# ring gap

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I ordered new piston rings.

Bores aren't anymore what the were.. I don't have a clue what the gap should  be with forced induction and being air cooled..

What do you guys run? 0.5mm?

Bore is 78.33mm if it is important

Thanks

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Usually piston manufacturers give a formula to calculate gaps for different bore sizes.

For 78mm Wisecos I used 0.4mm for the top ring and 0.45 for the second.

##### Link to comment
1 hour ago, Reinhoud said:

I ordered new piston rings.

Bores aren't anymore what the were.. I don't have a clue what the gap should  be with forced induction and being air cooled..

What do you guys run? 0.5mm?

Bore is 78.33mm if it is important

Thanks

I ran .14 inches on the top ring, so about 3.6mm

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12 hours ago, rerb said:

I ran .14 inches on the top ring, so about 3.6mm

I think you've misplaced the decimal point placement! - at 3.6mm ring gap you'd have no compression to speak of!

Rule of thumb - 0.004 - 0.005" per 1" of bore dia . . . . . so for 78mm, call it 75mm or 3" = 0.004 x 3 or 0.005 x 3 = 0.012 / 0.015" respectively

which equates to - 25.4mm / 1000 = 0.0254" x 12 or 0.0254 x 15 = 0.3048mm / 0.381mm

The above is usual for Normal Aspiration - Forced Induction can afford to go a little looser but you will get more blow by so 'swings and roundabouts' !

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6 hours ago, Gixer1460 said:

I think you've misplaced the decimal point placement! - at 3.6mm ring gap you'd have no compression to speak of!

Rule of thumb - 0.004 - 0.005" per 1" of bore dia . . . . . so for 78mm, call it 75mm or 3" = 0.004 x 3 or 0.005 x 3 = 0.012 / 0.015" respectively

which equates to - 25.4mm / 1000 = 0.0254" x 12 or 0.0254 x 15 = 0.3048mm / 0.381mm

The above is usual for Normal Aspiration - Forced Induction can afford to go a little looser but you will get more blow by so 'swings and roundabouts' !

Yep, I was off by a hundredth whoops. I went smaller on the ring gap for forced induction because my motor has never gotten hot before, and it's a very cool climate around here. Depending how my bore looks this winter I might go bigger, but so far no problems. I do have a larger piston to wall clearance though, .005". No signs of piston slap yet even though my machinist warned me about it

Edited by rerb
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20 hours ago, Arttu said:

Usually piston manufacturers give a formula to calculate gaps for different bore sizes.

For 78mm Wisecos I used 0.4mm for the top ring and 0.45 for the second.

I know, but for turbo you need more gap isn't it? And bikes are usually not turboo'd

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7 hours ago, Gixer1460 said:

I think you've misplaced the decimal point placement! - at 3.6mm ring gap you'd have no compression to speak of!

Rule of thumb - 0.004 - 0.005" per 1" of bore dia . . . . . so for 78mm, call it 75mm or 3" = 0.004 x 3 or 0.005 x 3 = 0.012 / 0.015" respectively

which equates to - 25.4mm / 1000 = 0.0254" x 12 or 0.0254 x 15 = 0.3048mm / 0.381mm

The above is usual for Normal Aspiration - Forced Induction can afford to go a little looser but you will get more blow by so 'swings and roundabouts' !

Do you know how much looser?

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47 minutes ago, Reinhoud said:

I know, but for turbo you need more gap isn't it? And bikes are usually not turboo'd

There were different values for boosted, NA, street and race. If I recall correctly this 0.4/0.45 was for boosted street. And it was working fine for me.

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Wiseco recommendations. Multiply bore in inches by the factor to give ring gap. 3" bore equals .015" top, .0165" second for street turbo. Go too tight and the rings can butt with heat and score bores or crack upper ring land. Loose is the way to go to avoid engine damage.

Edited by wombat258
info left out
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The rings came in today.

The instructions give the same numbers as Wombats list.

I need a gap of 0.4mm and 0.43mm. The gap was about 0.7mm.

But the rings don't fit in the grooves..

JE uses Total seal piston rings, but JE doesn't made my pistons so the they can take the rings..

So not impressed by JE..

