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MrFluffy
09-28-2012, 12:16 PM
I just bored some cylinders from 66mm to 69mm (738cc turbo motorbike engine becoming a 810cc) with a modicum of success, but I thought id post the pics up here to see if people could come up with any bits Ive missed. Boring bar is a hydraulic feed Burtonwood aero from the 40's, with a seperate motor which drives the bar via a drive cable setup. Ive cut them dry as the book says to cut cast iron.

My personal feeling is the bar isnt supported properly, yet the bores have all come out central, but it seems to me that the feet of the bar should be supported with a spacer shaped to the bore to support them at the front. There are some half moon's of steel which look like they fit round the front of the bar but I can't work out how to insert them as its impossible to remove the alignment tool with them in situ, and you clamp down the bar during alignment so they no longer slide into the space.

First I'm using the alignment mechanism, its a cap which fits the boring head, and has a hardened taper which push pins in the bore to centre it.
http://www.oldskoolperformance.com/forum/download/file.php?id=4107

Put the carbide cutter holder in the sharpening jig and touch it up on the 3 holes which generate the 3 cutter angles. I used some light oil (wd...) on the diamond lap as I haven't got any honing oil yet, although I will purchase some.
http://www.oldskoolperformance.com/forum/download/file.php?id=4110

Set the diameter on the setting mic, its the radius of the bore - head radius when the mic is 0, which happily is 1 inch. I work in metric normally but this bar predates me by a few decades and is english, so I just work in imperial.
http://www.oldskoolperformance.com/forum/download/file.php?id=4111

I made these spacers to sit under the sleeves where they protrude to get the block flat on the table for stability and to cut down any rocking or tendancies to displace the liners with bar weight.
http://www.oldskoolperformance.com/forum/download/file.php?id=4113

MrFluffy
09-28-2012, 12:17 PM
Cutting, you can see the unsupported front part of the feet.
http://www.oldskoolperformance.com/forum/download/file.php?id=4115

Post cut its within 0.01mm from top to bottom of the bore and side to side without honing. I measured some oem cylinders and they are 0.04 or worse in the same dimensions, although they have been in service.
http://www.oldskoolperformance.com/forum/download/file.php?id=4114

Final bore is 0.01mm undersize, so I can hone it 0.02mm and have 0.01mm clearance, but I'll hone to the pistons as they are used already so may be worn on the skirts.
http://www.oldskoolperformance.com/forum/download/file.php?id=4116


Surface finish on the bore without honing, but after a wash out.
http://www.oldskoolperformance.com/forum/download/file.php?id=4118

Anything obvious to more experienced hands I'm missing? these have come out really nice but it may just be beginners luck.

flylo
09-28-2012, 02:00 PM
That has to be one of the boring post I've read! Thanks, very informative. If they start doing the video's that would be a good one.

Peter.
09-28-2012, 02:06 PM
Looks great to me. You going after Lorcan's power record?

bob_s
09-28-2012, 02:36 PM
You say the piston skirts may be worn.\
Have you measured the pistons? If they are worn, it is best to just replace them.
Putting in a collapsed piston is a guarantee of failure.

MrFluffy
09-28-2012, 05:26 PM
Peter, no, this is just one of my road bikes that has been bubbling away on the back burner for a few years and giving me the evil eyes from the shed corner for not finishing it, and given the amount of 750's I blew up over the years experimenting, there was a shelf full of ruined 750 cylinders to use for practice.
I am instead mostly concentrating my resources on building a drag (comp) bike around the (GP)z1 base for 2013 and that needs extensive work on cylinders too, so this is a trial run as it were.

One thing I've forgot to mention is I ruined the first block experimenting by boring a cylinder off centre, until I went on the net and studied the newer professional bar operation's with the air tables, and smeared the plates under the bar in washing up liquid so it could slide round to centre more accurately for a poormans version of the same effect until the fairy liquid dried (just time to faff about clamping it all up after alignment). Since doing that the bore has been central in the liner when measured at the lower part of the liner furthest from the bar.

Bob, good point but I honestly don't think they'll be worn enough for that to be a concern, they are special forged wiseco's and very very strong compared to oem cast piston's. They run to $600+ a set new, and my resources are spread so thin I have to take what I can get and fettle the cylinders to match the limited piston wear.

