I am preparing a friends NSR250 MC28 for track work. I have not worked on 2 strokes for some time and whilst I find the mechanicals fairly straightforward, this carburettor systems is new to me. The bike has a recent TYGA 300 top end kit with expansion pipes. I am examining the carbs jetting following the previous mechanics assembly where he fitted richer main jets for the running in period. The owner said it was sluggish revving over 5,000RPM. It has MJ 175 and SJ 42 installed. The oil injection is disabled and sundry hoses blocked or looped back, which I assume at this point are correct.

One thing I am concerned about which I need advice on is this - I noticed a loose bolt on the flange of the reed valve manifold, thinking the mechanic has simply forgotten that. Its on the right alongside the throttle sensor plug. But then I saw on the forward part of the reed manifold, a hose stub at the rear of the left (rear cylinder) which has NO hose or block off at all. Given the recent TYGA kit build, I am suspecting a hose may have been left off by accident.

Could this be a problem? What does it do and how should I treat it?

Many thanks
Mike