Tri-z Carb

[Just-Tri-It]

Just curious and maybe it has been addressed already.
I noticed the 1980's YZ250 had a 38mm carb but the 85 Tri-z had a 32.
Any idea why such a difference?
Thanks

[christph]

I think there are a number of reasons. One, they are different cylinders with different manifolds, port specs, etc. Two, a smaller carburetor gives you more bottom end. A three-wheeler has more weight and will be ridden more often on slow trails, so Yamaha thought it would be better for it's intended use. Plus, by 1980 manufactures had already been at war for more than a decade building motocross bikes, so their design philosophy was less conservative. Who knows, if 3-wheelers had been around a few more years they may have ended up with 38mm carbs off the floor.

[3Z with Fangs!]

Two things, YZ250=Race bike Tri-Z 250 trail machine. Even still the Tri-Z is pretty "detuned" from the factory and a few mods really bring it to life. With that said there's a 39mm PWK on mine with mods to the cylinder, milled head, good pipe etc. It takes a little but it can come to life.

[Just-Tri-It]

Do you have issues with the 38 flooding because of the fuel pump pressure that some have talked about? If so, how did you correct it?
Thanks

[yaegerb]

Do you have issues with the 38 flooding because of the fuel pump pressure that some have talked about? If so, how did you correct it?
Thanks

Drill an 1/8” diameter hole in the return line T fitting.

[NeverLift]

Do you have issues with the 38 flooding because of the fuel pump pressure that some have talked about? If so, how did you correct it?
Thanks

He's got a 39mm it probably came off a sled with the smaller float needle and seat. Designed to be used with a fuel pump.

[3Z with Fangs!]

Do you have issues with the 38 flooding because of the fuel pump pressure that some have talked about? If so, how did you correct it?
Thanks
If you were asking me, no, I have a 39mm Sled carb. No issues at all.