just bought a 11' yz450f project that's got symptoms of a "locked up kickstarter"...any help?

Seems like the previous owner may have dropped something into the intake or exhaust ports or maybe spark plug hole. The roundish piece kind of looks like a valve stem keeper but I haven't had one out in a long time. To me the damage looks like what was done trying to kick the bike over with the FOD in there and not something that happened while it was running. It may have been an O sh*t moment with previous owner then he sold it.

bike is still locked up at the moment though with the head and everything off so it's not just the head that's dinged up. it doesnt really look like a valve keeper but its hard to tell by just looking at pictures, also all valve stem keepers are accounted for. the PO had said the bottom end just had a new gasket and seal kit installed because it was leaking oil, and the bike has only a few hours on it since. which I wouldn't have believed for a second except for the fact that while disassembling I have noticed all the gaskets are basically brand new. only thing I can think of is maybe something was left in the motor that wasn't suppose to be there when it got put back together.

bike is still locked up at the moment though with the head and everything off so it's not just the head that's dinged up. it doesnt really look like a valve keeper but its hard to tell by just looking at pictures, also all valve stem keepers are accounted for. the PO had said the bottom end just had a new gasket and seal kit installed because it was leaking oil, and the bike has only a few hours on it since. which I wouldn't have believed for a second except for the fact that while disassembling I have noticed all the gaskets are basically brand new. only thing I can think of is maybe something was left in the motor that wasn't suppose to be there when it got put back together.

Well that seems like a reasonable explanation.

I was wondering the same thing, but what piece of the motor would you think that looks like? I don't understand where those fragments came from or how they got up there, I can't explain it I was just staying that that looks like a piece of a main bearing, the round fragment, that is. as for the other piece I haven't the slightest clue. I was going to do a leak test this evening, but I'm staying optimistic.

 

Looking again at your first picture, it's the end of one of your valve guides.  Looking closely, right in the crease at the bottom of the intake valve cut outs in the piston, you can see where the valves touched.  That would account for the broken guide.

that's a good possibility. as an update, i removed the cylinder last night when I got home from a family function. Good news, once the cylinder was removed I had no problems or funny noises when turning the motor over completely. everything seemed good, the cylinder is marred up, nothing serious though which leads me to wonder why the motor was locking up at the top of the stroke with the cylinder on. I looked at the rod and it seems to be straight....is there any trick to determine if it is slightly bent or not? I'll get some pictures when I get off work. as far as the leak test on the head, both intake and exhaust valves are leaking slightly. I've found a "decent deal" on a head which I'm going to invest in. I will disassemble the old head later and remove the valves to check the guides. pics will be up later

Looking again at your first picture, it's the end of one of your valve guides. Looking closely, right in the crease at the bottom of the intake valve cut outs in the piston, you can see where the valves touched. That would account for the broken guide.

ding ding ding, we have a winner. anyways, had some time last night to pop the valves out and sure enough one of the guides was broken at the bottom. that's exactly where that foreign matter on top of the piston came from. as far as the bottom end and rod goes, I thought it was still locked up after I had originally removed the head, but I believe I made a super amateur mistake and had a little bit of slack on the cam chain causing it to catch while trying to turn it over by hand. I slid the cylinder back on and had no issues getting a full smooth rotation by hand. I believe it was stopping right before TDC is because where the metal fragments were when I first found them (not underneath the valves, they were on the very outside rim on the flat part of the piston) was just enough to catch between the piston and the bottom of the head which was causing the "locked up" symptom I was experiencing. so I'm very pleased I don't have to split the cases and remove the lower end completely from the chassis. I'm buying a head tommarow and I'm going to purchase a new cylinder/piston kit in the next week or so. I could salvage my cylinder I think, but id much rather just start fresh. so another question for anyone, has anyone had any experience with the cylinder works cylinders? I saw these or should I just go with trying to find a new OEM?

I forgot to add pictures in the last post and it wouldn't let me edit them in. If you look at the picture looking down on the head at the springs, you can notice the damage around the top two valves (in the picture), the part of the head that the buckets slide into, what do you guys think caused this? this is what led me to decide to buy a new head instead of trying to get my old one fixed.

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just a quick update. After removing the cylinder I noticed it had some slight scoring on the walls. I contemplated on sending it out to get replaced, but ended up just buying a standard bore cylinder,piston,gasket kit from cylinder works. I also decided to just start with a new head because of some foreign damage that I couldnt find out how it was caused. I ended up getting a really good deal on a very lightly used GYTR head for the bike so that should be here by Thursday I believe. Also bought a new cam chain and a Scott's reusable oil filter. Keeping my fingers crossed everything arrives by the weekened, I'll take pictures as it goes back together and hopefully I'll have her up and running

Edited by kxfreak

so the process is moving on slowly but surely. I received the new head, and topped kit. while going to replace the cam chain I notice the magneto/flywheel was damaged and the stator had a slight ding on it as well. I'm not sure how someone damaged the flywheel, my guess would be an impact gun while trying to remove the nut but it looks as if it happened while it was running due to the marks on the stator. anyways, here's a progress pic. when I received the head it didn't come with a valve cover, it had been sitting for awhile collecting dust. I gave it a through cleaning today only to find out the cam circlip where no where to be found. this put a damper on the rebuild, but I ordered them today and have yet to find a new flywheel. I saw 1 on ebay, just one and by the time I confirmed it was the one I needed(8 hours later) it had sold.

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got the bike back together, still have a few small tweaks but boy am I ready to ride next weekened. it was a long process buying and waiting on parts but boy was it worth it.

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Edited by kxfreak

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