Gearbox Ratio

[Sidewinder Jerry]

If you were using 26" wheels using a total reduction of almost 14.91:1 [4 × 41/11] at 6800 rpm you'd have a speed of almost 35.3 mph

 

[Sidewinder Jerry]

I'm fairly sure the 7G and knock off clones are all 4:1. The GruBee 4G is (4, 4.5, 5):1 depending on which one you order. I've always heard complaints about the poor craftsmanship of the 7G and it's clones. The 4G and the EZ Q-matic get the best praises for the belt drives.

 

[Deleted Member 4613]

Right, that's my calculation approximately 35 mph. It's the same formula
as mine. I do have a a q-matic, on another bike but I geared it for mid-speed torque.
Now, I'm looking for a little more top end. I agree, Grube and the Q-matics are top
of the line. I'm a little hesistant to pull the trigger on an ebay clone kit. Grubee and
Bicycle-engines.com don't offer 4 stroke kits anymore, just parts. I'm either going to
take a chance on a 53cc ebay clone kit or a cheap ebay or Amazon 80cc 2 stroke single
cylinder and head which I know will produce both torque and speed. Thanks for your input.

 

[CrazyDan]

With the 53 cc 4 strokes max hp rpm is around 6800 for around 2 hp. Generally 2 hp at best will get you around 35 mph on 26" wheels.

Tell that to my ungoverned 53cc that hits 47mph @9000 rpm and takes off like a bat out of hell in first gear. Used to go faster, but a lil too sluggish for me. Think I found the sweet spot.

 

[Sidewinder Jerry]

Tell that to my ungoverned 53cc that hits 47mph @9000 rpm and takes off like a bat out of hell in first gear. Used to go faster, but a lil too sluggish for me. Think I found the sweet spot.

Well I'm sure you've done mods to up the hp and rpm tolerance level. For all I know you might could qualify for a horse jockey.

But for a stock 53 cc 4 stroke engine that's only producing 2 hp at 6800 rpm anything with a total weight of more than 225 lbs isn't going to see 35 mph on level ground using 26" wheels. If the total weight is under 225 lbs you could squeeze out 35 mph using 26" wheels with a 15:1 reduction at 6800 rpm.

 

[CrazyDan]

Well I'm sure you've done mods to up the hp and rpm tolerance level. For all I know you might could qualify for a horse jockey.

But for a stock 53 cc 4 stroke engine that's only producing 2 hp at 6800 rpm anything with a total weight of more than 225 lbs isn't going to see 35 mph on level ground using 26" wheels. If the total weight is under 225 lbs you could squeeze out 35 mph using 26" wheels with a 15:1 reduction at 6800 rpm.

I'm around 145 lbs atm with with a near max modded 53cc and 3 speed hub. Reached 53 mph on a 55mph gear ratio in a previous setup. I exit turns and climb mountains at a higher speed than before with my new ratio, even though it's a lil slower on long stretches.

 

[Deleted Member 4613]

That's crazy fast for the ungoverned 53cc 4 stroke, but I'm planning to work with the
governed 53cc. 35mph is enough for me. Great that the engine can reach 9000 rpm
without suffering a broken crankshaft.

 

[Deleted Member 4613]

So my best bet would be buying an ebay 53cc 4 stroke kit with a 4:1 belt drive, ugrading the motor,
and using a 41 tooth rear sprocket, and 11 tooth drive sprocket (purchased) for a
theoretical top end of 35mph.

 

[Deleted Member 4613]

I just learned something about these 4-stroke belt drive engines that is
concerning: They are equipped with a stepped shaft which only fits the
supplied trans. That means if anything goes bad I may have problems
fitting another trans or clutch. Anyone know about this?

 

[CrazyDan]

I just learned something about these 4-stroke belt drive engines that is
concerning: They are equipped with a stepped shaft which only fits the
supplied trans. That means if anything goes bad I may have problems
fitting another trans or clutch. Anyone know about this?

Are you talking about the tapered shaft? Yes. You can only run transfer cases meant for a tapered shaft water pump or generator engine.
There is a straight shaft version but with my engine needs an adapter. If you use the straight shaft 49cc then use that. Enjoy that oilite bushing