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engine knock at first start up ( Buyers remorse)

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Well last week I bought an 06 crf450x. I had to fix a couple minor things ( I thought) and as usual I changed the fluids in it. ( I always do that when I buy a used bike) after the oil change I started it up and the engine kocked until the oil pressure built up. it has not done it on any restarts since, but that bothers me now I am thinking I got screwed and this thing needs rebuilt.:smirk:

does anyone elses knock after oil change until oil pressure builds up?

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Not an issue if it only did it that once. Jst took a few seconds for oil pressure to build up and for oil to get to everywhere in the engine.

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Nope, they are relatively quiet for a dirt bike.

Oil pressure in those bikes builds up almost instantly. If you don't believe it, start the engine with the cam cover off, and you'll have to clean the ceiling.

Does it sound like the bottom end?

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When I did a top end on my 450R, I completely drained the engine of all oil, and even took the flywheel/ignition cover off to clean out any remaining oil around the pickup. The engine quite literally had no oil left anywhere inside of it, including the oil filter housing.

I filled it with oil, and kicked it over about 5 times, I then pulled the oil filter cover off to make sure it had primed - the oil filter housing was just about full of oil from those few kicks. Like it was said, these engines build oil pressure very quick.

IMO, you should be prepared for a crankshaft + piston replacement.

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Hmmmmmm... Maybe that's good advice, after an oil change kick it through a few times to prime it, then hit the E-Button.

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Nope, they are relatively quiet for a dirt bike.

Oil pressure in those bikes builds up almost instantly. If you don't believe it, start the engine with the cam cover off, and you'll have to clean the ceiling.

Does it sound like the bottom end?

The 450 X isn't relatively quiet for a dirt bike! The engine is famous for sounding like a bag of spanners being thrown down the stairs.

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Hmmmmmm... Maybe that's good advice, after an oil change kick it through a few times to prime it, then hit the E-Button.

That wasn't the point. These engines build oil pressure so fast, that a few kicks is all it took to fill the oil filter housing up. Once running, it doesn't take a few seconds for these engines to build oil pressure, it will take well under a second.

Yes, these engines are quite noisy too. Lots of noise from the valve train. However, they shouldn't knock - ever.

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The 450 X isn't relatively quiet for a dirt bike! The engine is famous for sounding like a bag of spanners being thrown down the stairs.

Yeah, I looked at several before I bought me '07 with 27 hours on it, and even mine that is almost new sounds like a mixer in a container of gravel. :smirk:

They are pretty noisy. I've listened to thers on youtube and they all make noise.

Agree that it's fine, if it only was for a second or two after the oil change. If it doesn't do it again there isn't anything to worry about.

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" a bag of spanners thrown down a flight of stairs"

Throw in some scary low-level whines, an odd whirring, a whistle, and a box of gravel in the tranny, and you've about got it.

Noisy frigging motors.

I would not worry about it.

Try running the bike in a much higher than normal gear, and give it as much throttle as it will take, and listen for piston slap. Don't do this every day.

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I took it out and did some trail ridding today. I cant hear the motor because they took the baffle out of the mufler. ( has anyone got one to sell?)

But I didn't hear anything that sounded bad, but I also noticed that there are 2 pages worth of cranks for crf450's on ebay. now that throws up a red flag for me.

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I took it out and did some trail ridding today. I cant hear the motor because they took the baffle out of the mufler. ( has anyone got one to sell?)

But I didn't hear anything that sounded bad, but I also noticed that there are 2 pages worth of cranks for crf450's on ebay. now that throws up a red flag for me.

Not to worry. More 450X's have sold by a factor of 50 than anything else, so there will be lots of spare parts.

It is more profitable to part out a used bike that it is to sell it, in this economy. That is why you see so many parts.

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When I change oil and filter I will for sure hold the kill button and kick it a few times to make sure its back to prime and filter is filled before I fire it up.

My 250 is pretty noisey in the valve area...but what bothers me most is when I lug it down or drop the idle and hear abit of cam chain slap.

Not to worry. More 450X's have sold by a factor of 50 than anything else, so there will be lots of spare parts.

It is more profitable to part out a used bike that it is to sell it, in this economy. That is why you see so many parts.

That and factor all the bikes that went to the AF500 conversions. I like seeing so many used parts for any bike I own.....means I am able to shop around and make some great deals.

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When I change oil and filter I will for sure hold the kill button and kick it a few times to make sure its back to prime and filter is filled before I fire it up.

My 250 is pretty noisey in the valve area...but what bothers me most is when I lug it down or drop the idle and hear abit of cam chain slap.

That and factor all the bikes that went to the AF500 conversions. I like seeing so many used parts for any bike I own.....means I am able to shop around and make some great deals.

Thats a good point, one of the reasons I am selling my 09 xt250 is that there are no upgrades for it.

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I don't think I would worry about the noise. Mine always makes some noise. I have the baffle for it but run with it in and out on a regular basis. All these new four strokes make noise, even some idle rpm knock noises at times. They are a completely different design from older four strokes that many of us are used to. I ride with the baffle installed if I am riding in noise sensitive areas and then you can really hear some engine noise! Krannie had a good description of what you hear, especially if the exhaust is quiet. My yz400f makes some pretty good noises and it has been running for ever. It is much louder with engine noise than the crf450x. I would not be concerned with noise from the crf unless it suddenly got real loud or had a change in performance. Just remember it is not an xr engine. It only revs twice as hard and makes 12 times the power with style! It's a hotrod but it will run and last a very long time.

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When I change oil and filter I will for sure hold the kill button and kick it a few times to make sure its back to prime and filter is filled before I fire it up.

My 250 is pretty noisey in the valve area...but what bothers me most is when I lug it down or drop the idle and hear abit of cam chain slap.

That and factor all the bikes that went to the AF500 conversions. I like seeing so many used parts for any bike I own.....means I am able to shop around and make some great deals.

Blackwoodz,

My 450x has the same chain slap noise when I lug it. I originally thought it was the cam chain as well, until I looked down at the drive chain while doing it. I can look down and see it bouncing around down there. Even when the chain is adjusted according to the manual. Its not hitting anything, but it seems the power pulses are far enough apart at that engine speed to allow the chain to slack in between pulses. Your 250 may be the same.

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Blackwoodz,

My 450x has the same chain slap noise when I lug it. I originally thought it was the cam chain as well, until I looked down at the drive chain while doing it. I can look down and see it bouncing around down there. Even when the chain is adjusted according to the manual. Its not hitting anything, but it seems the power pulses are far enough apart at that engine speed to allow the chain to slack in between pulses. Your 250 may be the same.

100% correct.

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All slipper pistion engines are loud and have odd knocks.

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The chains on these bikes are stupid loud on these bikes

All slipper pistion engines are loud and have odd knocks.

What exactly do they mean by 'slipper piston'?

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