Use of Plastigauge

[Eadie McCreadie]

WITHOUT PULLING HIS HAIR OUT?!!!!!!!!!!      !!!!!!!!!!!!!!!!!!!!   

So off I go again... ge tthe file out and reduce the edges a bit.  Didn't take much to see that the conrod slipped in nicely... Great.

So I prepare everything, oil the bore, make sure everything is clean, big end, shells etc.  And commence lowering the piston, with rings, down into the bore...

DIDN'T GET FAR!

About 10mm in and the piston wouldn't budge.  Check level, check for obstructions, check, re-check, oil this, check it again... NO WAY.

Turn the piston upside down... fits well to the first ring, so what's going on?  Could it be that the bottom of the piston is wider than the top?

I gave up doing that, and put the piston in the bore from below (ie, off the engine) and lowered the whole shebang, carefully, onto the crankpin, and assembled the big end as normal.

Is the bottom of the piston larger than the top?  Or is the cylinder narrower at the top than its bottom?

I wasn't expecting this.

[SteveU.]

Hello Tim,
You are making me very nervous with your "piston won't fit" talk.
Unfortunatly none of us being there we are having to make too many assumtions.
So , please clarify any of these as right or wrong:
You have an indian manufactued Listeriod clone.
It is a 6/1 configeration. Means 4.75" bore and 4.5 " stroke.
The engine over heated and failed in service due to loss of oil. Why? Don't mean to embarasse you but any advise will change depending.
You are reassembling with the the preexistng piston and cylinder sleeve. Yes? No? Using replacements?

There are different style ring compressors. One style uses special pliers to sqeeze togather an incomplete band. Another style has an adjutable overcentering lock on a wrinkle formed incomplete band; these can both be removed for piston up from the bottom installs. Doesn't matter. Use what you've got.

I have an Indian clone. It has an unplated iron bore and cast iron piston. If it over heated do  to lack of oill I would have expected the cylinder to have premature wearing and scuffing in the ring and piston skirt areas, the piston itself to have worn, scuffed skirts and there to be a ridge of unworn material at the top of the cylinder bore. Yes? NO?
O.K. to reassemlbe with this as long as the ridge is reamed off(another special tool) to keep the new upmost ring from catching and breaking itself or the piston ring land. The worn bore would need to be deglased/reamed with a bead type hone (another special tool) to restore some measure of oil and compression control. You will only get a percentage of normal service life with these prematurely worn increased clearances.

So there's the advice problem: piston/sleeve clearances should be looser due to the premature wear, NOT TIGHTER, as your assembly says.

Bad things are going to happen such as a seized up engine unless you help us to figure out WHY your piston WILL NOT slide smoothly through the complete bore. Another member is experiencing an unresolved replacement piston overheating/low output power problem now.

If you can answer these questions the possibilty list can narrow down to something less confusing and useable.

SteveU.

[Eadie McCreadie]

You are making me very nervous with your "piston won't fit" talk.

Me too.

You have an indian manufactued Listeriod clone.

Yes, a clone.

It is a 6/1 configeration. Means 4.75" bore and 4.5 " stroke.

Yes.

The engine over heated and failed in service due to loss of oil. Why?

The simple truth is that I don't know.  The closest I can get to the truth is that maybe I have not been heating the waste vegetable oil sufficiently for proper
combustion.  I am only guessing here... has incomplete combustion left sticky oily deposits on the piston rings (as they were found like this) and allowed sump oil to be
burnt in the combustion chamber?  I don't know.

Perhaps I neglected the oil in the sump and it ran low anyway, causing some other problem at the top end that led to the ring gumming?  Again, I don't know.

You are reassembling with the the preexistng piston and cylinder sleeve. Yes? No? Using replacements?

Yes, using the same piston, but am using new rings.

I have an Indian clone. It has an unplated iron bore and cast iron piston. If it over heated do  to lack of oill I would have expected the cylinder to have premature wearing and scuffing in the ring and piston skirt areas, the piston itself to have worn, scuffed skirts and there to be a ridge of unworn material at the top of the cylinder bore. Yes? NO?

What I see in the cylinder bore is a darkened ridge about 10mm deep around the very top of the cylinder bore.  I have attempted to remove this by using 1000 grit wet and dry with WD40.
At the top of the piston, on its side, again for about 10mm, is some, what looks like to me, vertical scoring.  I can't see any reason for this, and maybe it was there form the beginning.  I don't see any damage to the skirt of the piston. 

