to re-ring or bore over?

[taterhead3133]

Ok so what would you guys do? I have an 82 XLH1000 that is already bored .030 over the skirts on my pistons are lightly scratched nothing bad normal stuff the cylinders have very light grooving (will hone out fine) my issue is they measure 3.2195 and 3.2210 is this ok?

[wedge]

Ok so what would you guys do? I have an 82 XLH1000 that is already bored .030 over the skirts on my pistons are lightly scratched nothing bad normal stuff the cylinders have very light grooving (will hone out fine) my issue is they measure 3.2195 and 3.2210 is this ok?

What's the spec?

[hcrashster]

Normal bore is 3.188 At 0.030 over bore you would be at 3.218. Assuming maximum wear limits of .006, your cylinder would be at 3.224. So you are just at the limit for an 0.040 over bore. That's assuming there are no score or concentricity issues. This choice is best left to the machinist doing the work. His tools are probably more accurate and hopefully he will have the experience to make the best choice.

[wedge]

Normal bore is 3.188 At 0.030 over bore you would be at 3.218. Assuming maximum wear limits of .006, your cylinder would be at 3.224. So you are just at the limit for an 0.040 over bore. That's assuming there are no score or concentricity issues. This choice is best left to the machinist doing the work. His tools are probably more accurate and hopefully he will have the experience to make the best choice.

I'm guessing he is hoping to not have to get a machinist involved. I think he is talking about honing the jugs and installing new .030 over rings, and it sounds like he could get away with it this time and bore it on the next go round. I always figured loose is better than tight up to a point.

[taterhead3133]

I am hoping to keep my cost down. I work with a couple of good machinist and thats where I got my numbers. We just do have the tooling to bore cylinders here. If my tolerances are 0.006" I should be fine I just finished honing the jugs and they now measure 3.2200" and 3.2210" which means that I'm still within specs. Right? just need new file to fit rings. But really the question was what would you do if it was your bike???

[hcrashster]

Keep costs down? I would do exactly what you did. Hell, I've done exactly what you are doing. You are still .003 from max wear. Change your oil every now and then and you'll get lots of miles out of the motor.

[ezmerf]

When you bore when you don't have to is one less time you can bore when you need to.I'd say ride it like you stole it.Hope you the best.

[wedge]

when you bore when you don't have to is one less time you can bore when you need to.i'd say ride it like you stole it.hope you the best.

+1.................

[racerwill]

the issue that arises as you get close to the loose limit is the amount of ring that sits on the lands......you still have 0.003" to go so you should be good for a while.......

Ww

[bustert]

i have seen way worst slop and they still performed fair but she will repay you if you do her right.
how much taper is in the cylinder? too much taper will cause ring fatique and a short lived seal. excessive skirt clearence will cause piston noise. for a machine that will never see harsh service, probably will be ok but for one that pushes the envelope, there's a whole lota rocking going on, skirt failure should be considered (probably would take more slope than you got). run a stock cast piston over a hyper, more forgiving.

[Mr.Gordon]

Taterhead, I think you got the right idea, and as long as the ring's fit the piston grooves well, you should be good to go for at least one season, probably more.

[DR DICK]

from my experance little bitty scratches in piston skirt are from crap in the oil. if this crap is coming from something that is disintergrating you may want to look deeper.

if they look like this it aint good news. 2nd pic.

http://xlforum.net/vbportal/forums/showpost.php?p=3465765&postcount=1

[taterhead3133]

oddly enough theres very little taper (0.0005") thats 1/2 a thousands and about the same for being out of round on both cylinders which really blows me away cause i would have thought they would have been worse as far as skirt clearence the pistons are fairly straight and round and in about the same condition as the cylinders. When you guys say awhile what do you mean 1000 miles or 20000 miles? BTW thanks for all the input.

[hcrashster]

15,765 miles. Give or take.

[taterhead3133]

so do you think that my valve guidescould have caused the scratches on my skirts? Ok let me explain that the guide seals were no longer existant and the guides were wore out so bad that the valves could move an 1/8" in either direction. I checked the rod play and neither one has more than 0.005" - 0.010" play side to side and no vertical play to speak of.

[taterhead3133]

give or take a 1/2 mile or so right.

[IronMick]

... the guide seals were no longer existant ...

IronHeads did not come with seals on the valves from the factory. They are optional on the intakes, and absolutely no-no on the exhausts where some oil for lube and cooling is needed.

[MDT]

What would I do? Obviously you have an idea how long it takes you to yank the cylinders off your bike. The second time around will be quicker. If you think the hone did the trick and your measurements are correct; re-ring it and go. If you guessed wrong, it won't take you long to yank it apart and have it bored. If you guessed right your gonna' have the meat on your jugs when you really need it.

[IronMick]

... If you think the hone did the trick and your measurements are correct; re-ring it and go ... your gonna' have the meat on your jugs when you really need it.

+1

The general principle is that you do not overbore unless it is necessary.

[taterhead3133]

so check this out I pulled the pistons off my rods to clean them up and install new rings when i removed the front piston and started checking it out the ring lands were broken and just sitting there kinda wedged in place between the rings ( about 1/3 of the way around the piston starting at the right side wrist pin hole going around the front of the piston ) the pistons seem very brittle like they have been very hot? dose this sound possible? i bought new custom crome pistons so no worries about me trying to use the old pistons just looking for input. could running super lean cause that? the guy i got the bike from rebuilt the carb with a paper bowl gasket and it was pulling air thru a tear in it. Man Harleys are tough ass bikes...

[hcrashster]

For peace of mind, measure those new pistons at the skirt so you will know bore clearance. Secondly, piston pin to connecting rod clearance should be .001. At room temperature the pin should slide in by hand, no side rocking. IMPORTANT!! Trust nothing till measured because even the best manufacturers make mistakes. Thirdly. Ring end gap is .004" per 1" bore diameter. Most builders set gap in the .014 to .016 range. If you know all this already, please excuse the reminder. PS. Sportsters are tough assed bikes. PPS Make that; Ironhead Sportsters are tough assed bikes.

[bobber58]

Usually busted ring lands are from piston rings with end gaps too tight. They expand when heated and if the ends butt together, they usually break the ring lands in the pistons. Ring flutter and detonation can do this as well.

[taterhead3133]

My pistons measure 3.218 on the money, they weigh 354.4/354.6 grams, my ring end gap is 0.015" on all 4 compression rings. my cylinders measure 3.220/3.221 the paper work that came with the pistons called for 0.003 - 0.004 with 0.0035 perfered clearence now i know that one cylinder is only 0.002 clearence (its the rear cylinder) i'm going to let it go as is. so what i'm geathering is that running lean can cause scratching/scoring but not really cause the ring lands to break. another question how far advanced would the timing have to be to cause detionation? i run 93 octaine (wish i could get 100LL at the gas station in stead of the air port) what a difference that would make.

[IronMick]

... how far advanced would the timing have to be to cause detionation? i run 93 octaine ...

I run 91 octane in my 1978: Wiseco 10:1 pistons, PB+ cams, Ultima EI at curve #1, 35` ignition timing, using a VOES.

It needs both the retarded timing and the VOES to eliminate the pinging.

[hcrashster]

Any chance of hitting that rear cylinder with a hone so it can be opened up a little more? Another .001 or so may keep you out of a situation where seizure may occur. Not being anal retentive here but aluminum expands much faster than cast iron and .002 clearance probably isn't enough.

[The Whammer]

Thanks for the info this thread offers, It has saved me some serious coin. Heck this whole forum is money in the bank!