RussZHC
09-28-2012, 07:20 PM
Not sure what to suggest, the "finished" bore looks pretty good.
The only suggestion, maybe, is bolting on a "blank" cylinder head to duplicate the bolt stresses (i.e. potential for putting a finished cylinder bore slightly out of "perfect" round/centered etc.).
"Blank" is the best way I can describe it, the versions I have seen are made specifically for such tasks and are, more or less, a piece that roughly duplicates the thickness of the cylinder head re: how much material the bolts needs to pass through but don't actually from a cylinder head...sort of like you have just continued the cylinder up [sorry, can't find the proper word and any auto performance catalog has way, way too many similarly named items for me to find it]
Also can't recall if that is more of the boring process or finished honing process.

justanengineer
09-28-2012, 09:05 PM
I'd suggest your work is just beginning if you want a really good engine. A bore gage is great for measuring the bore and taper, but thats only a small portion of the battle as cylinders often wear and/or are machined banana shaped or out of relation to the crank centerline. This is one reason you do not want to follow your initial instinct and reference anything off of the actual cylinder, nor constrain the free end of the boring bar inside the cylnder. If you think you must, constrain the free end otherwise, but in reality you shouldnt need to bc engine blocks and liners are generally easily machinable gray iron. As Russ suggests, anytime you machine a cylinder it should be done with a torque plate in place as cylinders will distort under head bolt torque as evidenced by many piston seizure tests.

Just to add my $0.02, and others will likely argue this, but IMO you shouldnt bore sleeves. Hone yes, but bore no as most dont have enough material, and boring is IMO something done to either correct misshapen/mislocated geometry or to go BIG. You can likely get away with it for a cheap rebuild if you had to, just as you can cut a brake rotor below minimum thickness and maybe get away with it, but they really arent designed with re-machinability in mind, which is why theyre easily changed. Irregardless, it looks like youve got a good start on a fun project. Good luck with the noning, and if you get a chance I for one would love to see more pics of the boring machine and your honing setup.

RussZHC
09-28-2012, 11:20 PM
well d'uh, "torque plate":o

anyway, found a couple of videos, first is more related I think, second is just an HD cylinder being done in the lathe (of more interest to me since it relates to some of the creative work holding threads); in the first I found the comment about using a hardened washer to gain more consistent torque readings of interest...

http://www.youtube.com/watch?v=goNVh8Dsspc&NR=1&feature=endscreen

http://www.youtube.com/watch?feature=endscreen&v=FfcukAV_Zhk&NR=1

MrFluffy
09-29-2012, 04:35 AM
I'd suggest your work is just beginning if you want a really good engine. A bore gage is great for measuring the bore and taper, but thats only a small portion of the battle as cylinders often wear and/or are machined banana shaped or out of relation to the crank centerline.

Ok, I did have a thought to make a upper and lower torque plates, the lower to carry the bar on the mating surface of the block to get a more accurate result to the crankcase mouth, assuming that is plane to the crankshaft proper which I'll be checking post case welding, but what is the best way to check for banana shaped cylinders? A clock gauge up and down mimic'ing the travel on the gudgeon/wrist pin somehow is the best I can come up with unless there is something specifically adapted for this job.
Perhaps I can mount it on the mill table and use a indicator in the head and the Z traverse to check.



As Russ suggests, anytime you machine a cylinder it should be done with a torque plate in place as cylinders will distort under head bolt torque as evidenced by many piston seizure tests.

I have something planned for the bigger 1100 motors along those lines, it'd be interesting to see how much they do change with application of the torque plates, I'll see if I can measure any distortion. I might have a spare set of crankcases with gearbox area damage that I can make a fixture from which will give a exact replica of in service mountings.



Just to add my $0.02, and others will likely argue this, but IMO you shouldnt bore sleeves. Hone yes, but bore no as most dont have enough material, and boring is IMO something done to either correct misshapen/mislocated geometry or to go BIG. You can likely get away with it for a cheap rebuild if you had to, just as you can cut a brake rotor below minimum thickness and maybe get away with it, but they really arent designed with re-machinability in mind, which is why theyre easily changed. Irregardless, it looks like youve got a good start on a fun project. Good luck with the noning, and if you get a chance I for one would love to see more pics of the boring machine and your honing setup.