Bad things are going to happen such as a seized up engine unless you help us to figure out WHY your piston WILL NOT slide smoothly through the complete bore. Another member is experiencing an unresolved replacement piston overheating/low output power problem now.

I hear you.

If you can answer these questions the possibilty list can narrow down to something less confusing and useable.

I certainly hope so.

Thanks for your post, Steve.

Tim
SteveU.

[xyzer]

Is the bottom of the piston larger than the top?  Or is the cylinder narrower at the top than its bottom?

Eadie,
To answer your question...yes the piston is larger at the top than the bottom of the skirt. A piston needs to be measured at the skirt to check for clearance. The top of the piston is small until combustion then it gets hot and expands to fit the bore. If the piston and liner are the original set something has changed with the failure you had that won't allow assembly.
Dave

PS

What I see in the cylinder bore is a darkened ridge about 10mm deep around the very top of the cylinder bore.  I have attempted to remove this by using 1000 grit wet and dry with WD40.

There can't be a ridge deposit or the piston won't fit.

[Eadie McCreadie]

yes the piston is larger at the top than the bottom of the skirt

If it's larger at the top than the bottom then why mightn't it fit in the cylinder when lowering it in?  What could have happened to alter this?

[1958steveflying]

Hi Tim, i think i would be inclined to remove the barrel and piston, take the rings off the piston and do some dry fit checks. The piston should easily fit into the bottom of the barrel and then pass through and remove from the top and vice versa. if it doesn't then clearance measurements need to be investigated or you are going to have further problems for sure if it is ignored. It does sound a very strange one though.
  Steve

[Eadie McCreadie]

I'm sure it won't pass through.

I now think I might be going mad.

I can pass the piston up into the cylinder and out through the top and a certain amount of th episton emerges from the top before becoming all 'sticky'.

I'm going to have to see a doctor before this is sorted.

And maybe afterwards as well.

Could it be possible that the engine will run with a poorly fitting piston (at it's skirt, and unnoticed by anyone until a strip down like this?).

[oliver90owner]

Eadie, The cylinder would have been bored parallel throughout.  The piston skirt may be oval - for several reasons.  It should go through the entire bore. 

The ridge at the top of your cylinder must be removed in it's entirety or you must have a stepped top ring in the piston.  The reason for this is that your top ring will just touch the ridge on every rotation and may well damage the piston or break the ring.  I would think this is the reason why the piston is sticking.  If the skirt is too much out of round it can be carefully returned to near round using a soft faced mallet or similar method.

These engines were so very forgiving that relatively large tolerances were allowable and simple fitting methods were used by a large number of home repairers 50 years or more ago.

Is this an indirect (IDI) or direct (DI) injection engine? Flat topped piston or combustion chamber in the piston?

IDI engines are much more tolerant with alternative fuels as the initial combustion (fuel spray) takes place well away from the piston ring area.  Any unburned fuel in a DI engine seems to gum up the rings and potentially cause this type of problem.

What type oil of are you using?  That, too, may not be quite so compatible with burning veggie.

I am wondering if there is a local stationary engine group you could contact/join.  There would be lots of potentially close to hand help with matters like these, I am sure.

Are you going to fit a low oil warning or, even better, a cut out?

Keep coming with the questions.  We will help if possible

Regards, RAB

[SteveU.]

Hi Tim
Good info feedback.
I actually didn't know the answer to the piston sizing; I'm glad xyzer/Dave did. Makes sense.
The cylinder will always be as perfectly round and straight as the manufacturer can make it.

I agree with 1958Steve you will have to pull it down (sorry) and get things dry fitted properly.

I think now your problem is hard carbon buildup at the top of the cylinder, and around the top edge of the piston above the top most ring. If I'm right that means it will in the bottom of the ring groove too.
Standard advice is to scrape carbon. That doesn't work very well anymore for me since the removal of the softening lead from gasoline and sulfer from the diesel.
I now (listen to the roar) dunk my pistons in a bucket of cold dip carburator cleaner for a day, two or three. Or if in a hurry use a propritor decarbonizing spray (Chrysler/Jeep Mopar#04318001AB). Its listed as a combustion chamber cleaner.
Yeah, nasty stinking chemicals. I don't know your availability for this stuff in the UK. You might try a spray oven cleaner. All of this stuff will melt rubber gloves and burn skin. Use nytril gloves, an old tooth bush and a broken ring as a scraper.

Before assembly remember to check the new ring end gap with rings individually pushed into and squared op in the bottom of the cylinder bore. File the ends as needed to get at least the minimum end gap.

