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Author Topic: Why is honing/boring a two stroke cylinder an art? what goes into it?  (Read 6050 times)

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Offline Dave Freist

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #15 on: December 13, 2010, 04:01:12 PM »
Twinline has cool stuff. Its a great place to visit, and I'm looking forward to my next one. Ohhh, and BTW...the best steak shop west of the Mississippi is 7 blocks down the street. Ummmmm, mmmmmm, mmmmm, mmm.

Grandpa was a self-made Professional Engineer. Got his PE in '42. He was a cranky old fart (not like me of course) and taught me how to use precision tools. "Here; feel that? thats the proper clearance. Remember it."
« Last Edit: December 13, 2010, 04:32:18 PM by Dave Freist »
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Offline SUPERTUNE1

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #16 on: December 13, 2010, 05:05:52 PM »

Here's a pdf on the sunnen honing equipment supplies:
http://www.sunnen.com/graphics/assets/documents/1931f2424f98.pdf

I use a Sunnen AN-112 portable hone (on page 140) with a honing tank for bores 64mm and up and a Sunnen JN-95 protable hone (page 138) for bores smaller than 64mm.
With the AN-112 honing head I have the quad stone, quad guide honing set for it.
Go to page 146 and use these stones, GY25-J45, these are made for honing cylinders that have keyway slots.
They work very good on 2 stroke cylinders without a lot of distortion and very little out of round like normal hone heads. 

Chuck
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Offline GSXRDman

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #17 on: December 13, 2010, 06:03:53 PM »
Thanks for the information Chuck.  I remember Judy really impressed w/ the 400 cyls. you did for her awhile back.  I think Judy sent those up to Dave F. when his first 350 became a flame ball. :flame:

RD400F modded to RD400 specs, 29.3mm R5 carbs, 240 mains, 2mm shroud 169-P2 needle jet, 5DP7-5 (full rich), stock R5 slides (2.0), #30 pilot @ 7/8ths airscrews.  2010 Spec II "classics", Y-boot UNI, TDR yellow one piece reeds, B9ES plugs / stock gap, 1.9mm BTDC.  Amsoil Interceptor 24:1, pingel tap!

Offline SUPERTUNE1

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #18 on: December 13, 2010, 07:00:29 PM »
I remember doing them for her, oh, what like 8 years ago?
I can't remember a lot of things, but I would have to say she was to only girl I did a bore job by mail order!
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Offline Vintage Smoke

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #19 on: December 13, 2010, 07:23:32 PM »
Honing a cylinder is not really any kind of mystery. It's just a matter of having the proper tools and knowing how to use them. You CAN get a near perfect job with less fancy tools that are still professional grade. The real high tech stuff just makes it EASIER and QUICKER to get the quality job you are after.

Personally, I have a boring bar and a hand operated hone(same as the Sunnen Chuck uses). I just don't machine enough cylinders to justify setting everything up and dedicating shop space for the job. So...when it does come time to bore a set of cylinders it is easier for me to send them out. The only reason I can do this is because I have a dedicated machine shop that I trust.
On the other extreme I have done it with JUST a hone though. I had a friend who had a shop out of state where he used to live "rebuild" a Harley engine for him. He moved back this way and 2 days before a cross country trip he started burning oil like a diesel. I didn't have a boring bar at that time (and he barely scraped enough coin together for the pistons..)and I actually HONED his cylinders .010" over. It took me the better part of a day, but I got his cylinders to within a ten thousandth or 2 (.0001 to .0002) of where I wanted. It involved constant measureing, honing, measureing, honing, etc. I also had to do a lot of spending more time honing the middle or bottom, etc to keep the cylinder straight AND keeping some side pressure in some spots to keep the cylinder round. IT SUCKED!!! I would never do it again. Funny thing though...the motor was torn apart a few years later to do the bottom end by a real old timer on the west coast. The guy actually called me to see if I really did a bore job with just a hone. He wanted to tell me that the cylinders were still perfect and while EVERY other moving part on the engine needed to be replaced, he was re-using the pistons and cylinders with just a quick hone and new rings.BTW...this bike has been my friends only transportation since the 80's and he has over 350K miles on it.

