xt550 - who wants to have a go at knock troubleshooting!!
 

long story of course ....

this is the sound of my 83 xt550 - not all that pretty.

it started to sound like this just after I had a really bad kickback incident due to a faulty pickup coil. - solved that one. but inherited this knock.

xt550 engine knock - YouTube - this is just after is started about a year ago.

XT550 - persisting knock - YouTube - this is a few months later.

I first diagnosed this as cam chain, so i went in and replaced the cam chain, checked the tensioner and replaced one slightly worn cam chain guide. put it back together and re adjusted the valves and yet it still persisted.

the knock is only at idle, and the lower the idle, the worse it gets. But sometimes, the knock will stop and the engine will run smoothly ... and quietly ... just like it is supposed to, then ... a moment later the knock will start up again. (pretty infrequent that this happens, once in a blue moon really.)


it is a knocking noise that appears to be coming from the right hand side of the crank case, although it is quite hard to spot, even with a stethoscope.

I have had the clutch side apart and there wasn't anything that jumped out at me as being wrong or too out of wack. Also showed it to a couple mechanic friends of mine, they said everything looked about right and said they couldn't really tell unless they took everything apart measured all the tolleranced and compared it to the manual.

well I am trying to advoid taking the crankcase apart. Although I am taking the head off to do my rings next week and thought I could tear into the clutch side a bit more if I knew what I was looking for -
Any ideas would be helpfull.

sheared woodruf key on the main gear?

anyone??
anyone??

Thanks in advance.

Don't know the xt550 engine at all but if your lifting the topend off do yourself a favour and strip the bottem end aswell and check the rod bearing,mains and balancer bearings.in my experience a knock nearly always comes from 1 of these on a big single.sorry i cant be more specific to your motor.cheers

i currently have the same exact problem on my '93 xt600 and i do very much agree with dodger on the bearing issue. i feel its a bottom crank bearing for mine but the inconsistency of the noise points out the fact that it would be a bearing. if it were a more steady knock id say valves, but it definately sounds like a bearing to me. ill upload a clip of my bike and let you hear it.

Something as simple as some sort of auto decomp clacking ?

A bottem end bearing going bad should also knock above idle....Atleast, thats the way I see it.

What is the idle supposed to be at from the factory? I would guess a couple hundred rpms faster?

Might be a loose nut - primary drive, clutch or balancer.
Makes sound on low revs, gets balanced on higher revs and sound almost disapears.

No idea how "deep" you have been into your clutch side - but I would
recommend to check all three of these nuts - as well as damping springs in
primary drive.

just my two cents

I think if it was a bearing it would get worse as the revs rise.
Nuts are worth checking, it sounds like the cam chain tensioner is not working erratically?
Have you used it over the last year and has it developed in anyway?

not necessarily on higher revs the bearing gets hotter which in turn makes it quieter. i had a buddy who had a spun bearing that would wine everytime he started his bike but it wouldnt make a sound the whole day afterward once it was warmed up only the first start of the day

Weatcoastrider is not online at the moment but might I point out, if you look at his you tube there is a third vid with the clutch cover off, where he points out one or two lose gearings. But I don't think this is his problem.
I would strip down the engine bit by bit, eliminating each part as I did so.

Whatever it is ain't going to get better, without help.

Socks

It's the erratic coming and going, not in time to the strokes, that swerves my judgement away from bearings. That's not to say it's not.......I've changed a wheel by text but diagnosing engine knocks via you tube........Take it apart, giving everything a good push-pull, up-down as you are doing it.

Id say you hit the nail on the head the first time, worn woodruf key in the balance shaft? or a worn 3mm washer next to the main bearing RH side.

This sounds like a similar problem Danny is having, read this.

Mezo.

I'm no mechanic but I remember an old XT once sounded like this, it had been sitting around for a while and the fuel had got contaminated.
Is the kick start disengaging properly ? that seemed to be the start of this problem.

i guess i've finally come to the right place.
 

hey unbelievable! i never expected so much feedback in one day! thanks so much.

I have been riding the bike like this all summer this year, even did some 200 - 400 km trips. Basically the noise is exactly the same. Its hard to say but the noise may even get a bit better once out on the highway for a 1/2 hr or more.

I think i will split the bottom end just out of curiosity, the weather here is starting to suck anyways and i have the time to dedicate to it so why the heck not right.

oothef - I am pretty sure the tensioner is working properly and as i said i did replace the cam chain already. also noise is really coming from the rhs in the middle near the top - as far as my ears can place it.

bubbla - where do i find these damping springs you speak of. http://i1237.photobucket.com/albums/...on_83XT550.jpghttp://i1237.photobucket.com/albums/...ch_83XT550.jpghttp://i1237.photobucket.com/albums/...on_83XT550.jpg

Jens Eskildsen- decomp is adjusted to spec and appears to be working properly.

Pboko2388 - would love to hear your bike, especially if you think you have found the problem. I am quite handy with a wrench but this is definitely as far as i have ever gone into the motor so i'm a learning noob but very curious, any feedback or hints welcome.

Mezo - thanks for the link to Danny's build - real nice BTW. i think my 550 is in need of some black wheels too - looks great. those vids are certainly going to come in handy once i open up the rhs.

