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

I picked up Trixie's re-honed scored bores that ended up 2.910" ID each. Would like to know what bore size variations is acceptable before a next size up rebore for a judgment call on fitting over size rings in file to fit or TotalSeal gapless expanders.

Grade A 750 standard bore is 2.875" so +.040" = 2.955". Seems even with a hone Trixie's bore are still fit and undersized over bore by .045" for a good sealing os ring fit. Am I on or off track with my measured reasoning?

hobot said:

Grade A 750 standard bore is 2.875" so +.040" = 2.955".

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:?:

2.875" + .040" = 2.915"

+.040"
=
Diameter + .040"
Not radius + .040"

Looks like ya got a little more honing to do. .005 more should get you perfect .040 over.

Thanks for the assessment. Total seal gave me a quote of $100 for a custom made special part number set of gapless 2nd ring size that should solve the smoking it that's the only source of the blow by blowing by the copper gasket. I thought the calc implied an under size over bore so all the better to leave the extra meat in for next time around, and i now know its silly not to expect a next time around too soon for one reason or another. If undersize tight over bore to begin with - makes one more pensive to measure the off the shelf Taiwan-ness after makert ring set fit before finding out the hard way ain't up to snuff as supplied. I am relieved by your report ahead of L.A.B.'s fast draw detailed references display.

hobot said:

Would like to know what bore size variations is acceptable before a next size up rebore for a judgment call on fitting over size rings in file to fit or TotalSeal gapless expanders.

I thought the calc implied an under size over bore so all the better to leave the extra meat in for next time around,

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Do I understand this correctly?

What you appear to be saying is that you intend to use a set of standard pistons fitted with oversize rings in bores honed to 2.910"?
If so, that would result in a piston clearance of: .038"-.040" which is about ten times normal clearance. :?
Or do you mean +.020" or +.030" pistons? Both of which would still give too much clearance.

Naw, just I'm sensitive enough to detect your annoyance, so what I mean is that Trixie *now* has *almost* a .040" over bore and the still like new .040" pistons came with too small OD ring sets to give tight enough ring gaps for the copper head sealing to take after most a year so must spend another c-bill and wait other week to have a long term solution on hand before hot buggy season arrives.. I had to dig up my own bore references and pow pow'd wit TS ring staff to realize I'm not a capable mechanic that measures to N'th degree everything before install like most the rest of the world seems to get away with.

So next decision I need hlep with is to buy TS rings for $100 or just ordinary os ring set for $60.

hobot said:

Naw, just I'm sensitive enough to detect your annoyance,

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Not annoyed, just a bit confused as you'd only given us half the story and left out some rather important information. :roll:

Yes well it annoys me to deal with the holes in my brain waves. Was hoping to get the range of acceptable 040" bore measures to decide if next bore up was the most logical choice or not. Surprised myself that the bores are a bit under size yet are the 2nd clean up hone and also tends to back up my simple logic holes I should of got away with the rings out of the box like my buddy and seems most others do. My wife could care less about this so ranting here, sorry takes all kinds ya know.

So now its one week $100 TS set or a few days standard os $60-ish rings? Any extra performance is total wasted on me on Trixie just want her for quaint smokeless slow shows.

I guess its a complement I thought of you for the minutia that matters.

hobot said:

so what I mean is that Trixie *now* has *almost* a .040" over bore and the still like new .040" pistons came with too small OD ring sets to give tight enough ring gaps for the copper head sealing to take after most a year .

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Some of us are still confused !
You usually get the cylinders bored to suitable clearances for your available next-oversize pistons, which your machinist should have had in his hands to measure.

So how can your cylinders, which seem to be still 5 thou too tight for +40 pistons, have rings which don't have "tight enough ring gaps".
And what has the copper head gasket got to do with it ??

