Pilot air screw on qt50

Hey guys i recently took apart the carb on my yamaha 1984 qt50 for cleaning and realized that the pilot air screw was completly missing. I ordered a new screw and spring from the local dealership and now i find that the screw does not fit whatsoever. It looks as if there is no threading for it to screw into and im wondering if that part may have broken off. Anybody ever hear of this happening?? Also at the end of the pilot air screw hole there is no opening. It looks as if there was but something is stuck or broke off in it. Please any help here would be a huge help.

Re: Pilot air screw on qt50

if a screw belongs in a hole it will be threaded .. and at the bottom of the hole will be an orifice of some kind that the tip of the needle-screw fits into.

maybe you're looking at some hole other than a mixture screw hole.. Carbs are drilled and plugged in several places for various reasons, although its very rare for a plug to come out on it's own..

got a pic? or know a web page with a good view of the carb?

Part 2 of the QT manual (Yamaha QT50 Shop Manual Part 2(PDF)) on THIS page ..

Page 4-1 (page 23 of 30 in the pdf file) has a good exploded view of the carb.. is that the carb?

I see nothing that coulda broken off the carb bodyt down at the "pilot air screw" hole..

Maybe the original screw is actually in there and it was turned in too deep into the hole? Or the screew broke in two?

Re: Pilot air screw on qt50

Hey upon further inspection it appears whats blocking the pilot air screw hole is an air bleed piece(circular piece with tiny little opening in the middle) sitting in the middle of the hole running perpendicular. My question now remains - is this somthing the previous owner could have custom installed or could this maybe be an aftermark or non 1984 qt50 carb. It looks like the air bleed piece could be screwed out with a flat head screwdriver. I've looked at the blown up diagrams and everything is the same except I'm missing the pilot air screw and have this bleed their instead.

Re: Pilot air screw on qt50

You might try here (http://www.yamahasportsplaza.com/parts.aspx), go to Motorcycle to find the QT, and they should have a schematic as well as the part should you need it. I've ordered from them before and been extremely pleased. Good luck! - David

Re: Pilot air screw on qt50

Upon even further inspection of the exploded view from the shop manual that air bleed piece appears to be the pilot jet. So it appears the pilot jet is blocking the pilot air screw hole. Could the pilot jet possibly have moved down and is covering the air screw hole. Even if this is the case there still seems to be no threading which the air screw could screw into to. If it would help anybody help me I could take some pics tonight and send via email. Let me know! Thanks for all the help everyone.

Re: Pilot air screw on qt50

Yes please, post some pics and I'll get back to you. I just rebuilt the carb on my 84 Yamaha and am pretty familiar with them.

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