L.A.B. may know bore size decision to make

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hobot said:
New Pistons stamped .040" fit normal loose, under .005" clearance. This 2nd score clean up hone left bores 2.910" and as .040" over should measure 2.945", Trixie's bores are now only .035" Under Size.
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How can the bores be .035" undersize?

+.040" is not 2.945" (or 2.955", refer back to page 1 of this thread)

You have apparently established for yourself that the bores are not undersize because the "new .040" pistons" already fit in the bores with at least some (under .005") clearance.
 
Come on, Hobot. Is this just a big chain yanking event you have decided to put on?

2.945 is .030 over .040 over. .030 over + .040 over = .070 over. 2.945 - .070 = 2.875 or standard bore.

Let me know where you get these .070 over pistons. :P

We have logical, illogical and of course hobotogical! :P

Here is some logic for ya. If you get to .157 over you'll have a stock 850 bore and it looks like you're well on your way. :P
 
Ok I admit I'm just a jerky pilot and Norton mechanics are over my little head to compute w/o help. I started the post with thought I'd get a range of acceptable .040" final measures, but have boned up on it now to point i might have more data on it than you'all to judge-decide myself. To sum up Trixie's current statistics...

Grade A standard bore = 2.875".
Over bore of .040" should = 2.915".
Current bores are 2.910".
So bores are now .005" under size for full .040" over bore. Yea!
.005" is the standard bore step accuracy to measure to order ring size steps for file to fit.

Just mic'd pistons @ 2.906" so piston clearance = .004".
Implies a bit on tight side of normal clearance, .045" -.005" for air cooled cast iron cylinders.
Going by interweb and Norton manual data I should gap 1st ring to .010" and 2nd to .0012+" for best sealing.
850's grade A bore = 3.030" so Trixie is still 0.12" smaller bore. Must remember to check gasket bores now.

I don't want anything 'special' in Trixie like TotalSeals I used in Peel, so next hang up is finding ring set the right size to file to fit. Any suggestions to source these?
 
hobot said:
Grade A standard bore = 2.875".
Over bore of .040" should = 2.915".
Current bores are 2.910".
Click to expand...

Now at least we are getting somewhere.

"Grade A" is 2.8746" - 2.8750" (the bore grades are basically irrelevant as it applies to the original build) however we can accept 2.875" as being the nominal bore size.


hobot said:
So bores are now .005" under size for full .040" over bore. Yea!
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No. The bores will be correct "if and when" the pistons fit the bores with the specified amount of clearance.

You seem to be approaching this from the opposite direction by saying standard bore size is 2.8750", plus .040" means the bore size is 2.915" when what you should be doing is arriving at the required bore size by measuring the pistons and adding the necessary clearance (once) onto the piston figure.



hobot said:
Just mic'd pistons @ 2.906" so piston clearance = .004".
Implies a bit on tight side of normal clearance, .045" -.005" for air cooled cast iron cylinders.
Click to expand...

.045" :shock: I hope you meant .0045" - .005"?
 
.045" :shock: I hope you meant .0045" - .005"?
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Ugh, yes, see what I mean about needing help to compute details, even w/o moonshine or loco weed mis-con-screwing the dot and number of Ohhh's...

But finally I got your expert data point I sought on what range bore measures and pisiton clearance should be rather than what I simply see listed in manual.

Anyone now the oil smoke is settled on cold surfaces...
bores = 2.910"
pistons = 2.906"
------------------
clearance = 0.004"

As Trixie didn't seize on even tighter piston clearance prior and pistons don't show scuff wear or even blow by staining my faulty logic says standard .040 os rings should fit right out the box or just a little filing to fit. One other good finding was the about pristine looking cam lobes and resurfaced lifter bottoms. Cam actually looks better than frist re-used untouched by machinist, just hand filing the worm drive from nicks gaps knocked out by re-used rod bolt let go a few years ago @ 3000-ish 50's mph low throttle sight seeing. The nuts were new though.
 
hobot said:
1. Rings in piston box were under size- maybe only a .020 over ring set was sent in error.
2. Pistons are normal loose in bores but not slappingly so, so only need to order os ring set - but which kind the Total Seal $100+ or more economical standard gap rings.

What part of stop dribbling shit do you not understand ?
Unless your pistons are 0.035'' oversize your bores are rooted
They didn't supply undersize rings YOU laped them out , as you said it was good for a while.
If you do have 0.035'' pistons and 0.004''clearance then gap a set of 0.040'' rings to suit ,but I would reject any new pistons that came in at incorrect size unless I knew why, they may have been dropped or incorrectly machined
Click to expand...
 
What part of stop dribbling shit do you not understand ?
Click to expand...

Just the adding and subtracting to end up with a desirable to me slightly under size bore with nice almost too tight pistons fit after two clean up hones - so mainly the mystery of what size rings were sent that gave .025" gaps in top to bottom of un=worn but slight scored bores.

