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Petcock option for Indian Mopeds
Measure the threads of the Indian where the gas exits. Measure the threads on the petcock. Cut a piece of PVC pipe. Hammer gently onto the threads of the bike, and do the same for petcock. The PVC becomes a bridge. Gas runs smoothly.
Indians are 4 strokes, which means less power and less go fast potential, and they're also considerably more difficult to work on. Indians use a one-of-a-kind engine, meaning NO cross compatibility with other engines, and parts are hard to find. They are poorly built Taiwanese clone of the Honda PC50; they can use parts from those, however it is equally if not more difficult to find parts for the PC50.
The easiest option is fabricating mounts for a Puch E50 engine or a Tomos A35. Either of these engines should cost around $100. A 70cc kit for an E50 is about the cheapest (and one of the easiest) kits available for any moped engine, and it would run around another $100 depending on the kit brand and quality up to 300 if you wanted to do a complete upgrade with new pipe, carburettor, crank and head, it could cost up to $300. The A35 is a faster engine in the end because it's a 2 speed, but it's also more work and it requires more maintenance (like replacing clutch pads). Swapping the engine should get you going easily 40+ for around $200, and for a full E50 build, 55 is entirely achievable for around $500 total (including engine + mounts). To keep it four stroke, there are Lifan and Linhai Honda clone engines around $300 new and complete that you could have also fabricate a mount for.
For upgrading the Indian engine you have a few options, most of which involve finding a good machine shop.
- First off, tune it. Get the valve timing perfect to spec from the manual, and the ingition too. This should get you running 25-30mph.
- Advancing the ignition can help the top end by revving higher and you might be able to get closer to 30 and a little over.
- You can also swap out gearing to get more top end, but you'll be slow off the line and probably unable to pull heavier people.
- Tires overfilled can actually give you 1-2mph on the top end as well.
Taking off the exhaust or drilling holes for more flow and removing the air filter (you can use pantyhose to keep crud out) will allow more fuel flow through. You'll loose some efficiency but gain power. You'll need to buy a bigger jet to match or the performance will probably drop. If you're feeling confident, you can try drilling up your existing jet, but that's easy to mess up, and impossible to undo.
You can machine the cylinder to a bigger bore, essentially increasing swept volume and effective cc's of the engine. To do this you will need to find a matching piston of increased size, probably 20-30 bucks and a machine shop, I'd priced one for my other 4 stroke 50cc at about 100 cheapest. About the biggest I think you can go is around 0.1 mm however so that'll get you not even a 5cc boost, though you may notice a slight increase in power. 33mph?
You can also machine the head down so the piston comes closer to the top, increasing compression, that'll give you more torque off the line and if you know a guy it's maybe only 20 bucks plus another 20 for new gaskets.
A bigger carburettor will also let more flow- best coupled with opening the exhaust out.
Like a car, you can experiment with changing out to a more agressive camshaft that holds the valves open longer, this can radically improve performance but you'll have to have the camshaft specialty made which would cost around $200-400 dollars and it will also put massive wear on your engine and probably ruin the valves within a few hundred miles. Fortunately they're pretty easy to replace if you do go that route. You can also mess around with porting and polishing the intake and exhaust for maximum flow similar to stock car race tuning. This requires a lot of knowledge and study or an experienced tuner and would probably run you a few hundred too.
You can swap out cranks and cylinder but you'll have to machine the case to match it. You could potentially rig up some sort of variated transmission by machining parts and fabricating a mount for a Honda Hobbit or Vespa Ciao rear wheel.