Engine still VERY slow and boggy after new carb and plug

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mastafoo

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Ever since I finished my bike I was amazed at how much power it had, I never took it to full throttle because it would probably break something. Now, the amount of power it has is ridiculously low. It very slowly accelerates to 10-15mph with the throttle wide open, and makes a strange boggy sound when I go full throttle. Before this problem, I could just slightly twist the throttle to achieve this speed. Fuel also comes out of the air intake, I can see the back of my bike is wet after rides. No oil is leaking, however. I installed a new carburetor, and the engine showed no changes in performance. I installed a new spark plug, and again it behaves exactly the same. I observed that before I had this issue, the gases coming out of the exhaust had more of a "punch", like little explosions even when idling. Now they are very weak. I flushed the exhaust with gasoline to clean out as much sludge as I could, but there is no improvement in performance. I remember leaving the petcock open a few times for a number of days and when I got back there was oil dripping out. I would start the bike and it would smoke but then get better and return to normal. My fuel is 32:1 and is relatively fresh. Anyone have any ideas on what is causing this?
 
If changing carby didn't help sounds like something going on around intake manni maybe. Have you checked to be sure it is unobstructed, tight to cylinder? Fuel mixture coming out air-intake sounds like backpressure.

Scotty
 
Also, maybe try taking muffler off and running for just a quick test unless you have a spare(good) one laying around. Sorry for the double post but I just thought about a process of elimination.
 
i recently had this issue and i found that if you move the needle in the carby it will yield results. take the top off the carb, remove the cable from the sleeve then remove the needle (don't lose the "c" washer ya need that. then there is a black clip on the needle, towards the short end is less fuel and towards the long end is more fuel. mind the carbon buildup on the piston head tho.
 
When the engine in my Hawthorne had fuel dripping out of the exhaust, I had to adjust the float level in the carburetor to a lower setting. It was too high and would not turn off the gas flow like it should. This condition caused fuel to pour out of the needle jet inside the carburetor throat, and into the engine, and out of the air cleaner. There is no way the carburetor can properly meter the fuel when the float level is too high.
The fuel eventually filled up the flywheel cavity inside the crankcase. The flywheels were "drowning" in fuel.
I had to blow out the fuel inside the crankcase with compressed air. It took about 2 minutes to get it all out.
 
Yeah well I checked the plug and it's black and oily. I don't unscrew it when the engine is hot but wait a few hours. Anyways, I'll try to figure out how to adjust the needle and see if that works, maybe the new carb is messed up as well. As for carbon on the piston/inside the combustion chamber its been only 200 miles, and If I do take off the head to clean carbon out will that ruin any seals or do damamge? Also, I'm trying to take apart my exhaust but the series of discs inside it won't come out. There could be blockage causing the backpressure, so I'll have to somehow pull it all apart.
I don't have any spare exhaust pipes and I think running the motor without one might not be a good idea. Gotta love these happy time clunkers...
 
Removing the cylinder head will require a new head gasket in order to guarantee proper sealing. In a pinch, you can anneal the old one with a propane torch or electric stove to soften and re-use it. Rub bar soap on it and get a good layer evenly on it. Heat the gasket untill the soap turns black, then remove it from the heat source and let it air cool. Being carefull to not bend the gasket, lay the gasket on a hard, flat surface and wipe the bar soap residue off as well as you can and your are done.
This in no way guarantees that it will re seal, but it will give you the best chance possible.

Excessive exhaust back pressure will cause poor operation for sure. Unfortunately I have not disassembled your style of muffler, so I am not of any help there.

The descriptions you have given towards gas residue on the rear of the bike, and excessive fuel dripping out of the muffler are classic symptoms of a float set too high.
Gently bend the float lever arms down, away from the carburetor body just a little bit at a time, perhaps 1/16 of an inch. It is better to sneak up to the proper setting by adjusting it a few times rather that bend it too much the first time and cause a lean condition in the carburetor. A lean condition can easily cause severe damage rather quickly.
Good luck, and have patience. I have a feeling you will need it!
 
Good news, I removed the muffler to rule out the backpressure theory and it turns out the bike performs like a beast without it. By that I mean better than it has ever before. Of course it is very loud and I've read that it is not good for the bike to run without one. So I guess the only thing I need to do do now is somehow dismantle and clean my pipe. That's much easier said than done. I've tried flushing it with gas twice, and a good deal of black sludge came out. The bike still performs the same, however, so there may be some solid carbon deposits that aren't dissolved by the gas and must be manually removed.
I also bent my float lever slightly before removing the exhaust, which didn't have any noticeable effect. Still, I would like to know how to distinguish between a lean and a rich condition to prevent any damage.
- nick
 
A rich condition will blacken the sparkplug with a wet, oily residue, and make the engine run sluggish at high engine speed. It will usually start easily without the choke engaged.
A lean condition will have the sparkplug color white, possibly silvery white.
Silvery white is very bad at the silver is actually aluminum deposited from the piston top. The engine will run very well at lower speeds, but surge at high speeds. Also you will notice that the engine runs very hot.
A tan colored sparkplug is desired, tan to light brown.
 
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