Planet Minis

FFR3247R

Newbe here so be patient. I just got a 74 Z50 from a original owner and its in really nice shape. I had to put the piston and cylinder back on when I got it. Bike runs great but the carb is tempermental. I took it all apart and cleaned everything. Bike is hard to start and seems like the mixture adjustment is touchy. It also leaks a little gas from the bowl. Should I buy a rebuild kit or jump for a new carb? I would like to go with a big bore kit later. I will only use it for a pit bike at the track.

I have already set the points and new plug.

Thanks for any help.

jrcirondog

Not sure how you cleaned the carb, but from my experiences here is what I recommend. Get a caustic carburetor cleaner (like Barrymans or Gunk) usually it comes in a gallon sized paint jug. Remove everything from the carb ESPECIALLY ANY GASKETS or ORING (if you miss an o-ring and place it in the cleaner it will swell up and be ruined). Place all individual metal carb parts in the metal bin inside the caustic carb cleaner and soak overnight. Next day get a pipe cleaners (or a needle from a sewing kit) and put it through all of the jets and passage ways you can. Make sure you put the needle or pipe cleaner through the idle and pilot screw (air screw) passage ways. Then take compressed air and blow all of the passage ways out. Re-assemble and see if there is a change. Where exactly is your carb leaking? If its leaking around the bowl drain screw can easily be fixed, but if its leaking around the gasket between the bowl and the main carb body then you might need a new gasket (or rebuild kit). Needle and seat could be another possiblility as well.

The very last thing I would do is up the pilot jet size, but I would use that as a last resort, because I am assuming that bike ran well with the jets it has in it presently. 90% of carb problems I have seen are resolved by Thorough cleaning.

mexicanyella

And 90% of those carb problems are actually electrical.

But you said you did the points and plug, plus your symptoms don't sound like a points issue to me, so I'll spare you my standard points info dump.

Are you sure you don't have an air leak? That can make getting a steady idle (or keeping it, once you get one) just about impossible; the tiny amount of mixture coming through the pilot circuit can be thrown waaaay off by a small air leak, resulting in an idle speed that drifts, or an engine that dies sometimes and not others. You adjust the pilot screw to compensate and it works for a little while and then you have to adjust it again some other way, or you find yourself running out of adjustment range.

Most of my experience is with the old Zs, though, with those archaic gaskets in them. I'm working on a Z50R now with a complete top end from XR/CRF parts, and these newfangled o-ring intake manifolds seem to seal well even if you forget to tighten them all the way. You are not to ask how I found that out. Just shut it.
A small air leak might not be noticeable once you come off the pilot circuit, because there's less vacuum in the intake then and more fuel and air coming in where it's supposed to and the air leak makes less difference.

It's easy to get small air leaks because in my experience the difference between "correct torque" and "stripped head holes" is about 3 ft. lb. on the head's manifold bolt holes. I like to run studs there instead of bolts, so I can be sure I've bottomed the stud out in the hole and am pulling on all of the soft threads, not just some of them. Stripped case screws are perfect for this. Don't throw them away, screw them all the way down in there and cut off the tops, then dress the cut area lightly with a file. Instant manifold studs. Not endorsed by restorers anywhere, but it's more practical for me.