Low Power Trouble

if you lost that much power check the condition of the cylinder wall, piston and piston rings. make sure to use the same blend of fuel and octane of fuel as before. if the engine sounds like it it revving high soon after you start off then your clutch is slipping and you will need new clutch pads, replacing the carburetor will not help although i recommend a cns carb and do lots of research how to tune it you will need to buy jets and a jetting hand drill to drill out the pilot jet if needed. you will see a big power incresase if your cylinder and piston/rings are in good condition. also be sure the carb is tightly fastend to the intake, is it possible you have a bad crank seal and sucking in air through crank seals.
 
velzie already said "check for leaks" which includes crank seals, base gasket, crankcase, head gasket, spark plug cracked or not screwed on completely, intake manifold leak.
 
A few thoughts:

Have you done anything to the motor recently? Are you running stock compression? Could the carb jet be blocked? Maybe exchanging parts from the poor running motor to the better running motor will help diagnose the issue( spark plug, carb, cdi, rotator magnet). What kind of leak testing are you doing? i.e. are you spraying aerosol around the motor and listening to rev changes??? Check around the bearing seals too...

hope that leads to something.
 
and dont get me wrong jag, but the head and jug wont matter if the gasket is bad. to test if its a leak like that without any other types of tools, release your clutch to lock your rear wheel and put some body weight on your seat from your chest. slowly try pushing the bike forward, if it moves easily, you have a leak somewhere, if it doesnt, then it's probably dealing with your carb or cdi as jaguar suggested.

It doesn't move at all. The wheel stays locked.
 
the multimeter don't tell you ****
I know. I'm an electronics technician.
There is no good way to test for spark strength other than possibly greatly increasing the gap and see if the spark can jump it.
When I test the CDI I make, the plug I use has a big gap.
But I don't have a specific recommendation for you. What complicates things is that inside the engine the compression makes it harder to spark.
Until you swap out the CDI and stator coil you can't rule it out as being the culprit.
All sparks are not created equal. The stronger the spark, the better the engine runs.

I didn't notice something kind of strange with the spark (on all of the spark plugs used too). It seems like the spark isn't very bright. I'm not exactly an expert with motors so I don't know if this is normal or not. The reason I suspect something is because in one of the diagnostic videos I watched, the spark looked way more powerful. But then again, it could just be me.
 
What are you complaining about.
That's faster than my bike goes and it has just about every aftermarket and billet performance part thrown at it.

Yes, that is indeed fast. But the problem is that the bike has low power. In Pennsylvania, (the area where I live anyways) there is a lot of hills. I just want to go for a cruise without putting too much work into it. Yes, I like to pedal from time to time, but sometimes I just want to relax.

By the way, I think you might be experiencing a problem as well. Your bike should go well over that.
 
Yes, that is indeed fast

Have you thought of not being so concerned about the 40 mph number and fixing the problem by properly calibrating your bike speedo to give a more realistic and accurate top speed figure?




I think you might be experiencing a problem as well. Your bike should go well over that.

I might be more to do with the fact that my bicycle speedo is properly calibrated and i haul a little extra weight.
 
Have you thought of not being so concerned about the 40 mph number and fixing the problem by properly calibrating your bike speedo to give a more realistic and accurate top speed figure?






I might be more to do with the fact that my bicycle speedo is properly calibrated and i haul a little extra weight.

What are you talking about? I can tell it's a lot slower. I compared it with the other bike I have (same kit).
 
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