WAY too low geared.

[lingeringstin...]

New Chinese engine on bike, 15 front sprocket and 43 rear sprocket, 16" wheels. Went through all five gears within about a hundred yards. Could have crawled up the side of a house if I could get the traction. Smallest blip on the throttle was, as Clarkson says, POWER!

The problem is that I'm using 428 chain and sprockets whereas everything else that uses this engine seems to run 520 so I could find no information about sprocket sizes for 428.

And yes I know any "normal" person would just use 520 chain and an 18" wheel and be done with it but over the last couple of years I'd bought two identical 16" cast wheels that had sprocket carriers to take 428 sprockets for the rear of my bike when I was running an MZ engine.

Then I went and changed engines.

It took a shitload of research to find out what 428 sprockets would fit my new engine and be readily available at a decent price (cheap). You can always find a sprocket for anything if you just search for it by make and model, but the moment you start doing weird shit you're on your own and it's no use just trying to get the same tooth sprockets the MZ used because the gearboxes will be wildly different between the two engines and anyway the new engine is made in such a way that it can't take anything as big as an MZ front sprocket.

Other sprockets have been ordered now based on scribbles and conjecture. I'll have to see what happens.

[DrDonnyBrago]

Ok.

[stinkwheel]

Balloon tyres are clearly the answer. Like those MZ swamp bikes.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[lingeringstin...]

It gets worse. Today I've been going around on 17/35 sprockets. Still way too low geared but could cruise at 40 without nailing the engine too much. Anything more than 40 and the engine would be screaming.

I am determined to stick with my 16" wheels. I quite like scuttling around at door handle level. In my experience really low bikes feel much more stable in dodgy conditions.

I have now ordered an 18t front sprocket, which there may not be room for on the engine but there's no way to know until it comes, and I've also ordered a 31t rear sprocket which is the smallest 428 one the JT catalog has listed that will fit my cush drive.

Rear sprockets of less than 31t are available but not ones that fit my cush drive so if I want to keep using the wheels I've already got then it's going to be adapter time which shouldn't be a problem to make if I have to using strimmer line, Super Glue, and walnuts mixed with the jellified foetus of an unborn Irishman's bairn at full moon, shot of scotch please, no water.


https://s26.postimg.org/hya3j5kcp/sprocket.jpg


.

[Stoker]

Front sprockets are easy, rears maybe too if you know someone with a lathe.
Front, Assuming that your existing front sprocket has useable splines, machine it down to a radius that can be combined with the machined internal radius of your new sprocket, get them tig'd together. Have used this method to keep a friends classic twinshock bikes running at trials.

Rear, have replaced like-for like gearing with different mountings using the same method.

[lingeringstin...]

The problem with the front sprocket is that there's only enough room on the engine to fit a 17 or 18. There's just no more room in there without taking the engine out, taking it apart and having the sprocket area on the engine case widened out, which is far too much trouble and expense to go to.

The rear is going to be the easiest way to go. I can't get a sprocket of the right number of teeth that will fit my cush drive so I'll just use an existing sprocket that does fit as an adapter. Easiest thing would be to lathe the teeth off my current sprocket so it's just a disc and then drill apprtopriate holes to accept a rear sprocket of the correct number of teeth for the gearing I desire.

Alignment won't be a problem. The front sprocket shaft is made in such a way that I've got a couple of inches leeway along the shaft and can use washers as spacers to line everything up.

The engine is a Honda copy which seems so far to be a very good copy that has almost universal parts interchangeability with Honda parts. Only differences I've found so far is that it uses a single cam chain instead of a double roller one like in a Honda engine.

The Honda engine this was cloned from seems to always be used with taller wheels than the 16" ones I'm using, and all the Hondas I've seen with that engine are much heavier than the skeletal framed MZ contraption I'm using now, so I can easily handle higher gearing than a normal Honda which is why I'm scratching about for sprockets. If people are claiming a truthful 80mph out of a Rebel, which is much heavier than my bike, then I'm sure I'll be happy with whatever mine does.

[Nobby the Bastard]

[tom_e]

I’m sure there’s a few places that can knock you up some custom rear sprockets with however many teeth you like and the correct shape to fit your setup for not too much cash. I’m sure Katy mentioned a place in another thread not long ago.

[lingeringstin...]

It would be nice to find custom sprockets at a reasonable price. I haven't looked into it for years but the last time I did was trying to work on vintage vehicles and they wanted a fortune just to make a sprocket so we resorted to cutting other things up and using a lathe to modify parts. Trouble is I don't have access to a lather anymore.

But I will check into custom sprockets. Most things are vastly easier to make nowadays than they were when I was working on vintage vehicles. Back then there were no computer controlled machines and a lot was done by hand. I would imaging a modern computer-encrusted "sprocket making machine" could knock up a sprocket to your own design specifics with no more trouble than making an OEM one.

[lingeringstin...]

[nowhere.elysium]

[G]

[Nobby the Bastard]

[Nobby the Bastard]

[G]

My bad - removed wrong quote.

[Nobby the Bastard]

[G]

We'll see - if someone could see to getting me one of these and somewhere to store it, it'd make that a lot more achievable!

https://i.ebayimg.com/images/g/MI8AAOSwi8VZO~oL/s-l1600.jpg

(Unfortunately with plans for the week after, emptying and reloading the van caused a lot of stress and lost work etc ... it did look like there'd be a week gap next year, but they got the dates wrong and there's not.)