Simple 4 Stoke Build-Gearing Questions

[krealitygroup]

Hello All,

I've been on some of the other sites and wanted to join y'all.. I need to build a 4 stoke based on the Honda GHX-50 in a 1990's diamondback outlook 66cm.. I used to have a 2-stroke kit, but it's not reliable enough for the long distance trips I need to take.

With a 26 inch wheel, what set of sprokets could I get at the engine output and at the rear wheel to get me 25 mph cruising speed with 300# (me and 100# of gear)
I want to avoid CVT's and jackshafts. simple chain from output to rear wheel and back..

I appreciate anyone's advice.. Thanks
K

 

[butterbean]

You may WANT to avoid jackshafts, but they don't make a rear sprocket big enough for you to go direct drive at 25mph, so you're not going to avoid a jackshaft. You will need some other type of gear reduction between the engine and the rear wheel. Check out www.affordablegokarts.com they may have a transmission you can use and it will be reliable and less expensive than others.

 

[butterbean]

www.affordablegokarts.com/mm5/merch...ode=A&Product_Code=2316&Category_Code=MTRBK49 yep, here it is and a good price for it too.

 

[krealitygroup]

www.affordablegokarts.com/mm5/merchant.mvc?Session_ID=b8625cb709e795ceff825cc33fde7f6f&Screen=PROD&Store_Code=A&Product_Code=2316&Category_Code=MTRBK49 yep, here it is and a good price for it too.

Thanks so much. That makes sense.. Question.. When I had my 2 stroke, It was just a chain tensioner and the stock 48t sprocket.. Why??

 

[butterbean]

Because the two strokes have internal gear reduction. The way the two strokes work is you have a crankshaft, with a magneto on one side and a 20 something tooth gear on the other, then you have a countershaft with an eighty something tooth gear. The crankshaft turns the small gear, which turns the big gear, which turns the counter shaft, which turns the 10t output gear, which drives the bike. No such internal gearing or countershaft on a four stroke.

 

[krealitygroup]

Ahhhhhh.. I see.. Thanks!

 

[Sidewinder Jerry]

You may want to consider the 4G kit.

http://www.bicycle-engines.com/49cc-4G-T-Belt-Drive-Complete-Gas-Powered-Engine-Kit.html

 

[KCvale]

You won't fit a 49-50cc 4-stroke in that Diamondback frame.
You pretty much need a beach cruiser S type frame for a 4-stroke.

I just finished this Pantera yesterday, note that with an S towntube you can get the engine base down to the top of the pedal chain and even then it barley fits, and that is the stock exhaust replaced.

The Honda 50cc is a fine engine, the HS 142F-1G 49cc is a nearly part for part knock-off of equal if not better quality for $50 less.
There is also an HS 144F-1G 53cc 4-stroke.
Consider it a factory 'bored out' 49cc with a slightly fatter piston for another 100 watts (.13hp).

As mentioned above you need a transfer case gear reduction on a 4-stroke.

There are multiple designs for this.
Skyhawk 4G, a no name 5-G and 7G, a Q-matic and the this AFG one referenced above.

What I have found is all but the 4G rely on your clutch bell and pulley/sprocket to spin on an oillite bushing on the output shaft.
I feel a bushing has no place in a drive train trying to do the job two bearings should be doing.

It doesn't take long for that bushing to wear and at idle, start sounding like one of those wind up toy monkey's playing cymbals... on crank, as the bell starts moving and vibrating on the shaft.

Next is gear reduction and how it is made.
The old Stage II's used 3 gears.
Newer stuff uses 1 or 2 chains, or a T-belt.

I don't like anything chain.
They are the backup vocals for the spastic monkey.

I like the HS 142F-1G 49cc and 2015 4G T-belt drive with bearing supported clutch bell and freewheel output shaft with 5:1 gear reduction and nice cover.
It's quiet, adjustable, and reliable.

I have a couple dozen 4-stroke builds here for bike idea's if you want.
http://kcsbikes.com/KCsBuilds.asp?motor=4-stroke&Drive=All

 

[butterbean]

I never had problems with clutch chatter at idle. Taking off is when I would have chatter and slip, but there were a few things I didn't know. You're supposed to oil the bushing every couple of days. I did this, but I used 3in1 oik, and you're really supposed to use motor oil but I never tried that before, what I actually ended up doing was taking it apart every couple weeks and greasing the s.o.b with red and tacky. Not really supposed to do that either, but it worked for me. Now I'm building a new bike with a brand new clutch, and I'm going to use a drop or two of motor oil, I have glass eyedrop bottles so I will be filling that up with oil. Another important thing to realize with the cheap clutches is the gearing, they don't take off as smoothly with higher gearing especially if you are on the heavier side like me. The bike I'm building is geared quite low compared to my last bike, and that will help with takeoff. Also, although the bushings do wear, most one way bearing clutches are needle bearings and I've read that needle bearings don't last as long as bushings. Now if you're talking about a ball bearing clutch, that would be the best way to go.

 

[KCvale]

Now if you're talking about a ball bearing clutch, that would be the best way to go.

I agree, that's why I like the 4G's, the clutch bell is isolated from the engine shaft and rides on a pair of sealed ball bearings in the transfer case.