80cc Bike bogging at higher RPMs

[Vincenzo Luciano Contessa]

Hello, I'm kinda new to this scene of motorized bicycles. But not to mechanics. I bought my 80cc kit about a moth ago. I'm on my 6th tank. The oil fuel ratio was at 10:1 for break in for the first two tanks and then the last two I used 16:1. Wanted to make sure it was well lubricated for break in. Now I've been using 20:1. I ride the bike 3.5 miles to work almost everyday. Have no problems until this morning going to work. I noticed the bike didn't want to go fast. It's topped out at 25mph. But now won't go pass 18mph. It's also not redlining. Once it gets to a high RPM it bogs and there is this raddling noise. Then it repeats over and over. I held the clutch in and gave it full throttle and the engine would peak and drop rapidly over and over again. Wouldn't stay redlining. Leads me to think it's a internal issue or something I'm not familiar with. Give me a hand guys?

 

[Deleted member 12676]

you'd better take the head and cylinder off and make sure everything is mechanically sound.
check for movement at the rod bearings and that the rings and piston are intact.
you should plane the head surface flat for a good seal.
make sure there are no air leaks.

 

[Vincenzo Luciano Contessa]

Took them off. The piston has a lot of carbon on it. Currently cleaning it off. The rings where fine. I'll take a picture. The rod has a slight wobble to it too.

 

[crassius]

in my opinion, you've been running too rich on oil if you're in the U.S. - gas and kits we get here, usually work well at 16:1 for first tank or two, then 32:1 thereafter

you may have fouled the spark plug, or clogged the muffler - riding only short trips will cause that also - change spark plug and loosen muffler just a bit to test (do not run motor long with muffler loose)

if that doesn't help, then check motor mounts and frame to see if that's where rattle comes from as this will also make it run poorly

edit: you added a pic while I was typing - looks like rubber in your mount that may be the cause of this - piston doesn't look all that bad

 

[Vincenzo Luciano Contessa]

I'm using royal purple 2 stroke synthetic oil. Maybe I should change the ratio.

 

[Vincenzo Luciano Contessa]

I added electrical tape and cardboard to the lower U bracket because it wasn't clearing. It would touch the engine before I started putting the washer and bolts on. The engine is perfectly sound. It's not wobbling at all. Fully secure.

 

[Deleted member 12676]

use it at 25:1 if it's semi-synthetic or 30:1 if it's full synthetic

 

[Deleted member 12676]

could be your chain hitting the frame or the engine cases

 

[Vincenzo Luciano Contessa]

After I clean it up I'll test it out. Could be the carbon build up. I cleaned the spark plug too so after I finish the piston I'll put it back together. Here's the bottle.

 

[Vincenzo Luciano Contessa]

I cleaned and reassembled it. Looks like the chain has kinks in it. It seems to redline now. So I'm going to change the spark plug, get a CNC sprocket assembly, and a new chain. Thanks for the tips guys. Helped a lot.