At present, you'd be hard pressed to even bang those +40 pistons into that bore size.
And the rings shouldn't even squeeze into there, with the pi r squared rule you'd have quite a negative ring gap. ?? (ie they'd need quite a lot of filing of the end gaps to even fit ?)(unless they weren't actually +40 rings to begin with ??

Enquiring minds, and all that...

Ugh. I think it's time for another toke.

Dave
69S

me thinks something been smoking a lot more than hobits bike in dem thar neck of the woods :shock: :roll:

maybe them razorbacks been rootin up somthin more than Ozark truffles?

Dog

Yes'em, all's you'all's have the correct understanding of the situation now, just not the initial reason that created the confusion for me too. If'n ya remember Trixie's 4th rebuild saga the machinist I was to bring pistons to quit the shop the day after I checked that the shop was capable of the finesse I sought so left the barrel there but didn't get pistons to him in time. The rest is history.

The second half of the tail is the off the shelf 0.040 rings should of been too tight a gap for the slight under size bores - not over twice as wide as expected. They sealed smokeless within a min and stayed good for few 1000 miles and I had fair amount of adventures w/o embarrassment till late last fall, ugh, I mean autumn. I admit I'm not cut out for mechanics, just a pilot.

You've got a Norton, you're a mechanic. No problem.

Dog

Ok DogT thank you I can't deny I'm a mechanic enough to suffer with Cdo's but its a sliding scale with a steep slope at my end. I've never dealt with the ring details prior as Peel's TotalSeals didn't need it and 2 prior Trixie re-rings worked fine out of the box. Btw putting pistons in barrel is one of the toughest jobs for me and have not yet done em w/o a helping hand. People give two ways to do it, slip barrel down on mounted pistons or slip pistons in barrel then piston pens. I like the 2nd way best now but Peels were impossible tight so had to do it the 1st way.
Every Commando is like a finger print that changes over time.

mikegray660 said:

me thinks something been smoking a lot more than hobits bike in dem thar neck of the woods :shock: :roll:

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That Mississippi ready rubbed wacky tabacky will apparently do that to ya!! :lol:

Well experience has shown intoxicated people tend to get through crashes better. Do ya know a jar of 'shine in an ice chest gets so cold the ice freezes fast to the jar. Hemp is shared freely in these parts too. hehe the stash part of a pipe forms a pre-oil filer on Peel and with the fabric braid hose, could remind some of a bong bodge I hope.

Hobitsis, 0.010'' clearance its rooted.Take it to a machine shop with sunnen power and preferably torque plates and get them to hone it out to +0.040'', don't let any one try and bore 0.005'' out, 0.003 with bar 0.002'' with hone wont work. No rings are succesfully going to work at 0.010'' clearance in regards to oil consumption and pay attention this time and stop dribbling on about shit

splatt said:

Hobitsis, 0.010'' clearance its rooted.Take it to a machine shop with sunnen power and preferably torque plates and get them to hone it out to +0.040'', don't let any one try and bore 0.005'' out, 0.003 with bar 0.002'' with hone wont work. No rings are succesfully going to work at 0.010'' clearance in regards to oil consumption and pay attention this time and stop dribbling on about shit

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fred likes this

Oh Brother, lets consider the facts of Trixie's situation. The Out of my control 1st re-hone left Trixie's bores under sized for 40 over piston/ring set, so out of the box rings should of had less than .010" gap or even need file to open gap to factory listed .010-.012" gap. instead we found .025" gap w/o evidence of ring or bore wear. 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. Sand or carbon grit scored bores so 2nd re-hone took those out this time.

1. Rings in piston box were under size- maybe only a .020 over ring set was sent in error. I error'd by not checking gap on initial install, live and learn eh and just enjoy the rubbing my face in it here as hurts less than blown engine or crashes.

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.

3. If I ever go to .060" over then will hunt down hi end machine shop with the goodies to do it well.

4. What ring gap to yoose guys shoot for in regular 1st and 2nd rings? Oil groove should be .0532" wide as my Pistons have.