Latest topics
» Interesting idea for CDI ignition on youtube.
Today at 8:49 am by rob spence

» Wiring for AMC trials
Yesterday at 9:58 pm by Bigjim

» cruiser 80 chain guard
Yesterday at 9:27 pm by william105

» Can anyone identify these pistons?
Yesterday at 4:02 pm by piston 197

» AMC 20T piston rings
Yesterday at 10:03 am by rob spence

» AMC engined Plover - Wont start
Mon Sep 18, 2017 8:23 am by Davidohyeah

» 1H Starting
Sun Sep 17, 2017 9:47 am by Jack Clegg

» Rolling 40 year MoT exemption starts May 2018
Fri Sep 15, 2017 6:48 pm by John Wakefield

» 1H ENGINE PARTS
Fri Sep 15, 2017 5:40 pm by Bigjim


4T twin stuck pistons - safest way to unstick?

View previous topic View next topic Go down

4T twin stuck pistons - safest way to unstick?

Post  fulmar88 on Tue Aug 01, 2017 11:53 am

I have recently acquired a 4T engined Cruiser 89 which was left for untold years without spark plugs. The pistons are stuck. However, there is no visible corrosion present in the bores so I would imagine it should be relatively easy to get them moving. Penetrating oil has been used for 6 days currently. I have made sure that the crank is free by feeling the 'slack' in the big and little ends. The situation is not being helped by the fact that one piston is approx 2mm from TDC whilst the other is allowing the penetrating fluid to escape via the ports at the bottom of its stroke. Judicious blows with a hammer via a block of wood are having no effect except that the penetrating fluid on the piston at the top of its stroke does escape past the piston to some degree now. I have removed the inlet manifold and carb and will remove the exhausts next hoping that twisting of the barrels may do the trick. Of course the 4T has studs through each barrel so the available twist will be minimal without removing the studs first, plus the barrels almost touch which also won't help. I don't have the facilities to apply heat so any suggestions welcome. I am eager to avoid damage as the engine looks in great condition other than for this minor problem..

Steve.
avatar
fulmar88

Posts : 491
Join date : 2010-03-15
Age : 50

Back to top Go down

Unstiking barrels

Post  piston 197 on Tue Aug 01, 2017 12:03 pm

Steve striking the one that is 2mm from top dead centre will do little as the crank will be near enough vertical and the shock will have no turning motion !
Suggest stripping off the gearbox and outer cases and submerging the whole cases, crank, and barrels in a bucket of Diesel for a while to guarantee penetration everywhere, best to leave it in there for about a week.
Then some brute force can be applied, if the one piston is almost at TDC then the other will be almost at BTDC so hitting either will not help a lot, might be easier to try to jack the barrels upwards, although it does not seem like you are going to get a lot of movement if the pistons are where you say ?, Might be better applying a turning motion to the crank nuts at either end with hammer and spanner ?, but you do risk stripping the threads on either the nuts or crank
JH
avatar
piston 197
Moderator

Posts : 3543
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

Re: 4T twin stuck pistons - safest way to unstick?

Post  fulmar88 on Tue Aug 01, 2017 12:21 pm

Thanks John. Plan for this bike is a thorough clean and to get it going without any 'restoration' as such as it's too nice and original. I guess it will be a lot easier to clean with the engine out of the way although I was hoping to avoid that. In for a penny..





Last edited by fulmar88 on Tue Aug 01, 2017 12:53 pm; edited 3 times in total
avatar
fulmar88

Posts : 491
Join date : 2010-03-15
Age : 50

Back to top Go down

Without restoration

Post  piston 197 on Tue Aug 01, 2017 12:26 pm

Best of luck with that Steve ! almost certainly if the pistons are stuck the rings will have corroded into the bore surface, and the 4T has the cast iron piston ring type centre seal, all of the re-conditioners throw this away and fit the 2T seal carrier and rubber seal, if you get away without a centre seal, cranks seals and a re-bore I will be very surprised ?
JH
avatar
piston 197
Moderator

Posts : 3543
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

Re: 4T twin stuck pistons - safest way to unstick?

Post  fulmar88 on Tue Aug 01, 2017 1:08 pm

I guess if it was too easy it wouldn't be any fun.

I've been in contact with Sandy (FB Vincent) who has pointed out that rather than aftermarket silencers fitted, as I had assumed, they are the originals, they've just had the ends cut off! I'm also in need of some correct handlebars with the welded lever lugs but 'U' clamp fitting. The rare angled air filter is missing its original mesh screen, filter element, and outer retaining disc (lost on the road I should imagine). Other than a fuel cap, horn/dipswitch, wipac ammeter, headlamp chrome rim, and rear number plate it's pretty much all there. It's even got a Lucas King of the Road battery still fitted.

