Whining noise then loss of power

Ya so i was riding at fairly slow speed on my 81 xj750 r and i hear this whining sound for one second then sounds like something is letting go, then engine stops. Still has electric and gas. Wont start. My immediate thought was cam chain. Took off valve cover, no problem. All valves are opening and closing, all pistons moving. I checked oil pump chain, it is fine. I thought maybe vacuum line letting go might make a whine. The noise seemed to come from the front left side of the engine. Dont think there are any vacuum lines there. Not in the manual anyway and not visually. Although it has been around freezing here the bike was warmed up when this went down, and now its down for the count. I am confused, can anyone shed some light. Anyone hear this noise and diagnosed it?

 

ignition pick-ups are under the cover on the left side

 

would they contribute to a whining sound. still getting a spark, but maybe the timing is all screwed, what do you think?

 

When I saw the "Subject" for this thread I thought maybe one of the guys on here was getting married! 8O
:twisted: :twisted: :twisted:

 

Now thats funny I dont care who you are :lol:

 

To be honest i don't think its the pick ups they either work or do not work. My guess is one of the timing chain tensioners failed and it jumped time. when you try to start it does it sound kind of funny like it has no compression? That's just my theory. Pull the side cover check make sure the timing and cam marks all line up. My guess the whining you herd was the tensioner grinding up. If you have fuel and spark that's about the only thing it can be. If it did you probably have some bent valves. Hope i am wrong

 

Hahaha

 

So it turns over, has spark, and won't fire?

The whining sound lasted how long? Does it make any sort of whining sound when you turn it over with the starter?

I agree that you should pull the valve cover and LH crank cover, and make sure the cams are still in time, but I somehow doubt that's it.

Did you turn the motor over using the big peg on the timing plate? I'm asking because I wonder if the timing plate coming loose was the sound. But if you've already used it to turn the motor over then it's obviously not loose.

Weird. Need more data.

 

Whining noise then loss of power,anything to do with the wife perchance?,joking aside its usually fuel or sparks,sound like sparks.

 

the whining sound lasted about one second, then i threw her out! no really one second then total loss of power. i didnt use the big peg to turn her over, used electric. so this morning i will check the timing. there is no whining sound when i turn it over now.

 

Check brushes in charging system how many miles on bike?

 

the odometer says 71,000 km. i put 17 on this past season, since i bought it. which brushes are you referring to?

 

Brushes in the generator. Disconnect battery. remove starter generator is forward of starter round cover with three bolts.

 

if these brushes are out of shape, would they go all of a sudden or would i have a warning?

 

Even if the alternator had died a horrible internal death it could only cause loss of spark. You have spark.

The alternator is certainly worth checking; but I doubt it's the cause.

 

You would get a warning The warning is a whining noise then it sounds like something lets go and then the engine stops running. I bet you wish it were that easy I know I do but Im afraid it doesnt work that way with machines. The reason I said to check the brushes is the sound you described seemed familiar to that area but what you describe as a whine might be a shriek to someone else. Im not familiar with the Maintenance schedule of your bike but the brushes are probably the most neglected maintainable part of any bike. Good luck to you

 

nothing seemingly amiss with the contacts. dont see anything abnormal with valves or cam chain. but maybe i dont know what to look for. all valves open and close no weird noises. chain is exactly the same tension as it was this winter when i replaced the valve cover gasket. dont have a timing light. guess i will try to get one today. but if its not running, will i get i get an accurate reading? probably not.

 

Timing is the same. If it did not fire at the correct time it would not start would it? Generator Brushes should have line scribed on them if you do not see the line then they are worn past limit.

 

thanks waldo, i missed your last post. that is the closest anyone has come to identifying the sound. i will check the brushes this weekend.

 

You don't need a timing light; you do need to double-check the CAM timing.

There is a "T" mark on the timing plate; align it with the pointer and ensure the little "dots" on the camshaft flanges are aligned with the little pointers cast into the cam caps.

 

plenty left on the brushes, at least 1/4 inch past score mark....

 

nowhere can i find a picture or diagram of the dots and pointers on the camshaft flanges and caps. it is not obvious to me what i am looking for. still looking.

 

On the tops of one of the sets of the inner cam caps, you should have little raised "arrows" that point toward the locating flanges on the camshafts.