End Gaps should be?
If no one chimes in with the correct spec. than for your bore I'd guess .005-7" or.125-50MM.

Hey, cheer up. Better than thinking you have heat warped piston. And RAB has adressed this posibility.

Cheers
SteveU.

[oliver90owner]

Eadie,

I just looked back at the thread and noticed how you broke your ring!

Do not do things like that! If putting the piston back in from underneath simply insert blocks to safely control the position of the cylinder and raise the piston from below by slowly turning the crank in a controlled manner.  Your techniques are somwhat awry and possibly positively dangerous, it seems to me.  

Before you do anything, make sure you have considered all the 'what ifs?' because you can be sure that Murphy is on hand with his law that says if it can go wrong, it will.

I know it is a steep learning curve for you.  If not absolutely sure ask here for step by step instructions from someone wio has done it before - they had to learn how to do it and may have made the same mistakes or developed the perfect method to avoid all the potential breakages.  

PM me if you are unsure and don't want to put your dilemma in front of the whole world-wide net.

I've been mending motor bike engines, stationary engines and lots of others for the last 45 years or so and watched Dad and others even before thaat.  I'm not an engineer but have lots of experience.

My biggest b---s up was not finishing a Mercette engine, and allowing the whole machine to be skipped.  Google Mercette and you may see why, in hindsight, I should have persevered!

Rgards, RAB

[MacGyver]

My biggest b---s up was not finishing a Mercette engine, and allowing the whole machine to be skipped.  Google Mercette and you may see why, in hindsight, I should have persevered!

Shall we assume you're referring to the cycle motor and not the birth control pill?  4-stroke even. Very Cute...

[xyzer]

Is the bottom of the piston larger than the top?  Or is the cylinder narrower at the top than its bottom?

Eadie,
To answer your question...yes the piston is largersmaller at the top than the bottom of the skirt. A piston needs to be measured at the skirt to check for clearance. The top of the piston is small until combustion then it gets hot and expands to fit the bore. If the piston and liner are the original set something has changed with the failure you had that won't allow assembly.
Dave

PS

What I see in the cylinder bore is a darkened ridge about 10mm deep around the very top of the cylinder bore.  I have attempted to remove this by using 1000 grit wet and dry with WD40.

There can't be a ridge deposit or the piston won't fit.

I'm so sorry I explained it right but  stated it wrong....what was I thinking...we will really get you upside down! To much coffee or somthin! Let me try again...The piston is large at the skirt...
Dave

[oliver90owner]

Mac,

4-stroke even. Very Cute...

I remember I was 13 at the time I was thrashing it around the fields.  I was quicker on  that than my 10 year old brother on a 200cc Excelsior (he couldn't quite handle all the power of the bigger bike).  Kept bending (and straightening) the push rods due to over-revving.  'Bout 47 years ago but only skipped about twenty years ago

Regards, RAB

[Eadie McCreadie]

Hi all, and thanks for the replies - I can't answer each one, but will re-read again and again and see if I have done everythng I can/should.

In particular, thought, I am happy that the ring grooves (lands?) are clear of coke - everything was soaked in paint thinners.  The rings have all been renewed.  Because the oil control ring could not be purchased on its own, I had to buy a new set anyway.

That black ring at the top of the piston... I have rubbed it down with the 1000 grit and WD40, but wil go back and re-check that.  It seems to corresspond with that part of the piston above the top ring.

The engine, I think, is IDI, RAB.  Also, it is a flat-topped piston. The colour of the top of the piston resembles that of that black ring inside the cylinder, which I don't find surprising.

Yes, I am certainly on a learning curve, I think that's why I am trying different ways of achieveing the same ends - this is why I screwed up the fitting of the rings in the first place - if feeding the piston in from underneath, I find difficulty in compressing the ring enough at the same time as moving the piston upwards - I end up using my knees to move the flywheel, as both hands are compressing the ring in question.. and using a compressor only works from above, well, at least the one I have.

Tim (Eadie)

[Petersbpus]

It looks like a normal 500 to 1000 hour de-carbonizing,(depending on fuel type and conditions) should always include ring removal and cleaning???
and if you don't want to break open the big end there is need for compressing the rings into bottom of cylinder.
My unit is not yet in service and I was hopeing piston removal( or yanking the block) wasn't going to be necessary each time?? What's common practice??

It seems that some sheet metal  and some hose clamps would suit as a removable ring compressor from the underside, even if you have to disassemble a ring compressor and substitute hose clamps using the origional blued steel.

If you strap a weight to the flywheel that should apply a gentle upward force without other assistance.
bob