Honda dirtbike compression question

[CritterGitter]

My younger brother has a honda , i believe 70 cc dirtbike. If i had to guess its probably a 2005 model. It never got ridden hard just occasionally around the backyard . It then sat for a few years . Ran flawlessly when it ran last. Me and my dad decided we wanted to get it back up and going so we cleaned the tank out , and carb. When we went to kickstart it there was no resistance, like it had zero compression. What would cause this ? And how would we go about fixing it

 

[Blockhouse]

My younger brother has a honda , i believe 70 cc dirtbike. If i had to guess its probably a 2005 model. It never got ridden hard just occasionally around the backyard . It then sat for a few years . Ran flawlessly when it ran last. Me and my dad decided we wanted to get it back up and going so we cleaned the tank out , and carb. When we went to kickstart it there was no resistance, like it had zero compression. What would cause this ? And how would we go about fixing it

Sounds like a valve may be stuck open. Take top end off for a look as you turn it over. Maybe it seized up over the long sit.

 

[TN Song Dog]

Double check the spark plug hadn't been removed.

 

[CritterGitter]

Sounds like a valve may be stuck open. Take top end off for a look as you turn it over. Maybe it seized up over the long sit.

You think it could be freed up ?

 

[Blockhouse]

You think it could be freed up ?

If you see that the rockers are moving but the valve is stuck in an open position some wd40 on the valve stem and a light tap or nudge might do it. Those little motors are pretty bullet proof.

 

[Blockhouse]

If you see that the rockers are moving but the valve is stuck in an open position some wd40 on the valve stem and a light tap or nudge might do it. Those little motors are pretty bullet proof.

I bought a 79 xl100 years ago in a box. Put it back together and it cranked right up. Made about 5 hp - I remembered them being faster as a kid

 

[dr]

Piston rings may be stuck, preventing compression.

 

[tacoma2002]

A partially stuck valve or rings are the only things that can cause this issue if it was running well when parked.

You can put a little motor oil down in the cylinder and let it sit for a few minutes. If this raises the compression for a few "compression strokes" chances are you've got a collapsed or broken ring. If the engine was "stuck" when you first tried turning it over you could have broken a "stuck" ring causing the issue.

Id pull the 10mm valve cover bolts and take a peak at the valves as stated before. See if they're actually moving or one is stuck down a bit. If one is stuck use a good penetrating oil around the valve guides...be generous. Let it soak; repeat. Chances are you'll free it up.