Cylinder liner thickness

[Kickaha]

What would be the minimum thickness cylinder liner you would want to run

Alloy Barrel with a cast in sleeve and looking to do a major overbore on it which at the moment would only leave 2mm wall thickness

Keeping in mind the engine will be absolutely thrashed everytime it goes out

[Brian d marge]

Size of bike ?
<tt>Old school rule of thumb was .190" minimum wall
thickness to prevent cylinder flexing and loss of compression control.

but I have it written down somewhere I ll try to find it unless someone else beats me to it

Stephen
</tt>

[Kickaha]

Size of bike ?


around 150-157cc single cylinder, around 66-66.5mm bore, stroke around 44-45mm

So going with your figures I'd need a total OD around 76mm?

[bsasuper]

I reciently finished my bigbore 92 cbr900 (1060cc) the liners were steel/plated and 2mm wall thickness.

[xwhatsit]

around 150-157cc single cylinder, around 66-66.5mm bore, stroke around 44-45mm

So going with your figures I'd need a total OD around 76mm?
Well 0.190" is just under 5mm. So ~71mm OD.

Didn't realise you could do them that thin. Half a mind to spend some extra money to have my XT350 sleeve cut down so I need to take less meat out of the CB250RS cylinder to fit it in. It's a stock sleeve so is relatively thick, maybe a 10mm or more.

[PeeJay]

What would be the minimum thickness cylinder liner you would want to run

Alloy Barrel with a cast in sleeve and looking to do a major overbore on it which at the moment would only leave 2mm wall thickness

Keeping in mind the engine will be absolutely thrashed everytime it goes out
Used to work on 100 thou but have run thinner. Thats on 80mm+ bore. High rod ratio as well. From memory Phil Irving reckoned 100-125 thou for liners in alloy barrels. Different engines in those days. But with a 66mm shortstroke Id give 2mm a go. I presume majority of the load bearing area would be supported by the barrel. Overbored a trident once, 60 thou liner worked ok used to rev the snot out of it

[popelli]

What would be the minimum thickness cylinder liner you would want to run

Alloy Barrel with a cast in sleeve and looking to do a major overbore on it which at the moment would only leave 2mm wall thickness

Keeping in mind the engine will be absolutely thrashed everytime it goes out

should be more than amble

my panhead has been resleeved in the past and rebored several times since, the sleeve is now only about 1.5 - 2 mm thick and it runs fine

[Kickaha]

Well 0.190" is just under 5mm. So ~71mm OD.


66mm bore with a 71mm OD would be a 2.5mm wall thickness

If I can get away with that the existing one might be close enough

[xwhatsit]

66mm bore with a 71mm OD would be a 2.5mm wall thickness

If I can get away with that the existing one might be close enough
Oh dear. I see what you mean :laugh:

No wonder I'm struggling to get through this math paper :rolleyes:

[Brian d marge]

all boils down to peak pressure and ring sealing, if the bore is flexing and thethe rings are flopping around you are going to get blowby , which causes a heap more problems ...2.5 mm on a 70mm bore sounds thin,,, but then I havent done the maths and my experience is with larger bores ( in fact i am ibn the middle of the calculation now for an 86 mm enfield bore )

Stephen

[speedpro]

You need to get the best material possible and that will allow you to run the sleeve thickness down a bit. I've ended up using LA sleeve co. sleeves at about 2.5mm thickness on a 72mm bore. If you are machining them yourself keep an eye on the top flange where the sealing loads are relative to the support where it drops into the barrel. Also make sure you follow best practice when it comes to chamfers and radii on that top lip, especially if you use o-rings and copper gaskets. The o-ring grooves must be over the supported part of the lip. I had a problem where the sleeves would crack round underside of the lip. The right fit in the barrel is essential as well, too tight and the block cracks and too loose you get heat transfer problems. I actually ended up dropping bore size and divided the extra meat between the sleeve and barrel. I still get slight banding up/down the sleeve from the fins but at least it's not blue and straw bands like before.

[Brian d marge]

You need to get the best material possible and that will allow you to run the sleeve thickness down a bit. I've ended up using LA sleeve co. sleeves at about 2.5mm thickness on a 72mm bore. .
Honda CRF are 3mm and while it possible to run 2.5 on engines that are run for short times its pushing it a bit

One assumes that these will be used for buckets , ie short time and that there is no signs of blow by , ring trapping and detonation , then go go go !

bigger is better ,,, :devil2:

Stephen

[Kickaha]

One assumes that these will be used for buckets , ie short time and that there is no signs of blow by , ring trapping and detonation , then go go go !


Our longest race is 55 minutes + 1 lap where it'll spend most of it's time at 11,000rpm+

Looking at the barrel I doubt I can go much bigger than 2.5-3 mm without the allloy casting getting to thin down the cam chain tunnel

[Kickaha]

After speaking to a engine reconditioner and explaining the usage he reckons I could do it with a 2mm wall thickness without problem

Although now I am currently investigating an alloy sleeve with nikasil plating

[Brian d marge]

file:///tmp/moz-screenshot.jpgblue is about 280 deg , Straw is about 230 deg c on the outside of a liner , add a few deg because of wall thickness and your running hot in there I would be using a good oil, That was with a 2.5mm liner, A 2mm liner if it is supported well,
but if the combustion pressures are up there , ie u intend to use high comp , then longitudinal and hoop fatigue stresses could be an issue as has been mentioned by the use of careful radii

Imay have some work lying around you can copy if you want

Stephen