Stuck slow jet. Help!

Tripod

Tripod

Well-Known Member
This weekend i started the process of rebuilding my z50 k0. In the process of gathering parts, i decided to start with the carburator. Im 99 percent sure its the original carb and it has had a rough life. Bowl is full of white residue.

Before i put the carb in chem dip, i stripped it down as much as it would let me. The slow jet wouldnt budge. I let it soak for six hours, the tried again. No luck and i stripped the screw slot. Ive had this happen on a k1 carb and it made the body pretty much a paperweight.

I ordered some left hand drill bits and a spiral fluted easy out, but id like to hear the experts chime in.

Can i apply some heat or will the cast pot metal make life harder?

The crf50 has the slow jet pressed in? Can i just run a cleanimg rod through this and be done? Am i just pissing in the wind?

I looked at the slow jet on my AT7B carb and its fully exposed inside the float bowl compared to the z50 with has it in a deep recess. Is there any functional reason for that? Could i hog out the sides leading down to the jet to get a better easy out in there?

Let me know how you guys have dealt with this issue. Thanks.
 

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wanrep

wanrep

Active Member
Been there....no fun. That's why I ground the tip of a screwdriver to fit that slot on the pilot jet perfectly.
Less chance of rounding it out.
Unfortunately, I've never found a way to get the jet out after rounding the slot.
What I've done at that point is, try to open up the hole in the jet with a cleaning wire.
If that doesn't work, use a .35mm drill bit and spin it with your fingers or pin vise until it opens up.
If your pilot is a #38, then use a .38mm drill bit.
 
hrc200x

hrc200x

Active Member
Have been in similar situation in the past with hard tail z50 carbs however I stopped before stripping them on all but one. I apply heat with propane torch around the outside of the jet to the carb body with good success so far. On the one I stripped believe was able to drill it out but ended up getting some of the threads, a new jet still grabbed a few threads though. Easy out maybe an option if they make them that small, but if that breaks off the carb would be junk.
 
6

69ST

Well-Known Member
FYI...the zinc alloy used for these carb castings has a low melting point. The exact transition, where it goes from solid to plastic state almost like solder, is virtually undetectable, until it's too late. Better to know this going in. Limit heating to 250-300F and you should be fine.
 
Tripod

Tripod

Well-Known Member
This was a good reason for me to order up some good vessel flat blade screwdrivers. These wont be used for cave man duties like my other ones.
Amazon is delivering some tools today, so i'll keep you posted.

Thanks for the tips.

No luck with a left hand drill and easy out.

I have one other carb body that I may be able to run a tap in there. Anyone know what the thread pitch is on a 35 slow jet?

Also, does anyone have a cutaway drawing of this carb body? Im curious what twists and turns this slow jet makes or if it is just straight.
 
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wanrep

wanrep

Active Member
The thread pitch is 0.6mm on a slow jet.
I mic'd one I have and it measures 3.4mm.
Good luck finding that tap. lol
Wonder if a 3.5mm tap would work?
 
6

69ST

Well-Known Member
wanrep said:
The thread pitch is 0.6mm on a slow jet.
I mic'd one I have and it measures 3.4mm.
Good luck finding that tap. lol
Wonder if a 3.5mm tap would work?
Click to expand...
If the carb is worth all of this effort, then I'd test that fitment theory on something other than the carb casting. Might very well be that a weird thread pitch was used, with the properties of the zinc casting in mind...maybe not. Either scenario is a nightmare, imo.
 
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