Sprockets 16.36:1 -> 9.6:1?

[mark20]

I haven't a clue how to apply that information to the gear ratio to answer the question of how much of a hit the acceleration/hill climbing will take. I don't know if there's a formula somewhere, and as for hills, if there is one, I don't think the numeric representation of how it would perform would mean anything to me without more reference points than whatever it comes out to now(going from 173 to 94 or whatever means nothing with no idea what the scale is or having any other reference points on it). Can anyone point me in the direction of some resource that I don't need an engineering degree for or shine the light of experience on this please? I'm not going to be able to buy a stack of sprockets to test out until after my home isolation is over and I can find employment, but getting one to cover more ground/day jobhunting would be fantastic.

id stick to around 12:1.
now, do you any preformence mods to the motor? (ie govener removal, intake re jet and exhaust kit?)

if you want top speed, try a 36 or a 40T sprocket, that should get you into the optimal ball park range.

and, keep in mind, a front sprocket will change the gearing pretty good, and your motor will struggle if you gear it down more than 12:1 (3hp isnt that much, trust me, ive had one) it will have a effect on on hills, how much? well, depends on the load, but dont expect it to climb hills without some light help.

and if your on a job hunt, please dont spend money on this thing before you get a secure employment, as thats just plain stupid.

 

[Sidewinder Jerry]

I was further researching your engine by looking at some owner's manuals. Here's what I found out. First I suggest getting an techometer/hour counter. You can get these fairly cheap off eBay. The tech is going to be helpful in letting you know what reduction will work best for you to maintain max horsepower rpm without over reving. It can also let you know if you're obtaining minimum rpm for max torque when hill climbing so that you don't experience engine strain.

The recommend idle speed is 1800 rpm +/- 150. The recommend governed operating speed is 3600 rpm for 2 horsepower. For ungoverened max horsepower 2.5-3 hp the max is 4200 rpm.

Let me do some calculation and I'll be right back.

 

[Primut]

Governor is removed, drilled two ½" holes through the muffler baffles and some smaller ones through the airbox cover. I am on the lookout for a new carb/air filter setup and a cheap header to bookmark for later, since as you said sinking money into it needlessly right now would be stupid. I don't have much choice on the clutch, it's either replace it or stop to lube it every 3 miles(which sometimes does nothing, hell, sometimes taking it apart and cleaning it and lubing it does nothing) so it won't kill the motor at a stop, and if I can get a sufficient bump in top end to get from shop to shop faster for a ~$12 sprocket then I think it's a small investment to increase my daily coverage hunting.

I also have my eyes on this tach, just not sure about the expense being necessary right now:

https://www.amazon.com/gp/aw/d/B0811CBCCH

 

[Sidewinder Jerry]

If you're at max ungoverned max hp rpm (4200) on 26" wheels using the 16.36:1 reduction max speed will be around 20 mph. With the 9.6:1 reduction max speed will be around 34 mph on 26" wheels. The draw back here is by lowering reduction you're also significantly lowering torque. I live in Tennessee where there's lots of very steep hills. My bike and I weigh close to 350 lbs. My state has a 50cc limit and an automatic transmission clause; to stay legal I built a bike that shifts engine driven gears automatically.

You're going to have a very hard time climbing hills with the 9.6 reduction especially using a single speed to leg assist the engine. If your engine can't reach 2500 rpm going up the hill it'll experience engine strain. Your acceleration is also going to be a lot slower on level ground due to the inefficient contributions from the single speed leg assist.

If you plan to stay with the left side engine drive system then I recommend at least getting a 5 speed internal geared hub and a bicycle computer with a cadence (crank rpm) meter on it. You should use a gear that you can comfortably maintain a cadence of 70-90. If you choose to use a derailleur drive system instead of an IGH then be sure the rear wheel has a cassette on it instead of a freewheel. A freewheel's axle is prone to bending.

I personally recommend getting a shift kit so that you'll have a variable reduction range for the engine.

 

[stretch7101]

I am running 18:1 with a well tuned engine and getting 30mph on one Phat and 18:1 with a bored and rejetted carb and slightly de restricted muffler and getting 34mph with that one. Both climb very well. I ride trails and rough terrain often and the low end power is great.

 

[Sidewinder Jerry]

I am running 18:1 with a well tuned engine and getting 30mph on one Phat and 18:1 with a bored and rejetted carb and slightly de restricted muffler and getting 34mph with that one. Both climb very well. I ride trails and rough terrain often and the low end power is great.

What size wheels are you using? Also what kind of engine?

 

[stretch7101]

The stock 26" wheels and the stock Lifan 152f. Both Phatmotos also have a freewheel incorporated into the drive train. One is a chain drive with the stock clutch tuned to engage at a higher rpm. The other is a tbelt drive made from 4G Grubee parts or 7G Gasbike tranny parts. The second system mentioned is my favorite. It is quiet and the shoed clutch(also tuned to engage at a higher rpm) is smooth as butter.

 

[stretch7101]

The main key is to remove the governor system and to use a up jetted HS142 carb or a up jetted clone GX100 carb.

 

[Primut]

Now I'm really confused. This thing hit 25 out of the box and after I pulled the governor, the heat shield off the front to cool the heatsink find better, and popping the holes in the airbox and muffler baffles it'll hit the low 30s if I let it, but without a tach I try to cruise about 28. Would like to know what carb you're running, Stretch, for future reference

 

[stretch7101]

A HS142 carb (with the fuel adjustment screw cap removed) works great. So does a GX100 clone carb. Both need up jetting. Also, I forgot to mention I opened up the air box also. My latest carb is a HS142 carb bored to 13mm and further up jetted. The bored carb has made a nice difference in power and smoothness. I have recently moved to non ethanol 91 octane fuel for all my bikes. I am finding they run much smoother with the non e fuel.