Grinding/scraping noise in 5th gear

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post_42

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hi. so, i'm having some difficulty with my 83 heritage.

in 5th gear, and only 5th, there are, what i can only assume, are grinding sounds. no other gears are affected, and no matter at what rpm (unless up on a stand and no throttle), it sounds like 5th is scraping/grinding on something.

so, i've tried doing some searching and i've done the cam chain and valves (.003 inlet and .006 exhaust) and it's still doing it. the only other thing that i've done to the bike, since i bought it a few years ago, other than oil, was fix the bendix.

has anyone ever had an issue like this?

thanks in advance for any and all help.

jon
 
one thing to add:

before i did the bendix, i did not have that sound. after i did the bendix, i only did city driving, never got into 5th. put the bike into storage for a year and half. i brought it out of storage, to sell and i noticed that the bendix didn't work. figured that it got messed up again.

ended up doing a clutch adjustment that required me to REALLY reef on the lock nut, to the point where i had to use a breaker bar and just heave on it until it loosened. adjusted my clutch and took it out for a ride. that's when i noticed the grinding/scraping noise. because the only thing i did on the bike was the bendix, i went back in to see if i had messed anything up.

took the cover off and noticed that the clip was not in the right spot (other side of the lip that holds it against the teeth of the gear) and the spring was compressed in the area that the clip belongs. the spring was still good, so i put everything in it's proper place and reassembled everything and the noise is still there.

just trying to give as much detail as i can in case anything i did might be the culprit.

thanks again.
 
Welcome to the forum, post_42.

A couple of things to try.

Listen carefully to the grinding sound during acceleration, and during engine braking.
Do this not only in 5th gear, but also in 2nd.

If there's sounds in 2nd as well as 5th, I would suspect the mainshaft needle bearing, which is near 2nd gear.

If no 2nd gear sounds, only 5th, then note if the sound is different between the accel and the engine-brake decel tests. If so, I would suspect failing contact faces of the 5th gearset.

I can't think of any way that your previous starter and clutch work would cause this.

Here's some tranny pics so you can see the gearsets.
The second pic is upside-down compared to the first pic...
 

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Thanks a lot TwoMany! I've been lurking a bit over the last year and finally decided that i needed to join. so many good and helpful people on here.

i have seen the last two links, but not the first one. i didn't see any teeth in the oil change. though i didn't go fishing up into the engine.

as for your earlier response, i will check again tomorrow, but earlier i had it up and reving all through the gears and could only hear it, and boy could i hear it, in 5th. and only really when on the throttle. goes away when i let off. so, i'll take it on the road to see if makes the noise during a decel on asphalt. i want to say no, but i'll make sure.

but either way it looks like i'm pulling it apart.

thanks again!
 
post_42 said:
...I've been lurking a bit over the last year and finally decided that i needed to join...
Click to expand...

Great! The more, the merrier. And, it appears that you're up-to-speed on this forum.

Diagnosing these things by sound is tough, especially over the 'net. Takes a 'trained' ear.

I can conceptualize a dozen things going on in there, and trying to think of a way to associate your previous work is challenging. All I can think of there is, hopefully, some simple funny business going on behind the clutch, maybe shifter stuff contacting the clutch basket, but only in 5th...(?)

Could try this: while it's doing its 5th grinding thing, apply clutch lever pressure. If the mainshaft double-row ball bearing is worn, this would push it, and the clutch, slightly to the right, and increase clearance behind the clutch. Then, if the sound changes, this would be the area to investigate...
 
just took it out for a spin. damn. it runs so nice, if it wasn't for that sound. but...

okay, no noise on decel. at all. no noise in any other gear, at all. noise persists all the way through clutch pull until the clutch is fully "on"/engaged(??). noise ONLY happens with throttle.

so, TwoMany, i guess i'm going to start with your contact surfaces option and go from there. so, is there where it needs to be opened up and i need to physically see 5th gear?

and, i agree about noises. "my bike goes whrrrr pop ping ping ping." "yeah, or is it more of a whhhhr ting ting ting?" "no, definitely pinging noise. and a grumbly scratch. not a grind, but a scratch." ha ha. awesome.

thanks!
 
Haha, yeah, kinda like listening to eastern european descriptions of animal sounds.

You can service the tranny without a complete teardown, but the right side cover and clutch still has to come off. Then the cases can be split, and the bottom removed.

Have you seen glennpm's videos with the borescope shoved up thru the tranny oil drain plug hole, observing the 3rd gear slider action into the 5th gear pockets? Pretty cool contraption, huh?

http://www.xs650.com/forum/showthread.php?p=417159#post417159

If you visualize the rotation of the clutch and mainshaft, due to gearing they spin backwards. Under power, the driving 5th gear is pushing downward on the driven 5th's gearteeth. It's those surfaces you want to inspect...
 
