Sprockets 16.36:1 -> 9.6:1?

[stretch7101]

Yes to the venturi. That is the Honda GX100 clone I was referring to. That will work better than the stock carb with just a up jet or even better if bored. With that carb you will need to work out the throttle cable. I can send pics of my set up later. With the HS142 the throttle cable set up is easier but I like the way the GX100 cabling works out better myself. Fyi, look up four stroke gas bike carburetor and you will find the Huasheng 142 carb.

 

[Primut]

I have access to everything I need to bore and jet the carb, except experience. How will I know when the main jet is large enough? How do I tell if it's too much, and do I solder it in from the input side of the jet? Which type of solder works best for this? I read somewhere that the idle jet should be left alone for this size motor unless it starts surging and cleaning it doesn't help, does that sound right?

 

[stretch7101]

Use the plug chop method to determine if you are running the correct fuel/air as you resize your main jet. Chances are after you bore your carb, it will idle but not allow your engine to rev up at all at first. I solder from the outside(input side). There are some good tutorials on Utube about doing this. Use the lowest temp solder you have. I usually use electrical solder. The carbs we have talked about do not have a idle jet just a fuel or air metering screw. You will want to adjust the low speed fuel air mixture as needed once you get the main jet right.

 

[Primut]

Never heard of cutting up a plug for a read. Seems awfully wasteful, especially if the jet needs to be upsized "quite a bit", "a little at a time". What size do the gx100 clone carbs have stock? Is there a size I could jump to that would put me close without going over, to avoid cutting up a dozen plugs just getting in the ballpark? What's the best option for a permanent plug after I get done cutting up cheapos to get the jet right?

 

[5-7HEAVEN]

Never heard of cutting up a plug for a read. Seems awfully wasteful, especially if the jet needs to be upsized "quite a bit", "a little at a time". What size do the gx100 clone carbs have stock? Is there a size I could jump to that would put me close without going over, to avoid cutting up a dozen plugs just getting in the ballpark? What's the best option for a permanent plug after I get done cutting up cheapos to get the jet right?

Another method is one that's used by hotrodders at the drag strip.
Do your normal race down the quarter/eighth mile strip, or maybe 100 feet with your mb at wide open throttle(WOT)..
At the end, place vehicle in neutral and IMMEDIATELY kill the ignition. Coast to a safe spot and remove one spark plug(For the sake of your hands and the head's aluminum threads, let the engine cool down first).
Inspect the sparkplug's business end. White means very lean, black is rich, brown is perfect.
I hope this helps.

 

[Frogslayer]

Another method is one that's used by hotrodders at the drag strip.
Do your normal race down the quarter/eighth mile strip, or maybe 100 feet with your mb at wide open throttle(WOT)..
At the end, place vehicle in neutral and IMMEDIATELY kill the ignition. Coast to a safe spot and remove one spark plug(For the sake of your hands and the head's aluminum threads, let the engine cool down first).
Inspect the sparkplug's business end. White means very lean, black is rich, brown is perfect.
I hope this helps.

This is considered "a plug chop" you don't actually cut up a spark plug lol

 

[Primut]

That's the method I'm familiar with, never heard it called a plug chop before. I looked it up and the first two how-to's I read and the first video I watched on it all said to cut the threads off to see the ceramic at it's base. I suspect that's done by hardcore racers in a much more high performance type scenario. Any recommendations on the best plug to run?

 

[5-7HEAVEN]

I might've heard the term "plug chop" before, but it never stuck in my brain.