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About jb497

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  1. Last week i did a top end rebuild on my 17 450sxf. It has 105hours. Everything looked good, could have went longer. I just replaced the piston, camchain and through a new clutch in it. The clutch basket had a little bit of play in it but nothing to be concerned about. All my riding has been intermediate motocross. I ride alot of sand. Air filter every ride and oil every 4-5 hours with filter every second oil change.
  2. I run 14-52. It allows me to pull a higher gear in turns and i don't have to shift nearly as much. I can ride most mx tracks just using 3rd and 4th. Im not sure how it would be in SX. It also makes the chassis handle better having bigger sprockets.
  3. I changed my back sprocket to a 50t. I love it, it allows me ride 4th gear in most corners and ruts. Ive always ridden bikes in the lower RPM ranger ather than revving bike at higher RPM. 3rd gear only gets used in really tight ruts. My bike has never seen 1st or 2nd gear (only on race starts). I do tend to use the clutch a bit but my bike has 80hrs and clutch is still in spec.
  4. . Have you done any work to the motor? I just bought one and I'm so impressed. I normally put 100-120hrs each year on a bike and then upgrade, so it would be good to get away with just doing one top end.
  5. Hey guys recently picked up a 14' yz450f with very low hours (about 8), Being new to yamaha (coming of 14 kx250f) and new to a 450… The bike is UNREAL! It handles very well and the extra torque is great in loamy,sandy condition. I must say I'm very impressed. A couple of things i would like to address…. Are 450's normally a bit harder to start then 250's? Ive noticed it has taken me 4 or 5 kicks to start when cold (using choke). When its hot, it starts first kick. When the bike has been sitting for about an 1 hour (in between practice sessions), I could only kick it over using the choke again… (live in australia, so the weather isn't cold). How long do you guys like to wait before replacing the top end? Im thinking around the 50hr mark? Im pretty strict with maintenance doing a air filter every ride and oil/filter every 4hrs.. How many hours have you guys got on your 14 yz450f? any problems? Thanks Jack.
  6. yeah maybe, I found the 4th gear input shaft was worn.... So even though the crank,piston all seem good, I'm glad I did rebuild it because of that tranny problem..... I don't think 30hrs for a piston and 70hrs for a full motor isn't over the top. I ride deep sand, if you have ever ridden sand, the motor is working twice if not three times harder than riding loam/hardpack. Sand is hard on bikes, I go through top dollar XW ring chains every 20-25hrs and that's just because of the sand, I keep my bikes well maintained...
  7. Has anyone else had to replace the 4th gear input shaft on their 13/14 models? I recently sent my bike in for a full motor rebuild. (hot rods crank,wiseco piston, oem valves). The mechanic said the 4th gear input shaft is worn. I purchased the bike brand new and its got 75hrs on it. I replaced top end at 32hrs. It's not a big issue, I'm not too worried as besides that this bike has been an excellent bike. I haven't got the bike back yet as he had to order the part from america as their were none in Australia however it will be interesting to see how well the original bottom held up and valves, seeing as they had 70hrs on them. Ive always used fully sythenic oil and changed it every 3-4hrs with the oil filter. I was seeing if it was a common problem on the 250f? Thanks Jack.
  8. Ive had a 13' and 14' Both Bikes have been pretty much faultless. The 13' had 75hrs on it, I did a top end at 25hrs, Piston hardly had wear. I didn't touch the valves or the bottom end, Bike started first kick hot every time. The 14' currently has 73hrs, I did a top end at 32hrs, again hardly any wear. Its currently getting a full motor rebuild (wiseco piston,Oem valves, hot rods crank). Im really interested to see how much wear their is…. I had to through a Hinson clutch kit in at 50hrs, as the stock was warned out. This is because i tend to slip the clutch alot. Only fault, the stock the chain setup is noisy as hell. Best best is to through a decent chain on and replace the chain guides with the T.m works one. I actually pulled the swing arm and linkage apart last week for the first time , and even at 70hrs of riding in sand. Only one bearing was worn. Wheels bearings were replaced at the same time.. The bikes are great stock, Honestly they tend to rev out quickly so I've found shift early and ride a gear higher. When everyone corners in 3rd, I'm in 4th, its just a lot smoother and eliminates the engine breaking which 3rd has. Aslong as your not riding on the limiter, keep the oil fresh ( i do oil/filter every 4hrs) these bikes should go for ages… Majority of my riding is done in deep sand,so I'm hard on the bike.
  9. Hi guys, Recently had a well known local performance shop rebuilt the top end on the 2013 kx250f. The bike had 25hrs and on it, i got him to rebuild it with a pro circuit high comp piston kit. He also remaped the ecu to suit. After riding the bike a few times (29hrs on it now) ive noticed i tend to rev out a bit quicker on straights in 4th gear, but in saying that i noticed ive gained more power down low , where i can snap third quicker on the inside or big corners i can labour around in 4th. Is this normal? Coming off a 10' yz250f, the bike outmatches the yamaha in all specs, handing,power and suspension. Is their anyway i can gain a bit more top end ? without hurting the improved bottom? Aftermarket exhaust? Also i replaced the chain/sprockets, would it be also worth replacing the chain slider/guide/rollers? My chain tends to be quite noisy. Thanks. Jack.