Strange Vibration 50-70 mph

[Metallicat]

My sled has developed a strange vibration that occurs between the speeds of 50 and 70mph. The vibration can mostly be felt through the handlebars as a thump thump thump occurring possibly 5 times per second, faster than I can count in other words but not crazy fast like a clutch vibration. Any ideas? Changed belts, it didn't help. All new driveshaft and idle wheel bearings this year. Clutches are clean. Thanks all!

 

[Metallicat]

I wonder if it is the track. I have 10,000 miles on it with lugs missing here and there. I just ran it on the jackstand and it sure does shake for and aft at 60 like the track is out of balance. Track clips are in good condition.

 

[steiner]

I had lugs missing, stud pulled thru and about 20 missing clips but no "thump thump thump" vibration.
Did you check the locking collar behind jackshaft bearing?

 

[4strokeluvr111]

Dumb questions - does the thumping sound go faster or slower depending on track speed? Or engine RPM's?

When you get home from your trip get the sled warm and dry, remove the belt and visually inspect every inch of the track. You may have a tear that a "quick look" wouldn't turn up?

 

[17Rambler]

Sliders ok?

 

[Metallicat]

Sliders are new, the vibration seems consistent, I don't notice it changing with speed. It feels like an unbalanced front tire through the steering, a constant high speed thump. I did not have this during my last trip. Inspection time once the ice melts off of everything.

 

[hibshman25]

You stated you tried another belt. Was it a new belt or a supposedly good belt? Sounds like belt to me. Maybe try another different belt just to be sure. New belts can have a defect in them too even though new.

 

[Metallicat]

I tried a brand new belt, washed and cleaned and in perfect condition. The old belt looked to be in great shape too.
The locking collar behind the secondary still feels tight.
With snow trackers and toe out set to zero, this did not happen.
I changed carbides to Bergstrom 8" with ski savers and shims, and then noticed it.
Could this be related to the carbides? Maybe one is "hunting" a bit and causing side to side movement in the ski since there is so much slop in the who steering system.
No idea, likely will not be able to test it again until....next December at the earliest.

 

[DaJudge]

Check the bushings in the secondary. Dont just look at it, take it apart. Mine was vibrating for a long time and I finally took the secondary apart and discovered the bushings were junk.

 

[Metallicat]

It was the snow trackers, they're gone now. Back to tripple points! People love them, the snow trackers that is, but I am the one out of 1000 who does not like. My real concern this year will be the fuel delivery problem I spoke about last winter. Have new fuel pumps to install, and new (used) carbs as a last resort.

 

[steiner]

I would never of guessed that something static would cause a vibration. What guided you to try and swap out the Snowtrackers?
I know I would have never thot of that.

 

[DGZRT]

Track drivers shot?

 

[Metallicat]

I would never of guessed that something static would cause a vibration. What guided you to try and swap out the Snowtrackers?
I know I would have never thot of that.

I purchased both Snow Trackers and the triple points last year. I wanted to try them both, and after changing to the triples the vibration went away.

 

[Sasquatch]

How are your front end bushings? Thump Thump is caused by something moving!

 

[Metallicat]

How are your front end bushings? Thump Thump is caused by something moving!

The bushings are fine, oilites. It was a phenomenon with the SnowTrackers for some odd reason.