So...nothing mysterious....just proper tools, knowing how to use them, and real attention to detail.

BTW....Fragster...you might want to get timing and jetting down properly before you try honing...cylinders can get REAL expensive!!!
 :lol: :lol:
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Offline GSXRDman

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #20 on: December 13, 2010, 08:05:18 PM »

On the other extreme I have done it with JUST a hone though. I had a friend who had a shop out of state where he used to live "rebuild" a Harley engine for him.  I didn't have a boring bar at that time (and he barely scraped enough coin together for the pistons..)and I actually HONED his cylinders .010" over. It took me the better part of a day.  would never do it again. Funny thing though...the motor was torn apart a few years later to do the bottom end by a real old timer on the west coast. The guy actually called me to see if I really did a bore job with just a hone. He wanted to tell me that the cylinders were still perfect and while EVERY other moving part on the engine needed to be replaced, .this bike has been my friends only transportation since the 80's and he has over 350K miles on it.

So...nothing mysterious....just proper tools, knowing how to use them, and real attention to detail.

BTW....Fragster...you might want to get timing and jetting down properly before you try honing...cylinders can get REAL expensive!!!
 :lol: :lol:

Wow. Now that's bustin' yer balls right there.  Sounds like the effort required to make ends meet and stay there on cone rolls.  But, the end result...amazing.   I can see why you would never do that again!

Maybe this summer i'll get it right (timing wise)...jetting really wasn't too far off....i've been so spooked by blown motors, i'll have this sucker swimming in gas.  Like i said before, it will rev to about 9.5k w/ a 220 and that's good enough, but i'm definitely putting a cap at around 8k for longevity.   

RD400F modded to RD400 specs, 29.3mm R5 carbs, 240 mains, 2mm shroud 169-P2 needle jet, 5DP7-5 (full rich), stock R5 slides (2.0), #30 pilot @ 7/8ths airscrews.  2010 Spec II "classics", Y-boot UNI, TDR yellow one piece reeds, B9ES plugs / stock gap, 1.9mm BTDC.  Amsoil Interceptor 24:1, pingel tap!

Offline Dave Freist

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #21 on: December 13, 2010, 11:52:13 PM »
Ha, ha... Fragster. Good one. Beats Detonator..... Kevin, you are now the FRAGSTER. :bowdown:
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Offline Vintage Smoke

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #22 on: December 14, 2010, 01:10:56 AM »
Ha, ha... Fragster. Good one. Beats Detonator..... Kevin, you are now the FRAGSTER. :bowdown:

Kevin came up with that one himself!! He had a string of them one night on the shout box....he didn't know I was reading though :ninja:

That was one of the milder ones!!!

BTW...I never said I was refering to him....at least he's a good sport!!
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Offline thatguy

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #23 on: December 14, 2010, 09:00:50 AM »
I hone just about anything .010". We have a pedestal hone (1600??) as well as a CV-616 powerstroke. Setting up the powerstroke for a pair of cylinders is a bit of a pain. Most of our work is big V8's so I have to break down one set-up and reinstall it when I'm done. So I just suck it up and get in a workout for the shoulders and arms. I pride myself in getting them straight and true to .0001" max. I use a soft 400 grit stone for a plateau finish,3 or 4 strokes at a lighter pressure. They live a long time when that straight and round.
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Offline GSXRDman

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #24 on: December 14, 2010, 12:57:10 PM »

That was one of the milder ones!!!

BTW...I never said I was refering to him....at least he's a good sport!!

VS knows what the other one is...which IMO is funnier, but a little on the colorful side.
RD400F modded to RD400 specs, 29.3mm R5 carbs, 240 mains, 2mm shroud 169-P2 needle jet, 5DP7-5 (full rich), stock R5 slides (2.0), #30 pilot @ 7/8ths airscrews.  2010 Spec II "classics", Y-boot UNI, TDR yellow one piece reeds, B9ES plugs / stock gap, 1.9mm BTDC.  Amsoil Interceptor 24:1, pingel tap!

