Reply To: Supa 5. Stuttering at low revs.

Forums Technical Two Stroke: Help needed Supa 5. Stuttering at low revs. Reply To: Supa 5. Stuttering at low revs.

Pete Lamb

Thanks Matthew

Sorry for the delay, I’ve been busy with other stuff.

I have completely dis-assembled the carb, so that I can check all the jet sizes and the other specs.

I have found a few anomalies.

1. I notice that my carb is a BVF30N2-5. Other info I have says it should be either a BVF30N2-3 or a BVF30N2-4. I’d like to confirm which one it should be, what the difference is and, whether it’s likely to matter.

2. The slow running (pilot jet) fitted to mine is a 45. The data you kindly provided (MZ manual) and the Haynes manual state 35. Any thoughts on this with respect to the running issue.

3. Do you know what the slide cutaway dimension means, and how do I measure it. The Haynes manual states “50-5mm”.

Jet sizes.
Main Jet is 135
Pilot is 45
Float needele jet 20
Needle jet 70

At this point, I think I essentially have 3 options.
1. Change the pilot and main jet sizes, to match the manual, 140 and 35 respectively. Also change the needle as a precaution, as there are no visible markings on mine.

2. Source a replacement carb, to see if that creates any improvement.

I would quite like to sort out the one I have, preferably, as it seems in good condition. But don’t want to waste time chasing shadows.

Any advice you can offer would be much appreciated.