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tkf

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About tkf

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  1. tkf

    Pin found on magnetic drain bolt

    Thanks again Kinger317. You were correct, and installing it gave the bike back its topend . Accidentally snapped a bolt off in the case during reassembly so getting to the track to test it out was a little delayed. All good now! Cheers all.
  2. Hi, Had my '07 YZ250 engine rebuilt about 5 hours ago by a shop which has since closed. Doing an oil change on the weekend I was surprised to see something attached to the end of the drain bolt (10mm socket for reference). It's difficult to identify what pin this is, but I think it could be part of the YPVS Governor. I found another thread on this forum that starts with the discovery of a different pin but also ends up finding one that looks just like mine. So before I start taking things apart, I have some questions: What is the role of this pin? Is it the pin in the attached diagram? If so, being part of the governor assembly, is it likely to be related to a weak top end? That would be my only complaint of the engine when i received it back. Riding this bike back to back with an '08 , theirs felt terrifying. How could it have come loose? Installer error? Should I be concerned it will come loose again? Is there anything I can do to prevent it coming loose again? If it shows no signs of damage, is it safe to assume the internals (i.e. the parts that would require a case split to inspect) have not been damaged during its journey to the drain bolt? If not, what specifically should I check? Lastly this post hopes to serve as a bit of a reference for anyone else who finds something similar. Thanks guys
  3. We have a theory the idle jet/needle could be blocked. It won't start without choke, and will only idle when the idle is wound right in leading us to think it's starved for fuel unless it gets some from main. Not 100% sure why it rev'd its tits off in the first video, could've been leaning out from a lack of fuel? Only had 15 mins to look at it the other night, started it with the TPS and solenoid disconnected and it idled uneventfully for 5 mins, albeit with idle wound in. Friday night here now so will spend some time on it this weekend. Will check the idle jet/needle and double check the reed block is OK. Don't have the gear to leak down test it, may have to make something up
  4. Hi, Have recently finished rebuilding my 07 YZ250 from the ground up. Having an odd problem where the idle revs seem to 'surge' slightly, and last time we were playing with the idle it rev'd itself - see the video below. Here's some of the stuff that may be relevant: Disassembled the carby and cleaned the bowl, cleaned the needles (didn't replace). Throttle re-assembled and lubed. Action is smooth and slide can be heard snapping back down on quick release. Bottom and top end both done by reputable shop (one of RC's former Honda guys). I received motor as one piece and bolted it back into the frame. Stock reed cage and reeds. No obvious damage. Checked gasket was OK before reattachment. Would really appreciate if someone could take a look at the vid below and tell me where I should start looking to troubleshoot this. Thank you! This video is the third time we had it running and it was warm by this point. No issues the other 2 times it ran, but they were very gentle and brief just to make sure it ran before I bolted everything else back on. (NSFW - I drop the F bomb at the end)
  5. tkf

    Crank Condition

    So each time I replace the piston I have to get it rebalanced? Or am I just tied to that particular type of piston, e.g. Wossner C variant? Newcastle/Sydney, cheers that would be great. I'm pretty careful with my washing and maintenance, but I bought this thing cheap and in shitty nick. Currently have no way to get it to the track so I'm taking my time to fix it up properly. Canon 7D Mk II with a Canon 70-200 F4 IS. Great combo for MX I think. Couple of my favourites:
  6. tkf

    Crank Condition

    I've popped most of the bearings out to replace them. The crank bearings spun freely but felt rough and made noise. One or two others felt.. stepped.. not at all smooth. There was 1 that felt smooth and tight like you described, but as the others were being replaced I figured I'd do the lot. Couple of pics for reference:
  7. tkf

    Crank Condition

    I've split my '07 YZ250's case to check everything out. Aside from vertical play and melted bits, what should I be looking for on the crank?
  8. tkf

    2007 YZ250 - Guess the condition

    Didn't wipe off easily. Much the same on the other side. Fairly clean on the intake/exhaust sides. Bit of lint in there from a rag I wiped some oil out with for the pics. Couldn't feel these marks at all.
  9. tkf