Offline GSXRDman

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #25 on: December 14, 2010, 01:00:38 PM »
I hone just about anything .010".  I pride myself in getting them straight and true to .0001" max. I use a soft 400 grit stone for a plateau finish,3 or 4 strokes at a lighter pressure. They live a long time when that straight and round.

yeah, our stuff has to be in ten thousands (inches).    0.0018" for prox pistons (lazy customer)....if you are really picky and sand your pistons and all that, you can go down to 0.0014" like Lyn does.  that's getting pretty small, but you have to run them in very carefully, take the cylinders apart, sand the high spots...


« Last Edit: December 14, 2010, 01:16:31 PM by GSXRDman »
RD400F modded to RD400 specs, 29.3mm R5 carbs, 240 mains, 2mm shroud 169-P2 needle jet, 5DP7-5 (full rich), stock R5 slides (2.0), #30 pilot @ 7/8ths airscrews.  2010 Spec II "classics", Y-boot UNI, TDR yellow one piece reeds, B9ES plugs / stock gap, 1.9mm BTDC.  Amsoil Interceptor 24:1, pingel tap!

Offline poppaweely

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #26 on: December 14, 2010, 01:11:23 PM »
how about horing/boning? there's some artistic skill in those activities i think.
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Offline GSXRDman

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #27 on: December 14, 2010, 01:14:42 PM »
how about horing/boning? there's some artistic skill in those activities i think.

Mark is the horologist   :rimshot:
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Offline yam3narthur

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #28 on: December 15, 2010, 01:37:30 PM »
there is only one way to run cylinders in imho. thats to give it full throttle and switch the bike off when it gets hot. first journey might only be a hundred yards.
treat them gentle and things dont seem to bed in.
i got mine rebored mine to 0.035mm cearance with oem pistons. ran it in slowly lengthening the duration of my journeys and also increasing my ceiling rpm starting off at 4k and working it up to 9k over 200 miles. overkill  maybe but with tight clearances its so easy for it to nip up.
ive run them in gently not giving them any load and the results are not as good. especially with dyles rings that need a good bit of pressure to seal.

i got some bores honed 2 months ago by a 74yr old timer and when i got them back they both tapered and one was 0.035mm bigger at the top and the other was 0.03mm bigger at the bottom!!
wont be using him again.
he claims to rebuild cranks to 2 thou and another guy i use does it to within 1 thou.
wonder what everyone else works to over your side of the water?
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Offline GSXRDman

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Re: Why is honing/boring a two stroke cylinder an art? what goes into it?
« Reply #29 on: December 15, 2010, 02:23:33 PM »

i got some bores honed 2 months ago by a 74yr old timer and when i got them back they both tapered and one was 0.035mm bigger at the top and the other was 0.03mm bigger at the bottom!!


035mm is .0014"~  .03mm is .0012" <----looks like definite seizure territory....not much difference there,but it's supossed to be the same all the way down right?...man you like your clearances pretty tight.    i've read elsewhere that you can take off in first and rev it and then decelerate off throttle in the next gear, keep repeating as you go up in gears...get the revs up and then let it coast off throttle ...so it wears going up in rpm and also going down in rpm.  I've been riding mine easy and i always get blowby.  Might have to try the harder run in.  In any event.i think the modern oils are to blame....you can find two stroke break-in oil...i think that Portland Motorcycle carries it.  Last time i was there, they had it on the shelves.
« Last Edit: December 15, 2010, 02:26:29 PM by GSXRDman »
RD400F modded to RD400 specs, 29.3mm R5 carbs, 240 mains, 2mm shroud 169-P2 needle jet, 5DP7-5 (full rich), stock R5 slides (2.0), #30 pilot @ 7/8ths airscrews.  2010 Spec II "classics", Y-boot UNI, TDR yellow one piece reeds, B9ES plugs / stock gap, 1.9mm BTDC.  Amsoil Interceptor 24:1, pingel tap!