Sounds like grinding rocks at low speeds, then hums.

#1
So, I may be in the wrong section but I was hoping for some input before I bought anything new.

I am running an old Murray Track 2 with a Predator 212 I bought recently. The engine hasn't been cared for too well but seems to be okay. The clutch is one of these:
https://www.OldMiniBikes.com/hillia...G-hR7R1UWg1ecQR3tRc-vN_ONb42EISQaAiXBEALw_wcB

When the wheel is free spinning there aren't issues but when I am accelerating from about 5-15mph, the thing sounds like there are rocks bouncing around and it is hammering a bit. Once I'm up to a cruising speed, everything smooths out (until I get to higher speed and vibration) and the engine hums like a little motor bike should. I feel like this all points to an issue in the clutch but all looks to be in order with it and was hoping someone might have experience with those and offer some tips before I replace anything.
 
#2
I have your exact mash up of Murray and predator.
I shoehorned the predator on her and used the original clutch for a little while until the springs in it went by the wayside.
Check your chain tightness. When it's a little loose that chain will rub the drum of the clutch and make some racket. There's not a lot of wiggle room on the in board side.
Also the spacer that goes through the front rim, in between the bearings, will rattle some too. I just greased it up good and it is quite for now.
 
#3
I have your exact mash up of Murray and predator.
I shoehorned the predator on her and used the original clutch for a little while until the springs in it went by the wayside.
Check your chain tightness. When it's a little loose that chain will rub the drum of the clutch and make some racket. There's not a lot of wiggle room on the in board side.
Also the spacer that goes through the front rim, in between the bearings, will rattle some too. I just greased it up good and it is quite for now.
Thanks for the reply! My bigger concern over the noise is how it feels like it is "knocking in to gear". The power comes in pops if that makes sense until it is rolling to 10-15mph then it can deliver power smoothly.
Care to explain where your greased again? Something on the clutch or...?
 
#4
It's the sleeve that the axle bolt goes through. I had to pull a bearing to get it out and greased it up.
My main rattle was and every once in a while is the chain being too loose. The predator is so strong that not matter how tight I get the motor it always will loosen after riding a couple hours.
Do you have you chain guard on? Make sure it's off and go ride her. Pay attention to your clutch and chain when you hear the rattle. I always noticed the chain rubbing the drum when it would do it's thing.
 
#5
What first comes to mind to me, is perhaps your rear wheel bearings are going bad.

I know when mine were going bad, it intermittently made a crunching sound, caused some vibration and affected power. Until they failed completely.
 
#6
I had the same issue with the Hilliard extreme duty especially when I modded the engine further. Seemed like some sort of clutch lockup chatter, shook the whole bike but other than that the clutch was fine. Eventually went to a Hilliard Flame and the engagement is totally smooth now.
 
#8
What first comes to mind to me, is perhaps your rear wheel bearings are going bad.

I know when mine were going bad, it intermittently made a crunching sound, caused some vibration and affected power. Until they failed completely.
My rear wheel free spins pretty well without any grinding sounds. I'll keep an eye on that though.
 
#9
Hey did you ever figure your issue out. I’m having exactly the same issue. Sounds like rocks grinding. The guys are trying to help me out but can’t find anything. Only at low speed. It sounds like a rock in the motor. Then up to speed it runs absolutely perfect.
 
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