66cc bofeng carb 4 stroking

[JPbaphomet]

Edit: bought new carb because gasket on old one is causing leaks. Tightened EVERYTHING, much less rattle and vibration. Now it's very boggy on startup, but a tad less 4 stroking. New needle at center notch. No voltmeter, but magnet and coil seem ok, recrimped wires to cdi/kill, one was wiggly.
Plug dark grey.
I'm thinking definitely new plug (hotter) and smaller jet, probably 65-68.


Bro setup an engine for me on a hyper cruiser. Break in was fine, I guess. Runs rich. Plug is darkish grey.
4 stroking most of the time: lightly at idle, just about every throttle position. It cleans up under load, then immediately 4 strokes.
Wicked vibration and crunchy rattling sound above ⅓ throttle, gets worse as throttle and speed increases.
Bro isn't helping me so here are adjustments done today.
-Check & clean carb. Lowered needle all the way.
-cleaned plug, reduced gap a tiny bit.
-using roughly 40:1 (~1.6, 1.75 to ½ gallon) after the first 2 tanks.
-chain tension seems ok

Rode around. Starts easier. 4 strokes a tad less, but still present. Vibration and rattling still present.
I'm guessing a smaller main jet is needed?
What am I missing?

 

[Johnny_]

Bro setup an engine for me on a hyper cruiser. Break in was fine, I guess. Runs rich. Plug is darkish grey.
4 stroking most of the time: lightly at idle, just about every throttle position. It cleans up under load, then immediately 4 strokes.
Wicked vibration and crunchy rattling sound above ⅓ throttle, gets worse as throttle and speed increases.
Bro isn't helping me so here are adjustments done today.
-Check & clean carb. Lowered needle all the way.
-cleaned plug, reduced gap a tiny bit.
-using roughly 40:1 (~1.6, 1.75 to ½ gallon) after the first 2 tanks.
-chain tension seems ok

Rode around. Starts easier. 4 strokes a tad less, but still present. Vibration and rattling still present.
I'm guessing a smaller main jet is needed?
What am I missing?

Not that this is your problem, but 40:1 is kinda too lean. I believe most guys here run around 25:1.
You may need a smaller jet like you mentioned. Are you SURE your choke flap is in the OPEN position??
If you could get a video that would help.

 

[Chainlube]

When you say Lowered needle all the way, do you mean the clip is on the top of the needle?

 

[JPbaphomet]

When you say Lowered needle all the way, do you mean the clip is on the top of the needle?

Yes. I went extreme to test what would happen. It's clearly too much. It's going back to center until I figure the rest out

 

[JPbaphomet]

Not that this is your problem, but 40:1 is kinda too lean. I believe most guys here run around 25:1.
You may need a smaller jet like you mentioned. Are you SURE your choke flap is in the OPEN position??
If you could get a video that would help.

Choke is always wide open. 32:1 was smoking a ton. Been doing roughly between 32 and 40:1
I've read that anything more than 32:1 is too much oil , and have seen a lot of dudes say 40:1 for life.

 

[Johnny_]

Yes. I went extreme to test what would happen. It's clearly too much. It's going back to center until I figure the rest out

Choke is always wide open. 32:1 was smoking a ton. Been doing roughly between 32 and 40:1
I've read that anything more than 32:1 is too much oil , and have seen a lot of dudes say 40:1 for life.

Sounds like you're getting wayyy to much fuel. You may need to adjust your float level. I'm not sure how to do that, maybe research it or I know some of the guys on here know how to do it.
In your case I think it was smoking at 32:1 just cuz you're running so rich. Right now during break on my current engine I'm running 16:1, and with a well tuned carb it still actually didn't smoke a lot.
So to clarify.... you moved the clip to the TOP of the needle?

 

[DAMIEN1307]

Wicked vibration and crunchy rattling sound above ⅓ throttle, gets worse as throttle and speed increases.

I was always familiar with that wicked vibration problem on my very first bike and found out it was the front motor mount that comes with these motor kits...They are GARBAGE and waaay too many pieces putting it together creating multiple points of failure.

And that crunch sound on mine was actually the chain as the motor vibration with the stock front motor mount would allow the motor to have some movement to and fro so the chain would also be moving to and from rather than being held rigidly in place by a motor that had no movement to it...I also do not use tensioners as you will see in pic below, I merely cut the chain down to custom fit.

I made my first replacement front motor mount using a piece of rollbar off of a dune buggy in a junk yard but improved on that about 5 or 6 years ago now by making my own out of 7075 T-6 military aircraft quality aluminum...lol...lol.

I found out after the fact of making this one that a version of what I did was already available on the market...lol...lol.
Too soon old, too late smart...lol.
Notice that I removed the studs and replaced with good steel bolts...I also used not just split ring lock washers on everything but I am also a firm believer in using blue lock-tite on everything as well.

https://www.amazon.com/CDHPOWER-Sil...Stroke/dp/B01N9OP3F3/144-9432958-2976701?th=1

My motorised bike also using the Hyper beach cruiser steel frame...Has around 5,000 miles on it over 5 years time now.

 

[Gordy]

I was always familiar with that wicked vibration problem on my very first bike and found out it was the front motor mount that comes with these motor kits...They are GARBAGE and waaay too many pieces putting it together creating multiple points of failure.

And that crunch sound on mine was actually the chain as the motor vibration with the stock front motor mount would allow the motor to have some movement to and fro so the chain would also be moving to and from rather than being held rigidly in place by a motor that had no movement to it...I also do not use tensioners as you will see in pic below, I merely cut the chain down to custom fit.

I made my first replacement front motor mount using a piece of rollbar off of a dune buggy in a junk yard but improved on that about 5 or 6 years ago now by making my own out of 7075 T-6 military aircraft quality aluminum...lol...lol.

View attachment 227087

I found out after the fact of making this one that a version of what I did was already available on the market...lol...lol.
Too soon old, too late smart...lol.
Notice that I removed the studs and replaced with good steel bolts...I also used not just split ring lock washers on everything but I am also a firm believer in using blue lock-tite on everything as well.

https://www.amazon.com/CDHPOWER-Sil...Stroke/dp/B01N9OP3F3/144-9432958-2976701?th=1

View attachment 227089

My motorised bike also using the Hyper beach cruiser steel frame...Has around 5,000 miles on it over 5 years time now.

View attachment 227091

I'm in the middle of reworking mine. I'll get some pictures when I'm done