ450F. I own a little machine shop here in WA, so I'm spending more time on these projects whenever I have spare time. If the shift-forks work, I am thinking about making kits that include all three shift-forks, three guide rods, a fixture and a custom reamer. That would allow anyone to do the upgrade with nothing more than a hand-drill. I am trying to design one set of forks that will work with YZ250 or YZ450F gears. Regarding the 450F gearbox, it can be done and it does work better than stock, but the machine work requires skilled hands and good tools. Here's the first race last year with the 450 gears. I couldn't keep up with Ryan Huffman, but finished 2nd in the 30+A. That weekend I won four of four motos in the 25+A class and took home my first purse money. It's a shame they put such a bad transmission in such an excellent motorcycle.
  8. cwtoyota

    Pacific raceways mx

    I'll be out at Moto West tonight (Tuesday May 3rd) riding an old YZ250 with number 31 on it. My name is Chris and I drive a white Chevy cargo van. I would love to offer any help for the layout that I can, I live just 15 minutes away and ride there quite often. I'm willing to pitch in just to help everyone have another safe, fun place to ride and race. Here is a lap on a 125 at the track I built at my place. My layout isn't necessarily suitable for a public track, but in terms of flow this may be in the direction Joe is looking for: https://www.youtube.com/watch?v=4TED3dBJliQ Here's a lap on MotoWest the week before last with the 250. This particular layout flows and is fun to ride: https://www.youtube.com/watch?v=GzTTOR8KuPg On the original topic, I don't go to Pacific anymore due to the layouts for the same reasons SmokinJoe stated in his post. It's not really that hard to get a layout that works for fast guys and beginners alike. In terms of layout, MotoWest is decent, so is Straddleline and Riverdale. I would make them a little more technical and maintain or improve safety if someone handed me the keys to the dozer. The main concern is avoiding blind double jumps and step-downs to keep people from being landed on, or if you do include those in the layout put a flagger on those every time there are bikes on the track. In my track I have a blind double, but you ride right next to it, then turn the corner so you can see if someone is there before hitting that section. A track that flows puts a big smile on everyone's face. Too easy / too much flow doesn't separate riders who are more skilled. I think Straddleline suffers from that a bit, but they are very family friendly so it's worth the trade off. A medium speed off-camber corner is a good way to reduce the flow or "highway factor" while allowing faster riders to pass and keeping things safe for everyone. The S turns and chicanes and stuff track builders put in to reduce speeds and spice up the track (as Joe mentioned in his post) just make things one lined. That sucks in a race because the faster guy can't make a pass. It also sucks in practice for the same reason.
  9. cwtoyota

    What happened inside my YZ250?

    Ring end gap. If you set the ring end-gap too tight, you're very likely to snag that ring in that port and have that exact problem. It will run fine for a while, then it will snag the port and your day is over. You have to set the ring end gap when you install them. The spec in my 2010 manual for ring end gap is .016" minimum and .022" is the service limit.
  10. cwtoyota

    BOOOOOOOOM! Jesus really!?!

    You don't have to balance these cranks. You have to "true" the crank assembly so that it all rotates on the same centerline or axis. The procedure for checking that alignment is shown in the Yamaha owners manual and there are probably a million videos on youtube that can give you an idea of how it's done and what you'll need. I do my own cranks and sometimes do them for friends. I suggest if you tackle the job that you use a complete OEM rod kit from Yamaha. You'll need a pair of dial indicators and a set of vee-blocks or a "Bench Centers". There are also companies who rebuild cranks for a reasonable fee plus parts. I have heard plenty of good reviews of the Hot-Rods kits, but haven't personally used them in a YZ. The only suitable alternative is a new OEM crank assembly. The Wiseco stuff is a bad decision; when they fail, the rods often shatter and destroy the engine cases and sometimes even damage the cylinder casting. At that point, the damage is so costly that the bike isn't worth repairing.
  11. cwtoyota

    premix in tank

    Some of molecules in gasoline can slowly evaporate out through the plastic fuel tank (or your plastic race-gas jug). If you store fuel in a plastic container, it has a shelf life and plugging the cap won't do much good. If you have any doubts about the validity of that statement, do some research. There is a reason graphics have holes or slots punched in them where they directly cover the fuel tank. Drain your fuel and store it in a well sealed metal can if you have access to one. If you are using pump fuel with Ethanol (Ethyl-Alcohol) like we have here in North America; you should drain the fuel bowl if you plan to store the bike for any length of time. The Ethanol suspends moisture and eventually your brass carburetor parts will turn a dull brown or even green with corrosion. Ethanol also attacks the rubber components like the OEM fuel line and some of the o-rings in the carb. They eventually get hardened up and crack. If you can find ethanol free premium fuel, run that in your bike and you'll get many years more life out of your fuel system.
  12. I haven't tried the engine kit on my '14, but the longer link sure makes a big difference in handling. Stock is 142mm, I am using a 143.5mm currently.
  13. cwtoyota

    Plug and Play Frames?

    It can be done, but the tanks are different and some chafing will occur if you mix them up. I see several differences that are more profound than the frame itself between my 2002 and my 2010. 1) Steel frame bikes had 46mm forks while aluminum bikes had the 48mm forks. 2) Steel frame bikes had triple clamps that mounted the forks 2mm closer together than the aluminum bikes. 3) Steel frame bikes had a different swing arm with different rigidity characteristics I have compared the old bike to the new bikes back to back on the same day. There isn't a whole lot of difference and I suspect that a majority of it has to do with the fork change. Both are excellent handling machines.
  14. cwtoyota

    Plug and Play Frames?

    It's probably a 2005... That's the first year of aluminum YZ's. You should seriously consider getting a fuel tank for an aluminum bike. Not sure if that old thread mentions it, but the tanks for the steel framed bikes will fit the aluminum frame and work OK. The correct tanks that fit the aluminum frame are shaped to fit the sharp corner profile where the frame forms a wishbone on each side of the upper shock mount. Using a steel bike tank on an aluminum frame wears through a piece of rubber that is glued on to the frame in that location. Once the rubber wears through, the tank and the frame start to wear. Over many years of riding, it might be possible for the frame dig it's way through the tank. The Clarke tanks that are listed to fit the aluminum bikes are the same as the steel OEM tanks in that location. I bought a white Clarke tank and put it on my 2008. It wore through that rubber and started in on the aluminum frame over the course of one racing season. That tank is now on my old steel framed 2002 YZ250. Check e-bay for a tank... they're fairly cheap.