160 questions

[Classictrial]

Hi

I am in the UK and in the process of trying to develop a 160 for use in P65 trials for a customer of mine. A bike with modified stock frame is already up and running and is going to be tested in serious competition tomorrow. Wonder if anyone on the forum has any experience of increasing power of the 160 motor? Customer has fully rebuilt narrow case 250 and 350 motors as well as a couple of 160s, but all seem to have quite a jump from 1st to 2nd gear which is not ideal for trials. Running a 64T rear sprocket which isnt ideal but there seems to be no easy way of making the primary ratio lower, even though a Fantic clutch drum appears to fit into the 160 cases this isnt likely to help. Be very grateful if there is anyone out there with any specific knowledge/experience on the above. Will post some pics of the modified stock bike being tested tomorrow...........

[SP3]

I have no answers for you. But, it sounds like a really interesting project and I look forward to reading about it. Post photos if/when they're taken. Good luck.

[ducwiz]

I'm not a specialist for Ducati n/c models, so no responsibility is taken for the correctness of this information:

- reducing the step between 1st and 2nd: Ducati made a 125SCR model around 1970, which today is very rare. It came with a 5speed gearbox. At least, the engine was made by Mototrans in Spain. The gearbox parts of this model might fit into the 160's crankcase.
- more power: afair early 200 Elite models featured the same(more or less) crankcase as the 125 or 160 models. From a certain eng. no., a widened case was used, and the lateral distance of the cylinder bolts as well. So, only the old 200 cylinder, head and crankshaft might fit into the 160 motor, giving increased displacement, and hence power.

cheers Hans

[ranton_rambler]

I'm far from being an expert, as I'm just in the middle of doing my first Ducati, which is a 175.
But I did have a flick through the tables at the back of my Mick Walker book. As far as I can see, the 160 has the shortest primary drive ratio and all 4-speed gearboxes have the same ratios.

Nigel Lacey sells close ratio conversion kits, but only 5-speed I think. They are aimed at racing, so probably not what you want. Not to mention the price!

I'm also in UK, near Stafford. Would be interested to see this bike in action if you're nearby at all.

Ian

[Jon Pegler]

The 4-speed narrowcase models do not all have the same gearbox ratios.
The early A series 175 and 200 models have a slightly higher first gear ratio, which could probably be used in a 160 with a bit of juggling. The input shaft would have to be changed, together with the output shaft 1st gear.

The Spanish 5-speed narrowcase gearbox is completely incompatible with both the 4 and 5 speed narrowcase Italian crankcases.This gearbox cluster is used in the Spanish 200TS, 24 Horas and narrowcase 250 Road as well as the late 125 Scrambler.

The close ratio kits sold by Nigel Lacey are for Italian narrowcase 5-speed and widecase engines, so not applicable to a 160.

Unless you have access to a large selection of early 175 or 200 gearbox parts, of which there is more than one length of input shaft, I fear that altering the internal ratios of a 160 is going to be difficult.

The relevant part numbers for a higher ratio 1st gear would involve changing the input shaft and the output shaft 1st gear.
Part numbers 0400.16.013 and 0400.16.053 ( 175CF51/2 and 175CF2001/2 In the old numbering system) respectively.

Jon

[Classictrial]

Thanks for all the replies. Bike was properly tested by a good rider yesterday who feels that with the motor running a bit better a lower 2nd gear isnt going to be needed. Gear set is something that can be made no problem (already have a price) but would be very nice to lower the primary ratio if possible but that seems problematic as impossible to convert it to chain drive as the crank and input shaft would then be revolving in the same direction. Will post some pics of bike in action a bit later.

[ranton_rambler]

The 4-speed narrowcase models do not all have the same gearbox ratios.

I had another look, and can now see that the early 125S had different 1st and 2nd gear ratios. But I've found inconsistencies between the MW book and other sources before.

Ian

[Jon Pegler]

I wouldn't rely on all that is written in Mick Walker's books.

I made some lists of gearbox parts numbers and ratios some time back, to enable me to cross reference which gears were interchangeable between different models, particularly between the Italian machines and the Spanish Mototrans bikes.
All my information came from original Ducati parts books or sets of gear clusters that I had in front of me.
This allows me to have an instant read out for all the gear sizes, part numbers and combinations of parts fitted into any gearbox.

Jon

[Classictrial]

Not looked closely at a bottom end yet but might be able to lower primary ratio by converting to chain drive and would fit a Fantic clutch at the same time.

[ducwiz]

but might be able to lower primary ratio by converting to chain drive

Do you really need 4 reverse gears?