If it's more noticable when the motor's cold, more than likely its the cooling fins vibrating......

 

Usually I hear it after I have road it awhile and the engine has had a time to warm up

 

My 300 Xpress has that same noise. I am not sure what it is. Mine has done it for the four years I've owned it. I have had mine rebored, wiesco piston, and ported it and still makes that same noise. I know everything is o.k. inside the engine so, I don't know what it is. For mine, it is normal. I would like to get rid of it but don't know what it could be. Oh well, time for some more mods.

 

My trail blazer dose the samething (knocks) Its a trail blazer thing!!!

 

Try a gas with a higher octane. I could be completely wrong, but try it anyway. You could also buy Octane Booster at Walmart. NOS makes an octane booster that works quite well, and is sold at Walmart.

 

The higher octane gas didn't help mine at all. I,ve always ran 93 octane anyway. I've used up to 104 octane and it did'nt change the noise any at all. I believe this noise could be found and eliminated but would it really matter? Mines done it for four years and has never changed no matter what I did.

 

My TB only started making this noise after I got my head shaved,
I was running 107 oct at that time also.
To me this noise sounded like detination to me but my mechanic said It was just the way TB's sound. After a my mechanic tuned it, I went riding & noise got louder, then she stopped.
After inspction turnes out to be hole in the piston & little end bearing gone...
Its been a month without a quad now & Im hanging out to ride....
Still dont know what caused probs, lean or head mod, all I know is its costing me heaps a daamn $$$$.

 

stinky,

I thought that shop was paying for a new motor for you or something like that? Sorry to hear you still don't have that running.

 

Hi Elroy,
They gave me my money back for the tune & an extra $200Nzd for a new piston.
Found this hot new engine over here, but the guys are havin heaps a probs tryin to tune it with the porting in this thing.
First they rejetted and boared standerd carb, (still not enough), then fitted a scram 400 oe carb etc, same again.
He called me today and said he fitted a Yz 250 carb to it,(Mikuni 38mm), & said its running heaps better, Now I need more damn clutch springs cause after these mods clutch needs more tweeking. Oh well this never ending money pit will one day fly...

 

If thats the 38mmTMX carb you are better off with a Keihn.
I HAD the 38tmx on mine and had alot of trouble with it. I was
always adjusting it for something! So beware!!!!!!!!!!!!!!!