TimeMachine
SeventyEighte
Canadaian rtgman, I think you folk measure mileage in "smiles per litre" ? From what I've seen of your local routes..
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WHERE DID IT GO , IM AM WORRIED
- Thread starter funky
- Start date
Totally agree, Griz. I'd even feel comfortable with 0.003".
That 0.0002" is 5 microns.
Once you start fussing about dimensions at this small scale, you have to consider other items that operate at this miniscule size.
Temperatures during measurements become important.
A 3" diameter piece of aluminum will swell 5 microns with a 5° F increase in temperature. Just holding it in your hand can give measurement variances greater than that.
High quality pistons have finely machined skirts. Budget cast pistons have rougher surfaces. Burnishing of the skirts will definitely reduce the piston diameter. Not to worry, that's expected.
Ring break-in will enlarge the bore a miniscule amount, then reduced by glazing.
Then, there's the machine shop's measuring tools. Take your pistons/cylinders to 3 shops, probably get 3 different measurements.
I'd need to microscope examine the ring edges to confirm anything related to ring break-in, glazing, microwelding, materials, ...etc.
My best suggestion here is to re-hone, re-ring with good rings, reassemble. Re-deck the head/cylinder surfaces, and/or follow 5twins headgasket treatment tips...
That 0.0002" is 5 microns.
Once you start fussing about dimensions at this small scale, you have to consider other items that operate at this miniscule size.
Temperatures during measurements become important.
A 3" diameter piece of aluminum will swell 5 microns with a 5° F increase in temperature. Just holding it in your hand can give measurement variances greater than that.
High quality pistons have finely machined skirts. Budget cast pistons have rougher surfaces. Burnishing of the skirts will definitely reduce the piston diameter. Not to worry, that's expected.
Ring break-in will enlarge the bore a miniscule amount, then reduced by glazing.
Then, there's the machine shop's measuring tools. Take your pistons/cylinders to 3 shops, probably get 3 different measurements.
I'd need to microscope examine the ring edges to confirm anything related to ring break-in, glazing, microwelding, materials, ...etc.
My best suggestion here is to re-hone, re-ring with good rings, reassemble. Re-deck the head/cylinder surfaces, and/or follow 5twins headgasket treatment tips...
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funky
XS650 Junkie
Thanks for the response I have just done all the taken all measurements Here they are .....Left and Right i am facing the front of engine
SKIRT 78mm left 0.0027 right 0.0026 spec 0.0020 > 0.0025 (Big Bore 707cc)
RINGS
END GAP
TOP left 0.0018 right 0.0014 spec0.008 > 0.0016
SECOND left 0.0013 right 0.0012 spec0.008 > 0.0016
SIDE CLEARANCE
TOP left 0.0060 right 0.0025 spec 0.0016 > 0.0031
SECOND left 0.0020 right 0.0020 spec 0.0012 > 0.0028
Piston skirt... Left +0.0005 Right +0.0001
Left top ring end gap +0.0002
Left top side clearance +0.0029
This explains why the was more carbon build up one the left Piston
SKIRT 78mm left 0.0027 right 0.0026 spec 0.0020 > 0.0025 (Big Bore 707cc)
RINGS
END GAP
TOP left 0.0018 right 0.0014 spec0.008 > 0.0016
SECOND left 0.0013 right 0.0012 spec0.008 > 0.0016
SIDE CLEARANCE
TOP left 0.0060 right 0.0025 spec 0.0016 > 0.0031
SECOND left 0.0020 right 0.0020 spec 0.0012 > 0.0028
Piston skirt... Left +0.0005 Right +0.0001
Left top ring end gap +0.0002
Left top side clearance +0.0029
This explains why the was more carbon build up one the left Piston
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funky
XS650 Junkie
Ok do you mean this
You didn't follow the "Leakless XS Assembly" tips that many of us use. Those consist of adding narrow beads of sealer to both sides of the head gasket around the cam chain tunnel, the 4 outside stud holes (the ones that flow oil), and as added insurance, across the front between the outer stud and the cam chain tunnel. Like so .....
The head gasket was installed dry by the factory but that was 30 years ago when the parts were factory fresh and new. Today, a little added insurance to make sure things seal isn't a bad idea. This pic that I "doctored" is from eBay of a new factory head gasket. Note the shiny areas on the gasket at the top and bottom of the cam chain tunnel. That is factory applied sealer so as you can see, a factory gasket came with some sealer in what Yamaha probably figured were critical areas. Note they pretty much correspond to where your untreated gasket gave way.
Yes, the "leakless XS assembly". Search on that.
My wore-out XS1B doesn't pump/burn oil like yours, but I gar-on-tee that it's piston and ring clearances are way beyond book values.
Simply installing the 2nd scraper ring upside-down can introduce oil pumping like yours...
My wore-out XS1B doesn't pump/burn oil like yours, but I gar-on-tee that it's piston and ring clearances are way beyond book values.
