I have a YS 140 FZ. The engine has no compression due to the valves being stuck. How do I free up the valves without tearing the engine apart?

Orlando

Take off the valve cover and put a little fuel on the rockers, valves and down the pushrod tubes to the lifters. Remove the glo plug and after soaking for a bit try gently pushing down on the rocker and see if the valve moves freely and returns to tighten up on the push rod. If the valve moves freely you may have a sticky lifter. Rock the crankshaft a bit and see if either rocker or valve is moving. The fuel you put down the push rod tube will help to dissolve any residue that is sticking the lifter but you may have to help it out here. Use your finger to put pressure on the push rod end of the rocker and move the crankshaft. You may be able to coax the lifter to move and follow the camshaft lobe. Take your time and use more fuel as needed. If this doesn't free up your lifter then you may have to do some disassembly and clean the residue on the lifter.

Dennis

All good suggestions. I would pull the valve cover and glow plug and soak the engine in raw fuel bath overnight. then exercise the crank and push on the valves to see if they will free up. It is most likely gummed up from varnish.

Sometimes a little heat from a heat gun will help to soften the gunk sticking the valves or what ever is stuck. Heat is especially helpful if the gunk is castor residue. Soaking in fuel is a first though as that will dissolve and lubricate. I have also used WD40 as the carrier is a pretty good solvent. Follow up with good oil as WD40 is a very poor lubricant. Good Luck on your fix.

Ken

Had exactly the same issue with a 110S that sat around for 3 years.

Did the following
1. Opened valve cover carefully to preserve gasket
2. Heat gun to blow the rocker arms. One got loosened up, the other did not.
3. Poured some isopropyl alcohol (or fuel would do too) over the arm that was still tight. Got it loosened it up slightly. More heat gun and more alcohol. Did the trick.
4. Valve still stuck.
5. Unscrewed the rocket arm and detached.
6. Poured alcohol into the valve holes. Soaked for awhile. Tapped the valves lightly with rubber handle of screw driver. Pushed the valves down using thumb. Not loosened yet.
7. Poured away the pool of alcohol in the valve holes. More heat gun.
8. Repeated steps 6 and 7 two times and got both the valves to dislodge
9. Lubed up the valves and rocker arms with Marvel Mystery oil. Fuel would do too.

I chose not to use WD40. If no choice but to use WD40, i would rinse with isopropyl alcohol. But that is me....

Gcflies

All good suggestions.
I have already loosened up the valves. Used similar recommendations as to the above. All seems to be working OK.

Thanks for all the recemmendations.

Orlando (AKA Crashlander)