    2007 YZ250 - Guess the condition

    Thanks to everyone who responded. I will pull the cylinder off and have a closer look at the possible flaking. Will post some better pictures with better light. If I can find the jets online I will grab them. LBS here are very price gougey. Plug was brown/black. Not too bad. I will see how easy it is to scratch the coating off the piston. Have dumped the oil already. Made the mistake of taking it apart beforehand though so I didn't warm it up.. woops. These are the crank seals, right?
  10. Hey all, Picked up a 2007 YZ250 in awful nick (externally) for cheap. I'm not very mechanically experienced below the cylinder (have done a 4T top-end before) and don't have the tools to split the cases, so I'm putting this out there in the hope that some more experienced mechanics can advise me. Reportedly 1 owner Reportedly sitting for a few years due to hand injury (covered in dirt, tyres flat, grips eroded away into some kind of blue goop) No hour meter Spark plug brown/black on removal Carby bowl gunked up but main jet OK Clutch baskets notching not tactile (pictured below) Clutch plates not discoloured or warped Piston head free of damage (pictured below) Cylinder free of gouges and tactile scratches (pictured below) I had the PO start and ride it before purchasing. Started in a couple of kicks with old fuel, ran OK, went through some gears, power wheelies with 14/45 (3.21) gearing suggests not sluggish? No obvious knocking in the short time I ran it at home Based on this information and the follow pictures, am I safe to stick it all back together and go rip for 10 hours before I re-check? Thanks! I suspect this scratching is from the casting process? Otherwise all of the other towers would be in similar condition.
  11. tkf

    Valve clearances

    Hi Grayracer, I'm doing my first top end on my 2012 YZ250F @ 59hrs (piston+rings+gaskets). It's mostly back together now and I'm checking the valve clearances before I close everything up. Intake spec: .12-.17mm .23, .18, .25 (170 shims) Exhaust spec: .17-.22mm .21, .23 (176 & 180 shims) You can see they're all on the high side of the spec. Is what you mentioned before (valve stem mushrooming) likely to occur on all valves? What else could cause all of the clearances to grow instead of shrinking as you say is the norm? Also, I don't think it matters, but the cam chain isn't on and the head+cylinder are not bolted on - is there anything I need to consider when measuring these clearances apart from having the cam caps correctly torqued? P.s. apologies for hijacking your thread Adrian but I figured this was fairly on-topic.
  12. Do they come shimmed? I bought it in July '13 with supposedly 18 hours on it. Now at 60 I'm replacing the piston etc. Having checked the clearances a few times since I got it and them being in spec, I never considered that the valves could have needed shimming prior to me owning it ("18 hours" and all), but I noticed the buckets have shims in them, and 3/5 have "HOT CAMS" on them which is suspicious - if Yamaha use HC why not 5/5 HC?. Having now put 40 hours on it without the clearances changing much or the new sprockets wearing as much as they had when I got it, I'm now suspicious of the previous owner's 18 hour claim. Is it also safe to assume that, shim thickness aside, intake buckets are identical and exhaust buckets are identical? I made the mistake of not taking note of what matched what when I removed them. Thanks in advance.
  13. tkf

    2012 hard to start cold

    Good to hear. I usually won't use the choke either unless it dies after a few seconds of running, then I'll repeat with the choke on, but maybe this is just because I'm paranoid after several 70-kick start-up-attempt sessions (you know the ones) that any extra fuel in the 2012 cylinder will land me another one.
  14. tkf

    Aussie Riders ?

    Newcastle! Usually hit MX Central with my bro.
  15. tkf

    2012 hard to start cold

    Hey mate, when I first got my 2012 I had endless problems starting it, probably due to my habit of winding the throttle on when kicking it over, as on my 125. Found that touching the throttle kills any chance I have of starting it, so much so that it's now habit to put my right hand on the rear fender whenever I'm kicking it over. When I'm at the track, it starts reliably cold after 2-3 gentle kicks (guy I got it off told me this was to "pressurize" the cylinder.. not sure of the reasoning behind this but it seems to work ok) and then 1-2 hard kicks. I haven't touched the throttle during start-up since figuring this out and haven't had problems. Of course your mileage may vary, hope this helps though.
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