Engine bogging down and backfiring.
 

So here is my situation, I tried to fix and start using my buggy again several months ago. The problem I had was a bad cdi. I replaced it, and the engine ran like it was new for probably 25- 30 minutes of riding. The engine then started bogging down under throttle, and backfiring on both acceleration and deceleration. The engine idled fine. I kept trying for 2 weeks, but I eventually got fed up with it, and stored it again.

Earlier this week, I thought I might give it another go. I replaced the carburetor and intake manifold. The engine started fine, and yet again ran flawlessly. I drove it for around 20 minutes, and then it started acting up again. It slowly started bogging down more and more, and also backfiring.

At this point I am very confused, because if it sits for a few months it seems to run fine for a few minutes then start having issues. I find it crazy that it will run perfect, then all of the sudden start acting up. Does anyone have a diagnosis?

Cheers!

If you have the old carb that came off it, check to see if the jets are the same size in the new carb. Assuming you got the same size carb.

I assume it ran fine with the old carb before it sat for a long time and got gunked up?

Same size everything in the new carb. The old carb ran fine, i was just tieing up loose ends by replacing it.

Check your electrical connections and wiring. You got something that's causing resistance as the motor warms up. The backfiring tells me you got a failure in the ignition circuit somewhere. I'd start with the plug wire then back up through the coil. When was the last time you put in a fresh spark plug? Worn sparks plugs will fail when they get hot.

I have a new plug coming tomorrow, but the one in there isn't that old. and the plug wire is fairly new (i got it with the CDI).

Any chance you got a partially clogged exhaust? Seen mice make nests in exhaust pipes before.

The thing that I find confusing is that it runs fine for 20 or thirty minutes. But it doesn't seem like it is something warming up that causes the bogging/backfiring; because the next day right after start up it will still bogg down. But if it sits for a month then it runs fine for another 20 minutes.

It's haunted.lol

could be a bad coil/wire. a lot of times they don't act up until they start getting warm/hot. Sometimes they come bad right out of the box.

sounds like a gas delivery problem to me. maybe float sticking and running out. even with a new carb. maybe a fuel line collapsing.

Look at the fuel cap making sure it is not deformed due to ethanol in fuel. Shake the cap and you should hear the check valve rattle.