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I must be wierd becaus i prefer the old carb over the newer carb. The low-mid range torque isnt worth giving up for a few more mph on the far top end. These bikes need all the instant power they can get, especially on the lower end. That being said the newer carb is less finicky and its smoother. I still miss the old bike when it comes to off-roading




Straight pull versions of the same CV carb are almost always more responsive off of the line. I'm surprised that it's not more responsive on the top end as well, but maybe the jetting and mouth opens wider on the CV version? And CV carbs are always more smooth because of the fancy vacuum action. You can move your hand on the throttle all you want, but the slide is only going to come up if there's vacuum to pull it up, haha.



I don't see how either design would be that finicky because they're so simple. Just the regular stuff that'd affect almost any simple Mikuni like torn diaphragms, plugged jets, worn out needle & seat valve... I got mine dialed in relatively quickly. All I ended up doing was using a 116 main jet up top and that's probably only richening it up a bit to make sure I don't overheat the engine running it full throttle. I changed the pilot out to a 42 and switched it back to a 40. I have my needle shimmed with three thin aluminum washers I made out of pop can tabs (cheapskate!)



I'm at 1000 feet though, so your mileage may vary, but I have the bike warming up off of choke quickly and running great throughout the rev range.



That said, I think with a Mikuni TM28 you could get it more snappy to where it wants to wheelie off of the line. I might be daydreaming, but the TK design is a round slide. The flat slides always have felt snappy to me.
 
I had problems with my original carb, it didnt work when I got it, and it doesnt work now. I put on a carb from a 1980 DT175. It is only a 26mm, compared to the 28mm that the stock carb was, but my logic involved was that the engine was still going to try to pull in the same amount of air, but the smaller tube would cause speed the air up, and hopefully result in a stronger vacuum to pull the fuel in. It is also a carb designed for a two stroke, which, in this case, is designed to have faster airflow anyway. Out of the box, the carb gave my bike instant throttle response when I snapped the throttle open(though I dont know how it would compare to the original, since mine never worked). It would sputter at high RPM, which I diagnosed as being too lean. Then i discovered an oil inlet passage(cause its a 2 stroke carb) that i thought was just a vent, that was just sucking in air. I blocked that off, and then it only had a slight sputter at high RPM. I made some adjustments to the carb, and the instant throttle response somewhat went away, but so did the high RPM sputter. After some new jets I am very happy with the carb. It takes off fast, and has no problem picking up the front. The throttle response is still good, and the entire throttle range is smooth. This carb does have the notches in the throttle needle to make it adjustable.
 
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