I just posted how I measured the bore wear. It does not look good on my 850

[DennisMo]

The pistons are marked + 0.040 and are not visibly scuffed or scratched
I set my calipers to 3.072" and then set up my bore gauge.
Here is the outcome with all measurements relative to 3.072"
I would say accuracy is +/- 0.001" (but could be 0.002')

Left Cylinder Right Cylinder

Unworn bore top 0 0
and bottom

Front to back maximum - 8 thou -10 thou
wear in bore

Side to side maximum - 10 thou -15 thou
wear in bore

Maximum top
ring gap 56 thou 53 thou
(about an inch down)

Top ring gap in 20 thou forgot to do!!
unworn bore

Your comments on whether I can't away with a new set of rings or not would be appreciated!

Thanks

Dennis

 

[DennisMo]

Format did not work. Let me try again


................................... Left Cylinder ...................................Right Cylinder

Unworn bore top .............0 .....................................................0
and bottom

Front to back
Maximum.......................- 8 thou ..........................................-10 thou
wear in bore

Side to side
maximum........................ - 10 thou....................................... -15 thou
wear in bore

Maximum top
ring gap ...........................56 thou............................................ 53 thou
(about an inch down)

Top ring gap in ....................20 thou..................................... forgot to do!!
unworn bore

 

[concours]

Ate you reading "thou"??
Or tenths??

If your "thou" is correct, it's wildly wiped out.

I'd wager on the latter unit of measure.

Respond please

 

[DennisMo]

Hi Concours,
Oops. I wrote minus instead of plus Corrected is below.
My bore gauge is metric so I converted the dial reading in 0.01 mm increments
to thou
All relative to 3.072" bore.



................................... Left Cylinder ...................................Right Cylinder

Unworn bore top .............0 .....................................................0
and bottom

Front to back
Maximum....................... +8 thou .......................................... +10 thou
wear in bore

Side to side
maximum........................ +10 thou....................................... +15 thou
wear in bore

Maximum top
ring gap ...........................56 thou............................................ 53 thou
(about an inch down)

Top ring gap in ....................20 thou..................................... forgot to do!!

 

[concours]

Hi Concours,
Oops. I wrote minus instead of plus Corrected is below.
My bore gauge is metric so I converted the dial reading in 0.01 mm increments
to thou
All relative to 3.072" bore.



................................... Left Cylinder ...................................Right Cylinder

Unworn bore top .............0 .....................................................0
and bottom

Front to back
Maximum....................... +8 thou .......................................... +10 thou
wear in bore

Side to side
maximum........................ +10 thou....................................... +15 thou
wear in bore

Maximum top
ring gap ...........................56 thou............................................ 53 thou
(about an inch down)

Top ring gap in ....................20 thou..................................... forgot to do!!

still way off.

What is your day job? You seem confused with these measuring tools.

 

[DennisMo]

Hi Concours,

Can you help me out and walk me through this.
It is the first time I have pulled my 850 apart.
What is wrong?
Thanks
Dennis

 

[marshg246]

That's by far the worst set of numbers I've seen so I'm guessing you have not measured correctly.

If any portion of the area swept by the rings is more than .005" larger than the unswept area, then you need to bore. Those are massive ring gaps as well. The top ring gap should be between .010" and .012" and you can get away with a little bigger but .056" is ridiculous.

To double check, measure the ring gap near the bottom of the skirt where the rings never touch and in the middle of the bore and report back.

To see if they were bored correctly to start with and as a double check of your measurements, put the pistons in the bottom flush with the edge of the cylinder with the wrist pin crosswise. Measure the cylinder to piston skirt gap at the front. Then move the piston to the center of the bore vertically and measure again.

The shop manual tells you how to measure.

Your bore should be between 3.0715 and 3.0725 for +.040" so I don't understand starting with 3.0720 or how you are measuring.

 

[DennisMo]

Hi Greg

Thanks so much. I really appreciate your time on this.

I will re-measure tomorrow but what I did today is as follows.

I set my callipers to 3.0720 inches. Then I took my bore gauge, put it between the jaws of my calipers (already set at 3.0720) and turned the bore gauge dial to zero while it was between the calliper jaws.

I then put it into the bore and did all the measurements.

For the left cylinder..
At the very top of the cylinder, where the rings do not wipe, I cleaned well and then I measured and it was basically the same 3.0720 (ie the bore gauge dial did not deviate from zero)

Then I went down the bore (oriented front to back in the bike orientation) looking for the biggest increase and measured 8 thou more. (Probably an inch or so down the bore)
Then I did the same for left to right side (of bike) orientation of the gauge and measured 10 thou.

My bore gauge is metric and when I set it to zero, it says that each division (ie mark on the dial) is 0.01mm so if (just for example) I measured a maximum
deviation down in the bore of 20 divisions from zeroing the bore gauge, this would be 20 times 0.01 mm equals 0.20 mm and it would convert to 8 thou.

