"CLUNK" sound in drivetrain

[4strokeluvr111]

Just did a search for clunking and looked thru 8 pages of posts. This sled has NEVER clunked as consistently as it did yesterday for 180 miles.

Sled history:

2005 Vector ER
15000 miles
M10 suspension
original drivers
original chain and gears
all chaincase bearings replaced just after Xmas 2013 (bad jackshaft bearings)
Chaincase oil changed at least 1X per year - Mobil 1 75W-90
Clutch side bearings have 6000'ish miles but feel tight
track tension is about where I've always had it. (could easily tighten it up)

I changed the track at 7500 miles and this CLUNK has come and gone in varying degrees. Why? I have no idea. Now it's happening all the time.

SYMPTOMS:
From a dead stop and I apply the throttle the sled moves forward with a noticeable CLUNK sound in the drivetrain.
If I am freely rolling down a slight incline and hit the throttle...same CLUNK
If I slowly feather the throttle and engage everything slowly there is no clunk...just a nice quiet engagement.
The CLUNK sounds like it's coming from the chaincase.
I changed the c/case fluid a few weeks ago. Checked it today and I see fine metal particles in it

ADJUSTMENTS TRIED:
Chain tension checked....adjusted both tight and loose....no change
Reverse linkage adjusted...both "ways"...no change
Primary and secondary clutches have been checked and are in good shape

I've had the chaincase apart a couple of times...once for the track change (changed the bearings)....and I think one other time before the Xmas 2013 change.

Did I not put something together right? Ideas?
The reverse gears with the little spring between them seem OK.
Is the chain stretched?

I am at a loss for what's wrong. I can't ride the sled like this and my son is home on leave from the USAF and we want to RIDE!!!!

Please help!!!! I can PM you my cell number if needed!

 

[Redbeard]

The clunck you're describing sounds like your drivers are ratcheting the track lugs. Are your drivers worn, and is the track too loose? If that is ok, and your drive train bearings are new, you may need to open the chaincase and take a look. Pull the drain plug on the chaincase. If there is an unusually high amount of metal in the oil, something is definitely wrong.
Hope this helps and I hope you get going soon.

 

[4strokeluvr111]

The clunck you're describing sounds like your drivers are ratcheting the track lugs. Are your drivers worn, and is the track too loose? If that is ok, and your drive train bearings are new, you may need to open the chaincase and take a look. Pull the drain plug on the chaincase. If there is an unusually high amount of metal in the oil, something is definitely wrong.
Hope this helps and I hope you get going soon.

Added some info based on your post. THANKS!

I know what track ratcheting sounds like and I don't think that's it. If I'm freewheeling down an incline I would think it wouldn't clunk.
How can you tell if the drivers are worn to the point of having to be replaced?
I can try tightening the track.

 

[09nytro]

Check the suspension rails in the front by the drivers , maybe they are catching in the windows of the track ( stabbing as they say )
Or if you have replaced the hyfax , maybe they are to long , lift the back in the air and spin the track to see if you can see anything hitting !

 

[yamahinn03]

Check your belt also.

 

[oldsledhead]

X2 on the belt, had same thing happen to me, checked everything all good, it turned out to be the belt after a lot of head scratching.

 

[Vandelay Industries]

X3 Belt.
This happened to my sled yesterday. Thought it might be in the chaincase too but looked around and found my belt lost 5 or 6 teeth.

 

[4strokeluvr111]

Checked the belt and it is fine. It is a newer belt with 300 miles on it.

 

[Redbeard]

Raise the track and turn the secondary by hand to see how the drive train feels.

 

[09nytro]

Raise the track and turn the secondary by hand to see how the drive train feels.

 

[4strokeluvr111]

Raise the track and turn the secondary by hand to see how the drive train feels.

Drive train is very smooth, both in FWD and REV if it matters.

 

[Redbeard]

I still think you have a bearing or something dying in the drive train. It may not show up until there is some ground speed present. I've even heard of guys having reverse gear needle bearings go out. Pull the chaincase drain plug and inspect the oil with a bright light. You'll only be out 8 oz of oil.

 

[OVR4D]

Sounds like the clutch to me. The clunk you feel could be the secondary clutch sheeves opening/closing. Warmer weather may be affecting the engagement, which could explain why you're experiencing it more frequently now.

 

[4strokeluvr111]

I still think you have a bearing or something dying in the drive train. It may not show up until there is some ground speed present. I've even heard of guys having reverse gear needle bearings go out. Pull the chaincase drain plug and inspect the oil with a bright light. You'll only be out 8 oz of oil.

The reverse gear system is a question mark to me. Numerous threads talk about the CLUNK being normal in Yamaha's and that the drivetrain can handle it. I disagree in that something is going to be affected and it's likely a bearing. None of the other sleds I have owned clunk like this but that doesn't matter really.

Yesterday when I pulled the dipstick out I could see very file silver colored particles on it. This c-case oil is pretty fresh...about a month old. I think I'm just going to bite the bullet and pull the c-case apart. Won't take long....I'm pretty good at it now! LOL!!

 

[Redbeard]

Sounds like the clutch to me. The clunk you feel could be the secondary clutch sheeves opening/closing. Warmer weather may be affecting the engagement, which could explain why you're experiencing it more frequently now.

I agree, but he said the clunk was there even while coasting and off the gas.