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There are XG and XC series rings. They have different ring thickness. You may have ordered the wrong series. Measure the width of your old rings. XG are 1mm top, 1mm 2nd, 2mm oil. XC are 1mm/1.2mm/2.8mm. Rarer are XA at 0.8mm/0.8mm/1.5mm

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2 hours ago, wombat258 said:

There are XG and XC series rings. They have different ring thickness. You may have ordered the wrong series. Measure the width of your old rings. XG are 1mm top, 1mm 2nd, 2mm oil. XC are 1mm/1.2mm/2.8mm. Rarer are XA at 0.8mm/0.8mm/1.5mm

Oh no, they fucked up!! The rings fit in the old pistons.. 1.2 - 1.5 - 2.8

They just don't fit..

Edited by Reinhoud
##### Link to comment
7 hours ago, Reinhoud said:

But the rings don't fit in the grooves..

JE uses Total seal piston rings, but JE doesn't made my pistons so the they can take the rings..

So not impressed by JE..

You are confusing me! You HAVE JE pistons but AREN'T using JE rings? Are these JE pistons custom 'one off's' and did you supply ring dimensions? If you didn't, then I don't see how JE are supposed to know what size to machine so have machined usual for them? Why are you not using JE rings? - Total Seal rings work ok.

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You need to weld them up, to get from 0.7 clearance to 0.40 .......

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16 hours ago, Gixer1460 said:

You are confusing me! You HAVE JE pistons but AREN'T using JE rings? Are these JE pistons custom 'one off's' and did you supply ring dimensions? If you didn't, then I don't see how JE are supposed to know what size to machine so have machined usual for them? Why are you not using JE rings? - Total Seal rings work ok.

I bought a 1238cc big bore, new JE pistons, new sleeves, never used. Con rod snapped, wrecked 1 piston.. and more..

JE has a service that they can make a copy of a piston. But the minimum is 2 pistons. The piston I send was a JE piston, but for some reason it didn't have a serial number in them.

The "exact" copies I got were 10 grams lighter and 0.05mm bigger and the oil ring groove was overlapping the hole for the wrist pin. So no full support of oil ring

I complained about this and they send me 2 other pistons. Never tried the rings on the pistons because of this.

I used the old piston rings because they had only done 3000km, cilinders bored up and honed, ring gap a bit was bigger, but took the risk.

Old piston rings fitted just in the grooves, they were a bit tight.

Took engine apart to balance the crank, had marks in cylinders, had them honed, and the rings were a bit tighter in the grooves.

Deceided to get new rings hoping they fit better in the grooves and getting a proper ring gap again.

New rings won't fit in the grooves, rings do fit in the grooves of the old pistons.

JE doesn't make rings, they get them from Total Seal, these rings come from Total Seal.

There aren't variations in 1.2mm and 1.5mm thicknesses, it's just that or a complete different size.

JE fucked up twice.

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• 4 weeks later...
On 10/2/2021 at 1:32 AM, Reinhoud said:

I bought a 1238cc big bore, new JE pistons, new sleeves, never used. Con rod snapped, wrecked 1 piston.. and more..

JE has a service that they can make a copy of a piston. But the minimum is 2 pistons. The piston I send was a JE piston, but for some reason it didn't have a serial number in them.

The "exact" copies I got were 10 grams lighter and 0.05mm bigger and the oil ring groove was overlapping the hole for the wrist pin. So no full support of oil ring

I complained about this and they send me 2 other pistons. Never tried the rings on the pistons because of this.

I used the old piston rings because they had only done 3000km, cilinders bored up and honed, ring gap a bit was bigger, but took the risk.

Old piston rings fitted just in the grooves, they were a bit tight.

Took engine apart to balance the crank, had marks in cylinders, had them honed, and the rings were a bit tighter in the grooves.

Deceided to get new rings hoping they fit better in the grooves and getting a proper ring gap again.

New rings won't fit in the grooves, rings do fit in the grooves of the old pistons.

JE doesn't make rings, they get them from Total Seal, these rings come from Total Seal.

There aren't variations in 1.2mm and 1.5mm thicknesses, it's just that or a complete different size.

JE fucked up twice.

Even though that sucks, it's good for me to know that shzt doesn't just happen to me.

I think the whole world is making mistakes right now. People are so stressed , my air conditioner repairman ordered me a new blower and the order got lost.

My lawyer filed a wrong paper for tax and now more problems.

I think there's something to it.

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