Simply installing the 2nd scraper ring upside-down can introduce oil pumping like yours...
funky
XS650 Junkie
I questioned that with Smed speed he said the second ring has beveled edges,, is that correct . I beleive one bevel is slightly larger .
Again I have no experiance in this but when i looked at the ring the second ring was double beveled and thought that was in the worng place I.E should be top
funky
XS650 Junkie
http://www.xs650.com/threads/top-end-rebuild.13212/
link to 5twins thread on Leakless assembly
link to 5twins thread on Leakless assembly
Stock rings have beveled outer edges on the top ring, sometimes a step on the second. I don't know how a big bore would be configured but I don't see why it would be done differently. Usually, the top and second ring are different thicknesses, top a little thinner. You can't mix them up because the 2nd ring plain won't fit in the top ring groove.
funky
XS650 Junkie
I am going to stay clam Breath DAWG .........If thats right then thats the issue hes put the rings in the wrong way the scraper rings in the top and the double beveld ring is in the middle...but it does not fit the other way round .... need to check this .
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I said the rings are usually different thicknesses - but not always. If they're not then they could get mixed up and installed wrong. Installing them upside down will also cause problems. Any markings on the rings, letters and/or numbers, usually indicate the top side and should face up. As you can see, that would really make a difference on a stepped second ring like in the drawing above.
Michaelo
650Mick
I think 5T has said the key statement with "I don't know how a big bore would be configured", the majority here would be going O/S or standard rings, in their rebuilding, so I am in unfamiliar territory here.
I've a set of standard rings and I'll have a look at them today, not that this will help, but we are getting to the thin end of the wedge...
Maybe Mr Smed has been snorting too much of his speed.... then got Funky with his rings ha!
I've a set of standard rings and I'll have a look at them today, not that this will help, but we are getting to the thin end of the wedge...
Maybe Mr Smed has been snorting too much of his speed.... then got Funky with his rings ha!
funky
XS650 Junkie
The Rings are marked on top with "300" scraper ring also has a "R" ...i tried them the other way do not fit 
Looked at this, seems that how it is ,big ring second, smaller ring top....Dont fit the other was any how 
wonder if the fellow is on the forums
wonder if the fellow is on the forums
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funky
XS650 Junkie
Just cleaned the bike, frame , wheels and chain ready for when i re build the engine. 
Also decided im going to run a 20/50 oil .
The only worry I have is that my cylinders will be too big for the new pistons. its amazing such a minisqual measurement like 4 thousands of an inch can have such a profund effect on an engine
Also decided im going to run a 20/50 oil .
The only worry I have is that my cylinders will be too big for the new pistons. its amazing such a minisqual measurement like 4 thousands of an inch can have such a profund effect on an engine
Hi TimeMachine,
yeah, we got all manner of great routes all over. And that multi-lane meat grinder around Toronto.
No biker smiles on that one, unless a rictus of terror counts as one.
But since Canada went metric they didn't change miles per gallon into Kilometers per litre
which you can convert into an understandable number (multiply kM/Ltr x 0.4 to get mpg),
or cut it in half like anyone can do; oh no.
The official "mileage" is now Litres per 100Km.
To convert that into real numbers involves doing inversion equations in your head.
Not a thing to do when riding in today's traffic.
Fred.....................I just ignore the Official government method. I use kms/litre, because that's the only way it makes sense.
My bike gets about 25 kms/L on long trips, and my tank holds 11 litres, but I round that off to 10 litres. With a full tank, its easy math....................I could go 250 kms, but I would have to go on reserve at around 175 to 185 kms. Having said that, 10 years with this bike, and I've never had to go on reserve yet.
My bike gets about 25 kms/L on long trips, and my tank holds 11 litres, but I round that off to 10 litres. With a full tank, its easy math....................I could go 250 kms, but I would have to go on reserve at around 175 to 185 kms. Having said that, 10 years with this bike, and I've never had to go on reserve yet.
FYI, more piston ring trivia:
http://www.xs650.com/threads/piston-ring-order.39295/
http://www.xs650.com/threads/no-mark-on-top-piston-ring.41615/
http://www.xs650.com/threads/piston-ring-order.39295/
http://www.xs650.com/threads/no-mark-on-top-piston-ring.41615/
funky
XS650 Junkie
Thanks TwoMany Im just waiting on parts now will most certianly be asking questions once i start the rebuild .All the best and thanks again
funky
XS650 Junkie
I just read an article on caoting pistons to acquire the correct tolerance to cylinder ..... A possible option if needs arise
You mean "coating pistons"?
Yes, seen those offerings, too. I'd recommend that over the old-school knurling...
Yes, seen those offerings, too. I'd recommend that over the old-school knurling...
Michaelo
650Mick
If it got to that point 2M I'd look at re sleeve and new pistons, don't know about coatings, sounds like hocus pocus to me
