Engine Dies when weight is applied

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Shika_Usstan

New Member
Apr 25, 2009
15
0
0
Wyoming
I recently bought a Skyhawk 40cc motor (the only ones that are legal in Idaho as a cop was so nice to yell at me when riding an 66cc). I got it all set up and took it for a test drive. When the clutch is down the motor can run fine and when I'm not sitting on the bike and have the rear wheel lifted up it runs fine. But when I release the clutch while riding the motor instantly stops. It doesn't matter how fast I'm going the motor slows down and stops turning over.

Well based on previous knowledge I checked the engine head and all 4 bolts are tight and nothing is leaking out there. The Spark plug is tight and nothing is leaking out there either. Experience stands to reason is that it does not have enough compression. But even with just a 145 lb person a 40cc motor should be able to handle it. I don't know where it is losing the compression from. At first I thought it was a fuel line problem because when the throttle was pulled it would die because it would take in a lot of air but no gas. But I fixed that problem and now this one has began.

If anyone could shed some ideas on to how to fix it please let me know!:-||
 
GearNut

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
Remove the spark plug and look at the color of the electrode insulator in the center of it.
If it is white to tan then you are too lean.
If it is medium to dark brown then the air to fuel ratio is good .
If it is black then you are too rich.
If it is shiny drippy wet then you are waaay too rich.
FWIW, these engines need to be on the rich side (dark brown) as the only oil they get is the oil you mix with the gas. Too lean and they will not get much oil, shortening their life.
A good example of the correct dark brown is chocolate brown.
 
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Shika_Usstan

New Member
Apr 25, 2009
15
0
0
Wyoming
I found out that the engine was getting flooded. What would cause that? It isn't because I pulled the throttle because it gets flooded as I ride. Thats why it keeps dieing when weight is applied. Would the reason why it is flooding be because the piston rings are not tight? Or because they are broken?
 
GearNut

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
Piston rings will have absolutely nothing to do with flooding, my friend.
Flooding is caused by dirt or crud getting stuck up in the internal float valve of the carburetor or the fuel level inside the float bowl is set too high.
When these carburetors are made, the factory does not pay good attention to the float height setting. They just slap the parts together and send them down the assembly line.
(Quality control... Bwahahaha!!! Wut?)
It is a very good idea to use a quality in line fuel filter between the fuel tank and carburetor to help prevent dirt and crud from getting in there in the first place.

Here is a link to Norm's tutorial on how to take good care of your carburetor.
http://motorbicycling.com/f39/motorized-bicycle-carburetor-install-rebuild-302.html

Good luck, and enjoy learning a little bit about your new engine!
 
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Shika_Usstan

New Member
Apr 25, 2009
15
0
0
Wyoming
Alright, I believe I got it working. I decided that the fuel to air ratio was to much air. The flooding of the motor was because there was to much air and so the gas just dribbled away into the motor. I took apart the Carb and cleaned it off (Didn't help much because nothing was there. . . brand new) Adjusted the float level all the way back up, and Adjusted the clip on the needle to the middle one.

Then I made sure the motor was tight on the frame. . . Which is wasn't completely tight. So once I tightened it up and got the carb back together it started to run. . .

Boy that was easy. . .
 
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