Is my engine too rich or too lean? (pics + vid)

FrizzleFried

Well-Known Member
Local time
5:18 AM
Joined
Jun 21, 2022
Messages
714
Location
Nampa, ID
The BoFengs come stock with the #70 jet...I am assuming your at a 3000 ft altitude thereabouts and that your needle valve C clip is at the second notch to the TOP of the needle??? If so, Move it up to the very top notch and see what happens.
One thing I have different on my BoFeng than you do is a much better, non restrictive airfilter that is a no fuss direct replacement for those stock ones...Less restriction, more air, is much better to run at altitude.


You can see it on my motor here below, I'm at 4500 ft.

Gasoline makes all the difference in the world too...I use Ethanol-Free gas which burns and powers much better than the regular gas that now has 15% ethanol.

View attachment 178010

Testing with no air-filter at all. I'm at 2200 ft and run the clip one notch up with the NT (I gain about 5mph going from center to top notch)... the Bofeng doesn't seem to help. Bottom end feels a bit more torque but once I get to about 16mph .... brrrrrrrr.

I wonder if they put a bigger jet in there in error? I'm none-too-keen on the jet kits for this carb either... the best I can find are 5-size increments (though I want to say I read a 2.5/3 size increment source in here somewhere... and at this point it seems (to me) like throwing good money after bad at a problem I really don't seem to have. The NT carb seems to work pretty decently... and do I really want to "chase" that 1mph gain? :D
 

FrizzleFried

Well-Known Member
Local time
5:18 AM
Joined
Jun 21, 2022
Messages
714
Location
Nampa, ID
Oh, and this motor hasn't seen anything other than 91 octane ethanol free fuel. I won't put ethanol tainted fuel in any of my small engines (generator, lawn mower, weed eater, now bike motor)...
 

FrizzleFried

Well-Known Member
Local time
5:18 AM
Joined
Jun 21, 2022
Messages
714
Location
Nampa, ID
the Bofeng doesn't seem to help. Bottom end feels a bit more torque but once I get to about 16mph .... brrrrrrrr.

Running 1 notch up did not do anything to rectify the 4-stroking issue. I want to say it "felt" a little zippier at low end... but the 4-stroking remained.
 

FrizzleFried

Well-Known Member
Local time
5:18 AM
Joined
Jun 21, 2022
Messages
714
Location
Nampa, ID
My apologies... I wasn't quite getting where the confusion was. 1 notch up from stock 'center'. I even tried 2 notches up (top) but that was worse.
 

DAMIEN1307

Moderator
Staff member
Local time
5:18 AM
Joined
Jul 23, 2020
Messages
5,620
Location
Alamogordo, NM, USA
And your sure that you have the barrel slide the needle valve rests in, is installed in the top of the carburetor properly???

The side of the barrel with the "slit" going the entire length of it is on the side with the fuel inlet, there is a little nub inside the slide compartment that the groove/slit must be in as it slides up and down...And on the other side, there is a little inverted step that the idle screw sets into...It must be assembled this way only.
 

FrizzleFried

Well-Known Member
Local time
5:18 AM
Joined
Jun 21, 2022
Messages
714
Location
Nampa, ID
Yup. If you remember, I had this same result originally... after reading about how if you get the c-clip screwed up it can create a rich condition I re-visited the carb. I made sure that the c-clip was right... and that everything was installed correctly... and I got the same exact result as prior.

I simply get much better results with the "asian language embossed" carb that was sold to me as a speed carb with a larger jet (I am running on the assumption it has a 72 in it).
 
Top