Bike motor has almost zero power, but starts.

[LMKarting]

I have a 66cc (I think) china doll motor that I bought in Q3 2023. This thing ran like an absolute dream hitting speeds of up to 66km/h bone stock sometimes I would use baffle out. I needed to change a couple things
throughout this period like CDI etc. And then it ran fine until about March 2024, where it got an air leak.I never bothered to trouble shoot this because thought it was minor, but then on a random day the thing was full air leak, went straight to limited and then blew up. This was granted as I hardly took thattt much care. The carburetor was damaged as the pressure blew back into it destroyed the cap and idle screw, making that carb unusable. Moving on.


After this about a month after, I took it all the way apart split the crank case all that to find the crank seals were majorly damaged, there ya go. i redid the top end blah bla bla. Fixed that stuff up.


Now I decided |wanted to get her back up and running. I did my tests and found that the magneto and CDI was bad(rust) the carb obviously was damaged, and the spark plug was fouled, so I fixed these, found out that
when I put it back together my magnet was backwards (rookie mistake) and then she was running a year later. I had bought as well a new HP carb off Amazon, new fuel lines and filter, and I have brand new unleaded 91 octane petrol with a 32:1 ratio of semi-synthetic 2T oil.


I took her out for a spin and she fired up and i could manage to keep her on with the clutch in, but I was revving her relatively hard, which shouldn't be necessary, and I didn't want to because I need to break it in. It was able to give me a little speed boost but couldn't keep me going on a straight, mind you I weigh 60kg.
(The video linked is the bike running in 2023 and I was a good bit younger)

Please let me know any tips as how I can get some more
power out of it. Thanks all!

 

[ImpulseRocket]

I have a 66cc (I think) china doll motor that I bought in Q3 2023. This thing ran like an absolute dream hitting speeds of up to 66km/h bone stock sometimes I would use baffle out. I needed to change a couple things
throughout this period like CDI etc. And then it ran fine until about March 2024, where it got an air leak.I never bothered to trouble shoot this because thought it was minor, but then on a random day the thing was full air leak, went straight to limited and then blew up. This was granted as I hardly took thattt much care. The carburetor was damaged as the pressure blew back into it destroyed the cap and idle screw, making that carb unusable. Moving on.


After this about a month after, I took it all the way apart split the crank case all that to find the crank seals were majorly damaged, there ya go. i redid the top end blah bla bla. Fixed that stuff up.


Now I decided |wanted to get her back up and running. I did my tests and found that the magneto and CDI was bad(rust) the carb obviously was damaged, and the spark plug was fouled, so I fixed these, found out that
when I put it back together my magnet was backwards (rookie mistake) and then she was running a year later. I had bought as well a new HP carb off Amazon, new fuel lines and filter, and I have brand new unleaded 91 octane petrol with a 32:1 ratio of semi-synthetic 2T oil.


I took her out for a spin and she fired up and i could manage to keep her on with the clutch in, but I was revving her relatively hard, which shouldn't be necessary, and I didn't want to because I need to break it in. It was able to give me a little speed boost but couldn't keep me going on a straight, mind you I weigh 60kg.
(The video linked is the bike running in 2023 and I was a good bit younger)

Please let me know any tips as how I can get some more
power out of it. Thanks all!

Get rid of that HP carb. It's a cheap Dellorto clone, and they are nothing but a nightmare that are almost impossible to get to run right for both low and high speed situations. Usually you can only get one or the other good. Sometimes neither.

