my bike is loosing power and shaking

[toast]

i'm new to motorized bikes so don't judge me to harshly. This is also my first build. im in the process of breaking in a new bike. I used the "ride it like you stole it method". everything was going well up until yesterday. the bike used to shake at 30 miles an hour. then for some reason I was loosing power and it wouldn't go above 27 and it didn't shake. Then I let the engine cool and it wouldn't go above 26. Today I took it out for a spin and it started shaking at 23 mph. I tried a new sparkplug and that didnt help. I put a new gasket on the muffler also. Another problem that started is when it is idleing, sometimes it goes crazy and the rpm's shoot to the moon so high that I have to use the kill switch to stop it. Sometimes messing with the idle pin helps, but not always. I also checked to see if I had oil coming out of the head gasket, and I don't.
have anybody ever heard of these issues before?

 

[Bikeguy Joe]

Sounds like an intake or seal leak. Look at both.

 

[Bikeguy Joe]

What color is the plug (old one)? Can you post a pic? An air leak will make it run lean and ruin the party pretty fast.

 

[toast]

checking gaskets and seals. thanks!

 

[Bikeguy Joe]

Check where the carb mounts on the manifold as well. I've had to seal that with an o ring before.

 

[toast]

come to think of it, I didn't have any problems until I pulled the carb off the manifold.

 

[Bikeguy Joe]

I have had them crack there at the carb/manifold joint.

 

[mapbike]

come to think of it, I didn't have any problems until I pulled the carb off the manifold.

Bingo...!!!

The inconsistent and racing idle is a good indicator that the engine is pulling air in from somewhere other than through the carb.

Something that concerns me about the power and speed dropping more and more every time you ride it as you described, is that I'm hoping you haven't rode it " like you stole it " so much that you have hurt the engine and its now lost enough compression from the increased heat on piston and rings that you will need to lightly hone cylinder and and put a new set of rings on piston so that you can recover te possible lost compression.

A lean condition (Out of balance air to fuel ratio/to much air compared to the fuel the carb is metering to the engine) this conditiin super heats the combustion chamber of an engine and can "burn it up"

The piston rings can get so hot that they lose there correct tension against cylinder wall and this will cause a compression loss which causes power to drop of course.

if its an air leak between carb and intake tube, thats a simple fix with a thin skim of RTV silicone in my experience.


Just smear a thin layer of the silicone all the way around intake tube about 1/2" - 3/4" wide, before it sets up, just slide carb back onto tube wit fuel bowl at close to 90° pointing out toward clutch lever arm and once carb bottoms on intake, simply twist carb until its in correct position, immediately tighten clamp on carb to get it tight on intake, at least let it sit a couple hours or even better overnight and if leak was between intake and carb. that problem should be solved after using this simple method.

 

[Venice Motor Bikes]

The shaking you're experiencing may be a loose chain

 

[#motored]

Hello, I'm new. I ordered a HP carb and it wouldnt fit. So I cut the manifold to make it fit. The carb was tilting towards the engine. It would run but noticed drastic power reduction. I learned that I have to re jet it to ride right. Well i put my NT carburetor back on. It too is tilted way too much towards engine. It'll start with very high rpm. But won't accelerate. Eventually dies. Is this the result of carb being tilted?

 

[Bikeguy Joe]

Short answer- "yes".

 

[mapbike]

Hello, I'm new. I ordered a HP carb and it wouldnt fit. So I cut the manifold to make it fit. The carb was tilting towards the engine. It would run but noticed drastic power reduction. I learned that I have to re jet it to ride right. Well i put my NT carburetor back on. It too is tilted way too much towards engine. It'll start with very high rpm. But won't accelerate. Eventually dies. Is this the result of carb being tilted?

to correct this problem, just put a 16" rear wheel and tire on back of bike and then put a 29" wheel and tire on the front, that should level that carb out nicely....LOL

Just messing with you..LOL, and yes carb is way to tilted forward to ever work right.

Get a new intake for cheap and problem solved once you get jetting correct.

 

[LaughingGas]

Try flipping the intake over, the angle looks almost right if you do that from the pick