1991 XTZ 660 Engine rattle / clanking

[enplanedrole]

Hi Guys,

I'm looking for some advice on my XTZ (this model: http://www.motorcyclespecs.co.za/mod...z_ten%2091.htm)

I just returned from a 4k trip through Norway and Sweden. Bike handled awesome both on and off-road. Unfortunately, in the last 250km, at the high way something happened. I was overtaking someone (150km/hr, Germany after all), the bike held back a bit (as if it was hitting the rev limiter or the clutch slipped). After that, it worked normally again. 2 min later, my neutral light came on and remained on (every gear). I pulled over and checked my oil. I had to put in 2l (topped it off before I left, so it had been using quite a bit, did not expect that much). Also, I noticed a rattle / clanking, kind of like a valve rattle but way louder. In neutral, the sound is the loudest, it fades off when riding off (but maybe the valves rattle a bit louder than normal).

What I've done:

1. I've read similar stories where the primary nut came loose. I pulled off the side cover yesterday and checked that, that was not the case.
2. Valves had good clearance
3. I pulled out the cam chain tensioner, was not at full extension, seemed to be in good nick.
4. Drained oil and coolant, no debris in oil nor on plug
5. When walking around the engine with a large screwdriver as a stethoscope, the front of the engine right in the middle about 5cm beneath the exhaust pipes heared like the loudest sound, right where the valves are, but I'm hesitant to go that way since the engine runs great apart from the noise.
6. Right side is definitely louder than left side
7. Does not go away when engine warmes up

Here is a video of it running: https://www.youtube.com/watch?v=axqIGtIAuZw

Now, I'd rather not take it to the garage (expensive), it seems like a relatively simple engine to work on and I have all the tools needed. I've found a replacement engine for around €500, could be an option. But I thought I would try to go this route first.

Any clue?

[xtzrick]

That is loud

The balance shaft nut can also come loose, they both need checking with a torque wrench.

If the noise started after your power and neutral light problems there's a good chance all 3 are related, something loose floating round your engine like a broken cam chain link wrong side I know, just guessing

Rick

[enplanedrole]

I'm taking the bike to a guy who races these engines, he'll know exactly what's up. After talking to some garage guys they think it might be the push-rod bearing that has gone, as it only happens whiles stationary. After that, the oil pressure goes up and then the rattle becomes less.

I'll know more after I take it to the guy, his racing bike has 95 horsepower, as the engine needs to be taken apart, I think I might have him fiddle with it a bit to go up in horsepower. Also maybe make fifth gear a bit longer (if possible) for that highway cruising.

If anybody has any info though, lemme know!

[scottieh]

I recently bought and rebuilt an XT550 and heard something very similar when I kicked the bike over and started it the first time. All three of the big clutch side nuts had come loose somewhere in its life. The crank nut, the counter balancer, and the clutch basket nut were all finger loose and while the bike still ran it sounded like hell - kinda like yours.

[xtrider]

I doubt it will be as bad as this 660 I took apart ,






That sound is much more tinny sounding than the rod bearing failures I've heard but it could be the microphone of the phone the video was taken and my laptop speakers. Those also tend to get louder right after you let off the throttle and the rpms are dropping. Sounds more like something broke off on one end and is spinning around hitting something else . Dropped valve seat makes a rather high ticking sound as it gets slammed back into the pocket each time the valve close.


.

[enplanedrole]

I'll be taking out the engine this weekend. I'm contemplating rebuilding it myself, but I have no experience rebuilding engines. I have done a bit of work on my old bmw (https://www.instagram.com/p/BUZ9N_Bhz86 ... landpeelen), but no engine work so far. I know how to use a torque wrench, how to apply gaskets and stuff. I'm assuming the thing that's broken will present itself as soon as I start taking the engine apart.

Is this a case of 'if you have to ask, don't'? If I take it apart, how much damage can I do? If I just follow the workshop manual, are there things that can go horribly wrong?

[xtrider]

Before digging too deep it's always good to do a little more probing , just incase it turns out to be something simple or fixable without total rebuild .

To test rod bearings take the sparkplug out and the stator cover center cap so you can turn the motor over by hand with a socket on the nut . Get yourself a rod , I use a 8mm or 10mm brass rod but a good dowel will work as well . You put the rod down the sparkplg hole till it's hitting the piston. Now turn the motor over counterclockwise with the socket/wrench while holding on to the rod keeping it so the piston doesn't pinch it . Turn the motor over slowly till you see the piston is at TDC(rod up as far as it goes) then turn it a bit more so the piston has traveled maybe 1/2" down from tdc. Now stop and hold the wrench so the piston can't move , push down on the rod on top the piston. With the garage quiet listen for any "clunk" or if the rod was able to move the piston at all without the crank moving . If one of the rod bearing are bad you'll feel and/or hear the movement .



.

[enplanedrole]

Before digging too deep it's always good to do a little more probing , just incase it turns out to be something simple or fixable without total rebuild .

To test rod bearings take the sparkplug out and the stator cover center cap so you can turn the motor over by hand with a socket on the nut . Get yourself a rod , I use a 8mm or 10mm brass rod but a good dowel will work as well . You put the rod down the sparkplg hole till it's hitting the piston. Now turn the motor over counterclockwise with the socket/wrench while holding on to the rod keeping it so the piston doesn't pinch it . Turn the motor over slowly till you see the piston is at TDC(rod up as far as it goes) then turn it a bit more so the piston has traveled maybe 1/2" down from tdc. Now stop and hold the wrench so the piston can't move , push down on the rod on top the piston. With the garage quiet listen for any "clunk" or if the rod was able to move the piston at all without the crank moving . If one of the rod bearing are bad you'll feel and/or hear the movement .



.

Awesome advice, will definitely try that. Anything else I can try myself with the engine on the workbench?

[xtrider]

With the motor held tight in the frame or clamped to the bench garb the flywheel with both hands and try to twist it forward and back listening for any clunking . Beyond that not much can be done other than taking the rocker cover off and inspecting everything looking for any signs of trouble . Drain the oil into a clean glass jar so you can look at it for excessive metal flakes .





.

[enplanedrole]

Yeah, thought so...

Allright. Small update. Took the engine out and removed the head. Tappets and valves looked quite allright, apart from a lot of black stuff on them (not sure of the word). However, the cylinder did not look well. Lots of scraping and the oil scraper ring is basically gone. This explains a lot. Will take it to be rebuild :)