Fuel mixture screw on BS34

[Dan50]

I'm still in the process of cleaning/rebuilding my BS34 carbs on a Heritage Special 650. The build date on the bike is 10-1981. I've ordered and received parts from Mike's including fuel mixture screws. The part # for the mixture screw, plug, washer, and o ring is 48-5012. The problem is that the replacement mixture screw is about 1/8" shorter and of a different shape than the "original" screw that I removed.

I am attaching pictures of both screws. As you can see, the longer screw measures at .972 in. That is the old one I pulled out of the carbs. The small needle area on the tip appears to be "stepped". The shorter needle is the new one from Mike's. It measures at .822 in and the needle area on the end tapers off gradually with no step.

I've been communicating with Mike's via email (though slowly, no phone number) and he claims that the kit he sent is the correct one for these carbs.

I don't expect anyone to necessarily pull there mixture screw out and measure it, but can anyone help me out with this conundrum?

 

[weekendrider]

This thread may help.

http://www.xs650.com/forum/showthread.php?t=32072

 

[scabber]

I bought the same needles and didn't use them for that reason. They might work perhaps someone has used them and can say they do.

 

[MartinNC]

Yes, I got the same idle screws from Mikes as one of the originals was seized and I had to drill it out. I rebuilt the carbs totally and used the new screws and they do appear to work. The only thing I have found is that the sweet spot is a lot wider than other bikes I've tuned. I did have a problem with hanging idle after blipping throttle and replaced a throttle seal that was leaking and it is now better but a big blip (3000 rpm)still causes a slight hang sometimes. The bike idles and takes off well but I will investigate this futher

 

[chizler62]

Just clean of the tip with scotch brite and reinstall. Unless theres a significant groove on the taper theyre typically ok.
Secondly let this be a lesson on purchasing non-Mukuni replacement parts. I've seen jet two sizes off when actually measured. Etc

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[weekendrider]

School me chizler. Where do you find OEM mix screws?

 

[MartinNC]

If new were available, I would have bought new and as for scotch briting a new idle screw????????????

I just wanted to let Dan50 know that the screws Mike supplies work and he should try them, my ones came in a Tourmax packet

 

[5twins]

It's very possible the new replacement screws will work better. The original stepped ones are the E.P.A. mandated pollution control type. These new screws appear to have a single taper just like the early mix screws on '77 and older carb sets. They will most likely require a different setting (less turns out) that the stock stepped screws but should work well, probably better.

 

[Dan50]

Thanks for all the replies. I believe I'll try the new screws, maybe 2 turns out for starters? In all honesty, the main reason I bought the mixture screw sets was just to get the new o rings. Now from your replies, I believe I'll try the screws also,