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About smdonald

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  1. smdonald

    Valve Lapping

    Installing stock valves into new stock 2010 KX450F head. Do I need to lap the valves, or just clean them up and install them? I know you should never lap titanium valves, but I guess my real question is "are the stock 2010 valves titanium or not?"
  2. ive checked all of the engine to frame bolts. all tight. is there a way to measure the cam journals to ensure they are in spec? i have a factory balanced and trued Hotrods crank. Im not sure what piston i have... Does anyone think this sounds like a head gasket leak???
  3. Hi all. This has been puzzling me for awhile. So i rebuilt a 2009 YZ250F i bought with a broken crank. You might have seen the post about that last month. Anyway, its all back together now and starts and idles fine. Before its warmed up, if you up the rpms, there seems to be a vibration of some sorts because the engine sounds like it tightens up and the r's just drop all of a sudden. Sometimes it just dies. Starts right back up. I did notice that once the bike has been fully warmed up, this problem seems to go away. Runs like a champion. Let me note that upon tearing into this beast, it was obvious the previous owner didnt do much along the lines of oil and filter changes. Everything looked ancient on that end. And when i installed the cams into the journals, the exhaust cam felt tight. when the retainers were bolted down, even with no tension on the cam chain, the exhaust cam still felt tight. It was hard to get it to move using my hands. I worked for hours trying to free it up. I know on my 426, this can be a pain sometimes. I was not able to get it any more free. But turning the engine over with a socket didnt seem hard. No rough spots at all. I could go on and on, but if any of you have an i dea as to what is causing this, please HELP! I have a sinking feeling that it might be the cam journals, due to the lack of oil maintenance from the previous owner.
  4. everything else besides the crank looks good. at least on the top end. guy said it was just rebuilt 45 hours ago by dealership. new clutch, suspension, valves, piston....the bike is in beautiful shape. got a steal at $1700. ordered a new crank, bearings, and gaskets last night. should be an easy fix if the cases arent shot. we'll see. either way for that price i think i come out ahead on this one!
  5. well i bought this bike on tuesday. guy said it had a loud noise and just wanted to get rid of it. i started it briefly when i got it home but immediately shut it off. it sounded like there was an elf inside the case trying to break his way out with a jackhammer haha... i just hope there wasnt too much case damage. the one lobe is completely separated from the crank. the only think holding it in there is the fact that the crank housing is circular
  6. Has anyone seen this happen before?! What can cause this. 2009 YZ250F. All stock. 45 hours. Havent split the cases yet but wow...
  7. vacuum release plate was on backwards. corrected that and made it a "little better". went to a 40 pilot as that was all i had laying around since the yami shop is closed mondays... made it a little better. looked at timing tried retarding the exhaust cam 1 tooth as it looked like it could have been a little off....not sure if that helped or not. pilot also did have the o-ring in good condition. overall i think all these small adjustments made a noticable difference. it still will not idle at all w/o the choke on. from the jetting charts i could find and the posts i read, the best suited pilot for my riding conditions is a 39. does that seem right? and will going from a 40 to a 39 really give me the large adjustment im looking for? tomorrow I will pick up a 39 and 3 or 4 sizes smaller. also i have the mix screw all the way in. backing it out makes no difference.
  8. I've been through all the stuff I can find on jetting in the sticky's and also search results. Im stuck once again. Thank God for TT though! I've got a 2001 YZ 426. Top and bottom end are new. Stock pipe for now. Bike starts easily but will only idle w/ the choke on. As soon as choke is released, it will die immediately, even if i try to rev it up w/ the throttle. Ive riden it very little, just up and down the street but it has to be w/ the choke on. Im trying to do some final tuning before my first ride. The carb i put on it i purchased on eBay. I replaced the jets that were in it as follows: Pilot: 42 Main: 152 Air Screw: 1.5 turns out Needle: 3rd position from top Elevation: 5500 I've messed around w/ the pilot going up and down w/ it. Also messed w/ the airscrew w/ no results. I've had every piece of the carb apart and cleaned extensively w/ carb cleaner and compressed air. Im not too knowlegable on jetting, but usually i can get by. This one is stumping me. Anyone have any suggestions?
  9. bearing replaced...leak stopped. now on to jetting. thanks everyone!
  10. they are normally a fairly noisy engine. Since you checked the nut, make sure the valve clearances are adjusted properly.
  11. going to replace the bearing tonight... will post results
  12. i just bought a lighting stator off eBay for $69.95. simple swap if you have a flywheel puller. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&_rdc=1&item=330551218505&ru=http%3A%2F%2Fshop.ebay.com%3A80%2Fi.html%3F_from%3DR40%26_trksid%3Dp5197.m570.l1313%26_nkw%3D330551218505%26_sacat%3DSee-All-Categories%26_fvi%3D1&viewitem=
  13. so i just looked at the bore on the shaft and can notice no "out of round" characteristics. the shaft itself "looks" ok, but we all know that just looking at a part doesnt make it OK. i watched closely while pulling the clutch lever and cant see any unusual side to side movement. im stuck on this one. i have no idea weather to just buy a new shaft or to tear down again and do what you said gray, and have a machine shop bore it out and insert some bushings. what do you think? the latter option would obviously require a ton of labor and time. i didnt have the shaft in wrong either. i tried using the ball bearing again and comfirmed my original statement, that it is too long w/ the ball. this has been racking my brain for days. this is the 4th 426 ive done, and i havent seen this before. gray, have you seen an oil leak from this area before? any advice helps guys!! im dead in the water.
  14. so the first attempt at fixing this problem would be to get a new actuator shaft?
  15. Thanks gray. It seems that the seal fits properly into the case. Not sure how to test that w/o trying a new shaft. Here's a question: i was looking through some parts microfishes just now, specifically at the clutch pushrod assy...i may have the rod in backwards, which may be causing the dimensional problem i stated about using the ball bearing vs. no ball bearing. If the rod is truely in backwards, can this somehow cause the oil to force its way out the seal? And also cause the length problem??
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