I will do it again, report, and I hope that I have made a mistake in the math or the process. I hope I misread the dial divisions or something.......

Lastly, I was not clear but the top ring gap was 56 thou when about an inch plus down in the bore. When I put the top ring in the very top of the bore (where there is no wear,) the gap was 20 thou. This gap should be the 10 thou (you mention) so clearly the ring is worn.

Grateful I am and I will report and I hope to say I made a big mistake....

Dennis

 

[kommando]

The change in ring gap shows 10 thou of bore wear, but that amount of wear on an 850 with oil filter means that bike must have either serious mileage or the air filter is useless.

 

[marshg246]

Hi Greg

Thanks so much. I really appreciate your time on this.

I will re-measure tomorrow but what I did today is as follows.

I set my callipers to 3.0720 inches. Then I took my bore gauge, put it between the jaws of my calipers (already set at 3.0720) and turned the bore gauge dial to zero while it was between the calliper jaws.

I then put it into the bore and did all the measurements.

For the left cylinder..
At the very top of the cylinder, where the rings do not wipe, I cleaned well and then I measured and it was basically the same 3.0720 (ie the bore gauge dial did not deviate from zero)

Then I went down the bore (oriented front to back in the bike orientation) looking for the biggest increase and measured 8 thou more. (Probably an inch or so down the bore)
Then I did the same for left to right side (of bike) orientation of the gauge and measured 10 thou.

My bore gauge is metric and when I set it to zero, it says that each division (ie mark on the dial) is 0.01mm so if (just for example) I measured a maximum
deviation down in the bore of 20 divisions from zeroing the bore gauge, this would be 20 times 0.01 mm equals 0.20 mm and it would convert to 8 thou.

I will do it again, report, and I hope that I have made a mistake in the math or the process. I hope I misread the dial divisions or something.......

Lastly, I was not clear but the top ring gap was 56 thou when about an inch plus down in the bore. When I put the top ring in the very top of the bore (where there is no wear,) the gap was 20 thou. This gap should be the 10 thou (you mention) so clearly the ring is worn.

Grateful I am and I will report and I hope to say I made a big mistake....

Dennis

Show a picture of your "bore guage".

If any part of the cylinder is more than .005" (.127mm) larger than the area not swept by the rings, you must bore. .008 does equal .2032mm

 

[baz]

I'm suspecting the +40 bore wasn't done properly when it was done
Add in a bit of overheating and this is the result
On the plus side it's not too terrible to resolve

 

[concours]

Hi Concours,

Can you help me out and walk me through this.
It is the first time I have pulled my 850 apart.
What is wrong?
Thanks
Dennis

Please post a close-up picture of your dial bore gauge, so that I can see the graduations printed on the face. Also show it at the maximum deviation (mid stroke). It sounds to me like your conversion from metric to inch is off by a decimal point.

 

[Carl H]

I have a set of new 850 + 60 pistons with Hastings rings for 139.99 on my E bay site It is the last set of pistons I have. Shipping to Canada is extra and I have no idea of what customs will be. It would be free shipping to the USA.

USA eBay item number: 362844568043

 

[DennisMo]

1) Hi Carl. Can you please hold the pistons for me for a couple of days please? I am in Vancouver, Canada
2) To All. I hope I have made a mistake reading the gauge because if I am off by a decimal point, bore wear is within tolerance.
.....................I do want my next post to all to say "Oops. I made a mistake!"
3) I will check measurements again in a few hours and post photos of my dial gauge
4) I just did a math calculation as to the top ring gap theoretical increase when placed in the worn part of the bore.
................The top ring gap is currently 0.020" when placed in the unworn part of the bore. If the bore
................truly does increase by 0.010", (as I have measured), then the increase in circumference for the piston ring
................when in the worn part of the bore is approximately calculated as pi (3.141) times the increase in diameter of 0.010" which
................calculates to plus 0.031". I measured the top ring gap in the worn part go the bore (0.010" of wear) as 0.056"
.................which is plus 0.036". This measured gap increase seems to fit with the calculated gap increase.
Will report and thanks to all
Dennis

 

[marshg246]

1) Hi Carl. Can you please hold the pistons for me for a couple of days please? I am in Vancouver, Canada
2) To All. I hope I have made a mistake reading the gauge because if I am off by a decimal point, bore wear is within tolerance.
.....................I do want my next post to all to say "Oops. I made a mistake!"
3) I will check measurements again in a few hours and post photos of my dial gauge
4) I just did a math calculation as to the top ring gap theoretical increase when placed in the worn part of the bore.
................The top ring gap is currently 0.020" when placed in the unworn part of the bore. If the bore
................truly does increase by 0.010", (as I have measured), then the increase in circumference for the piston ring
................when in the worn part of the bore is approximately calculated as pi (3.141) times the increase in diameter of 0.010" which
................calculates to plus 0.031". I measured the top ring gap in the worn part go the bore (0.010" of wear) as 0.056"
.................which is plus 0.036". This measured gap increase seems to fit with the calculated gap increase.
Will report and thanks to all
Dennis

Pi * d = circumference
A gap increase of .036 (unworn=.020 and worn = .056) means a circumference increase of .036

Assuming unworn diameter is 3.0720 then worn = 3.0834

So, .0114 larger - WAY TOO MUCH.

