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Another engine knock thread.

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Sorry to start another one but, after reading several old threads this weekend they all seem to end without mention of the cause found other than a bad cam chain tensioner. So, I put a manual tensioner on this weekend and was making some laps around the house, never got out of second gear and no more than half throttle. I made two or three rides and on the last one I heard an abrupt knocking down low that appeared to come from the right side, I had just let off the throttle from about 1/2 when it started. I immediately shut it off and pushed it to the shop. I don't know if the noise goes away on acceleration. I removed the valve cover to find all timing marks intact and no noise when turning it over by hand. Valves are in spec. I didn't check the decomp. gap but, none of the springs are broken and it appears to function normally. One thing I did notice that was odd is the radiators didn't feel as hot as they did on previous laps. The weep hole has been leaking a small amount of coolant only on start up and, coolant level was good on this ride. Would a failed water pump cause a very distinct knock down low?

I haven't drained the oil yet to look for metal and when turning by hand I could not detect play in the big end bearing. What is the best way to check for big end bearing play with the engine assembled? Any help or suggestions would be greatly appreciated. I would like to pin point the noise before tearing it apart and/or spending a bunch of money.

Also, I did notice a faint ticking noise this weekend that I had not previously heard. It appeared to be up top and got louder as the engine warmed up but nothing like the knock that caused me to shut it down. I adjusted the manual tensioner per instructions. Could having it too tight cause something to fail such as a cam bearing?

This is an 02 model that I recently purchased from the original owner. I also forgot to mention that it has a Rekluse Z-start. Has anyone experienced any knocking from a Rekluse?

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Anyone have a recommendation? I have been reading some threads on the clutch dampeners letting go. Would this cause the noise to come on suddenly or do you normally get some warning? Thanks.

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Is the engine noise new, as in did it start after you bought it, or has it been there since you have owned it. These engines are noisy, especially if you have an aluminum skid plate.

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yea lol i think mines been making all kinds of weird noises on my new bought 07 kx250f. i check/adjust the valves about every 10-15 hours. and i just intalled stage 1 hot cams INTAKE and EXHAUST. and i have a devol aluminum full skid plate. yea shes noisy.

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The knock is new. I had about 1 hour time on this bike before changing the CCT, it had been making typical new age 4st noise, quieter than my Husaberg, noisier than my WR450. The knock started about 20 minutes after putting on the manual CCT. I put the manual CCT on for peace of mind, I was not having any probs. with the auto CCT. I also ran a manual CCT on my 1994 Husaberg.

I had been riding it for about 20 minutes. The knock started immediately after letting off from about 1/2 throttle in 2nd gear. After checking all the tolerances noted in my first post I started it once more. It had the normal amount of compression and started first kick, the knock was immediate and the same as before. I immediately shut it down, did not rev it to see if the knock went away.

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Check the right side crank bearing by taking the little round cover off the right side behind the water pump and sticking a allen into the end of the crank for leverage. Also check to see if the piston rod bearing or wrist pin is shot by rocking the crank forward and backward with a straw cafefully inserted were the spark plug goes. If the straw hesitates to move up and down through the mid stroke of the piston that is a good indication the bearing or wrist pin is shot.

The noise and the weeping could be related. It's also possible that the water pump bearings are shot. The water pump is driven from a gear straight off the crank on the right side. The axle for the pump inserts into the counter balance shaft. It's possible that it is dancing around inside from the loose bearings and causing extra stress on the seals making it leak slowly.

I had both those problems once before. Turned out to be the left crank bearing. Once I took it out you could shake it and sounded like a tamboreen. The water pump issue was an indirect issue caused by the crank flopping around.

Since it's a 02 model I'd say tear it down and do a complete rebuild just to cover all bases. Better to spend the money now and have a good motor for another year or two rather than throwing a hundred here and a hundred there until you are sick of it all.

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The same thing happened to me last month. I had a very high frequency knock on the right side lower front of the engine. The noise was too fast for a crank bearing. So I went in and as soon as I got the whole clutch side cover off... my balancer nut fell to the garage floor. I got lucky.

I believe the balance shaft bearings were bad and causd the nut to vibrate off.

Take off your side cover and grab the balancer shaft and try to move it up and down, if it moves replace both bearings and the seal. A 1/2 " x 10" brass drift works great for pushing out the bearing race on the flywheel side.

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Thanks for all the input, greatly appreciated. I am off tomorrow so will drain the oil and inspect it then take off the right side cover and have a look. I hear what your saying VR about a rebuild, I have been leaning that way but, this bike has low hours (for being 7 years old) on it and was trail ridden only. I was hoping to get at least 1 year of trail riding out of it before a major overhaul.

RufusM, did you notice any unusual noise before the knock started? As stated in my original post I was hearing a faint ticking that I hadn't heard before, thought it was valve noise.

I got to thinking about it last night. If anyone has ever had a car with an auto trans die while it's moving then put the trans in park while it's still rolling, that describes the noise I'm hearing.

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The knock started about 20 minutes after putting on the manual CCT. I put the manual CCT on for peace of mind, I was not having any probs. with the auto CCT.

Have you thought about putting the auto CCT back on to see if that fixes it?

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You can use the frequency (speed) of the knock to help you get an idea on where to look. A low frequency knock at idle and I would look at crank/rod. A high frequency I would look at components like counter balancer/water pump...

Mine sounded just like you describe. like trying to put an auto in park while moving. I only heard the noise for 10 sec before I shut it off and went home to investigate.

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Well, I found the problem and it's pretty ugly. It looks like 2 or 3 of the clutch plates have come apart. It was obvious after draining the right side oil that it was catastrophic due to the large metal bits that came out. I don't know the extent of all the clutch damage because I don't have a Torx bit small enough to remove the Rekluse top plate. The clutch basket is not showing any significant grooves on the fingers though.

So, I guess the major overhaul will happen anyway. I'm quite sure the transmission needs to be disassembled, inspected and cleaned. While I have the cases apart I will probably replace the con rod assembly, crank bearings and etc.

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After several weeks of ordering parts I finally got the motor back together. All new bearings, left crank case half, new crank assembly, new clutch basket, hub and plates. I set the Rekluse to original specs and put in all new Rekluse metal plates. After the first run I drained the oil, crank case side was clean, gearbox side looked like metalic paint with several larger flakes. The flakes will not stick to a magnet so are apparentley clutch or case material. I put in fresh oil and ran it once more, the gearbox oil came out looking the same as before.

So, I took it back apart to inspect and found absolutely no evidence of wear, rubbing, scraping or any other damage that would produce a large amount of flakes.

Does anyone have a suggestion as to where so much metal flakes might have come from?

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