EZ1 with 4 stroke advice needed

I've got a Sun EZ1 recumbent and I'd like to mount a 4 stroke engine under the seat with the chain going to the crank so I will have gears. I'd like to use the bike for long distance touring and for putting up old mining roads. I don't need speed but do need a strong reliable machine that will handle steep dirt roads. I need advice on how to achieve this and also how to keep the chain noise down. I also would like to know if a 35cc 4 stroke would have the power at low to reasonable rpm or if I should get a 49cc 4 stroke. I don't mind engine noise as long as the engine isn't wrapped up.
It looks like the DAX gear box, 4 stroke engines, and crank freewheel would work.
If there are posts where someone has mounted an engine under a recumbent seat with chain going to the gears, I haven't found them. Any references or advice will be greatly appreciated.

Thanks,
roofman6

Barely,
What a great idea. If I understand Russell’s design correctly, you’d use a stock engine and clutch and gear reducer. You would chain this to a freewheel sprocket on the jackshaft and get some more gear reduction, and on the right side you’d put on two sprockets, one chained to the rear wheel cluster and a freewheel sprocket chained to the crank. You would still have a rear derailleur and some gears. When you pedal, you would be turning the jackshaft but not the engine. Looks like a great solution.
I’m concerned about chain and gear noise. I wonder if one of those timing belt gear reducers might be the way to go. Do you have any advice on that?
Thanks so much,
roofman
(Your Tadpole looks awesome. It looks like you used a complete engine and transmission setup to get your gearing).

Barely,
Thanks for the info and advice. The single “pedal” freewheel on the jackshaft also looks good to me. I’ve watched some videos and letting the engine help in braking would be nice. Right now I’m considering the $100 79cc 4 stroke from Harbor Freight. There are great teardown pictures on the 99cc engine at http://www.affordablegokarts.com/99cc-predator.php
The 22# engine is heavier than I wanted, but these people speak highly of the 99cc engine and I assume the 79cc one would be of the same quality. The gocart people also sell clutches that mount outside of the chain and I might have room to mount a v-pulley there and belt to a large one on the jackshaft. No timing belt though. I would dearly love to not hear chain and gear noise when touring. Your setup with internal gearing probably keeps the chains at reasonable speed and noise levels.
Thanks again,
roofman

Well, I ordered a $99 Harbor Freight 79cc 4 stroke today. Will move the gas tank and muffler, but I’m not sure the engine will fit as none are available in the local stores to measure. I might have to modify the frame.
I’ve decided to go with a friction roller design using stepped pulleys to get a range of gears. I want go up mountain mining roads and I think this will be the most bullet proof design. If the engine operates from 3000 to 6000 rpm and I use 2”, 2.5”, 3” and 4” stepped pulleys, I should get a range of speeds from 4 to 32mph. I’ll put a stepped pulley and centrifugal clutch on the engine and a stepped pulley on a jack shaft under and behind the engine. I’ll fashion some sort of slider that will push and pull the belts from one pulley to the next. I don’t know how easily the belts will change, and might have to use some sort of foot operated tension release. With small pulleys, the belts will wear out rather quickly I expect, but belts are cheap online.
I plan to use a 3” friction roller, possibly stainless steel wire brushes sandwiched and impregnated with resin, and ground slightly concave to fit the tire. I’m hoping that this will not slip and wear the tires too badly. I’ll make some sort of over center linkage to hold the roller in place.
After thinking about it, I just couldn’t see a chain drive getting me up steep mountain dirt roads unless I was using heavy motorcycle chains and gears. I think the 79cc 4 stroke will have the low end power that I want and the belts will be fairly quiet, but I don’t yet know how noisy the roller will be at high speeds, or how it will wear. I expect it won’t be as efficient as a chain drive, and won’t get great mileage.
If any of you have experience with stepped pulleys and friction rollers, I would appreciate your input. I’ll post pictures after I get the engine and start building things.
Thanks,
Roofman6

Cpt. Stevo,

Thanks for the advice and congrats on your bike. I went with a roller design and am not sure I like it. If I set the roller too loose, it grinds down the tire as it slips on steep hills. If I set the roller too tight, it produces a lot of drag. I have an over the center design with no spring and perhaps some sort of spring mechanism would help. The muffler isn't as quiet as I had hoped for either. I like the weight distribution however. It's a very comfortable ride. I'll see if I can attach some pictures.

Thanks again,
roofman6