Idle problem and poor performance

nickaloadien

New Member
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Oct 11, 2022
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Somewhat finished this build, boy was this one a pain in my ass. I’m not familiar with fabricating an engine mount as this bike isn’t suited for china dolls so it was a lot of trial and error, wasted hours, wasted money etc. I guess we learn from our mistakes though.

Anyways, I fired it up, ran bad, kept adjusting carb C-clip, richer seems to be working better for the idle. But it won’t stay idling and the power seems weak when I ride it. Also when it’s idling and I try to keep it running by hitting the throttle a bit, if I go too much with it the bike revs so high it sounds like it’s gonna explode!!

It has a reed valve on it (not too familiar with using these) I didn’t go with a windowed piston instead I tried a third transfer port at the intake with no boost port.

I think maybe it’s just a matter of carb tuning? Maybe a bigger pilot jet.

Cheers folks
 

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It's carb tuning, and you have some learning to do. The carb you have on it now is not like the single jet, ultra simple, itty bitty carbs the standard kits come with, like the Bofeng and NT.

This carb is a big boy carb, which means it has 2 jets in the bowl. A main jet, and a Slow Jet (aka Pilot jet). It also has a Needle jet and needle.

On the cheap simple kit carbs, they basically have no idle or low speed circuit, and they rely on the needle to do everything.

On big boy carbs, they have 4 major adjustments, all dependent on the throttle position as to their function.

The IDLE fueling is adjusted by the idle mixture screw, not to be confused with the idle speed screw. On this carb it is located on the left side of your bike where the fuel inlet to the bowl is. Right next to the fuel inlet is the idle speed adjustment screw. Right next to that is another screw angled down toward the bowl - THIS is the idle mixture screw. It controls how much or little fuel goes into the engine at idle, and ONLY at idle. It doesn't change fueling for any other part of the carbs operation. Turning it in makes it leaner, turning it out makes it richer. Ideally, this screw should be turned out from seated more than 1 turn, but no greater than about 2.5 turns out. If you find yourself less than 1 turn out, or more than 2.5 turns out, the pilot jet likely needs to be increased or decreased a size.

The idle mixture fuel flow volume is affected by the Slow Jet/Pilot Jet, so if you change this jet size, the setting for the idle mixture will need to be adjusted to compensate (going back to previous paragraph about idle mixture screw turns outside of ideal adjustment range). This jet, however, mainly controls fueling from just off idle (throttle barely opened) to 1/4 throttle.

The Needle controls fueling from 1/4 throttle to 3/4 throttle. Much like the idle mixture being changed by the size of the pilot jet, the needle adjustment is affected by the size of the main jet.

The Main jet controls fueling from 3/4 throttle to wide open throttle.

In essense, trying to adjust the idle fueling by moving the needle is about as effective as giving a prostate exam through your nostrils.
 
Lots of places there for an air leak, make sure all the unions are clean and sealed. Did the throttle cable come with a boot for where it goes into the carb? Might want to wrap some tape around it tightly for now.
 
wow thanks a lot for all that info I appreciate it makes a lot more sense now cheers
 
Not CARB Related BUT

Making your own mounts was not needed you could of gotten These

Also flip the Pipe down if it doesn't wanna fit just use a hitch and bend it slightly or get a Flex Viper Pipe Here

if you haven't gotten your back breaks on just bend the left arm a little upwards or use a slim washer to raise it some and it will go through the middle of the chain perfectly

i can't tell how you got the tank mounted but if you want move it up flip the bracket self tap them into the frame then you can seat the tank into the brackets so its not close to the seat

Also the OCC is a kids bike so reenforce the back of the bike it is known for snapping under the weight of a adult if you can weld make something like this or better i would suggest Better

if you get ANY chain rub on the fender just grind it down a little or drill another hole and move it up some allowing it to be away from the chain.

image.jpg
 
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Not CARB Related BUT

Making your own mounts was not needed you could of gotten These

Also flip the Pipe down if it doesn't wanna fit just use a hitch and bend it slightly or get a Flex Viper Pipe Here

if you haven't gotten your back breaks on just bend the left arm a little upwards or use a slim washer to raise it some and it will go through the middle of the chain perfectly

i can't tell how you got the tank mounted but if you want move it up flip the bracket self tap them into the frame then you can seat the tank into the brackets so its not close to the seat

Also the OCC is a kids bike so reenforce the back of the bike it is known for snapping under the weight of a adult if you can weld make something like this or better i would suggest Better

if you get ANY chain rub on the fender just grind it down a little or drill another hole and move it up some allowing it to be away from the chain.

image.jpg
thanks man lots of great info I will use cheers. Also I wish I had known about that chopper website before starting this!! Those metal mounts I saw on the website do they seat the engine far enough to the left so the chain is true/straight?
 
Links to Amazon may include affiliate code. If you click on an Amazon link and make a purchase, this forum may earn a small commission.
thanks man lots of great info I will use cheers. Also I wish I had known about that chopper website before starting this!! Those metal mounts I saw on the website do they seat the engine far enough to the left so the chain is true/straight?
Yes, they are made specifically for the OCC and offsetting the engine
 
Somewhat finished this build, boy was this one a pain in my ass. I’m not familiar with fabricating an engine mount as this bike isn’t suited for china dolls so it was a lot of trial and error, wasted hours, wasted money etc. I guess we learn from our mistakes though.

Anyways, I fired it up, ran bad, kept adjusting carb C-clip, richer seems to be working better for the idle. But it won’t stay idling and the power seems weak when I ride it. Also when it’s idling and I try to keep it running by hitting the throttle a bit, if I go too much with it the bike revs so high it sounds like it’s gonna explode!!

It has a reed valve on it (not too familiar with using these) I didn’t go with a windowed piston instead I tried a third transfer port at the intake with no boost port.

I think maybe it’s just a matter of carb tuning? Maybe a bigger pilot jet.

Cheers folks
New fuel line see how fuel tank foward looks
 
Somewhat finished this build, boy was this one a pain in my ass. I’m not familiar with fabricating an engine mount as this bike isn’t suited for china dolls so it was a lot of trial and error, wasted hours, wasted money etc. I guess we learn from our mistakes though.

Anyways, I fired it up, ran bad, kept adjusting carb C-clip, richer seems to be working better for the idle. But it won’t stay idling and the power seems weak when I ride it. Also when it’s idling and I try to keep it running by hitting the throttle a bit, if I go too much with it the bike revs so high it sounds like it’s gonna explode!!

It has a reed valve on it (not too familiar with using these) I didn’t go with a windowed piston instead I tried a third transfer port at the intake with no boost port.

I think maybe it’s just a matter of carb tuning? Maybe a bigger pilot jet.

Cheers folks
Try super heating the muffler and tucking it right under your engine. I don’t know but it probably wouldn’t want to flow like a stack. From what I’ve seen with mine you may be drowning your cylinder with unburned gas and oil
 
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