Honda Motra CT50

[zippy]

A little workhorse this thing.

Ermin did his 1st job today, escorting a engine home.

[Toby Leröhne]

I quite like the Motra, they look to me like a kind of single track "big red" ATC/Foreman.

[Alan CF]

asked to fit a 90cc in her,
Had to strip the ratio box down to get to rear sprocket.



sprocket sites 49 mm awy from the engine cases. looks like another plan is needed.

[steveST100]

Told him you needed to remove that ratio box to get that cover off.
Leaving it 3 speed or going to mod the shaft to make it 4 speed and keep the ratio box?

steve g

[Alan CF]

I would like to open up his cases and fit the 90cc top end to the 50cc motra engine, or the other option is to fit the internals of the motra to the 90.
but this means stripping two engines either way, but that takes time and my time = £30 per hour. so its zippys Decision,

we was thinking first of all to make a off set sprocket (before we stripped it ) for the 90cc motor. but at 49mm off set the output shaft or bearings would not last 5 minutes

[Diesel Dave]

Have you considered machining off the teeth of the original sprocket and button fixing replacement to the splined fitting.

Button fitting is the same as used on modern floating disks, and if they are capable of handling the braking force of a modern sports bike then it will be more than sufficient for 9hp.

I've done this for other bikes such as Enfield rear sprockets (because they are part of the brake drum so going 'non-standard' required a bit of imagination).

[Alan CF]

Have you considered machining off the teeth of the original sprocket and button fixing replacement to the splined fitting.

Button fitting is the same as used on modern floating disks, and if they are capable of handling the braking force of a modern sports bike then it will be more than sufficient for 9hp.

I've done this for other bikes such as Enfield rear sprockets (because they are part of the brake drum so going 'non-standard' required a bit of imagination).

Any links dave as to what it looks like. when we spoke he wanted to retain the orig engine for when he sells it on, and also you can not buy much for the motra, those front sprockets must cost a fortune. if you can get them.and i would presume he would want to keep the old sprocket with the old engine, and fit a new one.

parts list but i cant find the front sprocket

http://www.cmsnl.com/honda-ct50jc-japan ... partslist/




http://www.cmsnl.com/ct50-motra_model8227/info/

[Diesel Dave]

I don't have any photo's of the work I did but Hitchcocks' now offer the same conversion rear drums for Enfield owners:

[Diesel Dave]

Perhaps I need to explain a little further.

I turned off the original teeth on the drum, then turned/bored a hole in a sprocket so they were a close match. (had to heat the sprocket to fit over the drum). I also reduced the sprocket thickness near the centre to match the drum flange thickness

As the shrink fit held them firmly together I could then drill 6 holes around the joint (I used a dividing head but you really don't need to be that accurate).

Then I turned a set of silver steel 'buttons' to match the holes, drilled them through and tapped M5 or M6.

With the buttons set in the drilled holes I used to button cap heads and washers on each side to laterally secure the sprocket.

I was going to case harden the buttons but after talking it over with some other members of the SMEE I decided it would not be necessary.

Since doing this 'floating brake disks' have appeared on the scene and their fixings may be suitable although they are likely to be too large for your application.

Dodgy diagram...

[Alan CF]

Great idea Dave. But i dont think Zippy will pay me to make up anything like this. time wise..., people have grand ideas but rather others did them.
i think its back to a rebuild and swapping parts.

This is not my project, one of projects take time...

where is he anyway...