first four stroke build - advice needed

[Urban Fatbiker]

My lowly 48cc, just came back from a 38 mile ride thru the hills. That little engine wouldn't make half that trip without a well-built jackshaft, and 6 speed cluster.

My top speeds are limited to 35 WOT, 28 cruising, and it climbs really good dropped in 1st gear, course its crawling on the steep climbs.

I feel the call for more power! But...I resist. My bike, like the little bulldog puppy that chased me yesterday, a lot of giddyup in a small package.

From Fontanel, in the hills of north Nashville, its Buzzbike!

 

[Sidewinder Jerry]

My lowly 48cc, just came back from a 38 mile ride thru the hills. That little engine wouldn't make half that trip without a well-built jackshaft, and 6 speed cluster.

My top speeds are limited to 35 WOT, 28 cruising, and it climbs really good dropped in 1st gear, course its crawling on the steep climbs.

I feel the call for more power! But...I resist. My bike, like the little bulldog puppy that chased me yesterday, a lot of giddyup in a small package.

From Fontanel, in the hills of north Nashville, its Buzzbike!
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I was once told my 4 stroke 33cc 1.6 hp engine on the 30% grade hills, sounded like little slave children working in a gold mine lol

I can get 550 lbs up 30% grade hills at 6 mph; it requires a 66.79\1 total reduction to do it.

 

[Toby woodman]

I was once told my 4 stroke 33cc 1.6 hp engine on the 30% grade hills, sounded like little slave children working in a gold mine lol

I can get 550 lbs up 30% grade hills at 6 mph; it requires a 66.79\1 total reduction to do it.

having done some more research. while the hausheng engines may rev higher. I cannot find one with a straight shaft. I can't get good quality four strokes where I am and finding one with a belt drive or double chain drive seems impossible. so I am looking at a setup like this. would you be able to have a look at the gear ratios and tell me how effective for cruising on the flat and up shallow hills. I will pedal on moderate hills.

 

[Sidewinder Jerry]

having done some more research. while the hausheng engines may rev higher. I cannot find one with a straight shaft. I can't get good quality four strokes where I am and finding one with a belt drive or double chain drive seems impossible. so I am looking at a setup like this. would you be able to have a look at the gear ratios and tell me how effective for cruising on the flat and up shallow hills. I will pedal on moderate hills.

I think you should go for that. Then latter install Strumey Archer IGH if it can't handle the hill.

 

[Toby woodman]

okay. if I were to do that later. what is the the gear ratios of those hubs?

 

[SirLurksAlot]

What was your total reduction and did you use 26" tires?

Math wise to do 22 mph on 26" tires at 4000 rpm the total reduction would be around 14.06\1.

By standard do you mean

10>[32/10]>44 ????

Stock Phatmoto AT... 4.0 x 26 tires. 50t rear sprocket. Haven't counted teeth on clutch or jackshaft

 

[SirLurksAlot]

Over 5k rpm and it's probably floating the valves. Not that I would want to spin that motor a whole lot faster, but some heavier valve springs would likely tame the valve float.

No heavier valve springs are available, afaik. No high perf parts except carb and exhaust pipe are available afaik. This ain't a P79, unfortunately. Fwiw, imo bigger valves and more aggressive cam would come before valve springs - power falls off pretty rapidly above 4k rpm, ime.

 

[Toby woodman]

I’m looking for a reliable four stroke with good hill climbing. Maybe a 32 to 10 Jackshaft with a 32 on the back wheel. And a Honda gx120 with a torque converter

 

[ImpulseRocket]

No heavier valve springs are available, afaik. No high perf parts except carb and exhaust pipe are available afaik. This ain't a P79, unfortunately. Fwiw, imo bigger valves and more aggressive cam would come before valve springs - power falls off pretty rapidly above 4k rpm, ime.

And with a more aggressive cam you would need even stronger valve springs, which brings us right back where we were before.

Also, I bet I could figure out valve springs easy enough if I had the OE specs. It's not rocket science, just some math

 

[Toby woodman]

okay. having thought some more about wanting a reliable and fun bike. I have come up with this. a lifan 152 engine which goes to a torque converter with a 10 tooth sprocket. then to a 32 to 10 tooth jackshaft and to a 36 tooth rear sprocket. this should provide enough torque for hills and starting out with enough top end speed for it to be practical. can you take a look at this and guide me on whether or not this will be a good setup. also is 2.5 horsepower enough for a torque converter