New carb issues

[ricardoguitars]

Hello everyone, the stock carb on my Shineray XY250GY-6B (169FMM engine) started leaking gas from the drain screw and got me stranded on the side of the road, the thread is stripped even though I've never touched the thing self stripping threads anyone? Anyway, luckily the thing didn't catch on fire and there was a motorcycle shop a few blocks away, so I bought a new carb and installed it with the same jets that the old one had, same type of carb (Mikuni VM clone), the only difference is that the new one has the cable operated choke mechanism, the old one has the 3 positions black plastic tab, for some reason the new carb won't work under 4K RPMs when I apply the throttle, making the bike stall a lot of times at take off, and stubborn to get started when cold, slow motion on traffic almost impossible without revving the engine above 4K RPM burning the clutch and hitting the gears because of a high rev friction point.


Any ideas what could be wrong with this carb?

[Ariel Red Hunter]

Originally Posted by ricardoguitars

Hello everyone, the stock carb on my Shineray XY250GY-6B (169FMM engine) started leaking gas from the drain screw and got me stranded on the side of the road, the thread is stripped even though I've never touched the thing self stripping threads anyone? Anyway, luckily the thing didn't catch on fire and there was a motorcycle shop a few blocks away, so I bought a new carb and installed it with the same jets that the old one had, same type of carb (Mikuni VM clone), the only difference is that the new one has the cable operated choke mechanism, the old one has the 3 positions black plastic tab, for some reason the new carb won't work under 4K RPMs when I apply the throttle, making the bike stall a lot of times at take off, and stubborn to get started when cold, slow motion on traffic almost impossible without revving the engine above 4K RPM burning the clutch and hitting the gears because of a high rev friction point.


Any ideas what could be wrong with this carb?

The jet numbers do not cross over from one carb make to another, and the jets only work if you are really lucky. Put Mikuni jets in a Mikuni carb. Try a 20 or 25 pilot jet, and a 110main jet and then tell us what's happening. Have you adjusted the valves yet? Too tight of valves can also cause this problem.....ARH

[Rangerscott]

Another thing to check is to take all the jets out and blow every port out. Aluminum and brass pieces from the manufacturing can get stuck.

A pz30 carb is a pz30 carb so it should work the same.

[ricardoguitars]

Thanks for the answers guys, I ended up buying the Mikuni VM recommended on the Hawk mods thread, if I'm going to spend time tuning a carb, I would rather do it once and be done with it, this is a no brand carb that came wrapped on paper, it should keep me on the road before the Mikuni arrives.

Cheers.

[Ariel Red Hunter]

Originally Posted by ricardoguitars

Thanks for the answers guys, I ended up buying the Mikuni VM recommended on the Hawk mods thread, if I'm going to spend time tuning a carb, I would rather do it once and be done with it, this is a no brand carb that came wrapped on paper, it should keep me on the road before the Mikuni arrives.

Cheers.

Oh. My mistake. I thought you already bought a Mikuni VM-26 from a local cycle shop and put it on....ARH