I just measured a top ring OD, with un-touched out of the box gap closed - at 2.882". OD
bore 2.910" ID
--------------
= 0.028" OD difference

What's that imply on supplied ring size for intended 40 over bore size?
 
Piston spread the caliper to 2.906" measuring from bottom with jaws aligned with piston sides most the way up. The piston I grabbed still had the rings on so didn't measure the band above the rings. Did I goof again on this measure?

I've got feet firmly grounded in normal reality - its the motorcycles habit that drags my head into extra-ordinary cloudy states. I tease about the intoxicants but I'm so high naturally too much brings me down to ordinary states, yuk. Only Ms Peel though can launch me into psychedelic states where I function best w/o thought.
 
hobot said:
What part of stop dribbling shit do you not understand ?
Click to expand...

Just the adding and subtracting to end up with a desirable to me slightly under size bore with nice almost too tight pistons fit after two clean up hones - so mainly the mystery of what size rings were sent that gave .025" gaps in top to bottom of un=worn but slight scored bores.

I just measured a top ring OD, with un-touched out of the box gap closed - at 2.882". OD
bore 2.910" ID
--------------
= 0.028" OD difference

What's that imply on supplied ring size for intended 40 over bore size?
Click to expand...
Steve,

if the ring measures 2.882" in diameter, then you would have .010" - .011" end gap when installed in a 2.915 (nominal +.040" bore size). Sounds like normal +.040 rings to me.

Ken
 
Machinist put 2.910" on the box and the ticket as I asked especially for final bore measure to order new ring set. Wesley insisted to measure the ring gap before the hone and that I then checked too as .025" gap no matter where ring placed. Closed tight ring OD = 2.882".

2.915" nominal .040" over standard
-2.882" ring OD as tight as it gets
---------
=0.033" ring bore clearance slack with the used ring ends touching.

2.910" current bore
- 2.882" closed ring OD
---------
= 0.028" potential clearance slack in closed ring if re-used on current bores.

So the instant crazy making summary is Trixie's .005" under size "almost 40+ bores" gives too big a gap than expected using rings for a nominal 2.915" 0.040"+ bore. This leaves me confused on what to order-do next.

TotalSeal says they can custom Trixie a set but Wesley showed me that their custom part number is identical to off the shelf Norton rings p/n that he'd looked into and for same price, so extra confused even with a clear head. I've not talked to regular custom ring suppler yet. Likely they will want to know the ring groove depth besides just their widths.

Its my Norton karma you yourself got a taste of on Peel's crank issues, so over time I get to wallow in the Nth degree of minutia of every single component, mostly no fault of my own. I really though after Trixie's 4th rebuild behaving myself and a few 1000 miles oil tight smokeless - I'd broken the cycle...
Wes has gotten a few 1000 miles ahead of me this season.
 
TotalSeal was my no brainer way with Peel, so hunting alternatives for Trixie and stumbled on this interesting site and mystery ring construction that's not quite like the TS rings I've seen so far.

http://en.vintage-motorcycle.com/index. ... 49&limit=0

L.A.B. may know bore size decision to make
 
hobot said:
Machinist put 2.910" on the box and the ticket as I asked especially for final bore measure to order new ring set. Wesley insisted to measure the ring gap before the hone and that I then checked too as .025" gap no matter where ring placed. Closed tight ring OD = 2.882".

2.915" nominal .040" over standard
-2.882" ring OD as tight as it gets
---------
=0.033" ring bore clearance slack with the used ring ends touching.

2.910" current bore
- 2.882" closed ring OD
---------
= 0.028" potential clearance slack in closed ring if re-used on current bores.

So the instant crazy making summary is Trixie's .005" under size "almost 40+ bores" gives too big a gap than expected using rings for a nominal 2.915" 0.040"+ bore. This leaves me confused on what to order-do next.

TotalSeal says they can custom Trixie a set but Wesley showed me that their custom part number is identical to off the shelf Norton rings p/n that he'd looked into and for same price, so extra confused even with a clear head. I've not talked to regular custom ring suppler yet. Likely they will want to know the ring groove depth besides just their widths.

Its my Norton karma you yourself got a taste of on Peel's crank issues, so over time I get to wallow in the Nth degree of minutia of every single component, mostly no fault of my own. I really though after Trixie's 4th rebuild behaving myself and a few 1000 miles oil tight smokeless - I'd broken the cycle...
Wes has gotten a few 1000 miles ahead of me this season.
Click to expand...

Something is not right in at least one of your measurements. If you really have 2.910" bore, and the ring diameater is 2.882", you should be measuring .028" clearance between bore and closed ring. That's simple subtraction, 2.910 - 2.882 = .028. If the bore were 2.915", you would have .033" clearance. Again, that's just subtraction, 2.9i5 - 2.882 = .033. If your rings are 2.882" closed diameter, and the clearance in the bore is .033", the bore is 2.915", not 2.910", no matter what it says on the box. The end gap in the rings is just the clearance divided by pi, so if you you measure the diamter of the rings at 2.882", and the clearance at .033", your bore is 2.915", and the end gap is .0105". This isn't magic, just really simple arithmetic. You can't have 2.910" bore, 2.882" closed ring diameater, and get .033" clearance. At least one of those numbers is wrong.