 

[DennisMo]

Here goes how I calculated whether converting from metric to inches worked

Picture 1 is the Bore gauge
Picture 2 is end of bore gauge where I adjust it to fit the diameter of the bore
Picture 3 is the dial of the bore gauge says that each division equals 0.01 mm
..................I want to check I am converting properly and not out by a factor of ten therefore the following:
Picture 4 I set my calibers to exactly three inches (this exercise has nothing to do with bore dimension)
Picture 5 I put the bore gauge between the calipers and then zero the bore gauge dial
Picture 6 Shows zero on the dial. I then take bore gauge out of calibers
Picture 7 I increase the calipers to 3 inches plus exactly 10 thou equals 3.010 inches
Picture 8 I put the bore gauge into the calipers in picture 7 above to measure
Picture 9 The bore dial is now displaced 26 increments ie 26 times 0.01mm from its zero ie 0.26mm
Picture 10 I do the math to convert from .26 mm with calculation showing it converts to 0.0102 inches which is ten thou
Thus the extra 10 thou I added on the calibers has been measured by the bore gauge
Please comment how I have done here.
Next reply will show how I measured the bores
Dennis

 

[DennisMo]

This is an example of the measurements I made in the bore.
Just so you know, I oriented the bore gauge many different ways when doing each measurement to try find the minimum reading

Photo 1 measuring at top of bore where there is no wear
Photo 2 zeroing the bore dial gauge while measuring at the top of bore
Photo 3 measuring bottom of bore where there is no wear with the zeroed gauge to see if there is any difference between top of bore
Photo 4 dial gauge at bottom of bore shows no displacement on the gauge that was zeroed at top of bore
Photo 5 measuring from top of bore down where there is a lot of wear ( I don't like this part)
Photo 6 this shows the dial displacement for the measurement in photo 5. The zeroed needle on the gauge has been displaced by 35 marks which is
................. 35 times 0.01mm equals .35 mm This converts to 0.0137 inches (or 13 thou).

I think the news is bad for me on this one. But anyone who can turn this into good news is a hero!

Dennis

 

[concours]

Using a dial caliper as a precision measure aside, (which it isn't) you show a lot of wear. What air filter was on the bike?

Have you done engine work before? I ask because you talked about just putting new rings in it...
that much wear is visible to the naked eye.

Step 1) order new pistons & rings in the apropriate oversize

Step 2) supply them to the machinist along with desired piston clearance.

 

[marshg246]

Here goes how I calculated whether converting from metric to inches worked

Picture 1 is the Bore gauge
Picture 2 is end of bore gauge where I adjust it to fit the diameter of the bore
Picture 3 is the dial of the bore gauge says that each division equals 0.01 mm
..................I want to check I am converting properly and not out by a factor of ten therefore the following:
Picture 4 I set my calibers to exactly three inches (this exercise has nothing to do with bore dimension)
Picture 5 I put the bore gauge between the calipers and then zero the bore gauge dial
Picture 6 Shows zero on the dial. I then take bore gauge out of calibers
Picture 7 I increase the calipers to 3 inches plus exactly 10 thou equals 3.010 inches
Picture 8 I put the bore gauge into the calipers in picture 7 above to measure
Picture 9 The bore dial is now displaced 26 increments ie 26 times 0.01mm from its zero ie 0.26mm
Picture 10 I do the math to convert from .26 mm with calculation showing it converts to 0.0102 inches which is ten thou
Thus the extra 10 thou I added on the calibers has been measured by the bore gauge
Please comment how I have done here.
Next reply will show how I measured the bores
Dennis





View attachment 123043
View attachment 123044View attachment 123045View attachment 123046View attachment 123047View attachment 123048View attachment 123049

View attachment 123050View attachment 123056

OK a real bore gauge.

You're making way too much work of this.

Simply take a reading at the very top (if the carbon is removed) or at the bottom where the rings don't touch. Note what the gauge says. Move it to about 1/2" from the top of the bore and notice the new reading. Subtract the 1st from the 2nd. If more than .005" (.127mm) you must bore. Personally, if more than .1mm I would bore. You could check several spots in the ring swept area, but if any are over .005" you must bore and if over .004" I would bore.

 

[DennisMo]

Thanks to All!