Engine Trouble Engine only works under heavy load

MotorMac said:

Your engine is toast, the HT engines are mostly not worth fixing if it involves major worn internal engine parts. Just get a new engine kit.

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You think I should get a $100 engine instead of a $6 bearing? That makes no sense.

From what you were describing about your engine I think there is more internal damage, you said the piston was wobbly that could indicate damage to the rings and cylinder wall, as well as your bearing.
If you have the time to fix it then that's ok.
To
me it would not be worth it.

MotorMac said:

From what you were describing about your engine I think there is more internal damage, you said the piston was wobbly that could indicate damage to the rings and cylinder wall, as well as your bearing.
If you have the time to fix it then that's ok.
To
me it would not be worth it.

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I agree.

save your time and money. get a new motor. the bearing broke in half. you found half in the crankcase, im assuming.

metal debris through the inside of an engine?

by the time you replace your piston and rings, and the bearing, wristpin, all that... your halfway to a new engine and more than likely stray debris from that bearing cage is going to find its way into places its not meant to be...then youll be back at square one with even more problems than you just fixed...


if you hit the wrist pin with a hammer and had no backup on the piston when doing so, the conrod "could" be damaged. takes a bit to bend one, but once bent...its another issue lurking, waiting... and the bend doesnt have to be observable. ie, less than 1mm will ruin it. the two bearings have to be perfectly parallel.

new piston and pin...if its a tight fit...fine abrasive, and start lapping the hole in the piston, until its a sliding fit. any need to use pressure for installation means virtually impossible to remove later on. they should slip in with a push from the pinkie finger.

point tags on circlips in direction piston travels, not at right angles.

Thanks guys. I happen to have more time than money to fix things. So I don't mind spending a lot of time to fix something vs just replacing it.

Broken parts:
Piston rings (broke when trying to get the wrist pin out)
Wrist pin bearing

That's it. I did not find any metal inside the case. Meaning it must have been sucked out the exhaust in little shards or something.

If I get a whole new engine I'm going to have the same cheap parts inside. I'd rather take that $100 and buy quality parts for the engine I have.

You might want to look at this? http://www.ebay.com/itm/80cc-2-Stro...rcycles_Parts_Accessories&hash=item2342ed3231

crassius said:

sounds like a loose motor mount

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These posts are for real bike enthusiasts. .all u people that r as dumb as dog #**t please refrain from posting ur idiotic comments. .its just frustrating when someone like me is asking a serious question. I am a commercial boat captin I work around engines for a living. .I have found that with these motors it's all about having flow..
by the way I said that because I think the Guy would know if is motor mount was loose

Before you start buying anything-

(This assumes it doesn't start 4-stroking as it cuts out, although that would be pretty unlikely)

Take the air filter off. Blast the bike up to full speed. The moment it cuts out, reach down and give it a quick shot of QuickStart in the carb. If the bike starts pulling again when you do this, then it's official- it is leaning out. (Yes, it is possible for it to be leaning out even with the black plug because since it's getting too lean to run, the blackness will never get burned off). So IF this ends up being the case, start messing with the carb (someone already mentioned engine vibrations spashing the fuel around in the bowl once it hits X rpm- try squeezing the carb with your hand to dampen the vibrations).

If the QuickStart didnt change anything (assuming the engine doesn't 4 stroke as it cuts out) then I'd go straight to the ignition and check that.

About the piston slap- I'm guessing it isn't a big deal because if you had conpression problems the engine would actually PREFER the higher rpms (less time for stuff to leak), but-

If it's just enough gap that the corner of a sheet of office paper can get down the side, then it's not a problem. If you can fit like 2-3 layers on top of eachother, THEN you might have a problem.

If the gap is big enough to actually be making your engine run any differently, then there would be scoring and aluminum rubbed all down the cylinder walls.

Taking out the piston pin-

I have no idea how one is supposed to get a big ice cube into the little piston pin cavity, i can't imagine that working too well.

Here's what I do- my vice has a little hole on one of the jaws, otherwise you can use a wood block with a hole in it.
I line the pin up with the hole, and put a little bolt up between the opposite end of the pin and the jaw of the vice. Crank the vice closed and the pin gets pushed out through that wonderful little hole.

EDIT- just saw the date, I'll leave this up incase the guy is still having this problem

I forgot to ask how is that tape doing with the temperature can't imagine it's any good

My guess is most likely a fuel problem. .what carbarator do you have on it if its the stock one I've heard that they have lots of problems. Do you have plenty of rubber between the motor mounts and ur bike frame. I used about 10 strips of old inner tube cut into one inch strips cut in half so they wrap around my frame and then e tape to frame itreally helped in reducing engine vibration. These motors tend to vibrate a lot