Alot of 2 strokes I've had have never quite stayed crisp. Particularly the sound the motor makes. From brand new the bike sounds sweet. All you hear is the 2 stroke pop of the thin walled pipe and well packed silencer. Almost no motor crank or bearing noise. After the bike is clapped and rebuilt I've never been able to get that sounds back to stock again there is always some level of crank noise (I assume) and the bike just doesn't sound nice. What are some things you guys have learnt over the years to get a 2 smoker sounding super smooth and crispy? Is there a trick to packing? Specific bearings? Super balance crank? I do take care when installing bearings and pressing things so I would say my motor building skills are not bad. I've rebuilt around 20 engines in my life time so I'm not a total idiot when it comes to this but ya just never got 2 strokes sounding great again.
Proper pre mix and jetting
I know exactly what you mean and find it as equally frustrating with my old RM's.
I guess it's the culmination of a lot of wear and tear... cylinder/nikasil wear, combined with the powervalve system wear. The entire pipe gets coked up with carbon. Carburettor wear including minor wear to the slide, needle, needle nozzle etc etc.
Fueling and jetting is such a fine balance that minor wear throughout the system can throw it off from what it once was. Replace as much as you are willing to replace, ensure everything is spotlessly clean. Obviously pay attention to jetting but also don't ignore ignition timing and also things like squish clearance etc, as different rods/pistons can change this number.
Clean and properly packed silencer.
What would you consider a properly packed silencer?
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a short silencer.
A new pipe because it is not coated on the inside with carbon
Not running it wide open, when you put around it get's spooged up.
my 2007 kx250 with pc mod top end & perfect jetting on the pipe WFO
I already burnt the pipe out and repacked the silencer. I think the packing may be too much, I basically took a sheet and rolled it up around the perforated tube inside the silencer then forced it in the aluminium body. It is a shorty. I rate loosely torn stuffed packing would sound better.
One thing that helped me was really taking the time to take a metal pic and really work each and every hole all the way around the perforated tube in the silencer and get every little bit of carbon build up out of each hole.
You'll be suprised how much carbon you'll still have even after wire brushing the tube very well.
I also take a metal coat hanger and double it up in a drill and work it in and out of the tube while spinning it up in the drill to knock off as much carbon as possible from the inside of the tube where you can't really get to as well.
Its tedious and takes some time but it made a very noticeable difference with the exhaust note on my 05 CR250R and a YZ125 I did a build on recently.
Obviously a new or very clean (on the inside) pipe, jetting etc. play a large part and if you're getting clutch or bearing or crank noise thats totally something different that you should also address.
All good points, but a torch solves all those problems too. Try extrude honing your exhaust too.
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