drummerboy

Hi, just joined the site and thought I'd drop in to introduce myself. I've got a few old Brit bikes but recently bought the TZR 50 for my son (his first bike). Not sure how to find my way around the site yet - so apologies if this is the wrong place, but I could do with a bit of advice on the TZR. Does anyone know what the little valve unit is for - it is at the end of the stainless steel pipe that branches off from the exhaust pipe? Which way around is it connected? Thanks in anticipation :-) Mike.

Hi, I'm new on here and new to 2 strokes but I am a qualified engineer so not entirely guessing at it!! I would think the restriction is likely to be in the inlet manifold. If you have a look on the reed valve block it will have a circle with a line through it followed by a number. Mine says 20 and I'm guessing yours will too? Having measured the carb, 20mm is the choke size (the diameter of the internal bore of the carb). The area of that is 314mm2. I took off the inlet manifold rubber piece between the carb and the reed valve and measured it - it was 20mm x 15mm : area is 300mm2 I'm not entirely sure, but I think if you could get a reed block and manifold piece with an opening of 20 x 20 then you would gain an extra 14mm2 (it is only a 5% restriction but a restriction nonetheless). I might be barking up the wrong tree though!! In any event, 2 strokes need exhaust back pressure to work properly, without it, the fuel charge would blow straight through into the exhaust pipe and would run even slower than it does now. So removing the silencer really isn't an option.