Whats the problem?

[sgp56]

I was riding the bike around then it just died. I checked the piston and it was blown. Got a new piston, put it in and it wont start. i pulled it aroung with a truck goin about 30 and it will start but wont stay started. It has good spark and is getting gas. What could be the problem?:confused:

[TtownJoeShow]

what happend to the piston?

[sgp56]

it was the original piston so it was old and just broke

[TtownJoeShow]

did the broken piston scar the cylander walls, is there any pieces in the cylander? could b your timming if its a 4 stroke, what was it that you were riding?

[sgp56]

its a 2 stroke and no it didnt scar the cylinder walls

[TtownJoeShow]

lol did you go wide open till it blew? if so, if its a magneto the mag could b melted too

[sgp56]

no i was in 3rd gear and i already said it gets good spark

[TtownJoeShow]

D'oH missed that, well the only other thing i can think a is something isn't tightened properly

[sgp56]

like what?

[TtownJoeShow]

head, cyl, reed cage, carb boot, sparkplug

[sgp56]

took the reed cage aprt yesterday and reinstalled it spakplug is good. could the head or clyinder be to loose?

[84honda200s]

yea it could be. did you deglaze the walls? if not sometimes that will cause it not to start/run rite. but i would check the head and make sure its on tight.

[jason 32]

?? bad crank seals??
what did it run like???
did you get all of the piston pieces out of the motor and the exhaust pipe??
check the fuel line

[atctim]

it was the original piston so it was old and just broke
:lol: LOL

"Petey died"
"What happened to him?"
"His head fell off - he was pretty old though"

There is a reason that the piston "broke" other than just age. Did you have the cylinder checked for round and see if it was in spec? What exactly did the cylinder walls look like. I think if you piston broke you need to have it professionally inspected - honed / bored and the correct piston then put back in it. What about the rings??? are they new??? So much is needed here to diagnose your problem. Give us more info......

[sgp56]

This isn't my bike its a friends so i didnt put the piston in he took it somewhere and got it done. they said the cylinder was fine but it dosent really feel like it gots a lot of compression. The place that put it in said thats all the compression its supposed to have. I can move the kickstarter down really easy. I can do it with a finger but i can feel when its in TDC. should it have more compression?

[SYKO]

sounz like they over bored it, and the crank case could be wet sumped with gas, tell him to take it back to them.

[atctim]

Yeah - if he had "someone" do it, shouldn't they stand behind it??? Sounds like they didn't know what they were doing.

[sgp56]

they didnt bore it just put in new piston

[sgp56]

how can a crankcase be wet sumped with gas? would that cause it not to start?

[RedRider_AK]

Pistons don't "just break", you usually have to try to screw them up for a while to get them to do that...

[TravEX]

Sounds like a Mongolian CF to me!

[InPiEcEs]

First thing I would do is hook up a compression guage. I would say it should be at least 120 lbs and more, depending on the machine.With a fresh top-end, it should have some good resistance on the kicker.
You said you can roll it with your finger. That ain't good. I am willing to bet that it needs a bore and an oversize piston. Maybe it just needs a honing so the rings seat to the cylinder.
Bring the jug/piston to a GOOD motorcycle/ATV shop and have them take a look.
If they tell you that it needs a bore, I would be making a call or two to the other guy who looked at it.
As long as you got all new gaskets, and installed and torqued them properly, you should not have a problem with compression with a new piston/rings.. Sounds like whoever inspected the cylinder and put a new piston in just did a quicky, no give a care job on ya.