80cc swapped to another bike now breaks up

kapicarules

New Member
Feb 27, 2017
7
0
0
Illinois
Recently I swapped over the engine (80c 2 stroke sat for 3-4 months) to another bike. Once I got the bike running it ran good when the engine is cold (all the way to 30 mph/maximum rpm which is the highest I got it to go) but once it warms up the engine breaks up and has no power at higher speeds and only tops out at 23 mph (its only running at about 1/2-2/3 of its maximum rpm). I cleaned the carburetor and cleaned the oil fouling from the spark plug (don't have another one on hand). Bike is fine at lower rpms.
 

crassius

Well-Known Member
Sep 30, 2012
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USA
first thing to check would be vibration at motor mounts, but I've often struggled with motors that sit a long time - they will often come back to decent running after being run for a while, but occasionally they will remain under-powered - not sure if it is seals hardening or case gasket deteriorating or what, but problem isn't obvious
 

kapicarules

New Member
Feb 27, 2017
7
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Illinois
It's not the engine falling apart I'm saying it runs bad at higher rpms. He will run it for awhile and pray it smooths out. If not then It's got to be something's I haven't checked. I haven't check the ignition and the compression is good
 

crassius

Well-Known Member
Sep 30, 2012
4,032
156
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USA
zip-ties could cause exactly the kind of vibs to make it run badly - bolt a flat plate & u-bolt to it
 

kapicarules

New Member
Feb 27, 2017
7
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Illinois
I will have to secure it down more but why is the engine not affected by the vibrations when you start it up in the morning?? And i will do some research And make my own front motor mount on it with some metal or wood
 

Kartooo

Member
Nov 18, 2016
178
3
18
MA
HOLY CRAP !!
zip ties are dangerous to mount an engine.
the vibration could be causing your fuel to foam and go lean.
looks like an aluminum bike, i would never trust an aluminum bike for a gas engine build.
 

kapicarules

New Member
Feb 27, 2017
7
0
0
Illinois
Ok I never knew that fuel can foam up And Lean the engine out. I used an aluminum bike too as I had the motor before him. That could be my problem the whole freaking time. When the fuel has no air (sitting overnight) it runs fine, after warming up it runs like it's starved for fuel aka the engine breaking up issue that its having. I will tell him that right now