Alt. 4-Stroke Engines (frame mount)

ocscully

Member
Joined
Jun 23, 2007
Messages
661
Currently the only game in town for frame mount 4-stroke seems to be the Honda GXH50 or its Chinese Copy. Has anyone considered using one of the smaller Mini Honda 35cc or Robin 35cc motors in a frame mount? Both of these engines are currently being used in Rack Mount set-ups and seem to provide plenty of power and speed? Both of these motors are quite a bit lighter (7.5 lbs.-8 lbs.) vs. the 13 lbs. weight of the GXH50. Also I would think they both would provide vastly improved MPG over the 50cc Honda. Alternative thoughts and comments would be greatly appreciated.

ocscully
 


5

5-7HEAVEN

Guest
:cool:the advent of the HUA SHENG/HONDA midframe installation kit into the bike's midframe makes it easier for almost any engine to find its place where the happy time engine resides.

the key component is the flat engine mounting plate. the 49cc pocket bike engine has more than 4 mounting holes on its bottom, the ROBIN has 2 holes. however, the oil pan holes could probably support longer bolts and a spacer to facilitate its mounting. of course, new mounting holes would need to be drilled onto the $50 bolt-on plate.

the major obstacle would be to calculate optimum gearing to ensure that any engine operates in its best rpm range. since the happy time engine starts with 4.15:1 gear reduction, other engines would need much larger rear sprockets or jackshaft/gear reduction.(STATON sells a small 3:1 gear box which might work with a 50-tooth rear sprocket.)

i looked at the mounting plate on bicycle-engines.com it'd probably work well for my twin-engine install, but i already have a 12"X5" X 1/8" steel plate that should fit the bill.
 

ocscully

Member
Joined
Jun 23, 2007
Messages
661
Viza Gearbox

5-7HEAVEN,

Wouldn't a Viza gear-box provide the reduction necessary to work with a bike with 26" wheels. This gear-box I believe bolts right up to either the Honda or Robin Mini 35cc Four Stroke engines.Wouldn't you think that this combination would provide a smaller, lighter, higher MPG set-up than the Honda/Chinese 50cc with gear-box. I read in another thread that the current 50cc Four Stroke set-ups run 10 lbs. - 12 lbs heavier that the Chinese Two Stroke setups. I would think that smaller & lighter has to be better?

ocscully
 
5

5-7HEAVEN

Guest
:cool:as i recall from another post weeks ago, the VIZA gearbox is 5:1 gear reduction, with maybe 8-tooth sprocket. you might need 15:1-18.75:1 gearing total.

so with that 8t engine sprocket, you'd need 80-tooth rear sprocket.

Myron
 
A

Alaskavan

Guest
5-7 I trust your ratio knowledge, so what am I missing here? The Happy Time has a 4.15:1 initial reduction. An R/S with the Visa setup would have a 5:1 reduction. How do we get to the need for an 80 tooth sprocket from that? I'm probably just dense, but gotta ask.
 

ocscully

Member
Joined
Jun 23, 2007
Messages
661
Viza Gear Box

5-7 is correct that the Viza G4 Gearbox the one that is compatiable with BMX Type Chain does come with a 8 tooth drive sproket. But I don't see any real diffculty in getting something larger (11t or 12t) or perhaps even a toothed belt drive systen adapted to the output shaft of one of these gearboxes.

5-7 10 days ago you were advising Dan Hunter about the final drive ratios on the bike he made for his daughter. He was using a Viza gearbox driving I believe it was an 18t freewheel on a Staton Rear Hub with 20in. rims and tires. I don't remember exactly what rear sproket you suggested but I seem to remember that it was well with-in the range that is currently available. Is the reason for an 80t one of wheel size or or the 8t output from the gearbox?
 
J

JemmaUK

Guest
I would love to have a centre mount motor on my bike, the stability is an issue... where can you get the mounting kit?

Also, why bother with a chain drive? use the old sunbeam/indian/ajs system.

Take engine - 13/14 gear (assume GEBE) then run to with a short belt to 13/14 gear on frame to standard sheve on the rear wheel that comes with kit. problem solved. Plus the space on the rear fork isnt so important as to remove the drive you just slack off the primary *short* belt and remove...

Another advantage - there isnt all that ******ation with removing the rear wheel if you have a puncture... and you can reuse quick release :)

Just a thought...

Jemma xx
 
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gone_fishin

Guest
just wanna answer the "easier" rear-wheel thing.

it's still going to be going at higher sustained speeds than intended, there will still be some sort of drivetrain to the rear wheel.

so jemma, i wouldn't be counting that chicken too soon, because it prolly won't hatch....you see what i mean? you don't want to be mechanically-cheaping-out too much, like smaller rear axles and such, and another drawback (so far) to frame-mount is that rear-suspension is all but exluded.

interesting thread...there is so much cool stuff going on here lately...:cool:
 
J

JemmaUK

Guest
just wanna answer the "easier" rear-wheel thing.

it's still going to be going at higher sustained speeds than intended, there will still be some sort of drivetrain to the rear wheel.

so jemma, i wouldn't be counting that chicken too soon, because it prolly won't hatch....you see what i mean? you don't want to be mechanically-cheaping-out too much, like smaller rear axles and such, and another drawback (so far) to frame-mount is that rear-suspension is all but exluded.

interesting thread...there is so much cool stuff going on here lately...:cool:
Hi Augi :)

why would it be running a higher speed? 14 tooth to 14 tooth is equal to 1 to 1... ie no reduction or increase on the gearing. if you put two 14s on a stub axle and have one to the engine and one to the sheave then its the same as direct driving the sheave from an engine above the rear wheel. There is a drivetrain, that is true - what there isnt is any reduction therefore its effect will be the same as a single belt or chain.. the other option is a single guided/tensioned belt as used in the L&K surface carburettor machines.

As the frame I have is a hardbody as of now and will only be front suspension anyways the rear suspension isnt an problem, although the double belt arrangement would allow for suspension movement to a degree, just not the massive travel that some full sus bikes seem to have...

I agree there are some great articles on here - incidentally has anyone thought of semi-diesel or hot bulb engines?

Jemma xx
 
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gone_fishin

Guest
hi jemma, i think you misunderstood.

i'm too ratio-dumb to get into the juicy stuff. i let y'all figure it out, then i use what i can.

i was referring only to your thinking that you could "lighten up" when it comes to the rear wheel assembly. these are bicycle parts that are running at higher-than-intended speeds. when i saw your thinking that a change in drive-style would allow for a rear wheel that would be easier to deal with, i thought to remind you of the bicycle parts themselves.

i think a rear flat on anything but a friction drive will always be a "great big hassle."
 
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