07 yz450f stall then hard to start when hot

If it's galled up the interior of the cam caps, to the extent that it created all that extra clearance, it's an exceptionally bad idea, yes. The good news is that the head's almost always salvageable by having an outfit like EDCo line bore the head with the caps bolted on. Usually runs less than $300 to save an $800 head.

My bike started do this last ride too. I also have an 07 Yz450F. I just thought I ran it a little to hard. What should I do first?

I'm going to send the head and cams to Edco. I'm thinking about changing the oil pump too. Do I have to split the cases to change the oil pump? Any ways to check its operation? I want to make sure it's working properly before I reasemble the head. So I'll need another top end gaskets set. If the cams are spent I'm thinkIng about changing them out to hot cams stage 2 cams.

Edited by Family Man

The pump comes right out from behind the clutch, no need to split. Just look for major scoring or damage, that's all.

EDCo said the bike was run out of oil. They said the head was realy bad but they salvaged it along with the cams, just doesnt look that pretty. So I think Im going to replace the oil pump. Where are the oil screens located?

There's only one, and it's for the return oil. To service it, the cases have to be split.

I removed the oil drain plugs and hardly any oil cam out. I usually warm it up from a minute or so before I drain it, but cant in this case.

If the return screen is clogged would that prevent the oil from draining?

No, but I'm sure you already know that on that model, the dipstick needs to be loosened to drain from the feed reservoir (front/left drain).

A clogged screen would prevent oil from returning to the "tank", letting it build up in the sump. This would cut off oil feed to the system by keeping oil away from the feed pump. The screen is so large, however, that the likelihood of such a thing happening by any normal means is pretty remote.

At this point Im thinking I forgot to put oil in it?

Or it burned it, or it leaked. Doesn't take much of either when you only have a quart to work with.

The oil that is left looks blackest of the black and Ive had the bike since new. I can remmember changing the oil, I drain the oil until none comes out and there was some in there. There are metal shavings and oil on the oil filter which makes me think that there was oil and it was circulating. The bike started seizing 20+ miles from the truck so it had to be ridden back, maybe it had oil on the first seize then it burned out along the way? Sound about right? I know youve said 9 times out of ten cam cap torque is the culprit. What do you recomend for cam torque again? I remmember you said you thought the manuel reccomended torque is to high. I know youve also said to leave the oil filter cover alittle loose to make sure oil is coming out, then tighten. To check if the oil pump is working. Im going to change the gaskets and cam chain and fire it up, and run it for a minute or two then drain the oil again.

The cap torque I always set to 75 inch pounds as opposed to the 86 that the manual calls for.

Leaving the cover loose is a bit messier than necessary, and that should only be done if you've already established that oil's not getting farther downstream. There's a little 8mm plug on the left side of the head right up against the intake port that's made for checking oil delivery to the top. Loosen that a little and see what you get.

Black oil usually means it's way too old, got way too hot, or the clutch has problems.


Got my head back form EDco and they included a slip that says do not torque yz400/426/450 cam caps to more than 5 foot pounds.

So when I set mine to 6 and half I was way over torque.

The spec is 86 inch pounds, or 7.2 ft/lb, with oiled threads. I use 75 inch pounds (6.25 ft/lb) without any problems. However, the caps will be marginally weaker than new because of the material used, so 60 inch pounds (the 5 ft/lb you were quoted) is probably enough with oiled threads. If you used 6.5, torqued them evenly and in steps, you wouldn't have hurt them by doing so.

I was wondering if the torqueing of the cam caps was going to make the top end fail, would it be almost immediately after the first startup?

It could, or not.

Well, I got it back together. The oil pump works great. The bike was hard to start at first, but its been sitting for weeks in the cold. The bike is starting 1st kick and runs strong, but its smoking. Im thinking about tearing it down again and changing the gaskets again? I made sure to keep the gaskets clean when intalling them. I was able to rock the piston in the bore so I figured the rings were in right? Hevent ran it for very long yet, warmed it up and dumped the oil 3 times.

Or is is normal for it to smoke after rebuild, and for how long?

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