Steve.
avatar
fulmar88

Posts : 491
Join date : 2010-03-15
Age : 50

Back to top Go down

Re: 4T twin stuck pistons - safest way to unstick?

Post  dalgrae on Wed Aug 02, 2017 7:31 am

I would also recomend using diesel ,but if possible make up something to go accross each cylinder that puts a load onto the top of piston to try and encourage it to free off with the help of the diesel,I have used in the past ,anything from steel bits and pieces to wood to achieve putting a load onto the pistons

Regards. Colin

dalgrae

Posts : 34
Join date : 2017-04-08
Age : 67
Location : Bristol

Back to top Go down

Pistons

Post  kerabo on Wed Aug 02, 2017 11:21 am

Try a blow lamp and leave it heating the piston direct for a good amount of time
Can you double nut the studs and remove them? You could then fit some spacers under the barrels leaving tension on the piston . Then give it the wood again.
Ken
avatar
kerabo

Posts : 2019
Join date : 2008-02-11
Age : 67
Location : Falcon 87. Trials 93 Special. Powerbike 56. Falcon 81 Green Lane bitsa. Sunbeam S8. Honda Deuville.

Back to top Go down

We have movement!

Post  fulmar88 on Wed Aug 02, 2017 4:20 pm

I'm not sure what helped today as I had tried a different penetrating oil overnight and I realised that with the 4T stud design that the barrels were free to 'bounce' perhaps lessening the impact with the hammer. So, I refitted the head sleeve nuts and nipped them up. I also used the only heat source I have which is a hot air paint stripper thingy. After many many blows I noticed 0.1s of a mm change so I kept hammering away. After an hour or so I had managed to get the pistons at mid stroke. Unfortunately I don't think the pistons are the problem. The only way I can get the pistons to move is to hit them. I can't even move them hitting a spanner on the crank nut. The crank is free as I can feel the tiny movement due to slack in the little ends? Are the symptoms consistent with a seized big end? As the crank angle improved each blow of the hammer moved the piston a greater distance. A little end failure wouldn't have this effect whereas the additional mechanical advantage of the crank/conrod angle would if the big end had seized. The crank has only rotated a quarter of a turn so far but I felt it prudent to stop and ask for advice.
Steve.
avatar
fulmar88

Posts : 491
Join date : 2010-03-15
Age : 50

Back to top Go down

Piston problems

Post  piston 197 on Wed Aug 02, 2017 4:43 pm

Steve if you can get someone to hold the cylinders so that the engine is just off the ground ( Heavy) and continue to hit the pistons , you will also have gravity helping you, plus the weight of the engine and you will not be dependent on the crank needing to rotate ? At this stage you will realise whether it is the pistons being stuck which is the problem ?
JH
avatar
piston 197
Moderator

Posts : 3543
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

4T pistons stuck?

Post  colk2004 on Wed Aug 02, 2017 5:39 pm

I thought I'd got a similar problem on my 20T but it turned out the alternator was rusted up and that why it wouldn't shift. I'd strip off everything on the engine you can, you might find all the like bits of corrosion add up to a fully stuck motor like they did on the MZ I'm doing as well.

Cheers Colin
avatar
colk2004

Posts : 216
Join date : 2015-04-13
Age : 55
Location : York

Back to top Go down

Re: 4T twin stuck pistons - safest way to unstick?

Post  fulmar88 on Wed Aug 02, 2017 7:47 pm

As usual JH it seems you are correct. I haven't taken the engine out yet so removed the exhausts and nuts holding down the barrels and now that they can move independently managed to rotate the crank resulting in the Left piston moving to the bottom of the barrel. The right piston is still stuck in the barrel (I ran out of time) but the crank freely rotates now that the piston can push the barrel up and down the studs. As the barrels can't be removed off the studs in the frame I'll take the engine out as the next step. Why it's so tight is unclear though as there's little corrosion where the rings have been sitting for the last 40 years.

Thanks for everyone's suggestions.

Steve.
avatar
fulmar88

Posts : 491
Join date : 2010-03-15
Age : 50

Back to top Go down

Re: 4T twin stuck pistons - safest way to unstick?

Post  fulmar88 on Sat Aug 05, 2017 11:13 am

It took another hour to remove the engine and finally free the pistons. The left was tight but the right was a nightmare. Looks like some deposits ( perhaps alunimium corrosion?) was the problem. Rebore and new pistons needed as JH suggested would be required.


avatar
fulmar88

Posts : 491
Join date : 2010-03-15
Age : 50

Back to top Go down

Re: 4T twin stuck pistons - safest way to unstick?

Post  Sponsored content


Sponsored content


Back to top Go down

View previous topic View next topic Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum