Air to fuel ratio problem with HP carburetor

jhami970

New Member
Joined
Nov 1, 2019
Messages
7
Hey, I have a china made 80cc bike engine running a 20-1 oil gas ratio. I am using a HP carburetor from Top Corporate and also a high performance exhaust. I understand that when the spark plug is black and oily it means you are running too rich but I don’t know how to adjust it. I’ve seen on the forums that you adjust the need but my carborator doesn’t have that. I am at high elevation so I installed a smaller jet but it didn’t help much. I would really appreciate it if some one could help me out because I get to about 23 mph but only about 3/4 of the rpm I know it can get. If I can adjust the air to fuel ratio I think that would fix it.
 


jhami970

New Member
Joined
Nov 1, 2019
Messages
7
Yeah maybe but I broke the stock one. I took the jet from the stock and put it on the HP because the hole is smaller but no number was posted on it.
 

GreasyChris

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Joined
Jan 3, 2019
Messages
767
20:1 is too much oil. Try 32:1 and yes you will have to rejet it. A stock jet is about 70. So you'll have to go down in jet size to lean it out.
 

Frogslayer

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Joined
Jan 20, 2019
Messages
789
I couldn't find what I needed on Amazon. I think it's bicycle motor works that has the jets in sizes we need.
 

Frogslayer

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Joined
Jan 20, 2019
Messages
789
What you can do if you want (what I ended up doing) is solder the jet shut that you already have and drill a smaller hole in it with a micro drill bit.
 

jhami970

New Member
Joined
Nov 1, 2019
Messages
7
I don’t have any drill bits that small unfortunately. Do you recommend I buy the high 60’s or low 60’s pack?
 
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