Get a Bofeng carb. It's basically a much improved version of the older NT carb, with all of the design flaws more or less eliminated. Thicker casting, no fuel tickler to leak, etc. The JRL brand Bofeng is a good one, and we can buy them here in the States for $12 through Amazon. This is the one in question just for reference. https://www.amazon.com/JRL-Carburetor-Stroke-Motorized-Bicycle/dp/B08N9WYS1V/ref=sr_1_2?crid=DQNRQP1UV013&dib=eyJ2IjoiMSJ9._8XlbZcMSSpLOnI2FzAJZkzMnvQ46E8FvefzC1khLw4uuXIHDZ3M2e-WarL1gXx3eejfrytLkD6VvS-y8yYv1DMEDg7iet1vKCIZ6BzXXsEg-xkbJRaA0p2OexT_ScROidgGsj0KsshvgSekTx_20BteBBZGifMav0PBxsKLEafRrmST5JnK-nLlnvwu-Vod0Cq-a1-9kTFXeccjHjgZQYXtGw6lAGuaqNlVLgOt56pijK0f581Mi4HyjEyGT6DCAXLKi9XA2WpFKpojzTT1FLaVl32WvHinyq3p6hW8vGE.PCSXJ7gWBTbmEW2koONXysywlyWP6pqszsN8H5sF-NI&dib_tag=se&keywords=bofeng+carburetor+motorized+bicycle&qid=1744103350&sprefix=Bofeng,aps,188&sr=8-2

The Bofeng is the carb that most of the "higher end" engine kits come with as standard now, and it's a good enough carb to support engines like the Phantom and Avenger enignes, both 85cc and making 5 and 4 horsepower respectively.

 

[LMKarting]

Thanks for the tips. My kit came with a Bofeng carb same as they all do, but when my throttle got stuck, it blew apart the carb, including the idle screw and throttle housing and it's having some troubles idling in general the whole bike. I did try the Bofeng a couple hours ago but it still has low power and I don't know what I'm doing wrong.

 

[ImpulseRocket]

Thanks for the tips. My kit came with a Bofeng carb same as they all do, but when my throttle got stuck, it blew apart the carb, including the idle screw and throttle housing and it's having some troubles idling in general the whole bike. I did try the Bofeng a couple hours ago but it still has low power and I don't know what I'm doing wrong.

Then I would be curious to know what the compression of the engine is.

 

[LMKarting]

I don't quite know how I can easily test compression. By best idea for you is that I can not spin the wheel without sitting on it, I can't move the bike from a stand still without clutch, but above 8kmh with pedalling I can turn it over a few times. Any tips on how to tune the idle screw on the carb? I forgot how and I know it's kind of a thing u need to feel for but still would like to know a good idea.

 

[Johnny_]

I don't quite know how I can easily test compression. By best idea for you is that I can not spin the wheel without sitting on it, I can't move the bike from a stand still without clutch, but above 8kmh with pedalling I can turn it over a few times. Any tips on how to tune the idle screw on the carb? I forgot how and I know it's kind of a thing u need to feel for but still would like to know a good idea.

Maybe this video has something on it.


View: https://www.youtube.com/watch?v=hkbaixHwPyI

 

[DAMIEN1307]

Maybe this video has something on it.

It's direct from Bikeberry, they will publish anything to get you to buy their products no matter how bad they are known to be.

HP carburetors are pure crap on our bikes.

The only thing a bikeberry video has with "something on it" is when they are about to relieve you of your wallet for some other piece of garbage add on product...The ONLY thing I ever will buy from bikeberry is the 3 spoke mag wheels, they are made by STAR mags and have stood the test of time and miles with me already.

 

[Johnny_]

It's direct from Bikeberry, they will publish anything to get you to buy their products no matter how bad they are known to be.

HP carburetors are pure crap on our bikes.

The only thing a bikeberry video has with "something on it" is when they are about to relieve you of your wallet for some other piece of garbage add on product...The ONLY thing I ever will buy from bikeberry is the 3 spoke mag wheels, they are made by STAR mags and have stood the test of time and miles with me already.

WELL HE ALREADY HAS THE CARB and since they sell it PERHAPS they know how to tune it.

 

[DAMIEN1307]

since they sell it PERHAPS they know how to tune it.

I have heard that song sung many, many, times on this forums since I joined it almost 5 years ago...lol...lol.

The bikeberry song still has all them off tune notes to it, be patient, he will be back to tell you he can't tune it even with the bikeberry instruction video and it still will not work right...Same old song once again...lol...lol.

 

[LMKarting]

I was gonna say that the video was pretty informative and I ordered a set of jets from 52 -70 so I'll give the #65 a shot. I don't have the HP carb from bike berry I got it from Amazon. Hopefully it works!