[strudelpoodle]

I've just removed the spark plug from my Honda F400 rotavator only to find that there's a lot of corrosion around the business end (the machine has sat in a dry shed unused for the past 30 years) and when I try to pull the pull-start cord it won't budge -feels like the piston is locked solid. 

My question is what do I do next?  Is it worth squirting penetrating oil into the cylinder and leaving it to stand for a day to see if that frees it?  If that doesn't work do I remove the cylinder head next or take it straight to the dump?

Steve

[Flatcat]

Noo whatever you do don't dump it!!!

I must say it doesn't sound good. I'd remove the cylinder head to see what's going on inside.

Damon

[lazydog]

a bit of diesel down plug hole leave for 24 hrs then try and if you can a spanner on the shaft rather than using the pull start

[richyrich7]

Nah don't give up on her. She probably just needs some tlc.
Soak her with diesel or penetrating oil for a day or two and try to rock the piston/s back and forth. Is what I'd do.
Then sit back and wait for Gwiz to reply

[strudelpoodle]

Thanks all, I'll give the diesel a try.

[Gwiz]

Diesels a good idea, so to is WD40 or the equivalent that can be bought in a bottle rather than an aerosol.
I expect that the engine stopped turning on the inlet or exhaust stroke so that either valve was open allowing damp air to penetrate the engine over time, and rust the piston rings and/or the valves/rockers.
Be very careful when trying to get the engine turning again, gentle force rather than brute strength is needed here, and as Richyrich says, a gentle backwards and forwards motion. If all goes well (depending on the level of corrosion) you won't need to do too much to get it going, but keep us informed of how you get on.

[Kleftiwallah]

Don't give up.  I bought a cylinder (sidevalve) for my vintage motorcycle.  It was in a bath of penetrating oil for 18 monthsbefore the cast iron piston finally decided to move !

The autojumble stallholder didn't know there was a piston inside the cylinder !  Bargain at £20:00.  On the overhaul this winter, I'll swop the ally piston for the cast iron job,  may reduce a bit of vibration I've got.   Cheers,   Tony.

[strudelpoodle]

a bit of diesel down plug hole leave for 24 hrs then try and if you can a spanner on the shaft rather than using the pull start

Lazydog -the shaft that I believe is the output from the engine has a pulley on it with a small nut screwed into the shaft end.  I'm loath to apply a spanner to this because I'm sure I'll just shear it off.  I agree it needs a spanner applied to get more force into my attempts to turn it over but where else can I apply it to?

[Bigbadfrankie]

a bit of diesel soaking, and it will be fine   mine went first pull oday an has been abandoned for 6 mths or more

[smud6ie]

a bit of diesel down plug hole leave for 24 hrs then try and if you can a spanner on the shaft rather than using the pull start

Lazydog -the shaft that I believe is the output from the engine has a pulley on it with a small nut screwed into the shaft end.  I'm loath to apply a spanner to this because I'm sure I'll just shear it off.  I agree it needs a spanner applied to get more force into my attempts to turn it over but where else can I apply it to?

If you use to much force before the diesel / penetrating oil has had a chance to work the more chance you have of breaking the piston rings ,softly softly and all that.

smud6ie

[strudelpoodle]

Its freed up now, thanks for the advice (diesel soak, patience and a gentle tap with a hammer on block of wood onto top of piston) -its all worked.  Just waiting on a new head gasket before I try to run it.

[strudelpoodle]

Success!  My Honda F400 is running and sounds as sweet as a nut.  Today it rotovated its first patch of ground in 30 years!