Those flanges have a small partially drilled hole (forming a "dot") on them that should line up with the little arrows on the cam caps when the crankshaft pointer is at the "T" mark on the plate.

The little arrows should be relatively easy to spot, as they're raised and cast onto the inner cam caps. The drilled "dots" on the flanges won't be apparent until they come around to hopefully line up with the arrows, or at least come close.

 

got the cams set up so the marks match the arrows when the timing plate is set. i have to tell you it sounds different when i hit the starter. a lot quieter. anyway wont start, is getting spark, engine turning over. this is the weird part. poured a little gas in each cylinder through the plug hole. nothing. not a cough , nothing. every 8 seconds or so, the pipe (supertrapp), coughs. like its expelling air, no exhaust. so i figure there has to be compression. is it possible to time it 180 degrees wrong? i now have the feeling, that the timing wasnt the problem but something else all along. i have a spare coil, i'm going to throw it on and see if maybe my spark is weak.?? thanks for all the help i have gotten so far...

 

So everything wasn't all lining up, you had to do something? Or was it just a case of getting the pointer at the mark and looking again?

If you did have to "intervene" run a compression test; if the cams DID jump time you may have a bent valve or two that can no longer close.

 

If it is sounding different when you turn it over, and you get that little coughing sound - then I'd put my money on bent valves and the whining sound was the sound of your engine turning over out of time. The compression check will quickly identify this problem.

 

i did have to realign the cams. the whole deal with taking the carbs off to loosen the cam chain tensioner et al. am doing comp test now

 

How far off were the timing marks? Did you have to set both the intake and exhaust cams?

Kenneth

 

This is a major "interference" motor; if it was running and jumped cam timing, it almost for sure has at least 2 bent valves, maybe more.

Hopefully, no piston/rod damage.

 

Bigfitz...that was what I was thinking, however, if the cams were out enough to allow a valve to hit a piston, I would think he would have found a slack timming chain, a broken chain guide, or a broken chain tensioner.

Kenneth

 

I was afraid of that. Check the compression. then i hate to say it fix or replace the motor. There has to be a reason it jumped time so besides fixing the head your going to need a timing chain and guides

 

These things are "choreographed" pretty tightly; roll your motor over sometime and watch the valves through the spark plug hole; they barely get out of the way of the piston in time. A tooth or two might prove disastrous.

I agree that there has to be a root cause; I'm betting that a close inspection of the cam chain guides reveals a big hunk of "lining" missing somewhere. Something "let go" so it should be able to find pretty easily.

 

both exhaust and intake cams were off the same amount. not a quarter turn but maybe 2 out of ten if you know what i am saying. 1/5 of a turn. need to know where i can get some valves at a decent price yamaha here is cost prohibitive. locating compression gauge tonight, will post findings tomorrow.

 

Did you check the timing plate and mark itself to make sure they are correct. I doubt that they are incorrect but you should check them to make sure.

 

That sounds like alot....I agree with the other members, its time to do a compresson test.

Kenneth

 

Even without a compression guage, you're going to be able to determine the damage. Just pull the plugs, put your thumb on the hole, and hit the starter. I doubt you have enough compression to push your finger away.

 

correct, no compression. i have purchased a cylinder head ll loaded and ready to go. i agree, dont really want to repeat the same process again, there has to be a cause. could this be the cam chain tensioner?

 

Maybe. Or one of the chain guides broke, or broke free at one end. I'm betting that's where the "whining" noise came from at the time of failure.

Pull the sump and see what kind of pieces you find. You can inspect the chain guides from above using a mirror and flashlight with the valve cover off. I thought you said you pulled the tensioner itself, what did you find?

Here's a link to a good parts fiche for reference: http://www.yamahapartshouse.net/pages/p ... amaha.aspx

 

There was nothing in the oil pan so i changed the cam chain and put a new cylinder head on her. Craigs list $40 dollars. The cam chain tensioner seemed like it wasnt taking in enough slack so i manually pulled the slide out halfway and reefed her on. Chain is tight now and she runs better than ever. Thanks for all your help guys.You can bet i will be checking that tensioner often from here on in. Also got the elusive right side cover from the same guy on CL. Happy days.