I am not familiar with what bad bearings should look or feel like - if anyone has a good description of a bad bearing I'd be keen on hearing it.

thanks again for all the help, - I'll post my results after i get into this weekend.

cheers

A good bearing should have no play radially and be smooth turning, no notchiness or grating. Take your time, be methodical and label stuff.

results
 

update:

A+ for Bubbla and Mezo ! - balancer shaft woodruff key was almost completely sheared in half and the tab on the lock washer that sits in the groove was also missing. after removing the clutch i noticed the balancer nut was just spinning around loose.

The only thing I just can't figure out is why i didn't see this before. I had already checked these nuts and they all seamed fine. Hopefully this will be the source of all of the knocking and once re-assembled will purr like a kitten again. good news is that all the bearings appear to be in good condition, no real play anywhere as far as i can tell.

some piscs that are not great. I always get so excited to find something broken that I am too busy to stop and take great photos. at least it gives the idea.

http://i1237.photobucket.com/albums/...r/IMG_0820.jpg
http://i1237.photobucket.com/albums/...r/IMG_0822.jpg
http://i1237.photobucket.com/albums/...r/IMG_0824.jpg

i noticed a small amount of play on the primary gear as well coming from the way it fits over the key, not the bearing. Should i just replace this key as well, for good measure? I can't imagine this is a bad idea.

will get some video tonight and post again with some better images etc.

Good to hear it's something that's easily remedied,you must be relieved.Is the keyway still in good shape?

My first impression was that the keyway is still ok, I might order some larger key stock just in case the stock part seems too loose when I reinstall it.

Will keep updating ...

Update - keyway slightly worn
 

Well upon closer inspection I think the keyway is worn.
http://i1237.photobucket.com/albums/...ider/image.jpg

It is not so so bad but I won't really know until the parts arrive.

My research led me to think that I might be able to fill the gap in the keyway with a product called loctite 660. There is a bit of www documentation of it being used to repair worn keyways and fills gaps up to .5 mm


Anyone ever tried this product? Feedback ? Advice?

I've used the Loctite product in industry on pumps etc with good results.

The thing you need to consider is the key is not designed to take shear forces (ie to stop the balancer rotating on the shaft) but only to provide the correct location. The rotation is prevented by the nut being done up to the correct torque.

I'd be checking that the balancer is still a snug fit on the shaft and that the movement in use hasn't caused any slop when bolted up. If there is any doubt there are various other Loctite (and others) products that can help. Loctite have a product called "Bearing Fit" ( or something similar - sorry can't remember its number) designed to stop bearings spinning in their housing. If there is any doubt I would assemble the balancer onto the shaft with some of this before torquing the nut to the correct figure.

Hope this helps.

I agree, make sure everything is spotless clean and degreased. Make sure the nut is well tight then the key as no stress on it. It's only worn the keyway because the nut was loose, allowing it to move.

play in balancer shaft
 

still awaiting parts (key and breather plate) but started to wonder if this "in and out" play in the balancer will be remedied once i torque the nut to spec. Is the balancer supposed to have all this movement in and out? or is the bearing shot or is the balancer shot? I will probably wait to reassemble and see how it moves afterwards. but if this is obviously a problem i guess it would be good to know at this point. split the cases and get the wallet out again. check this video to see the play. The bearing itself appears to be in good shape and there is no movement in any other direction just the bit of play in and out.



not sure if the embed will work ... if not here is the link. xt550 balancer play - YouTube

as always, thanks for the advice everyone, much appreciated.

If it was me I'd build it, torque it, and check the end float again, I don't know but it will most likely remove most of it. It looks like a roller bearing in there, they have no means of controlling axial float, but are very strong radially.

The bearing will be fine as theres only lateral play. If you were to split the cases you would find only that the balancer shaft will be very slightly mushroomed out where the spinning forces have bashed it around and wear will have occured. With the nut back on some of the play will disappear as it is now limited to the amount of free movement between the gear wheel on one side of the bearing and the inner race face on the inside.

As this is something that is set by design I convinced myself that this was to allow for either mechanical expansion through heat. Its one of a kind in the engine, the other side is just a small common ball race so they must have designed it like this for some purpose.:mchappy: (or so I'd like to think.)

I know I gave it lots of thought when I had mine apart. One idea was to space it out with shim washers on the other end of the shaft. In the end I did replace the bearing to gain no difference what so ever. Shied away from shimming it out as assumed there must be a reason for it and slightly to lazy to take it apart again.No engineers blue either!

update
 

hey A.L.F.
Curious to know if your efferts reduced any sort of knocking noise.
If yours remained with a bit of play - could you still hear this play in the engine while running?

Anyhow, here is the balancer with new parts installed. Installed a new key and used that loctite 660 to make up the small wear gap on the side of the keyway, new breather plate and new lock washer. Torqued to spec from the manual but there still is a little play in there. Guess I'll have to get it running again to see if this solved my problem. Crossing my fingers.


I should have the rest of the motor back together next week. New 1st oversize Yamaha piston, cyl rebore and recut valves by mongoose in poco, bc.

Hope the weather here holds (ie no snow) so I can get the old girl out for a break in run.

Looks O.K. to me, run it and see......

fixed the knock - but more new problems
 

thanks again for all the advise everyone.
the new parts for my balancer have indeed stopped the bottom end knock. I will post another vid soon.

i got the bike all back together and it ran great for the first warm up run anyhow.

now i am having issues with poor running condition, won't idle and a lot of backfiring.

if you have any advice check my new post out.

http://www.horizonsunlimited.com/hub...963#post361102

thanks.

XT550 Service Manual - Index of /josip/manuali/yamaha/xt550 (Long download be patient).