Sprockets 16.36:1 -> 9.6:1?

[Primut]

I type slow af, sorry far asking a question you'd already answered.

 

[Sidewinder Jerry]

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

Exactly what method did you use to determine how fast you were going?

You'd also be surprised how much a slight decline and/or strong tail wind can increase your speed.

 

[mark20]

i think OP problem is that he needs to upjet, since right now hes running pretty lean, id suggest getting a jet kit, OR drilling out the jet yourself (kinda risky, but you can always go back down with solder and a smaller drill)

the jet drill kit is like 8$ and it comes in handy when modifying hard to find parts engines
https://www.ebay.com/itm/20pc-Mini-...378148&hash=item415dd5024b:g:PA4AAOSwDk5UEGWU

 

[stretch7101]

I use the completely non scientific speed limit sign with radar system or the also non scientific phone app system. Either way I am satisfied. I ride in the twenty or so mph range for most part(gas BICYCLE not motorcycle). I build my bikes to pull and climb well and ride smooth and reliably. BTW, I am not surprised at all. I have been building and riding gas bikes since '09. Just to let everyone know, I am not out to prove anything to anyone. I am merely sharing "my" experiences with "my" bikes and if it is useful to someone else that is great. I learned and still learn quite a bit from forums.

 

[Primut]

I use the same. There's a radar sign on the other side of my neighborhood, and I use a GPS speedometer app. And I was under the impression that the black fouling covering the plug meant that it was running rich, and that white was lean? Am I backwards on that? I'm still running the stock plug and gap.

 

[Primut]

So if I replace the clutch with a 10t instead of the original 12t or the plan A 12t, and get plan A's 32t rear sprocket that puts me at 11.52:1, is that close enough to mark20's "around 12:1" mark? I could also go ahead and get plan A's 12t but with a 40t rear sprocket instead of the 32t, putting me right at 12:1. Or a couple other configs in between. Is there any difference or effect from bigger drive/smaller final or vice versa other that the variation to top/accel/climb from ratio? Such as significant changes to strain/wear on different parts?

 

[mark20]

So if I replace the clutch with a 10t instead of the original 12t or the plan A 12t, and get plan A's 32t rear sprocket that puts me at 11.52:1, is that close enough to mark20's "around 12:1" mark? I could also go ahead and get plan A's 12t but with a 40t rear sprocket instead of the 32t, putting me right at 12:1. Or a couple other configs in between. Is there any difference or effect from bigger drive/smaller final or vice versa other that the variation to top/accel/climb from ratio? Such as significant changes to strain/wear on different parts?

well, your clutch will slip more the higher ratio you go (ie the clutch will slip more with a ratio of 10:1 vs a 15:1 ratio)
id go with the 12T and the 40T sprocket, as you want to be on the higher range, since you want to have some torque left (the higher you gear up (ie going from 15:1 to 10:1), the more HP is required to use the gear range effectively)
hopefully this helps!

 

[Primut]

I'm a machinist, but never done any carb/engine work, is "HS142 carb bored to 13mm” just the intake side up to the Venturi? I don't know what a hs142 carb looks like, but I've seen some cheap carbs on Amazon that look like the stock carb except the af screw(I'm guessing) next to the engine side opening is not bobbed like stock. Is there a curved or offset manifold that would allow me to use a mikuni style carb when funds allow? Also wondering if a 79cc predator straight pipe header is compatible, or could be made so by extending the bolt holes into slots? Sorry to get so far off the original topic and turn this into a catch-all, but I figure I should ask a few things that have been bothering me while there's some people who would know the answers paying attention to the thread.

 

[stretch7101]

The HS carb is the stock carb for the Huasheng 49cc four stroke bike engine. It is the same size as the stock Lifan 152f but the low speed circuit has a fuel metering screw under the brass plug on the left side of the carb. A GX100 clone carb is again the same size but has a air metering screw for the low end fuel/air adjustment. Either works fine. To bore out the carb I ran a 1/2"(12.7mm) drill bit all the way through the carb on the drill press then cleaned up the work with a Dremel ending up at roughly 13mm. Obviously the carb has to be disassembled first. The main jet will need to be up sized quite a bit. I use a torch tip cleaner and ream the jet a little at a time until I like the mixture. If you go too far solder the jet closed and use a micro drill bit to start over. Another super easy thing to do to make the carb mod more effective is remove the spark arrester from the muffler. Just grab the screen just inside the exhaust outlet with some needle nose pliers and pull it out. I turned to muffler to face rearward also so the exhaust isn't pushing against the ram air effect from the front of the bike.

 

[Primut]

So the venturi is what you're actually opening up then? I looked for an "hs142 carb" but no luck, what's the difference between that and this carb on amazon? Any reason this one couldn't be bored the same?

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