Hi all, just taken the carb apart for the first time on my 2010 Evo 4T. Couple of questions.

1. this small part fell out from somewhere, however I no idea where! Any ideas?

2. Pages on this forum talk about the correct tuning of this carb. The jet sizes and mixture screw are now setup. However they also talk about a spacer and needle position. The needle position is supposed to go from 2deg to 3rd and the spacer is to be removed. Anyone know how to set the needle position and spacer? I don’t know what these parts refer to…?

http://www.mikuni36.com/Images/BSR36-carburetor.jpg

http://www.carbrescue.com/pdfs/mikunibsr36.pdf
 

These aren’t exactly the same as the Beta carb but are very similar. I don’t remember seeing anything like it in my carb and there is nothing obvious on the diagrams. If it fits in the recess over the idle mixture screw it could be what was left of the anti tamper cap after some one drilled it out.

the diagrams show the build up of the carb needle. The spacer is a thin washer that allows you to set the needle the equivalent of half a slot. 

 

 

Many thanks, that’s really helpful!

On another topic, any idea where I can get a replacement fuel mixture screw in the UK for this carb? Ideally one which is easy adjustment….

I use an extended one off eBay listed for a vm26. May not quite be the right profile as the adjustment is a little sharp. Works ok but there is nothing easy about adjusting it unless you have long thin heat resistant fingers. 

Jitsie do one, have this on my Beta.

Was quite hard to find one in the UK but here is a link for information - https://www.zonetrial.com/ArticleDetail.aspx?langue=E&Modele=Mixture+screw+carburattor+Beta+4+st&Id_Article=11140

Have also seen a mod were a small hole is drilled in the OEM screw and a thin wire with a 90 degree bend in the end is soldered in.  Just enough to make a manual adjustment beneath the carb in-situ.

Edited January 25, 20224 yr by stu109
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