KTM 640 Horrible engine noise!!!!

[moto_psycho]

http://www.wossnerpistons.com/tech/piston-installation

I'm guessing by this I just go by my smallest average measurement? Bore gauges are at work so I'll get it done tomorrow

[Boon Booni]

Originally Posted by moto_psycho

Definitely what I would call 'too much play' on the big end.
.

What kind of play? Axial? Radial?

[moto_psycho]

Plenty of axial, not much radial. I'll make a video when I'm out of the bath

[moto_psycho]

http://www.youtube.com/watch?v=Cf81Z...ature=youtu.be thoughts anyone?

[Boon Booni]

Originally Posted by moto_psycho

http://www.youtube.com/watch?v=Cf81Z...ature=youtu.be thoughts anyone?

According to the shop manual, the tolerances for the conrod are:

Radial: 0.05mm (0.0019")
Axial: 1.00mm (0.04")

My mark 1 eyeball says your axial play is within spec.


EDIT Just went back and listened to your original video. What noise was it that was giving you worry? The loudest to me is a whirring from the left side. Mine makes a similar whirring when the motor is hot and the clutch is released. The noise goes away then the clutch is pulled.

[moto_psycho]

More the "donk donk donk donk donk donk" noise, far more harsh when warmed up, and loudest at the front left of the engine, not really noticable when completely cold. Clutch nut was tight, and no change to the noise when clutch pulled in. 1st picture shows loads of swarf on sump plug, there was plenty on the oil change before that as well. Haven't actually seen anything with that much wear on it yet...

sounded exactly the same as this video, http://www.youtube.com/watch?v=Cyq5_rYbeIo

[moto_psycho]

Locked the crank and felt again, can't get any up/down play, even when just holding the piston. Now going to upload a video of play in the rockers etc... I honestly cannot find anything capable of making that racket!!! Piston slap perhaps?

[gunnerbuck]

Originally Posted by moto_psycho

http://www.youtube.com/watch?v=Cf81Z...ature=youtu.be thoughts anyone?

Looking at the video it is easy to see that your con rod bearing is totally shot...

Your piston and cylinder still look servicable going by the pictures... You can pull the piston rings and push them up in the cylinder to measure the ring end gap, I am sure they will still be within spec but you may want to replace them anyways... The rub marks on the piston do not look excessive so it should be good to go unless you find defects around the crown after carbon removal... The cases split quite easily on these engines as the tight crank races remain with the crank...

Because you have had a con rod bearing failure I would also recommend you also replace the 2 crank end bearings as well because of the debris that has been washing around the crank chamber... You can take the bearing #s to a bearing supply shop and they should be able to fetch you a set at a more reasonable price... You will need a race puller to change them or better yet take your crank into a dealer and have them pull the races for a small {hopefully} service fee...

[moto_psycho]

http://www.youtube.com/watch?v=WBrZ9...ature=youtu.be

[gunnerbuck]

Originally Posted by moto_psycho

Locked the crank and felt again, can't get any up/down play, even when just holding the piston. Now going to upload a video of play in the rockers etc... I honestly cannot find anything capable of making that racket!!! Piston slap perhaps?

That noise may be all due to conrod slap but I still think your left side crank end bearing may also be shot and part of the cause, you'll know better when you split the cases... What you could do now is remove the piston and spin the crank by hand and listen for a gravelly grating noise coming from that bearing...

[gunnerbuck]

Originally Posted by moto_psycho

http://www.youtube.com/watch?v=WBrZ9...ature=youtu.be

Your rockers look fine, even the rollers look OK, but really check the smaller one for any up and down wiggle...

[moto_psycho]

Do you know the part numbers for the crank bearings? Are they a pain in the arse to change at all?

[Boon Booni]

Originally Posted by moto_psycho

Locked the crank and felt again, can't get any up/down play, even when just holding the piston. Now going to upload a video of play in the rockers etc... I honestly cannot find anything capable of making that racket!!! Piston slap perhaps?

How do your exhaust seals look, any signs of blow by?

I had an old XS Eleven that had a bad exhaust seal, which sounded just like a bad conrod. Once I got a new seal and torqued the header down properly it quieted right up. Exhaust leaks can sound just like mechanical knocking.

[gunnerbuck]

Originally Posted by moto_psycho

Do you know the part numbers for the crank bearings? Are they a pain in the arse to change at all?

left side nj306c3
Right side nj207ecp

The bearings are not difficult to change it is the race removal from the cranks and re shimming to spec that are more of a problem...

This page gives an outline: http://advrider.com/forums/showthrea...=632893&page=4

[Boon Booni]

Originally Posted by gunnerbuck

Looking at the video it is easy to see that your con rod bearing is totally shot...

From what I can tell the conrod bearing doesn't control the lateral play. There are two thrust washers in there that do that. But if the spec is 1mm, I'd measure it before I declared it shot.

IMHO it's hard to tell just from looking at it.

Originally Posted by moto_psycho

Do you know the part numbers for the crank bearings? Are they a pain in the arse to change at all?

Gunner has a great thread showing how to change the crank bearings, and how to correctly shim them.