Loss of power all speeds

Richluhring · Jun 13, 2014

help, my new 66cc motorized bike has lost its power, i just ran my second tank of gas through and ran out. when i added more fuel and started it my power was all gone. i have replaced the plug, fuel/oil, cleaned carb, new fuel filter, replaced exahust, cleaned air cleaner and still absolutleyt no power. oh i even checked the float settings.. any ideas, could it be my reed valve malfuntioning? i have spent hours trying to figure this out.there are no vac leaks and it idles fine..just no power from bottom to top..only goes 10 to 15 mph if i am lucky. if i choke it it dies..im ready to pull my hair out..im a diesel mechanic and have verry little two stroke repair experience. but i do understand the workings of the motor..i also checked the head and jug gaskets. seems to be no leaks anywhere. it does sound strange and it is 4 stroking i belive but float levelis fine and its not straving for fuel i dont think.. it starts and idles fine...please help

maniac57 · Jun 13, 2014

Check for signs of debris in the cylinder, pull the head if you're not sure.

Check for some tiny debris plugging your main jet (The hole in the hexagonal post inside carb float bowl)
I'd check the carb first and go from there. You can pull the intake and look at the side of the piston through the port. The gasket is reuseable if you're careful, and easy to make a new one if you're not careful.

Richluhring · Jun 14, 2014

thank you for your reply, i have removed and cleaned that heagonal float post valve, no debris in carb. i will pull the head next. i have not looked at that yet. but will do

Richluhring · Jun 14, 2014

checked head and intake into jug..no debri anywhere...still no power.. starts and idles fine...doe anyone know where the stock reed valve is located? could this be the problem?

maniac57 · Jun 14, 2014

No reed valve. Piston port engine. If there is no engine damage, check for some kind of restriction somewhere, clogged exhaust or clogged air filter, clogged fuel valve or in tank screen, clogged jet.
Does the carb slide open all the way? Take off the air cleaner to check.
Try it with no muffler (JUST to start it! DON'T ride it far like this!)
Try another CDI and/or engine coil if you can find known working units.
Try a different sparkplug.
Check for oil or grease inside case (blown seals)
If it sat for long, the jet could be clogged with crap gas debris. Don't have to be plugged completely to cause problems.

2door · Jun 14, 2014

Look at the obvious things. Does the bike roll freely with the clutch disengaged? Brakes not dragging? Wheel bearings free, lubricated and adjusted?

What rear sprocket size, rider weight, terrain? What carburetor?

What fuel to oil ratio? If you're using the kit recommended 16:1 that's too much oil. Try it at 24 or better yet, 32:1.

Tom

crassius · Jun 14, 2014

I'm thinking seals or loose case bolts.

KCvale · Jun 14, 2014

2door said:
Look at the obvious things. Does the bike roll freely with the clutch disengaged? Brakes not dragging? Wheel bearings free, lubricated and adjusted?

What rear sprocket size, rider weight, terrain? What carburetor?

What fuel to oil ratio? If you're using the kit recommended 16:1 that's too much oil. Try it at 24 or better yet, 32:1.

Tom

Got to agree with Tom, sometimes it's just the bike itself.
If it don't roll free slow it sure won't trying to go fast.

If the bike rolls free an easy check is remove your air cleaner and exhaust and try it.

Another easy check is when you get back from a test ride use a torgue wrench and do your head bolts to 20#, that is over spec but perfect for these 66cc engines.

Last and worst is you may have a blown bearing seal.
Now a harp seal may like a blow job, these engines don't ;-}

CTripps · Jun 14, 2014

Hmm... just ran your second tank through gives me the thought of checking your exhaust.. if you were running a heavy mix through then there's a good chance you'll have some oily gunk/deposits built up inside the muffler. Pull it, and spray some brake cleaner into the pipe (hold the muffler over a jar of kitty litter, or a stubborn weed you want rid of) as the black gunk will dribble out the end.. do so from both ends, then bolt it back on when it stops dribbling black gunk everywhere.

KCvale · Jun 14, 2014

Just got the post that seems to have been deleted now about Tom.
Nice to see that kind of crap don't stick around long.
Well done site staff.

Richluhring · Jun 15, 2014

okay, i have taken the head off and checked for damage, the intake to, carbs clean, gas is new, cdi is replaced.still no power..this motor is new and just broke in. my old 66 cc had way more power and this one was fine until i ran out of fuel and refilled it. i added washers to head and re tourqed. checked case and jug for leaks, no leaks..idles fine just wont break 10mph now

Richluhring · Jun 15, 2014

oh exhaust has been checked and replaced for good measure

KCvale · Jun 15, 2014

Got me stumped, sorry I couldn't help.

crassius · Jun 15, 2014

before taking barrel off to check for blockage in transfer ports, I'd clean motor very well along case seams and ride it a lot - then check for seepage along seams and near seals

if it stays clean, then I once found a bit of metal flashing left by the factory that had folded its way into the transfer ports until it blocked one significantly - you'd want to check for that

SuperDave · Jun 16, 2014

Everyone is missing the obvious, the fuel. It ran fine til it ran out, the only thing changed is new gas. Could be the oil mix is different(too rich), or the gasoline itself is bad or stale. Try this: drain the tank & carb. Refill tank with FRESH fuel & proper oil mix. See if that doesn't fix it.

2door · Jun 16, 2014

Hmmmm, three days and no response from the OP. I wish we knew what he's found, if anything.

I also agree with Superdave. Maybe a bad batch of fuel. It does seem obvious given his description of the problem and how it started.. Maybe it wasn't gasoline he mixed. Kerosene?

Tom

Richluhring · Jun 19, 2014

Thank you to everyone, I really appriciate all yall's advice/help. As it turns out it was bad gas. amazing that i got bad gas twice from different sources. Changed out the fuel a third time and she ran much better. Then i cut the sube that runs to the exhaust pipes end and i go alot more bottom end. I am guessing when i cut that i must have created a small bottom end power band. At any rate it takes off 30% faster and harder now.

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Loss of power all speeds

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