This is a "big bore" piston kit (albeit used) and the manufacturer wiseco recommend boring only required to take it from 66 to 69mm, 738cc to 810. I have some reservations around how thin the liners are now and I think I'll try and find some oversize sleeves to match the block and my budget but there are enough of these kits in service working fine to suggest I could be overthinking it, plus they are stepped in diameter at the lower mouth section where they are really thin, and this area does not see high combustion pressures. The bike itself is 30 years old so there may be some mitigation which doesn't apply to more modern ultra thin wall liner engines.

For the dragbike engine, its having oversize sleeves pushed in, then bored to final dimension, as the liners are supplied to cover a range of final piston sizes to make it more economic for the supply chain. For that the cylinder block has to be changed because the original has air space between the cylinders (aircooled engine), and the new liners encroach onto those spaces and are not supported properly as a result, so it has a new solid "big" block cast to avoid this. Cooling suffers, but in 1/4 of a mile the heatsoak isn't a issue.

I will photo the boring bar next setup but the honing setup is a project in itself but not finished yet. I have a old lathe cabinet with suds pump and a mesh floor in it so I can put honing oil on constant flow for the operation, and a BIG old double handled alloy drill (1/2 hp...) that I know has the torque and speed I need as I've used it freehand in the past for this mounted on springs from a beam. I have a raybrook rigid hone (similar to the delapena's) with a selection of stones which fit in this drill also.
I am at the stage of mounting this on a dipping arm above the honing tank so I can set limits and speed of plunge before the operation as when used free hand its difficult to get the stroke just right and if the hone overshoots the cylinder, its dangerous to operator/equipment etc. I plan on a crank to do the nodding action, with a adjustable throw on the crank by dint of a slot in the crank cheek and a bolt in pin to accomodate the range of travel it will need to cover and a vfd controlled motor for crank speed.
That's a poor mans mimic of the nodding donkey style commercial power hone setups but carrying the drill at the end of the arm rather than inside and relying on a series of uj's to transmit the rotation.
Its a lot of work, but I think you are right, this is the start of the journey to a perfect block, not the end.

vpt
09-29-2012, 10:21 AM
http://www.oldskoolperformance.com/forum/download/file.php?id=4113



Those sleeves look fairly thin already. You sure they are going to hold up to boost after the boring? I know with honda car motors (aluminum with sleeves) that people run into cracked sleeve problems when going 3mm + over without boost. Many resleeve the motor with thicker sleeves and then bore them out. Just putting what I know out there.

http://i55.tinypic.com/5ugvaa.jpg

vpt
09-29-2012, 10:23 AM
Oops, I see a few already mentioned thin sleeves.

531blackbanshee
10-03-2012, 05:57 PM
a small engine boring bar table would be a great investment if you have any more cylinders to do.
i have a kwik way,here is a blurry pic,
https://lh5.googleusercontent.com/-dQrKeUHol-E/S4WN3PVv5UI/AAAAAAAAAk0/Y90qYiTh_Ts/s800/PICT0030.JPG

kz 750 cylinders get bored to 810 cc all the time with no problems.

they sell oversize piston kits for engines because it is safe(as long as you are using quality pistons) to bore them to that amount.if not they will tell you to go to a big bore sleeve.

not all cylinders need torque plates for boring and honing.

harley cylinders do,i have measured as much as .011 thousandths distortion after removing them from the torque plates,after honing.

as for honing you are over thinking it.

i use a sunnen an100 adjustable hone in an old black and decker half inch drill(hooked to a dimmer switch for motor control) with the cylinder clamped in the vise.the stroke i set by how far i extend my arms.
the crosshatch is built into my shoulders.
i keep a check on progress with a mitutoyo bore gauge.

here is a yamaha banshee cylinder getting the treatment.

https://lh3.googleusercontent.com/-NVvZsZU7xVM/UGymBZVhzoI/AAAAAAAACCQ/qGxBABRRb8s/s800/bansheebore%2520%25281%2529.JPG

i have been boring and honing for the last 19 years.

ymmv,

leon