Sudden loss of power.

Gregory Neighbors

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Feb 27, 2018
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Ok, here's the run down and I apologize in advance for being long winded. My muffler pipe snapped and I got a flat within a week of each other. Needless to say, I had to park it while I waited for payday to arrive. I ordered a new muffler, new intake (not much room to do maintenance on the carb) bucking bar (I dropped and lost the original, please don't judge me), new rear tire with a smaller outer diameter than the factory tire, and a new chain tensioner pulley.
After reassembling everything and going for a maintenance ride, I discovered that I am only getting about half of the power and speed that I got previously. I did adjust the engine angle also to get the carb to set level, since the extended intake has an odd angle to it.
I have checked and found a vacuum leak where the intake mates to the engine head. Could this be the entire problem? or could the change in mounting angle also play into my massive reduction in power?
This is my first build (and like a moron I bought the cheapest engine available on amazon), it was listed as a british built engine, but after receiving it, I learned that it is a Chinese engine. The seller hasn't replied to email and Amazon isn't helping much either. I'm not even sure if it the 80 cc that it was sold as. I have it mounted to a Huffy Nel Lusso.
 

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Just check my bike computer new record speed 35.4 MPH this morning so Im doing something right can still jiggle a couple things try for 40 MPH.
 
your CDI unit cracked because you used the metal strap and screws to mount it - better kits these days just give you some zipties to mount it with to avoid cracking the plastic from vibration - shouldn't cause a power loss until some water leaks in there and makes it completely dead (or a foggy morning)

an air leak could cause a loss of power, but is usually associated with a very high idle or a motor that will not return to idle after throttle is released

my first guess would be that your head gasket is leaking a bit and needs to be torqued down (this often needs to be done several times during run in)
 
I took it for a short run a little while ago, air filter is clean and tire pressure is good. There does appear to be a gap at the head. Tried tightening it but everything was tight and without owning a torque wrench I didn't want to over do it. I did that after it cooled down.
 
bummer, that is the most common cause - you could run it a bit with new muffler about 1/8 inch loose in case something fell into it and is blocking it a bit, check that choke isn't loose and falling about half way on, I don't see an extended intake in pic, but some bikes vibrate those too much for the carb to work right

something changed after you worked on it, so you could re-examine everything you did to see if something you did it wrong - if nothing found, then clean motor well with paper towel and gas using old butter knife to get between fins, then ride a while and check again with dry towel to see if oil stains show a leak - at this time, you should be able to check spark plug for rich/lean condition
 
I actually followed your suggestions before you made them, though I'm glad to know we are on the same page here. Muffler is clean, I actually had to tie down the choke to keep it from vibrating closed. There is significant oil leakage from around the head, so I plan to order a new gasket kit and hope that it fixes the problem. I also need to adjust my clutch some more, because it wants to die when I stop unless I throttle up a little bit.
Two strokes are new for me, I've worked on plenty of big engines but these little ones can be frustrating, lol. Thanks for the tips so far, I'll keep everyone posted.
 
waiting with abated breath

the 2 rules are:

1 don't get in a hurry

2 don't get lazy
 
Not going to do either. I want this to be running flawlessly because I'm making a cross country move 1100 miles away. I plan to ship my stuff and ride the two lanes. Thanks again for the help. I got my gasket set ordered and plan to install them, S L O W L Y when they arrive. Providing the rain stops.
 
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