Have you actually measured the bore?

Ken
 
Ugh, yoose guys are so hard to grasp my Trixie's dilemma. One of us needs to really understand situation to solve it.

Machinist finished and measured both bores at 2.910". This Is .005" Under Size, not a full 0.040+ re-bore at 2.915".

By subtracting the piston OD form current bore ID gives .004" piston wall clearance. Implies pistons about right out the box.

Rings had .025" gap in bores Before they were honed *again*. Just checked another top ring in the new 2.910 bores to get a.025" blade in gap with nil resistance but not a .026". So gap increased maybe .0003", which pie ratio implies the bore scores were only about .00015" deep to remove, so bore hone opened bores up 'roughly' only .001". Score evidence can still be seen but not felt by finger or tool and the hone grit texture is greater and feel-able.

*Ok* just measured the other top ring compressed and held tight by vise grips to get 2.850" OD. 2nd ring gives 2.854". I must of had the prior ring tipped in the micrometer jaws but it cracked while compressing it just now. So these ain't 40 over rings then - are they?

Summary - bores and pistons seem good to go, just need source of correct ring sets, but don't know where to shop other than TotalSeal @ $100 a set - that'd be wasted on plain old Trixie.
 
hobot said:
Machinist finished and measured both bores at 2.910". This Is .005" Under Size, not a full 0.040+ re-bore at 2.915".
Click to expand...

You still appear to be approaching this from the wrong direction by thinking of it as: nominal + x = y instead of: piston size + clearance = bore size.
If the oversize pistons fit the bores with the correct clearance then the bores are not undersized!
If the piston size + clearance results in a bore dimension slightly less than, or slightly more than nominal + .040" then that is mostly irrelevant.

However, if the ring gaps are out of spec. at that bore size then they are obviously wrong.
 
LAB, thanks for the attention but the bores and pistons I've determined are a nice combo fit *but* the rings supplied are under size is all. I did not know the over bore size measures tolerances at first nor how to check rings OD until some hours ago, so final solution is a correct set of new rings, which I don't yet know where or what to buy. Trixie's challenge is to keep her as un-special as possible so don't desire TotalSeal. Hunt is now on to refresh contacts with world wide vendors that know for me for year as 'easy money'.
 
Ive been in the recon industry long enough now to smell bullshit, what arn't you telling us hobotsis, what size is stamped on the top of the pistons ,what size is on the box,
 
hobot said:
Ugh, yoose guys are so hard to grasp my Trixie's dilemma. One of us needs to really understand situation to solve it.
Click to expand...
I don't think any of "us guys" are having trouble grasping your dilemma. I think a lot of the problem is the numbers you're giving us. The relationship between bore size, closed ring diameter, and ring end gap is real simple math. If your numbers don't add up right, it's the numbers that are wrong, not the math. The difference between 2.882" and 2.850" for the closed ring diameter is a bit more than the difference between Tweedledee and Tweedledum.

Just for fun, I went out in the shop and measured the closed ring diameter for top rings from three NOS ring sets. I did them the same way you described, holding the ends together with visegrips, and measuring accross the diameter at 90 degrees to the gap. The +.040" Powermax rings, still new in the Norton box, measure 2.903/2.904". The +.020" AE Wellworthy rings measure 2.887/2.890". The Norton AE standard bore rings measure 2.863/2.865". A single Hepolite Atlas +.040" ring measures 2.882". A set of used +.040" AE Powermax rings out of one of my old race bikes measures 2.903/2.903". If your's measure 2.850", they are certainly not correct, but it they measure 2.882" as you originally said, they are probably normal +.040" rings. You need to be fairly careful measuring with calipers. It's pretty easy to compress the rings several thou by clamping them too tight with the calipers.

If your bore really is 2.910, you should be able to just buy a normal set of +.040 rings and have plenty of room to file the ends for the right end gap. No need for expensive Total Seal rings.

One last suggestion. If you haven't already, verify your piston clearance by making sure that the piston will slide all the way into the cylinder with a .004" feeler gauge against the skirt at 90 degrees to the pin. .004" should be enough clearance for a cast piston.

Ken
 
Ugh, yoose guys are so hard to grasp my Trixie's dilemma. One of us needs to really understand situation to solve it.
Click to expand...


Hobit, you are very fortunate that a lot of guys here are offering their personal time and a hell of a lot of experience in an effort to help you out.

Yet your above quote indicates that you believe it is those other guys rather than your own apparent inability to be clear, that seem to lack the intellect to understand "Trixie's" current problem.

Whether you really do believe it is their failings or not, it would probably not be a good idea to state your belief.

Many here have posted their frustration with wading through your posts to find the point.

And combining that difficulty with an "attitude" from you is the reason for the recent retorts from those others.
 
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