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Ironside · 06-22-2014, 08:24 PM

Thanks for the feedback guys, I will attempt to clarify.

Thanks Peter S, I am aware of the Chinese 'copy' engines, many of my fellow c90 club members have fitted these motors, some have given many thousands of miles of trouble free use, others have expired rather quickly. Gearboxes invariably fail at around 6000 miles, I suspect the five speed gearbox may be even weaker.
These motors will fit a later model frame, but modifications are required for my frame and I believe the 'postie bikes' also.
I am keen to stay with genuine Honda motors, given good maintainance they are virtually indestructable.

I have just taken delivery of an identical spare motor, ATC 125m circa 1984. This will be dismantled and rebuilt with as many new parts as is neccessary, this will save any down time.

According to Honda, the standard motor produces 8.6 BHP at 7,500 rpm., (but will rev quite easily to 8,500 and more in top gear) and maximum tourqe 6.45 ft.lbs at 5,500 rpm.

I've been using an internet program called 'gearing commander' to calculate my gearing changes. I can confirm that the bike pulls away easily in first gear, and now that I have a spare motor I can experiment with larger front sprockets. There is enough room for a 16 tooth front sprocket, I will then have options from 36 - 42 at the rear. Should I be aiming for peak torque at my normal cruising speed?.

I feel that using that using the highest gearing possible may be counter productive, as with such a low power output, I'd be spending more time in third gear ( I live in a very hilly area ).

Regards,
Ironside.

06-22-2014, 08:24 PM	#95 (permalink)
Ironside EcoModding Lurker Join Date: Aug 2013 Location: West Wales,UK Posts: 88 Thanks: 16 Thanked 57 Times in 24 Posts	Thanks for the feedback guys, I will attempt to clarify. Thanks Peter S, I am aware of the Chinese 'copy' engines, many of my fellow c90 club members have fitted these motors, some have given many thousands of miles of trouble free use, others have expired rather quickly. Gearboxes invariably fail at around 6000 miles, I suspect the five speed gearbox may be even weaker. These motors will fit a later model frame, but modifications are required for my frame and I believe the 'postie bikes' also. I am keen to stay with genuine Honda motors, given good maintainance they are virtually indestructable. I have just taken delivery of an identical spare motor, ATC 125m circa 1984. This will be dismantled and rebuilt with as many new parts as is neccessary, this will save any down time. According to Honda, the standard motor produces 8.6 BHP at 7,500 rpm., (but will rev quite easily to 8,500 and more in top gear) and maximum tourqe 6.45 ft.lbs at 5,500 rpm. I've been using an internet program called 'gearing commander' to calculate my gearing changes. I can confirm that the bike pulls away easily in first gear, and now that I have a spare motor I can experiment with larger front sprockets. There is enough room for a 16 tooth front sprocket, I will then have options from 36 - 42 at the rear. Should I be aiming for peak torque at my normal cruising speed?. I feel that using that using the highest gearing possible may be counter productive, as with such a low power output, I'd be spending more time in third gear ( I live in a very hilly area ). Regards, Ironside.