hi there, i have a 1979 yam xs400 with twin mikuni bs34 carbs

David Houston

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i got a rebuild kit for carbs as they were not perfoming l, when i was replacing all the parts i noticed the pilot screws (the ones with plastic pastic caps to stop you altering them) on both carbs were broken and the thin end of the needle of the screw was siezed in the carb bodies , when you look in to the carb with the screw out it was very corroded and gummed up . i tried to release them but they would not move therefor the new ones would not go in.
basically are the carb bodies beyond repair (if so such is life), everything else on the carbs look fine and accepted the replacement parts no problem .
i would really appreciate your advise.
cheers dave
 
Somebody will have to explain 'CO2' cleaning to me, I smell a rat.

If OP can't get those holes unblocked the carbs are scrap. May be anyway as turning the screws a set amount is based on the as machined openings and the angles of such as well as the hole size the screws go into. That damaged means you have no idea of how to adjust the screws as the entrance and flow ratings of the holes have changed.
 
I was able to unblock the 2 seized needles in my carbs by heating them up slightly with a heat gun and then pushing the needle pieces back through using a piece of a sewing needle glued to the upper jaw of some Channellocks. I got this idea from a post on this forum by @Greasy Fingers. You can see my account here
http://www.xs400.com/threads/the-dreaded-broken-pilot-screw.19679/
You need to get the diameter of the needle piece right and you don't want to clamp too hard when you clamp the Channellocks down pushing your sewing needle piece in because you don't want to enlarge the hole. I was surprised at how easily they came out.
 
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