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those videos are pretty slick. that's really cool to see.

and that's good to know that i can service without a full tear down. i guess, drain it and flip it and split it. i'll try to skip forward a bit in the clymer mag to where they split the cases and go from there. but it's definitely going to save me some time. and hey, now i can change that pushrod oil seal and bushing!
 
post_42 said:
...and hey, now i can change that pushrod oil seal and bushing!
Click to expand...

Great. If you do get into it, maybe you can help us with a pet project.

The clutch pushrod bushing is supposed to be 8mm long, but the recess in the mainshaft is deep enough to allow a 12mm deep bushing. However, there's an oiling hole in there in the mainshaft, for the needle bearings.

This diagram shows the oiling hole set back enough that a 12mm bushing won't block it.
Bush-OilHole.jpg



Some tranny pics we've seen show that oiling hole to be much closer to the mainshaft end.

So, now we're wondering if a 12mm bushing could block that hole...
 
i'm not sure if i got this right, but here's a photo i took.

20150826_210724.jpg

from the edge of the engine case (where the seal meets the outside of the engine) to the curvy thing on the top left, it's 7mm.

but, if you need it to the hole thats in the middle, which is what i think you're asking about, it's 13mm.

i hope this is what you're asking.
 
okay, so i, obviously, was able to get it open. right after i sent the last message, of course, and no teeth are missing. nothing looks odd at all. the gears look fine.

says the guy who is looking upon xs650 gears for the first time.

so, replace 5th anyway, while i'm here, with overdrive? i know some people on here have had issues, but some on other sites seem to love the things.

again, thanks.
 
post_42 said:
i'm not sure if i got this right, but here's a photo i took.

from the edge of the engine case (where the seal meets the outside of the engine) to the curvy thing on the top left, it's 7mm.

but, if you need it to the hole thats in the middle, which is what i think you're asking about, it's 13mm.

i hope this is what you're asking.
Click to expand...

Well, that was quick. What we're looking for is on the mainshaft, per this pic:

MainShaft-OilHole.jpg
 
post_42 said:
okay, so i, obviously, was able to get it open. right after i sent the last message, of course, and no teeth are missing. nothing looks odd at all. the gears look fine.

says the guy who is looking upon xs650 gears for the first time...
Click to expand...

This is where we call upon the detective/sleuth in you.

To have a sound that loud, must be some form of metal lash or interference, but the failing contact areas can be very small. Look closely at all parts for signs of abnormal contact and scraping. In those other 5th gear threads, and their links, are some good pics of gears, gearteeth, shift forks. You're looking for some very small and subtle signs of abnormal contact.

Think about the sound, its intensity and pitch. Things are spinning in there at certain rpms, determined by the gearing. If the engine is spinning at 2700 rpm, then the clutch and mainshaft are spinning at 1000 rpm. That's 16 revolutions per second. A single broken tooth would make a sound at that frequency. With a 23 tooth 5th gear, if each tooth was damaged, the sound would be around (16 x 23) = 368 Hz.

Lay the transmission shafts back into the case, shift forks appropriately fitted into their respective gear slots. Spin the shafts, and cycle thru all the gears. Observe how the forks slide the gears in and out of engagement with adjacent gears, and see if the movements are smooth and symetrical, middle positions leaving equal spacings between adjacent gears.

Check the sides of the shift fork tabs for burning, grinding, gouging. Check the corners of dogs/cogs/slots for excessive rounding. For 5th gear, the only thing that happens there is the shift fork slides the splined 3rd gear into the 5th's slots. But, there is a history of weak dogs on that 3rd slider, so look for cracks there.

Also, closely check the entire area behind the clutch, looking for signs of scraping.

post_42 said:
so, replace 5th anyway, while i'm here, with overdrive? i know some people on here have had issues, but some on other sites seem to love the things...
Click to expand...

That's your call.
Precision measure the shaft first, and review the comments in those 5th OD threads...
 
well, i've taken a good hard look and couldn't find anything. with the gears. looks like they all go in to gear properly, and out. the only thing i found in the casing, just sitting there, was ths...

20150828_103849.jpg

but, i don't know how that could've been in a position to cause that noise on 5th gear.

i will continue to keep looking though.
 
and, as for the other thing...

from the edge of the hole through the shaft, and not the bevel edge on the shaft itself, is 11mm. well, more than 10 and only slightly less than 11. but it really looks like 11.

however, as the picture shows,

20150828_103656.jpg

the bushing is indented in the shaft. i tried to get an accurate reading, but without the proper tools, what i got was 2mm for the indentation.

so, from the start of the bushing until the start of the hole in the shaft, 8.5-9mm.
 
Great info, post_42. So, does this represent what you're saying:

End of Mainshaft to edge of oiling hole = 11mm

MainshaftOilHole.jpg


Dogbunny, you catching this???


On your 5th grinding issue, another possibility would be if the 5th gear slider on the countershaft comes too close to 2nd gear, maybe allowing the dogs/cogs/slots to contact while in 5th gear. This could happen from a hard/skipped shift to 3rd, bending the 5th slider's shift fork away from 3rd toward 2nd.

5th-Slider-2nd.jpg
 

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