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Author Topic: 5/1 CS with to less compression  (Read 4888 times)

taeuber

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5/1 CS with to less compression
« on: July 01, 2008, 10:39:54 AM »
Hi there,

my to be restored 5/1 CS asks me some questions I can't find an answer for.
The problem is the compression ratio or better the head <-> cylinder clearance in TDC/UDC.
The measured clearance is 1,95mm (~0.077 in). This is by far to much. A 6/1 CS should have 0.040"-0.050". And I thought it was build with the same dimensions and measurements.
This clearance was measured by me with a solder wire after removing all shims between crank case and cylinder.
What could be the reason for this? Are the bearings worn out this strong/huge/heavy?
Which bearing should I change at first? I already removed the flywheels. But I'm not sure if the crankshaft bearings or the con rod bearings or both are the reason.
I'm not a mechanic so to change the bearings is a challange for me.

Are there any other things I could do first?

Thanks
Lars

oliver90owner

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Re: 5/1 CS with to less compression
« Reply #1 on: July 01, 2008, 04:45:35 PM »
taeuber,

If there is that much clearance on the journal, it would knock very seriously!  It should be checked as a matter of routine while you have the engine apart as far you have it stripped . 

There is nothing on a Lister that is high tech and there are lots on this forum who will help you even if you have it completely dismantled and didn't know where to start assembling it.  Dont worry it can be rebuilt!!

The mains may well be seriously worn and if they are, you would probably be able to feel movement on the crank now that you have it apart.  The bearings may have been re-metalled in the past and the crank set low - who can tell with these old machines.  It could be the big end or the mains that has been remanufactured.  you will need to investigate further.

BTW where are you situated?

Regards, RAB

Doug

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Re: 5/1 CS with to less compression
« Reply #2 on: July 01, 2008, 06:02:44 PM »
Its possible to detect (***not measure***) as little as .003 of an inch by touch with large shaft and bearings

Oil will mask this so its very hard to detect on a plane bearing. Odds are if you can feel movement you have problem......

When I was a winder with golden hands ( younger and stronger back too ) I could feel the .003 clearence on a C3 bearing and make a judegernt call on how tight things were.
What didn't feel right durring fitting would have to be followed up with a mic and odds were if you could feel you had a problem.

Now I don't do this for a living anymore and I don't have the golden hands I once did.
However if you start from a good bearing and as part of your Isnp/PM routine touch, poke, prod and feel as meany moving parts as possible you can learn what things should feel like. A Stethiscope is also a fantastic tool for doing you Inspections, if your a little hard of hearing ( like me ) you can focus right in on parts and places and listedn for thuds or unusual noises.

In almost everything ( rotatign electrical machine, gear box ect )  I have ever done PMs and inspections on I have found they don't just fail, they  anounce themselves long before failure happens.
It's a Good Life, If You Don't Weaken

taeuber

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Re: 5/1 CS with to less compression
« Reply #3 on: July 01, 2008, 10:25:32 PM »
Hi RAB, hi Doug,

just some last sentences for this day. It's 3 quarters to midnight here in Berlin/Germany. The engine is two hours away from here and I only can get there once in a while.

I can't feel any worn out bearings. They all seem to be tight but going and they don't knock or sound strange. I put a good load of fresh oil inside before trying to start for the first time. This is what you meant with »Oil will mask«, didn't you Doug?
The only odd thing I realized was the con rod moving left and right some millimeters on the crankshaft after I removed the cylinder but hat could be normal I think. There is no clearance sensible on any of the bearings. Only the bush bearing of the camshaft breathes when cranking. This bearing looks worn out.

Doug, I didn't understand all your writing. What do you mean with »Isnp/PM routine touch«? Sorry for that, it's just my little English.

Good night!
Lars

oliver90owner

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Re: 5/1 CS with to less compression
« Reply #4 on: July 01, 2008, 10:55:42 PM »
 lars, con rod moving left and right some millimeters on the crankshaft

That is normal.  As long as you cannot move the small end from side to side while the big end is held still!

It is not a service specification, but I remember my Honda motorcycle engine (of 40 years ago) had a maximum small end movement specified - it had (needle?)roller bearings.

Also the thickness of the head gasket could be excessive and make for a high piston/head clearance.

Regards, RAB

Doug

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Re: 5/1 CS with to less compression
« Reply #5 on: July 02, 2008, 01:16:17 AM »
hi Doug,

I can't feel any worn out bearings. They all seem to be tight but going and they don't knock or sound strange. I put a good load of fresh oil inside before trying to start for the first time. This is what you meant with »Oil will mask«, didn't you Doug?
The only odd thing I realized was the con rod moving left and right some millimeters on the crankshaft after I removed the cylinder but hat could be normal I think. There is no clearance sensible on any of the bearings. Only the bush bearing of the camshaft breathes when cranking. This bearing looks worn out.

Doug, I didn't understand all your writing. What do you mean with »Isnp/PM routine touch«? Sorry for that, it's just my little English.

Good night!
Lars

Sorry about that.
What I mean is Inspection and preventative maintinance, before you run and when you do oil changes and adjust things.

A bearing that is warm and has just been run and still has a lot of oil in it will not feel the same as a cold one that has not run for some time. It best to check things over cold after the oil has drained back to try and feel for slack rather than when its warm.
I am not a mechanic and most of this advice is based on the feel of plain bearings in gear boxes and electric motors so take my advice with a grain of salt but but can still feel a lot things and you can feel changes in things and thats what is most important when you are doing regular inspections of your machine you want to look and feel listen ect for change.... 
It's a Good Life, If You Don't Weaken