Greeves 380 1973

[Dave Smith]

Hi all, as a (very) new member, I am looking forward to all the chats and friendship. My question is: my QUB sat in a Canadian paddock for the best part of 40 years so when I started stripping the engine, I find the piston is well and truly STUCK near the top of its stroke. Any ideas on how to safely get it out without ruining the bore and barrel?? Cheers

[Colin Sparrow]

Hello Dave, welcome to the GRA and to the forum.

Patience and not too much force. Assuming you've established that the crank is free to rotate, try plenty of WD40 in the bore above the piston and into the exhaust ports and leave it overnight or even longer. Try gently tapping the piston using a large diameter wooden drift. If it doesn't free, apply more WD40 and after a couple of days try again. If still no go try applying some heat - but obviously not so much that you damage the barrel.

I'm sure there will be more (and possibly better) advice coming your way, but the approach I suggest might work and won't do any harm - as long as you don't hit it too hard!

Best of luck!

[scott151]

Good advise from Colin.

However if it's really frozen..

I would strip the primary side of the bike in situ.

Then remove the engine/ gearbox assembly from the frame.

Then remove the gearbox from the motor..

Then make up a tank or a big plastic box, fill with neat diesel, drop the motor in..

Leave for a week or so..

That should free it off..

Scott

[Rob]

I was just about to suggest that Scott. We save the dieasel that gets spilt when doing fuel filter changes on the tractors and use this in an old bucket. Submerged, it is amazing what it will shift and like that, it gets into every crevice.

The most important thing is not to rush it as I learned to my cost. I had a new old stock 34A barrel with a stuck inlet stud. Like a plonker, I gave it a quick squirt, applied locknuts and a spanner and promptly snapped the end off the carb flange. I said the usual words such as 'gosh' and 'deary me' and wondered how I could have done such a stupid thing!

[Dave Smith]

stuck 380 piston

Hi guys and thanks for the advice/suggestions.
Unfortunately, I have tried all that has been suggested.
My problem is I dont know if the crank is also seized.
It has been soaking in (an expensive) can of mechanic's anti-seize goo thanks to my friends at the local garage.
I have tried the wood drift.
I think my only option is to cut out the top of the piston with a hole cutter (in a drill) and see what lies beneath????
The piston is stuffed anyway.
I will keep updated with progress...................
Cheers from downunder - the better of the two downunder countries

[Dave Smith]

380 piston

Oh, almost forgot Colin,
I did make a donation to your retirement fund by purchasing your Greeves story via Amazon.
Great resource and interesting reading.
Would recommend others buy it.
(no commission necessary )

[dave higgins]

Freeze.

Hi dave, we use a two pack product similar to freeze free, a quick spray from can one freezes the corroded item down to 45 degrees, & causes micro fractuering of the seized joint, then spray on can two which gets in & penetrates to free off.
Best product i`ve seen, does the impossible in 30 secounds.
Quite expensive, but it is league`s apart from the likes of wd40 etc.

PS the reason i say similar, is because i have forgotten the exact name of brand we use..........

[Brian Catt]

How about WD41?

[Colin Sparrow]

Dave, unless the piston is stuck at the top of the stroke you should be able to establish if the crank is locked by removing the nuts that hold the cylinder on and raising it. If the crank is free it will lift a short way, piston and all.

[Dave Smith]

Dave, unless the piston is stuck at the top of the stroke you should be able to establish if the crank is locked by removing the nuts that hold the cylinder on and raising it. If the crank is free it will lift a short way, piston and all.

Hi Colin, I undid the base nuts, but nothing happened I think partly because the piston is about 8mm from the top. My only remedy I think is to destroy the piston in situ. It will need a new piston anyway as the bore will have to be re-bored. There is metal decay in the exhaust port but I think the port bridge will be okay.. Cheers

[Dave Smith]

How about WD41?

Tried that Brian. I think the rings have rusted themselves to the bore. Also tried heating the piston and cooling it to shrink it. CHeers

[Dave Smith]

Hi dave, we use a two pack product similar to freeze free, a quick spray from can one freezes the corroded item down to 45 degrees, & causes micro fractuering of the seized joint, then spray on can two which gets in & penetrates to free off.
Best product i`ve seen, does the impossible in 30 secounds.
Quite expensive, but it is league`s apart from the likes of wd40 etc.

PS the reason i say similar, is because i have forgotten the exact name of brand we use..........

Hi Dave, using Dr Google I have found a CRC Freeze Off product in Christchurch which sounds similar?? to your suggestiong. Will try during the week. Cheers

[Dick F]

Hi Dave,
Any suggestion that Dave Higgins makes on mechanical work go with his idea, there is not a lot that he does not know about engines

[Dave Smith]

Hi Dave,
Any suggestion that Dave Higgins makes on mechanical work go with his idea, there is not a lot that he does not know about engines

Hi Dick, thanks for the advice. I am sure there will be plenty more questions over time.