Re: Honda Hobbit PA50 low end power and gearing

Alan Wattam /
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That exhaust looks great, nice work. I'd be interested how you get on with changing it and the difference it makes. Definitely looks like a fun project. I wonder what a straight pipe (no box) with a silencer would do? That's what 2 stroke trials bikes do for low end torque and smooth power.

I'm be tempted to make an expansion chamber pipe, but with numbers aimed at low end power rather than top end like most. I've got Graham Bell's 2 stroke tuning book and it goes through how to calculate exhaust dimensions if you know the revs you want to tune for and the exhaust port duration.

If you're tuning for low RPM it looks like the exhaust would be crazy long, like 3 metres, but I'd like to work it out properly and see.

Does anyone know the exhaust duration for this engine?

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